大氣成分和大氣化學
Atmospheric Composition and Atmospheric Chemistry

大氣成分和大氣化學研究進展

2014年，大氣成分研究所圓滿完成了承擔的各項任務，在分析方法建立、比對校驗、質量控制，大氣成分及相關特性的觀測、環(huán)境氣象模式發(fā)展應用，影響評估等方面均取得了明顯的進展。

1 分析方法、比對校驗和質量控制研究

1.1 中國氣溶膠遙感網Cimel太陽光度計積分球標定方法的建立

參考美國國家標準技術研究院對于積分球標定的方法，建立了中國氣溶膠遙感網絡（CARSNET）Cimel太陽光度計的積分球標定方法和流程。利用該標定方法和操作流程對4臺CE318太陽光度計進行了標定試驗。結果顯示，與出廠參數相比，本方法獲得的可見光波段標定系數相對偏差小于3%，而紅外波段相對偏差約5%。太陽等緯圈(ALMUC)和主平面(PPLAN)現場驗證實驗數據顯示，天空散射輻亮度在±6°表現出良好的一致性，所有波長的差異小于1%，表明該標定方法和流程適合CARSNET太陽光度計的校準，并有利于提高數據質量和網絡觀測的精度。（車慧正）

1.2 四級桿質譜與全二維氣相色譜聯用鑒定大氣中的揮發(fā)性有機物

大氣揮發(fā)性有機物的準確測量對空氣質量評估、大氣光化學機理研究和污染控制政策制定等具有重要意義。全二維氣相色譜技術有助于準確測量復雜的大氣揮發(fā)性有機物，但是對快速檢測器的要求限制了全二維氣相色譜與四級桿質譜的聯用。通過研究將四級桿質譜與全二維氣相色譜聯用，并應用于大氣揮發(fā)性有機物的鑒定。在對標準混合氣體和北京城市空氣測量中，鑒定了包括烷烴、烯烴、芳香烴、含氧烴以及鹵代烴等125種揮發(fā)性有機物，并將鑒定化合物逐一對應至全二維氣相色譜-氫火焰離子化檢測結果中，從而完成了后者的譜圖解析和進一步定量分析。對譜圖中部分色譜峰保留時間隨二維調制周期環(huán)繞的現象進行了詳細討論。全二維氣相色譜分別與四級桿質譜和氫火焰離子化檢測器聯用進行定性和定量分析的方法不僅可靠實用，而且降低了儀器成本。該方法和研究結果可應用于其他揮發(fā)性有機物的分析中（圖1）。（王瑛）

1.3 本底大氣CO2觀測分析過程中QA/QC方法的建立與評估

建立科學規(guī)范的本底大氣CO2采樣觀測分析過程中的質量保證與質量控制方法，是實現該數據資源同化和共享的基礎。本研究以中國氣象局溫室氣體網絡化采樣觀測經驗為基礎，以便攜式采樣觀測堯波長掃描光腔衰蕩光譜（WS_CRDS）分析技術為例，系統介紹了我國青海瓦里關全球本底站大氣中CO2采樣觀測過程中的質量保證措施、樣品分析過程中的玻璃瓶質量保證措施和樣品分析過程中的系統質量控制方法、數據處理過程中的校正方法、數據分級質量標記和數據擬合插補方法等；并重點對該方法中幾個關鍵步驟進行了評估驗證；最后，應用本研究方法，對我國3個區(qū)域大氣本底站CO2的采樣觀測數據進行了處理和濃度變化特征分析。本研究方法也可以較好地捕捉區(qū)域和局地環(huán)境因素對觀測結果的影響，并客觀、準確地反映該區(qū)域的自然和人為活動特征。（劉立新）

1.4 龍鳳山本底站大氣CO2數據篩分及濃度特征研究

針對黑龍江龍鳳山區(qū)域大氣本底站2009年1月至2011年12月低層（離地10 m）和高層（離地80 m）大氣CO2在線觀測數據，選取低層數據重點開展研究，分析地面風向和風速等因素對觀測CO2濃度的影響。結果表明，龍鳳山低層大氣CO2濃度明顯受局地源匯影響，其與高層觀測結果差異在白天08∶00—17∶00相對較小，小于（0.5±0.5）×10-6（物質的比量）。春、夏和秋這3季節(jié)E-ESE-SE-SSE扇區(qū)來向的地面風會明顯抬升大氣CO2濃度、而冬季N-NNW-NW-WNW扇區(qū)CO2濃度明顯較高。該站4個季節(jié)近地面CO2濃度隨著風速增大而逐漸減小，在冬季尤為明顯。結合日變化及地面風的影響對低層觀測數據進行初步本底/非本底篩分，篩選出代表東北區(qū)域混合均勻CO2水平的本底數據占總數據的30.7%。本底CO2濃度季節(jié)變化顯示該站大氣CO2濃度呈現冬季高夏季低的趨勢，季振幅為（36.3±1.4）×10-6，明顯大于同期WMO、GAW同緯度站點觀測結果，2009—2011年龍鳳山大氣CO2年平均增長率為2.4 ×10-6。（方雙喜）

1.5 MeteoInfo: 氣象數據顯示分析GIS軟件

MeteoInfo是為氣象數據分析和顯示開發(fā)的一套軟件工具，包括一個面向軟件開發(fā)人員的.Net類庫和一個面向最終用戶的桌面軟件。MeteoInfo包含了一些基本的GIS功能，并能讀取氣象領域中常用的數據格式，如NetCDF和GRIB。對于格點和站點數據提供了能夠進行復雜氣象分析的數據模型。類庫提供了豐富的空間和氣象數據操作方法和控件，可以方便地用于相關業(yè)務軟件開發(fā)。桌面軟件具備友好的用戶界面，是查看和探究氣象數據的一個方便和強有力的工具。通過編寫IronPython腳本程序，MeteoInfo可以自動運行并進行批處理操作。MeteoInfo是一個免費軟件，已經在國內外有廣泛的應用（圖2）。（王亞強）

2 大氣成分及相關特性變化的觀測研究

2.1 我國上甸子區(qū)域本底站大氣六氟化硫（SF6）在線觀測研究

通過國際合作，采用歐亞地區(qū)鹵代溫室氣體觀測網（SOGE）和改進的全球大氣實驗網（AGAGE）技術，利用自組裝氣相色譜-電子捕獲檢測系統和氣相色譜-質譜聯用系統，在我國上甸子區(qū)域本底站自2009年6月至2011年5月開展了2個完整年度的在線觀測。觀測期間SF6平均本底和非本底濃度分別為7.22×10-12和8.66×10-12。上甸子站本底濃度與AGAGE同緯度本底站（Trinidad Head站和Mace Head站）濃度一致，大于南半球本底站（Cape Grim站和Cape Matatula站）濃度。觀測期間SF6本底濃度快速增長，年增長率達到0.30×10-12。SF6本底濃度季節(jié)振幅為0.07×10-12，非本底濃度季節(jié)振幅則達到2.16×10-12。SF6的濃度峰值出現在秋季，地面風向來自W-WSW-SW-SWS-S，而SF6低濃度出現在地面風來自N-NNE-NE-ENE-E扇區(qū)。（姚波）

2.2 我國瓦里關和上甸子本底站大氣CO2及其穩(wěn)定同位素變化

利用2007—2010年瓦里關和上甸子站大氣CO2及其碳穩(wěn)定同位素觀測數據，對二者的變化特征、相關關系和源匯特征進行了分析研究。結果顯示，瓦里關站大氣CO2及其δ13C具有顯著的長期變化趨勢和季節(jié)變化規(guī)律，同時二者呈明顯的鏡像關系，年際變化規(guī)律顯示出北半球中高緯度陸地生態(tài)系統源匯季節(jié)變化特征。CO2年均濃度呈線性增長趨勢，年均增長率為（2.1±0.1）×10-6；δ13C年均值則呈線性下降趨勢，年均增長率為（-0.02±0.001）‰。在上甸子站，受陸地生態(tài)系統和人類活動共同影響下，大氣CO2年均值亦呈線性增長趨勢，年均增長速率為（1.8±0.1）×10-6；同時CO2季振幅達到23.0×10-6。2009—2010年度δ13C年均值由-8.27‰降至-8.36‰。瓦里關和上甸子站δs分別為（-25.44±0.72）‰和（-21.70±0.67）‰；在瓦里關站，冬春季δs偏負；而在上甸子站，由于受到夏季C4植物光合作用和冬季生物質燃燒的影響，其δs全年偏重并較瓦里關站更偏正。（劉立新）

2.3 我國4個大氣本底站大氣CO2濃度觀測研究

利用基于光腔衰蕩光譜技術，于2009—2011年對我國4個世界氣象組織/全球大氣觀測網（WMO/ GAW）全球或區(qū)域本底站（浙江臨安、黑龍江龍鳳山、北京上甸子和青海瓦里關）大氣CO2濃度進行連續(xù)觀測研究。其中臨安站位于經濟發(fā)達區(qū)域（上海），龍鳳山站位于農田和森林區(qū)域，離省會哈爾濱較近，而上甸子站距離北京約150 km。瓦里關站代表我國內陸本底清潔大氣水平，該站也擁有國內最長的大氣CO2觀測記錄。觀測期內4站大氣CO2濃度年增長率分別為（3.7±1.2）×10-6（臨安）、（2.7±0.8）×10-6（龍鳳山）、（3.5±1.6）×10-6（上甸子）、（2.2±0.8）×10-6（瓦里關）。相比而言，臨安站CO2濃度最高，在2011年平均濃度為（404.2±3.9）×10-6。通過對各站大氣CO2濃度日變化、季節(jié)變化以及局地源匯影響分析，研究了各站濃度特征以及影響因素。以上研究為認識我國大氣CO2濃度特征以及模式研究提供了基礎支撐。（方雙喜）

2.4 長三角區(qū)域臨安站大氣CO2本底信息的評估

結合氣溶膠觀測記錄和氣象資料，對長三角地區(qū)大氣中混合均勻的CO2本底信息進行了提取研究?；谛卵邪l(fā)的方法，對浙江臨安站2009—2011年觀測的CO2濃度記錄進行篩分，并評估了人為活動對觀測濃度的影響。結果表明，通過本方法提取的CO2本底濃度與R篩分提取的信息基本一致，在重污染條件下，本方法對于區(qū)域本底CO2信息的提取明顯優(yōu)于R篩分法。2009—2011年臨安站年平均CO2濃度分別為（404.7±8.2）×10-6、（405.6±5.3）×10-6、（407.0±5.3）×10-6，明顯高于全球平均。人為活動排放對臨安區(qū)域大氣本底CO2濃度有明顯影響，抬升約9.1×10-6。（方雙喜）

2.5 上甸子本底站鹵代溫室氣體大氣濃度短期波動的個例分析

利用軌跡分析法、印痕分析和流場分析法，結合上甸子站鹵代溫室氣體H-1301、HCFC-22、CFC-11和SF6在線濃度觀測數據，選取2012年9月7—12日上甸子測站鹵代溫室氣體濃度短期波動典型個例進行分析。軌跡分析結果表明：9月7日12∶00污染發(fā)生前，氣團主要來自較遠的偏西北、偏北方向，水平輸送距離長、移速快、垂直高度高，對應的鹵代溫室氣體濃度偏低，H-1301、HCFC-22、CFC-11和SF6的體積分數分別為4×10-12、350×10-12、260×10-12、10×10-12；9、10日有一定比例的氣團在測站的偏南區(qū)域近地面回旋打轉，水平輸送距離短、垂直高度低，在邊界層內緩慢移動，不利于污染物在邊界層內擴散，導致鹵代溫室氣體濃度偏高，對測站濃度的短期抬升貢獻較大，9日12∶00 H-1301、HCFC-22、CFC-11的峰值體積分數分別達到45×10-12、200×10-12、310×10-12，10日03∶00 SF6的峰值體積分數達到28×10-12；11日西南方向回旋氣團消失；12日氣團完全來自較遠的西北方向且軌跡移動較快。印痕分析與軌跡分析結果一致：7、8日敏感性系數較高區(qū)域主要分布在測站以北，9、10日敏感性系數較高區(qū)域分布在測站偏南，11、12日測站偏南的敏感性系數較高區(qū)域消失。流場分析結果表明：9、10日環(huán)流形勢有利于污染物在測站區(qū)域累積，造成測站濃度的短期抬升。（安興琴）

2.6 北京上甸子區(qū)域大氣本底站甲基氯仿（CH3CCI3）在線觀測研究

利用GC-ECD在線觀測系統，在北京上甸子區(qū)域大氣本底站開展了CH3CCl32年在線觀測，利用逐步逼近回歸法進行本底值篩分，討論了上甸子站CH3CCl3濃度水平及其變化趨勢。該站2009年和2010年的年均大氣CH3CCl3本底濃度（摩爾分數，下同）分別為(9.03±0.53)×10-12和 (7.73±0.47)×10-12，本底數據出現頻率為61.1%（2009年）和60.4%（2010年）。上甸子站CH3CCl3濃度水平與北半球同緯度帶本底站觀測結果基本一致，低于文獻報道的2001—2005年間我國華南區(qū)域和城市觀測的結果。觀測期間本底濃度呈下降趨勢，年下降率為1.39×10-12。結合風向分析，該站CH3CCl3平均濃度最高的風向來自西南扇區(qū)，而平均濃度最低的風向來自東北扇區(qū)，不同風向的濃度差值分別為0.77×10-12（2009年）和0.52×10-12（2010年）。2010年各風向CH3CCl3平均濃度比2009年降低1.03 ×10-12～1.68×10-12。（姚波）

2.7 氣團垂直輸送對中國西南香格里拉區(qū)域大氣本底站近地面臭氧濃度的影響

根據2007年12月到2009年11月在中國西南香格里拉區(qū)域大氣本底站（28.006°N，99.726°E； 3580 m）的近地面臭氧、一氧化碳以及氣象數據的現場觀測，發(fā)現臭氧和一氧化碳的季節(jié)峰值在春季而臭氧的谷值在夏季、一氧化碳的谷值在冬季。根據月均歸一化的臭氧、一氧化碳和水汽值的變化，提出了一個用于指示來自高層大氣、富含臭氧氣團向下輸送到近地面的歸一化指示因子（標為Y）。這個組合的因子具有較少受季節(jié)或偶然個例變化影響的優(yōu)點。 通過對Y值的分析，發(fā)現大多數有效的向下輸送經常發(fā)生在冬季（占總數的39%，當Y的指示值大于4時），導致了近地面臭氧濃度顯著地上升。來自較強的向下輸送事件導致冬季近地面臭氧濃度增加9.6×10-9（21%）?；赮值與位勢渦度、臭氧總量和后向軌跡很好地分析了一個由西風槽主導下較強的臭氧向下輸送個例。亞洲季風在壓制夏、秋季近地面臭氧的積累中扮演了一個很強的角色，而由Y值指示的香格里拉高層臭氧向下輸送的季節(jié)變化與青藏高原地區(qū)的平流層-對流層輸送、副熱帶高空急流的季節(jié)變化有一致性。（鄭向東）

2.8 超大城市北京冬季過氧乙酰硝酸（PAN）：化學與氣象過程的作用

亞洲超大城市大氣過氧乙酰硝酸（PAN）的測量研究過去很少，而且主要局限于夏季較短的時段。本研究給出了2010年1月25日至3月22日北京市區(qū)中國氣象局大院同步觀測的PAN、O3、NOx等的分析結果。PAN小時平均濃度為0.70×10-9（0.23×10-9～3.51×10-9），與NO2濃度呈較好的正相關，但與O3濃度卻不相關，這表明冬季城市PAN和O3是脫鉤的。風速風向和氣團輸送條件對O3、PAN等污染物有非常顯著的影響。到達測點的氣團來自嚴重污染N-S-W扇區(qū)的邊界層或者來自W-N扇區(qū)的自由對流層。自由對流層的下沉空氣富含O3，其平均PAN/O3比值小于0.031，而污染扇區(qū)邊界層空氣含高濃度PAN和一次污染物，其平均PAN/O3比值為0.11。這些有關輸送條件的事實可較好地解釋觀測到的PAN與O3的脫鉤現象。北京冬季光化學生成對于PAN仍是重要的。形成PAN需要的PA自由基濃度估算值介于0.0014×10-12和0.0042×10-12之間。計算了PAN的生成反應和熱分解反應對PAN濃度變化的相對貢獻，發(fā)現即使在北京較冷的時期，兩者的作用都是顯著的，其中生成作用超過分解作用（圖3）。（徐曉斌）

2.9 北京及周邊地區(qū)3個典型站點NOx和CO的變化特征

為了研究華北平原北部區(qū)域不同類型站點光化學前體物的共性與差異，在華北平原北部地區(qū)西南—東北主導風向上選取間距大于100 km的3個站點，即中國氣象局（CMA）、上甸子（SDZ）和固城（GCH）依次代表北京城區(qū)、華北本底地區(qū)和相對污染的農村地區(qū)，進行了近地面NOx和CO觀測。結果表明：2008年6月至2009年5月，CMA、SDZ和GCH 3站NOx體積分數的年均值依次為（42.4±21.8）×10-9、（13.8±5.5）×10-9和（26.9±15.2）×10-9；CO體積分數的年均值依次為（1.13±0.37）×10-6、（0.67±0.17）×10-6和（1.11±0.62）×10-6。3站的NOx月均值體積分數以及CMA、GCH 2站的CO月均值體積分數呈現出冬季高夏季低的特點，而SDZ站的CO 6月均值體積分數（1.03×10-6）為一年中最高。SDZ站的NOx和CO體積分數值在中午12∶00前后出現一個低谷，比CMA和GCH站的提前3～4 h，此后呈上升趨勢，體現了午后西南風輸送對SDZ站的影響。盡管不同的源排放和大氣輸送影響導致3站的NOx和CO體積分數在日變化特征上有所差異，但3站的NOx和CO日平均體積分數之間存在極其顯著的相關性，體現了區(qū)域性污染和氣象條件共同影響的特征（圖4）。（徐曉斌）

2.10 浙江臨安大氣本底站CO濃度及變化特征

利用基于光腔衰蕩光譜（CRDS）技術自組裝的大氣CO在線觀測系統，于2010年9月至2012年2月在浙江省臨安大氣本底站對大氣CO進行了在線觀測。結果表明，臨安站四季CO日變化明顯受人為活動影響，分別在每日07∶00—10∶00和19∶00—20∶00出現峰值，夏季CO日平均濃度和振幅均最低，分別為（314.3±7.6）×10-9（摩爾比，下同）和（50.1±47.9）×10-9。該站全年大氣CO濃度呈現冬春季高、夏季低的趨勢、與北半球瑞士Jungfrauioch站、青海瓦里關等站基本一致，但平均濃度明顯高于其他國際站點，全年CO月均值振幅為（286.8±19.2）×10-9。軌跡聚類和地面風結果分析表明，臨安站非本底CO濃度主要來自N-NNE-ENE扇區(qū)內城市及工業(yè)等人為排放，春、夏和冬季最大的濃度抬升均出現在NEN風向，冬季抬升值最大為（106.3± 58.0）×10-9。（方雙喜）

2.11 長江三角洲區(qū)域本底站氨氣和銨鹽氣溶膠季節(jié)變化特征

2009年9月至2010年12月在位于經濟快速發(fā)展的華東長江三角洲之臨安區(qū)域本底站使用被動采樣器對大氣氨進行了強化觀測，同時在2010年對該站大氣細粒子PM2.5開展了為期1年的觀測。觀測期間臨安站NH3濃度變化范圍為（0.1～41.8）×10-9，2010年NH3年均濃度是（16.5±11.2）×10-9。2010年臨安站PM2.5中的NH4+質量濃度變化范圍為0.02～19.2 μg/m3，年均濃度為（4.3±3.5）μg/m3。NH3濃度季節(jié)變化明顯，夏季最高冬季最低，其主要與周邊農業(yè)活動和氣溫呈正相關。NH4+濃度在秋季最高可能是受到農業(yè)殘余生物質燃燒的影響。2010年臨安站NH3/NHx的比值為0.8±0.1，說明NHx主要是受到當地源的影響。后向軌跡分析表明，臨安站因受到長江三角洲區(qū)域及偏北氣流引起的污染長距離傳輸影響，呈現出高細粒子水平特征。臨安區(qū)域本底站高NHx沉降說明了在長江三角洲區(qū)域減少NH3排放的緊迫性。（孟昭陽）

2.12 北京PM2.5中水溶性離子的變化、形成以及酸性特征

總結了北京城區(qū)2009年6—11月期間PM2.5日均濃度、PM2.5中水溶性無機離子小時平均濃度以及PM2.5氣態(tài)前體物濃度。結果表明，水溶性離子總濃度為44 μg/m3，占PM2.5的38%，其中硫酸鹽、硝酸鹽和銨鹽是主要的離子成分。硫酸鹽在夏季和秋季濃度差異在30%以內，而硝酸鹽和銨鹽的濃度在兩個不同季節(jié)差別明顯。由于源排放、生成機理以及氣象條件的不同，導致多數離子成分及其前體物濃度的日變化特征明顯。硫酸鹽、硝酸鹽和銨鹽的氧化/轉化率分別為63%，15%和15%。盡管環(huán)境大氣中存在大量氨氣，但銨鹽的轉化率仍然很低，說明氣態(tài)氨的濃度水平不是銨鹽生成主導因子。銨鹽的日變化特征也與氣態(tài)氨的日變化特征不同。對PM2.5中氫離子濃度以及氣溶膠酸度的估算結果顯示，有75%的樣品顯強酸性，只有極少部分樣品顯堿性。（張養(yǎng)梅）

2.13 我國中東部高山站PM1中主要化學組分和粒徑分布特征

自2010年6月至2012年1月，對泰山高山站亞微米氣溶膠主要化學組分質量濃度和粒徑分布特點進行了歸納和總結。結果表明，該站點亞微米氣溶膠中有機物、硫酸鹽、硝酸鹽、銨鹽和氯化物的年平均質量濃度分別為11.2、9.2、7.2、5.8和0.95 μg/m3。這個濃度水平明顯高于美國和歐洲的高山站，但比我國城市近地面站點濃度要低。在整個觀測階段，主要化學組分濃度具有明顯的季節(jié)變化規(guī)律、邊界層高度的季節(jié)變化特點，近地面污染物濃度以及區(qū)域傳輸過程等因素是導致秋季濃度低、夏季濃度高的主要原因。

為了更好地探討不同類型污染天氣對亞微米氣溶膠特性的影響，本研究將氣團分成了受邊界層影響（PBL）、受自由對流層影響（LFT）、新粒子生成事件（NPF）、云中過程和污染過程等5類。其中，有機物在新粒子生成事件中占有主導地位，而硫酸鹽在云中過程中對亞微米氣溶膠的貢獻最大。

整個研究期間，有機物、硫酸鹽、硝酸鹽和銨鹽的質量譜均值粒徑分別為539、585、542和545 nm。該均值粒徑比在華北地區(qū)地面觀測的均值粒徑要偏大，說明高山站氣溶膠粒子相對老化并混合均勻。在PBL、NPF和污染事件中，有機物在小粒子范圍貢獻最大，尤其在污染事件中，在100～200 nm之間，有70%的組分是有機物。在云中過程中，無機物在整個亞微米粒徑范圍貢獻70%，其中硫酸鹽在小粒子范圍貢獻40%，表明硫酸鹽在云形成過程中起到至關重要的作用。

根據氣團軌跡特點將該站點受到的主要氣團來向分為7條，大多數氣團來源于短距離的區(qū)域擴散，主要氣團來自站點南方，其中有機物和硫酸鹽是這類氣團的主要污染物種。遠距離傳輸氣團通常載帶著清潔和干燥的氣團影響泰山站點。

利用正矩陣因子分析方法對有機物進行的分類解析結果表明，泰山站有機氣溶膠中，氧化類有機氣溶膠在春、夏、秋、冬4個季節(jié)分別占總有機物的49%、56%、51%和41%，說明夏季有機物氧化程度較嚴重。此外，生物質燃燒類有機氣溶膠夏季占有機氣溶膠的34%，燃煤類有機氣溶膠在冬季占有機氣溶膠的22%。（張養(yǎng)梅）

2.14 中國不同區(qū)域大氣氣溶膠化學成分濃度、組成與來源特征

為獲得中國不同區(qū)域大氣氣溶膠化學組成的總體“圖景”，進一步探討污染治理方向，需要分區(qū)域評估其化學成分濃度水平、組成與來源特征。通過對近地層中國內陸大氣氣溶膠中6種主要化學成分（硫酸鹽、硝酸鹽、銨、有機碳、黑碳和礦物氣溶膠）至少有1年觀測研究的評估分析，獲得不同區(qū)域氣溶膠化學成分質量濃度水平與組成的評估結果。在氣溶膠污染最嚴重的4大區(qū)域（即北京以南的華北與關中平原區(qū)域、以長三角為主體的華東區(qū)域、以珠三角為主體的華南區(qū)域以及四川盆地）的PM10中礦物氣溶膠（所占20%～38%）、硫酸鹽（占14%～24%）、有機碳（占11%～18%）是3個主要組分；其中華北與關中平原氣溶膠污染在中國最重，硫酸鹽濃度為35～47 μg/m3（遠高于北京的（13～18 μg/m3））、有機碳為28～45 μg/m3（約是北京（19～22 μg/m3）的1.8 倍）、硝酸鹽為19～22 μg/m3（約是北京（9.9～12 μg/m3）的2倍）、銨為14～16 μg/m3（比北京（6.2～8.4 μg/m3）高1倍），黑碳在北京和北京以南城市的濃度差別不大（9.1～12 μg/m3）。這其中燃煤對硝酸鹽和有機碳氣溶膠的貢獻超過50%，農業(yè)活動是銨的最重要來源。華東、華南和東北城市區(qū)域氣溶膠化學成分濃度水平與北京相近，但四川盆地城市站各組分濃度均高于北京，污染較重。西北蘭州城市站，除了黑碳濃度低很多、硝酸鹽濃度稍高外，其他氣溶膠化學成分濃度水平與北京相當。西北偏遠區(qū)域沙漠站點，各種氣溶膠化學成分的濃度都遠低于北京。青藏高原和云貴高原城市站氣溶膠化學成分濃度與北京相比也明顯偏低。不同區(qū)域氣溶膠化學組成分析顯示，燃煤、機動車、城市逸散性粉塵和農業(yè)活動是4個最需要關注的污染源，加強除發(fā)電行業(yè)外的燃煤脫硫，進一步消減燃煤氮氧化物、一次有機碳和揮發(fā)性有機物排放，并有效減少農業(yè)活動排放到大氣中的氨，更有效限制硫酸鹽和硝酸鹽的形成是已有大氣污染治理對策基礎上，未來應特別關注的控制方向。（張小曳）

2.15 泰山PM10及其中化學成分變化特征

為研究具有區(qū)域背景代表性的氣溶膠成分及其變化特征，在泰山頂從2010年6月至2011年7月采集了64個PM10濾膜樣品，分析了樣品的PM10及其中無機鹽離子和有機碳（OC）、元素碳（EC）的質量濃度，并對各成分相關性等進行了分析。泰山PM10年均質量濃度約為68.4 μg/m3，其中無機鹽離子約占總質量的64.8%，碳氣溶膠約占17.4%。無機鹽離子的質量濃度從春季逐漸增大，夏季達到峰值，秋季下降，冬季最??；OC質量濃度從春季至秋季逐漸增高，冬季最低，EC變化類似，但夏秋兩季差別不大。二次有機碳（SOC）與OC的比值四季均在50%以上，年均值約為58.5%。通過后向軌跡聚類分析，發(fā)現在經過城市的較短軌跡以及南方較短混合軌跡的影響下，泰山PM10質量濃度較高，而西北長距離傳輸氣團PM10濃度均較低。（王亞強）

2.16 北京上甸子典型天氣個例的大氣氣溶膠數譜分布特征

使用差分淌度粒徑分析儀（TDMPS）和空氣動力學粒徑分析儀（APS）對上甸子區(qū)域本底站顆粒物（直徑3 nm～10 μm）數譜分布特征進行觀測。利用2008年的觀測結果，分析了不同天氣（包括沙塵天氣、干潔天氣和霧霾天氣）條件下大氣氣溶膠數譜分布及其與氣象要素和氣團來源的關系。結果表明，沙塵天氣條件下，上甸子站受西北方向的氣團控制，風速較大，粗粒子數濃度明顯增加，PM10的質量濃度可以迅速增加到毫克每立方米的量級。典型的“香蕉型”新粒子生成事件通常發(fā)生在比較干潔晴朗的天氣條件下，西北氣團主導，大氣中背景氣溶膠數濃度較低，核模態(tài)氣溶膠數濃度迅速增長，氣溶膠的粒徑呈現明顯的增長過程，核模態(tài)可以平穩(wěn)地增長到80 nm左右，達到成為云凝結核的尺度。霧霾天氣通常是在西南氣團影響下，細顆粒物（1 μm以下）的不斷累積、相對濕度不斷升高的條件下發(fā)生的。霧霾天氣條件下數譜分布的幾何中值粒徑出現在積聚模態(tài)，積聚模態(tài)數濃度也高于非霧霾天。個例研究表明，霧霾天氣條件下PM2.5質量濃度可以達到非霧霾天的10倍左右，其中以細顆粒物的貢獻為主。在霧霾天氣條件下，上甸子地區(qū)數濃度較高的積聚模態(tài)顆粒物主要來自城區(qū)的傳輸，因此對背景地區(qū)氣溶膠數譜的研究可以為解析城區(qū)氣溶膠復雜來源提供依據。（沈小靜）

2.17 基于地基太陽光度計測試的2013年中國華北平原嚴重霧霾月數據進行的柱狀氣溶膠光學特性和氣溶膠輻射強迫研究

2013年1月，華北平原經歷了幾次嚴重的霧霾事件，在2013年1月1—30日，基于Cimel 太陽光度計在華北背景、郊區(qū)和城市等7個站點進行了觀測，研究氣溶膠光學參數的時空變化和氣溶膠輻射強迫。研究結果發(fā)現，500 nm氣溶膠光學厚度在無污染時期每個站點都低于0.30，在污染事件發(fā)生時期，氣溶膠光學厚度顯著大于1.00。在大多數時間段，所有的站點Angstrom指數都大于0.80。污染和非污染時期，在北京的3個城市站點，500 nm平均氣溶膠光學厚度從北向南逐漸增加。在城市站點污染期間細模態(tài)氣溶膠光學厚度大約是無污染時期的2.5倍，而在郊區(qū)和農村站點達5.0倍左右。在2013年1月，對于所有站點675 nm細模態(tài)氣溶膠光學厚度所占比例大于80%。污染時期，675 nm氣溶膠光學厚度吸收在農村站點約為0.01，而在其他地區(qū)的污染和非污染時段，分別為0.03～0.07和0.01～0.03，單次散射反照率在0.87和0.95之間。霧霾最嚴重時期，北京城區(qū)氣溶膠粒子譜分布呈現出明顯的3峰分布特征。在污染時期，細模態(tài)氣溶膠有效半徑為0.01～0.08 μm，大于非污染時段；而粗模態(tài)粒子有效半徑，在污染時段為0.06～0.38 μm，比非污染時期小。總體、細模態(tài)和粗模態(tài)氣溶膠體積變化分別為0.06～0.34 μm3，0.03～0.23 μm3和0.03～0.10 μm3。在霧霾最嚴重的時期（1月1—16日），氣溶膠輻射強迫在農村、郊區(qū)、城市分別超過了-50 W/m2、-180 W/m2和-200 W/m2。在大氣層頂，農村和城市地區(qū)氣溶膠輻射強迫數值分別為-30 W/m2和-40～60 W/m2。由于積雪覆蓋導致的高反照率，惠民城市站點大氣層頂正的氣溶膠輻射強迫不同于其他站點。（車慧正）

2.18 2013年1月中國東部一次重度霾污染事件的天氣成因分析

應用加密地面氣象要素觀測資料、經緯儀氣球探空資料、NCEP再分析資料以及T639模式輸出產品，采用大氣環(huán)流三維結構合成分析、穩(wěn)定邊界層物理量診斷分析以及軌跡模式HYSPLIT4跟蹤等方法，研究2013年1月6—16日中國華北大范圍霧霾天氣過程發(fā)生和持續(xù)的氣象成因，探討氣象條件在2013年1月10—12日北京PM2.5質量濃度連續(xù)上升過程中的作用與影響。結果表明：（1）大氣環(huán)流從經向波型調整成為緯向波型的過程為中國華北地區(qū)提供了有利于霧霾天氣發(fā)生的靜穩(wěn)型環(huán)流形勢；（2）邊界層大氣層結穩(wěn)定、對流高度值低，使邊界層湍流運動受到抑制，為霧霾的形成提供了有利的氣象條件；（3）黃河河套以東廣大地區(qū)（包括山西、河北等地）在對流層低層存在一支低空西南氣流（6～11 m/s），有利于這些地區(qū)的污染物向北京方向遠距離輸送，加劇北京的空氣污染程度；（4）美國NOAA研制的HYSPLIT4模式對氣團72 h后向軌跡追蹤與高空探測結果相吻合，具有參考價值。（王宏）

2.19 中國北京嚴重霧霾條件下氣溶膠光學特性的研究

2013年1月，在中國華北地區(qū)發(fā)生了幾次嚴重的霾污染事件?；谥袊鴼庀罂茖W研究院站點2013年1月1—30日期間的Cimel太陽光度計的數據，詳細研究了氣溶膠的光學特性。研究發(fā)現，2013年1月霧霾期間，當北京城區(qū)氣溶膠光學厚度大于0.60時，Angstrom指數大多大于0.80。在霾發(fā)生之前，北京城市地區(qū)氣溶膠光學厚度大約可以穩(wěn)定在0.40，而之后，伴隨霾的產生，500 nm氣溶膠光學厚度急劇上升超過1.50。在嚴重的霾污染時期，細模態(tài)大氣氣溶膠是粗模態(tài)的20倍。在440、675、870和 1020 nm 4個波段，單次散射反照率接近0.90±0.03，細模態(tài)粒子單次散射反照率在440 nm波段相對一致，而在675、870和1020 nm波段變化很大。除1月12日和18日外，所有的細粒子體積都高于粗粒子體積，表明由人為產生的細粒子是霧霾產生的主要因素。對2013年1月嚴重霧霾污染事件氣溶膠類型分類分析表明，占主導地位的氣溶膠類型能夠被分為“混合”和“城市/工業(yè)/生物體燃燒”兩種類別?；旌闲图s為31%，而城市/工業(yè)型約為69%。（車慧正）

2.20 使用Prede天空輻射計在北京城市站點反演的氣溶膠光學特性

SKYNET是基于Prede天空輻射計的國際氣溶膠光學特性觀測網絡，主要目的是研究氣溶膠-云-輻射相互作用。利用最新SKYRAD.pack軟件（版本5.0）反演了北京城市站點氣溶膠光學特性，包括氣溶膠光學厚度（AOD），波長指數（α），粒子體積譜分布及單散射反照率（SSA）等。研究結果表明，北京500 nm 的AOD值變化區(qū)間在0.11（第5百分位）到1.14（第95百分位），中值為0.34，季節(jié)平均的α最大值出現在夏季，為1.05±0.36，最小值出現在春季，為0.82±0.39。500 nm的SSA值在夏季和春季有相似的較高值，為0.96±0.03，但在冬季較低，為0.93±0.04。在北京全年的氣溶膠粒子清楚地表明了雙峰尺度分布：春季粗粒子，夏季細粒子。α隨著AOD增大而變大，表明在北京細粒子在氣溶膠光學特性中起著重要作用。根據沙塵標準閾值（α＜0.47并且 SSA400nm-SSA1020nm＜0.018） ，在所有的觀測數據中沙塵類型氣溶膠發(fā)生率在春、夏、秋和冬季分別占4.1%，5.1%，0.5% 和1.2%。（車慧正）

2.21 2013年1月一次持續(xù)性重度霾污染事件的綜合觀測研究

針對2013年1月6—16日中國東部地區(qū)的一次強污染過程， 對其能見度、PM10、SO2和NO2濃度、550 nm的ODIS AOD、440 nm的CARSNET AOD和CLIPSO 532 nm的氣溶膠消光系數等觀測資料進行了綜合分析。 研究結果發(fā)現，東部地區(qū)這次持續(xù)性大面積霾污染過程伴隨著低能見度、高PM10和AOD。污染最為嚴重的地區(qū)是京津冀以及河北中南部、山東西部和河南北部在內的緊鄰周邊地區(qū)。霾污染擴散到了中國東部到125°E 的海面，甚至對整個140°E以西的洋面都有所影響。京津冀及其周邊地區(qū)PM10的變化趨勢呈現出很大的相似性， 顯示該地區(qū)污染物跨城市輸送的可能影響。在這次嚴重霾污染事件中，超級城市群的郊區(qū)顯示出和城市非常相似的嚴重污染狀況。大部分污染物集中在地面以上1500 m高度， 特別是100～800 m高度是污染物最為集中帶。（王宏）

2.22 中國華北平原地區(qū)區(qū)域背景大氣柱狀整合的氣溶膠光學和物理特性

基于興隆站2006年2月到2011年7月的氣溶膠光學特性數據研究了北方平原區(qū)域背景氣溶膠光學和物理特性以及在沙塵和霾條件下的時間變化情況。結果表明，興隆年平均氣溶膠光學厚度和消光波長指數分別為0.28±0.30和1.07±0.38。季節(jié)平均的AOD440nm在春季（0.40±0.3）和夏季（0.40±0.42）高于秋季（0.20±0.22）和冬季（0.19±0.21）。興隆站的消光波長指數約為1.25，吸收波長指數為1.0～1.5，這表明占主導地位的類型是混合氣溶膠（當AAE＞1.0時占88.2%）。幾乎所有的沙塵觀測都發(fā)生在春季。細模態(tài)和粗模態(tài)顆粒的體積濃度隨AOD的增加而增加。在春季，粗粒子氣溶膠的增加程度大于細粒子；然而，在其他季節(jié)觀測到相反的現象。興隆站的高值AOD可能與細模態(tài)氣溶膠增長及粗模態(tài)粒子有關。該背景站不僅受來自中國西北和蒙古國南部沙塵氣溶膠的影響，也受到來自南方城市和工業(yè)化地區(qū)人為氣溶膠遠距離輸送的影響。沙塵天氣的平均AOD為1.49，而霾天的AOD為1.10。沙塵天和霾天的平均波長指數分別為0.09和1.43。（車慧正）

2.23 1980—2009年塔克拉瑪干沙漠沙塵氣溶膠對驅動表面太陽輻射呈上升趨勢

研究了塔克拉瑪干沙漠在1980—2009年表面太陽總輻射（SSR）的長期趨勢及其與總云量（TCC）、低云（LCC）、水汽含量（WVC）和氣溶膠光學厚度（AOD）的關系。該地區(qū)年平均SSR每10年增加了1.21 W/m2，除了冬季，SSR均呈上升趨勢。TCC，LCC和WVC有所增加，而AOD和嚴重沙塵時間發(fā)生頻次均呈減少趨勢，表明在塔克拉瑪干沙漠是沙塵氣溶膠而不是云層和水蒸汽驅動SSR的長期上升。（車慧正）

2.24 中國四川盆地基于地面測量的氣溶膠光學特性

測量并分析了2007年2月到2009年12月中國四川盆地成都站點的氣溶膠光學厚度（AOD）和Angstrom指數以及氣溶膠光學厚度與PM10之間的關系。觀測中發(fā)現AOD月平均高值出現在3月、8月和12月而相對較低的值出現在10月，Angstrom指數在3月和8月的變化與AOD相反，平均PM10呈顯著的季節(jié)性差異，冬季存在高峰值，總的AOD值與近地面層的PM10之間存在一個復雜的（非線性）正相關關系。沙塵和霧霾條件下的3個案例表明，AOD值在沙塵天氣條件下最大而在霾天氣條件下最小，然而3種天氣條件下Angstrom指數分布與AODs相反。3天的后向軌跡分析表明，空氣質量的起源很大程度上影響四川盆地上方的氣溶膠光學特性。（車慧正）

2.25 利用CloudSat衛(wèi)星資料分析云微物理和光學性質的分布特征

利用2007年1月至2010年12月高垂直分辨率CloudSat衛(wèi)星的2B數據產品，對云微物理特征量（包括云中液態(tài)水/冰水含量、液態(tài)水/冰水路徑、云滴有效半徑等）以及云光學參數（云光學厚度等）的全球分布和季節(jié)變化進行了統計分析，并研究了云微物理性質對光學性質的影響。結果表明，冰水路徑分布在北美南部、南美大陸、非洲大陸、澳大利亞和南亞的陸地上空，以及太平洋、大西洋和印度洋的洋面上空，高值區(qū)最大值達600 g/m2以上，垂直方向上高值區(qū)位于赤道地區(qū)8 km附近以及中緯度地區(qū)4～8 km高度上。液態(tài)水路徑在300 g/m2以上的高值區(qū)主要位于太平洋、印度洋和大西洋的中低緯度海域上空，垂直方向上液態(tài)水含量隨高度遞減。冰云有效半徑在高緯度地區(qū)近地面層達200 μm以上，在赤道附近4～8 km上有1個高值區(qū)，南北半球中緯度地區(qū)2～4 km上有2個高值區(qū)，最大值均達到80 μm以上。在1 km以下的邊界層水云有效半徑值較大，達到12 μm以上。總云光學厚度在全球大部分地區(qū)＜40，高值區(qū)普遍位于中高緯度的廣闊地區(qū)和低緯度靠近大陸的洋面上空；垂直方向上云光學厚度的高值集中在2 km以下的邊界層。云光學厚度的分布受云量、云水含量和云滴有效半徑的影響，云量大的地區(qū)基本為云光學厚度的大值區(qū)。（王志立）

2.26 青藏高原及其周邊地區(qū)衛(wèi)星Aura-MLS的臭氧與水汽廓線產品的驗證分析

根據Aura衛(wèi)星微波臨邊探測（MLS）2.2、3.3版水汽和臭氧廓線，采用線性內插方法，將夏季在青藏高原（西藏的那曲和拉薩）及其周邊地區(qū)（云南騰沖）通過冷凍霜點儀（CFH）和電化學反應池型（ECC）探空儀分別測得的水汽和臭氧數據插值到與衛(wèi)星產品規(guī)定的氣壓高度進行比較分析，以檢驗MLS水汽和臭氧廓線產品。結果表明：MLS 2.2、3.3版水汽相對誤差在100 hPa的對流層頂附近分別為（9.8±46.0）% （n=18）、 （23.0±45.8）% （n=17）；在小于并包含82.5 hPa在內的下平流層則分別為（2.2±15.7）% （n=74）、（0.3±14.9）% （n=75）；而在對流層316～ 121 hPa高度則分別為（21.5±90.6）% （n=104）、（6.0±83.4）% （n=99）。相應MLS 2.2、3.3版臭氧的誤差分別為：（-3.5±54.4）% （n=27）、（-8.7±41.6）% （n=38）（100 hPa）；（-11.7±16.3）% （n=135）、（15.6±24.2）%（n=305）（下平流層）；（18.0±79.1）% （n=47）、（34.2±76.6）% （n=160）（對流層上層）。MLS水汽和臭氧的誤差垂直分布在對流層上層-平流層低層振蕩和離散分布明顯，部分誤差可能由此高度層水汽和臭氧濃度梯度大和用線性插值探空數據引起。 “臭氧低谷”期間，拉薩地區(qū)70 hPa高度以下MLS衛(wèi)星臭氧濃度誤差明顯增加；騰沖、那曲與拉薩3地的MLS臭氧誤差的垂直分布特征較一致。衛(wèi)星產品與探空測值的初步關系表明，MLS廓線的靈敏度與水汽和臭氧在大氣中垂直分布有密切聯系，3.3版水汽產品的靈敏度在82.5 hPa以上高度略有提高，臭氧產品靈敏度沒有明顯變化。對MLS水汽和臭氧廓線產品誤差的可能因素也進行了討論。（鄭向東）

3 大氣成分模式的發(fā)展應用及大氣成分的影響研究…

3.1 APEC環(huán)境空氣質量預測和減排效果評估

實施了APEC會議1個月前的污染趨勢預報，在臨近APEC和APEC期間，實施了精細化預報。對北京城區(qū)和會議區(qū)域（懷柔）的空氣質量進行了7～10天的預報。與此同時，對APEC期間的減排措施進行了評估和分析。綜合分析表明，2014年11月3—12日APEC會議期間，北京及周邊采取的大氣污染物減排措施使北京城區(qū)PM2.5濃度約降低35%，NO2濃度約降低33%，有效避免了重污染天氣發(fā)生。APEC會議期間，由于南風弱，大氣污染物跨區(qū)域輸送不明顯，北京本地減排對改善空氣質量的貢獻率為83%～89%，周邊地區(qū)減排的貢獻率為11%～17%。分析還發(fā)現，APEC會議期間，周邊300 km范圍內采取減排措施對北京的影響效果與600 km范圍內的減排效果相當；外地機動車的減排措施對北京影響不大；周邊區(qū)域高架點源減排對降低北京地區(qū)PM2.5濃度的貢獻約為9%。（龔山陵，劉洪利）

3.2 氣溶膠-氣候在線耦合模式BCC_AGCM2.0.1_CUACE/Aero中云微物理過程的改進、評估以及更新的氣溶膠間接效應

將一套能同時預報云滴和冰晶質量濃度和數濃度的雙參數云微物理方案應用到氣溶膠-氣候在線耦合模式BCC_AGCM2.0.1_CUACE/Aero中，詳細評估了模式對氣溶膠、云性質和氣象場的模擬性能，計算了氣溶膠的間接輻射強迫。較之前模式，新模式能更真實地模擬出氣溶膠的質量濃度和光學厚度。新模式模擬的全球年平均柱云滴數濃度為3.3×1010m-2，與衛(wèi)星反演結果4.0×1010m-2相當。新模式模擬的全球年平均云頂云滴有效半徑為8.1 μm，小于相應的觀測結果10.5 μm。新模式模擬的云液態(tài)水路徑明顯低于舊模式的結果，特別是在中緯度一些區(qū)域，年平均的云液態(tài)水路徑低了近100 g/m2，但是與衛(wèi)星觀測結果更加一致。新模式對云輻射強迫和降水的模擬在一定程度上也有所改進。新模式模擬的大氣頂輻射能量收支為-0.6 W/m2，相比舊模式的結果（1.8 W/m2）有明顯的差異。當沒有設置云滴數濃度的較低限制時，新模式模擬的大氣頂人為氣溶膠的間接輻射強迫的全球年平均值為-1.9 W/m2。但是，當設定一個云滴數濃度的最低限制時，氣溶膠的間接輻射強迫明顯減小。(王志立)

3.3 氣溶膠-氣候耦合模式系統BCC_AGCM2.0.1_CAM氣候態(tài)模擬的初步評估

討論了國家氣候中心第2代大氣環(huán)流模式BCC_AGCM2.0.1 和加拿大氣溶膠理化模式CAM 所組成的耦合模式系統對5 種典型氣溶膠（硫酸鹽、黑碳、有機碳、沙塵和海鹽）和氣候要素的模擬效果。結果表明，耦合系統對5 種典型氣溶膠的模擬總體上比較合理，尤其是對硫酸鹽、沙塵和海鹽的模擬比BCC_AGCM2.0.1 原有的月平均氣溶膠資料有很大的改進。耦合系統模擬的全球平均氣候態(tài)參量與觀測/再分析資料比較一致，在總云量、陸地表面溫度和降水等方面要略優(yōu)于原月平均氣溶膠資料的模擬結果。耦合系統對沙塵和海鹽氣溶膠模擬的改進使得撒哈拉沙漠和南半球中緯度海洋大氣頂凈太陽輻射的模擬也有所改進，而這將直接影響地表溫度尤其是陸地表面溫度。而不同氣溶膠方案在赤道海洋上引起的云反饋不僅引起輻射的改變，還將對降水產生明顯影響。（王志立）

3.4 不同時刻污染減排對北京市PM2.5濃度的影響

利用空氣質量模式Model-3/CMAQ及京津冀地區(qū)高分辨率排放源清單，針對有代表性的污染時段（2012年2月7—16日），設置了5種不同時刻的減排方案(在污染峰值提前4天、提前3天、提前2天、提前1天及當天減排)，對比在同樣的減排比例下，不同時刻開始減排的效果差異。研究發(fā)現，提前采取減排控制措施比污染峰值當天開始減排對降低PM2.5濃度的影響更為明顯，而且提前采取應急減排的時間越早，PM2.5濃度下降越明顯。提前1天、2天、3天 減排海淀站和城6區(qū)峰值濃度下降率分別為23%和22%、31%和30%、39%和38%，均明顯高于當天減排的峰值濃度下降率10%和9%。但隨著提前天數的增加，PM2.5峰值濃度進一步下降的幅度越來越小，減排效益較之前顯著降低。提前4天減排海淀站和城6區(qū)峰值濃度下降率分別為40%和39%，提前4天減排和提前3天減排對降低污染峰值日PM2.5濃度的效果已沒有太大差別。同時針對另一個污染時段（2012年1月11—20日）進行了相似的敏感性試驗，得出了類似的結論。因此，針對某些污染事件的應急減排，綜合考慮減排成本和減排效果，根據氣象條件的預報，在可能引起重污染事件的不利氣象條件來臨時提前2～3天采取減排措施效果最好，既能有效降低PM2.5濃度，也可以避免因盲目長時間減排造成的成本過大。（安興琴）

3.5 NASA／Goddard長波輻射方案在GRAPES_Meso模式中的應用研究

將NASA/Goddard的長波輻射方案引入到GRAPES_Meso模式中，對2006年4月中國地區(qū)進行了1個月的模擬試驗，并與相應的NCEP再分析資料進行了對比分析。試驗結果表明： 在模擬區(qū)域內，GRAPES_Meso模式24 h、48 h預報晴空大氣頂向外長波輻射通量(OLRC)、地面接收到向下長波輻射(GLWC)分布形勢與NCEP再分析資料具有較好的對應關系；模式24 h、48 h預報OLRC和相應NCEP再分析資料月平均誤差百分比控制在-10%～+10%以內，GLWC月平均誤差百分比比OLRC略大，但總體上兩者誤差在合理和可接受范圍之內。模式24 h、48 h預報的OLRC和GLWC的距平相關系數都在0.93以上，標準誤差都在31 W/m2以內，GLWC預報與NCEP再分析資料的相關性比OLRC略好，OLRC與NCEP再分析資料的標準誤差比GLWC小。本文研究結果表明，引入NASA/Goddard的長波輻射方案后的GRAPES_Meso模式整體上能夠較好地預報OLRC和GLWC，該輻射方案可以作為模式GRAPES_ Meso的備選輻射方案之一。（王宏）

3.6 對流層氣溶膠的直接氣候效應對平流層的影響

通過 WACCM-3模式中氣溶膠光學厚度與衛(wèi)星資料的對比發(fā)現，模式可以很好地再現全球氣溶膠的主要分布特征，但在一些區(qū)域還存在數值上的差異。利用數值試驗研究了對流層氣溶膠的直接氣候效應對平流層氣候的影響。結果表明，對流層氣溶膠對平流層氣候有明顯影響，平流層化學過程在這一影響中起重要作用，而對流層氣溶膠對平流層輻射的影響不是其直接氣候效應對平流層影響的主要原因。其機制可能是對流層氣溶膠改變對流層的輻射平衡，影響對流層的溫度和大氣環(huán)流，進而影響行星波的上傳，使得平流層氣候發(fā)生變化；影響區(qū)域主要位于高緯度和極地地區(qū)，南半球的變化比北半球大，溫度變化最大達10 K，緯向風變化最大可達12 m/s，臭氧體積分數最多減少0.8×10-6。（劉煜）

3.7 城市排放與輸送對北京上甸子站溫室氣體本底觀測的影響分析

以北京上甸子區(qū)域大氣本底站CO2和幾種典型鹵代溫室氣體（HFC-134a、PFC-218 和HCFC-22）濃度在線觀測為例，統計分析并匹配計算了各風向濃度距平與濃度載荷，探討了各季節(jié)城市排放和輸送對上甸子站溫室氣體本底觀測的影響。研究期間，CO2本底數據比例約為21.2%，受局地和城市排放與輸送影響，非本底濃度比本底濃度偏高（3.7±1.3）×10-6；HFC-134a和PFC-218濃度距平和濃度載荷的特征反映了2個物種源區(qū)特征的差別；HCFC-22濃度特征與空調制冷劑夏高冬低的季節(jié)排放規(guī)律相一致。(姚波)

3.8 利用FLEXPART模式反演中國區(qū)域SF6排放量

六氟化硫( SF6) 是一種長壽命鹵代溫室氣體，被列為《京都議定書》限排物質。隨著經濟高速發(fā)展，中國的排放量受到世界各國的關注。采用傳統的“自下而上”清單方法估算排放量時，所需排放因子、活動水平數據的準確性和時效性存在較大局限。因此，本文利用拉格朗日粒子擴散模式FLEXPART，結合2009 年北京上甸子區(qū)域大氣本底站濃度觀測資料，嘗試建立中國區(qū)域排放量的反演方法。結果表明，初步反演的2009年中國區(qū)域排放量為1.25×103（0.53×103～1.97×103）t，與文獻結果相當，源排放量的不確定性從1.05×103t減小到0.72×103t。與先驗源相比，反演源的相關系數從0.37提高到0.43，均方根誤差減小了2.64%。(安興琴)

3.9 不同氣象條件下的氣溶膠對暖云特征變化影響的衛(wèi)星觀測研究

考慮不同氣象條件，研究了長時間序列的夏季長三角地區(qū)（YRD）和下風向的中國東海（ECS）等2個區(qū)域的氣溶膠-暖云相互作用（ACI）。氣溶膠和云特征數據來自于MODIS/Aqua Level 2，氣象場數據來自NCEP再分析資料。為了減少氣象條件對氣溶膠-暖云相互作用統計分析的影響，本研究主要考察了不同云頂氣壓(CTP)、相對濕度(RH)、氣壓垂直速度(PVV)和下對流層穩(wěn)定度(LTS) 條件下的ACI。結果表明，ECS地區(qū)的云滴有效半徑(CDR)隨氣溶膠光學厚度增加而減少，而在YRD存在相反的變化趨勢。再研究氣溶膠對云量（CF）影響時，考慮了CTP和RH等2個氣象參數。當氣溶膠變化較小時，無論RH大小，YRD地區(qū)的CF隨氣溶膠的增長速度明顯快于ECS地區(qū)。因此，本研究認為云的水平覆蓋特征的改變主要由氣溶膠而非相對濕度這一氣象特征驅動。同時，針對AOD-CF、AOD-CTP的聯合統計分析結果表明，CTP對AOD-CF相互作用非顯著。本研究也考察了不同LTS和PVV條件下的CDR-AOD相互關系，發(fā)現了2個地區(qū)在大氣熱力條件相對穩(wěn)定時，CDR隨AOD增加而減少。而在大氣不穩(wěn)定時，存在截然相反的結果。通過研究不同動力條件對ACI的影響，發(fā)現在大氣上升的時候，陸地和海洋2個典型地區(qū)的CDR隨氣溶膠變化存在一個更顯著的改變，一個可能的解釋是上升氣流更有利于促進云滴的形成?？傊谠苾却嬖诟鼮閺碗s的熱力和動力條件影響下，很難把觀測到的云特征的改變完全歸結為氣溶膠。（郭建平）

3.10 西藏地面和衛(wèi)星觀測降水的日變化特征及其影響因子

基于2010—2011年2年夏季加密的西藏地區(qū)自動氣象站和衛(wèi)星降水產品（CMORPH），首次得到了該地區(qū)空間覆蓋度最為廣闊而全面的降水日變化特征。約60%站點的最大降水量和降水頻次的峰值出現在下午-傍晚時分。由CMORPH數據也得到了同樣的日變化特征，但它沒有抓住有些站點臨近中午的上午峰值。觀測到的降水峰值時刻基本與該時刻附近容易出現降水的天氣條件吻合。從空間上來說，沒有明顯的自西到東的日變化傳輸過程，表明該地區(qū)的降水主要由局地對流或環(huán)流而非大尺度環(huán)流導致，因此，該地區(qū)的降水日變化特征主要取決于地形和地形特征。進一步研究發(fā)現，降水峰值存在明顯的地理依賴，即從山區(qū)的白天降水峰值過渡到山谷和湖泊（地形較低地區(qū)）的傍晚-夜間降水峰值。位于山峰（山谷）的站點在接近中午或午后時刻（傍晚時分）容易出現降水峰值?？傮w而言，無論降水量或降水頻次，均出現類似的地形依賴特征，表明山谷環(huán)流效應（山谷風）在大（中）尺度降水特征比較弱的情況下對本地的降水峰值存在顯著影響。同時，針對西藏空間異質的降水日變化特征提出了一種可能的機制，即在分析青藏高原降水日變化時空分布特征時，不僅需要考慮高原尺度的大尺度環(huán)流特征，更要考慮由復雜地形導致的局地環(huán)流因子的影響。（郭建平）

3.11 基于觀測和模式模擬的華北地區(qū)山區(qū)和平原站點的降水和大氣污染研究

利用華北太行山地區(qū)7個站點（4個平原站＋3個高山站）40年夏季的日平均能見度和小時降水數據，分析了其時間變化趨勢。發(fā)現所有站點的夏季降水量均沒有出現明顯的變化趨勢，而同期隨著能見度減少，出現了小雨減少而大雨增加的趨勢。小雨的減少表現在由地形降水和中尺度層云降水等產生的兩類降水上。同時觀測到的不同能見度、降水和地形因子變化趨勢表明存在明顯的氣溶膠間接效應。同時，也深入分析了諸如可降水、對流有效位能、垂直風切變等大尺度環(huán)境因子對降水的潛在影響，發(fā)現他們之間不存在明顯的內在直接聯系。為了驗證由觀測得到的關于存在的氣溶膠間接效應假設，使用了帶譜分辨微物理方案的WRF模式進行云解析尺度模擬研究。模式模擬結果進一步確認了氣溶膠間接效應是導致山區(qū)小雨雨量和降水頻次減少的主要原因。當不考慮地形影響時，小雨對大氣污染的效應出現相反的結果，表明地形可能是山區(qū)和平原站觀測到不同的小雨變化的原因之一。（郭建平）

3.12 沙塵輸送和沉降以及對黃海浮游植物生長的影響

利用地面PM10濃度、天氣現象觀測和衛(wèi)星反演的氣溶膠和海洋顏色數據，結合沙塵的數值模擬和后向追蹤軌跡， 對發(fā)生于2010年19—22日的一次強沙塵過程及其對黃海浮游植物的影響進行了研究。研究發(fā)現，沙塵天氣發(fā)生期間葉綠素a增加了4倍，而且10～14天之后， 浮游植物量顯著增加。 嚴重沙塵天氣帶來的鐵離子使得黃海南部的葉綠素a增加了10%～68%。研究結果表明，沙塵暴發(fā)生時給黃海地區(qū)帶來的生物性養(yǎng)分有利于該地區(qū)浮游植物的成長。（王宏）

3.13 中國及東亞其他地區(qū)不同區(qū)域至酸性物質的濕沉降：采樣升級的NAQPMS模式模擬研究

研究源與受體關系的傳統方法是開展敏感性模擬，但是這種方法對涉及到非線性的二次形成的污染物（如臭氧、硝酸鹽等）的研究存在弱點。本研究在嵌套空氣質量預測模擬系統（NAQPMS） 基礎上建立了一種在線源追蹤方法，并首次將其與云過程模塊耦合。新的模式不僅能更精確地確定硫酸鹽、硝酸鹽和銨鹽總的濕沉降量，而且可追蹤酸性物質的前體物。研究結果表明：（1）華東和華中是2個主要的污染物輸出區(qū)，對其他區(qū)域的濕沉降分別具有15%～30%和10%的影響；（2）除了以上2區(qū)域外，我國西南和東北區(qū)域的酸沉降也達到或超過了各自環(huán)境條件下的臨界負荷（圖5）。（徐曉斌）

3.14 1-硝基芘和1,2-萘醌的聯合細胞毒性和致DNA損傷

以人肺上皮細胞A549為研究對象，運用MTT方法檢測1-硝基芘（1-NP）處理后A549的細胞存活率；測定細胞培養(yǎng)液中乳酸脫氫酶（LDH）的漏出率，評價細胞膜損傷；運用彗星試驗檢測DNA損傷；通過熒光探針的方法測定細胞內產生的活性氧自由基（ROS）。通過1,2-萘醌（1,2-NQ）預先染毒24 h，再使用1-NP染毒24 h的方法，評估1-NP和1,2-NQ對A549的聯合細胞毒性和DNA損傷。結果表明，1-NP對A549暴露24 h和48 h的半致死濃度（LC50）分別為5.2 μmol/L和2.8 μmol/L。LC50隨著染毒時間的增加而降低，提示暴露時間越長1-NP的細胞毒性越強。A549在1、2、3和4 μmol/L濃度的1-NP染毒下，DNA損傷顯著增強，ROS水平不斷升高，呈現劑量-效應關系（P＜0.05）；但LDH漏出率無顯著變化。1,2-NQ（5 μmol/L）預染毒A549細胞24 h，能明顯減弱1-NP造成的DNA損傷和ROS升高。結果說明，1,2-NQ預處理可能通過抑制1-NP暴露產生的ROS，來降低A549的DNA損傷。（李怡）

3.15 大氣顆粒物攜帶醌類物質引發(fā)細胞毒性以及DNA損傷：氧化應激作用

大氣顆粒物對人體有重要的健康影響。已有證據表明，顆粒物上攜帶的醌類物質可能通過氧化應激造成損傷，但是，肺部細胞的DNA損傷是否與醌類物質氧化應激有關，還缺乏相關研究。本研究選擇了5種代表性醌類物質，在肺部上皮A549細胞中，研究了它們引發(fā)氧化應激的能力以及相應的DNA和其他生物學意義的損傷。這些醌類物質能夠因劑量-效應引發(fā)細胞內Ca2+濃度增加，表明氧化應激是一個重要的途徑。本研究結果再次證明了大氣顆粒物對健康影響的重要性（李怡）

圖1 北京空氣樣品GC×GC-qMS（a）和GC×GC-FID（b）的色譜圖Fig. 1 GC × GC-qMS (a) and GC × GC-FID (b) chromatograms of a Beijing air sample

圖2 MeteoInfo軟件主界面及站點數據圖形示例Fig. 2 MeteoInfo GUI and sample plot from station data

圖3 中國氣象局大院站點冬季PAN、O3、Ox、CO、NOx和氣溫的平均日變化(垂直線段表示各平均值的平均標準偏差)Fig. 3 Diurnal cycles of PAN, O3, Ox, CO, NOx, and air temperature at the CMA site during the wintertime. The vertical bars represent one standard error of the mean

圖4 中國氣象局（CMA）、上甸子（SDZ）和固城（GCH）3個站點CO和NOx均值體積分數變化Fig. 4 Variation of the monthly CO and NOx concentrations at the CMA, SDZ and GCH stations

圖5 模擬的S（a）、N（b）、NH4+（c）的沉降空間分布以及東亞區(qū)域2007年3種致酸性物質模擬值和觀測值的比較（d）（（d）中的黑點和紅點分別表示來自東亞其他站點和中國境內站的觀測數據）Fig. 5 Simulated patterns of wet deposition of (a) S, (b) N, (c) NH4+ and (d) scatter plot of the three acidifying substances over East Asia during 2007. Black and red points in (d) represent the observation data from other sites located in other East Asia and in China, respectively

Progress in Atmospheric Composition and Atmospheric Chemistry Research

In 2014, the Institute of Atmospheric Composition completed several tasks and made obvious progress in analytical methods, comparison and verif cation, quality control, observation of atmospheric composition and atmospheric chemistry process, model development and implementation, and in assessing the impact of atmospheric composition and related factors on climate, weather, and human health.

1 Analytical methods, comparison and verif cation and quality control

1.1 Establishment of the integrating sphere calibration method for China aerosol remote sensing network Cimel sunphotometer

Based on the integrating sphere traced from the National Institute of Standards and Technology (NIST, USA), a sphere calibration method and protocol for the China aerosol remote sensing network (CARSNET) Cimel sun photometer was established. Four CE318 sun photometers were verified using the proposed calibration method and operational protocol. The calibration results showed that the instrument coeff cients differed by less than 3% for visible (～5% for infrared) wavelengths from the original ones stated by Cimel electronique. In situ validation experiment data showed that radiances at ±6° measured by a sun collimator (aureole) were consistent with those measured by a sky collimator (sky), under both almucantar (ALMUC) and principal plane (PPLAN) scenarios. Differences at all wavelengths were less than 1%, indicating that the method and protocol are suitable for CARSNET f eld sun photometer calibration, and would benef t data quality and accuracy of network observations. (Che Huizheng)

1.2 Coupling of comprehensive two-dimensional gas chromatography with quadrupole mass spectrometry (GC×GC-qMS): Application to the identification of atmospheric volatile organic compounds

Observation data of atmospheric volatile organic compounds (VOCs) are highly needed in air quality assessment, photochemical mechanism study, and emission control policy-making, while it has been a challenge to accurately and comprehensively measure them. Comprehensive two-dimensional gas chromatography (GC×GC) is one of the advanced techniques in analysis of complex mixtures, providing a good choice for measurement of VOCs. However, the requirement for a fast detector limits the application of quadrupole mass spectrometry (qMS) in GC×GC analysis. This paper presents a method on how to apply a common qMS detector coupled with GC×GC to the identif cation of atmospheric VOCs. About 125 VOCs including alkanes, alkenes, aromatics, oxygenated hydrocarbons, and halocarbons were identif ed in the measurement of standard gas mixtures and/or urban air samples from Beijing. The results were applied to the analysis of GC×GC-FID by one to one correspondence of the equivalent peaking compounds between the GC×GC-FID and GC×GC-qMS chromatograms, and the retention times of the identif ed components in GC×GC-FID in turn underwent the qualitative analysis without the further help of MS. The wrap-around phenomenon which may confuse the match of peaks was discussed in detail. The co-use of GC×GC-FID and GC×GC-qMS in the identification process makes the GC×GC device more affordable and the qualitative and quantitative analysis more robust. The method and the identif ed results can be further used to analyze other volatiles (Fig. 1). (Wang Ying)

1.3 QA/QC method for and assessment of atmosphere background CO2 sampling and analysis

To strengthen scientific management and sharing of greenhouse gas data obtained from atmospheric background stations in China，it is important to ensure the standardization of quality assurance and quality control methods for background CO2sampling and analysis. The observation and study of atmospheric greenhouse gases in the Waliguan station (Qinghai) by CMA were begun in 1980s, with rich experience in data sampling，analysis and processing having been accumulated. In this study, the QA/QC method for atmospheric CO2concentration observation and analysis by portable f ask sampling and the CRDS system are discussed in detail. Then, several key steps of this method are evaluated. Finally, by using this method, the variation features of the three typical regions,, atmospheric background CO2concentration are preliminarily analyzed. (Liu Lixin)

1.4 Study of atmospheric CO2 mole fractions at the Longfengshan WMO/GAW regional station

Out of the in-situ observation results of atmospheric CO2mole fractions from two levels (10 m and 80 m above the ground) at Longfengshan (LFS) regional background station in Heilongjiang Province from January 2009 to December 2011, this study mainly focused on the lower (10 m) level (a.g.l.). The results indicate that the observed data from 10 m were strongly affected by the local sources/sinks. The differences between the 10 m and 80 m results were relatively small during the daytime (08:00–17:00) with values being lower than (0.5±0.5)×10-6. In spring, summer and autumn, higher CO2mole fractions were observed when surface winds came from the E-ESE-SE-SSE sectors, while, in winter, surface winds from the N-NNW-NW-WNW sectors obviously enhanced the observed values. Generally, lower CO2values were accompanied with higher wind speed in the four seasons. This phenomenon was most obvious in winter. Based on the analysis of the observed diurnal cycle and the local meteorological conditions, the observed data from 10 m were filtered into background/non-background events. About 30.7% valid hourly data turned out to be regional background representative. The background CO2variation displayed a peak in winter and a valley in summer with a seasonal peak to peak amplitude of (36.3±1.4)×10-6, which was higher than the values at similar latitudes from marine boundary layer (MBL) references and WMO/GAW stations. The annual CO2increasing rate at LFS was roughly estimated to be 2.4×10-6. (Fang Shuangxi)

1.5 MeteoInfo: GIS software for meteorological data visualization and analysis

MeteoInfo is a suite of software tools which has been developed for meteorological data visualization and analysis. It includes a .NET class library for software developers and a desktop application for end users. MeteoInfo also supports several basic GIS functions and can read common meteorological data formats such as NetCDF and GRIB. Complex meteorological analyses of grid and station data can be processed using provided data models. The class library can be conveniently used to develop software routines for manipulating spatial and meteorological data. The desktop application has a user friendly GUI and is a powerful tool to view and examine meteorological data sets. MeteoInfo can also be run automatically using the IronPython scripting language (Fig. 2). (Wang Yaqiang)

2 Observational studies of atmospheric compositions and related properties

2.1 Atmospheric sulfur hexafluoride (SF6) in-situ measurements at the Shangdianzi regional background station in China

We present in-situ measurements of atmospheric sulfur hexafluoride (SF6) conducted by an automated gas chromatograph-electron capture detector system and a gas chromatography/mass spectrometry system at a regional background site, Shangdianzi, in China, from June 2009 to May 2011, in which the system for observation of greenhouse gases in Europe and Asia and Advanced Global Atmospheric Gases Experiment (AGAGE) techniques were used. The mean background and polluted mixing ratios for SF6during the study period were 7.22×10-12and 8.66×10-12respectively. The averaged SF6background mixing ratios at Shangdianzi were consistent with those obtained at other AGAGE stations located at similar latitudes (Trinidad Head and Mace Head), but larger than AGAGE stations in the Southern Hemisphere (Cape Grim and Cape Matatula). SF6background mixing ratios increased rapidly during our study period, with a positive growth rate at 0.30×10-12yr?1. The peak to peak amplitude of the seasonal cycle for SF6background conditions was 0.07×10-12while the seasonal f uctuation of polluted conditions was 2.16×10-12during the study period. Peak values of SF6mixing ratios occurred in autumn when local surface horizontal winds originated from W/WSW/SW/SWS/S sectors, while lower SF6mixing ratios appeared as winds originated from N/NNE/NE/ENE/E sectors. (Yao Bo)

2.2 Background variations of atmospheric CO2 and carbon-stable isotopes at Waliguan and Shangdianzi stations in China

Observational data from 2007 to 2010 at the Waliguan (WLG) and Shangdianzi (SOZ) stations in China are used to study atmospheric CO2, its δ13C composition, and their potential relationship with sources and sinks. Results suggest that at WLG station, both CO2and δ13C feature a long-term variation and seasonal cycle that correlate well with each other. CO2and δ13C inter-annual variations indicate terrestrial ecosystem’s alteration in source-sink by season in the mid- to high-latitude Northern Hemisphere. CO2annual means vary from 384.0×10-6to 390.2×10-6, increasing in an approximately linear manner averagely at an annual growth rate of (2.1±0.1)×10-6. The δ13C annual means vary from -8.30‰ to -8.35‰, decreasing almost linearly and averagely at an annual rate of -0.02‰ ± 0.001‰. Given the terrestrial biosphere and anthropogenic activities at SDZ station, the CO2annual means vary from 385.1×10-6to 390.6×10-6, approximately increasing linearly and averagely at an annual growth rate of (1.8±0.1)×10-6. The peak-to-peak annual seasonal amplitude is 23.0×10-6. The δ13C annual means vary from -8.27‰ to -8.36‰ between 2009 and 2010. Mean values of (-25.44±0.72)‰ and (-21.70±0.67)‰ for the respective sources are obtained at WLG and SDZ. The estimated δsvalues are rather negative in winter and spring than in summer and autumn at WLG. While because substantial C4photosynthesis occurs in summer and biomass burns in winter, the estimated δsvalues at SDZ are heavy throughout the year and rather positive than those at WLG. (Liu Lixin)

2.3 In situ measurement of atmospheric CO2 at the four WMO/GAW stations in China

Atmospheric carbon dioxide (CO2) mole fractions were continuously measured from January 2009 to December 2011 at four atmospheric observatories in China with cavity ring-down spectroscopy instruments used. The stations are Lin’an (LAN), Longfengshan (LFS), Shangdianzi (SDZ), and Waliguan (WLG), which are either regional (LAN, LFS, SDZ) or global (WLG) under the World Meteorological Organization’s Global Atmosphere Watch program (WMO/GAW). LAN is located near the megacity of Shanghai, in China’s most economically developed region. LFS is in a forest and rice production area, close to the city of Harbin in northeastern China. SDZ is located 150 km northeast of Beijing. WLG, boasting the longest record of measured CO2mole fractions in China, is a high-altitude site in northwestern China registering background CO2concentration. The CO2growth rates are (3.7±1.2)×10-6yr-1for LAN, (2.7±0.8)×10-6yr-1for LFS, (3.5±1.6)×10-6yr-1for SDZ, and (2.2±0.8)×10-6yr-1for WLG during the period of 2009 to 2011. The highest annual mean CO2mole fraction of (404.2±3.9)×10-6was observed at LAN in 2011. A comprehensive analysis of CO2variations, their diurnal and seasonal cycles as well as an analysis of the inf uence of local sources on the CO2mole fractions allow for a characterization of the sampling sites and of the key processes driving the CO2mole fractions. These data form a basis to improve our understanding of atmospheric CO2variations in China and the underlying f uxes using atmospheric inversion models. (Fang Shuangxi)

2.4 Estimation of regional background concentration of CO2 at Lin,an station in Yangtze River Delta, China

A new method of extracting regional background concentration of CO2in Yangtze River Delta was developed based on the observations of both black carbon concentration and meteorological parameters. The concentrations of CO2and black carbon were observed at Lin,an regional background station from 2009 to 2011. The regional background concentration of CO2in Yangtze River Delta was obtained by means of this new method, and the impact of human activities on CO2concentration in this area was also assessed. The results show that the regional background concentration of CO2extracted by this approach was comparable to the values obtained by R statistical f lter method, and moreover this new method was better at picking up episodes heavily polluted by anthropogenic emissions. The annual regional average background concentration of CO2in Yangtze River Delta from 2009 to 2011 was approximately (404.7±8.2)×10-6, (405.6±5.3)×10-6and (407.0±5.3)×10-6, respectively, much higher than global average value, indicating the distinct characteristic of this region. The anthropogenic emissions from Yangtze River Delta had significant influence on the concentration of CO2in this area, increasing the local value by roughly 9.1×10-6. (Fang Shuangxi)

2.5 A case study of short-term f uctuation in atmospheric concentration of halogenated greenhouse gases at Shangdianzi regional background monitoring station

By means of trajectory analysis method and footprint analysis method, combined with the online observed concentration of H-1301, HCFC-22, CFC-11 and SF6, a typical case about short-term f uctuation of halogenated greenhouse gases at Shangdianzi background station during 7–12 September 2012 was analyzed. The results show that before the occurrence of pollution, air masses at 12:00 BT 7 September 2012 are mainly from the far-away north and northwest, with a long horizontal transport distance, rapid moving speed and high vertical height; meanwhile, the corresponding halogenated greenhouse gases concentrations are relatively low, which are 4×10-12, 350×10-12, 260×10-12and 10×10-12for H-1301, HCFC-22, CFC-11 and SF6, respectively. However, on 9–10 September 2012, a certain percentage of air masses convolutes over the south of the station with a short horizontal transport distance and low vertical height, moving slowly in the boundary layer, thus hindering the spread of pollutants in the boundary layer and resulting in relatively high halogenated greenhouse gases concentrations. Such situation contributes a lot to the short-term rapid growth of concentration levels and H-1301, HCFC-22 and CFC-11 respectively reach the peak concentrations of 45×10-12, 200×10-12and 310×10-12at 12:00 BT 9 September and SF6reaches 28×10-12at 03:00 BT 10 September. On 11 September, the convoluting air mass in the southwest direction disappears and on 12 September, air masses all f ow from the far-away northwest and have rapid moving trajectories. The result by footprint analysis method is the same as that by the trajectory analysis, which is that on 7–8 September, regions with a high sensitivity coeff cient are mainly located in the north of the station; on 9–10 September, they are seen mainly in the south of the station. Then on 11 and 12 September, the regions with high sensitivity coeff cients in the south of the observation station disappeared. In addition, a flow field analysis also showed that the circulation pattern on 9 and 10 September is favorable for the accumulation of pollutants in the observed region, resulting in the short-term lift of pollutants’ concentrations. (An Xingqin)

2.6 In-situ measurement of atmospheric methyl chloroform at the Shangdianzi GAW regional background station

An in-situ GC-ECD monitoring system was established at the Shangdianzi GAW regional background station (SDZ) for 2-year atmospheric methyl chloroform (CH3CCl3) measurement. Robust extraction of baseline signal f lter was applied to the CH3CCl3time series to separate background and pollution data. The yearly averaged background mixing ratios of atmospheric CH3CCl3were (9.03±0.53)×10-12in 2009 and (7.73±0.47)×10-12in 2010, and the percentages of the background data to the whole data were 61.1% in 2009 and 60.4% in 2010, respectively. The yearly background CH3CCl3mixing ratios at SDZ were consistent with the Northern hemisphere background levels observed at Mace Head and Trinidad Head stations, but lower than the results observed at sites in South China and some Chinese cities from 2001 to 2005. During the study period, background mixing ratios exhibited a decrease at a rate of 1.39×10-12yr-1in trend. The wind direction with the maximum CH3CCl3mixing ratio was from the southwest sector and with the minimum one was from northeast sector. The differences between the maximum and the minimum average mixing ratios in the 16 wind directions were 0.77×10-12(2009) and 0.52×10-12(2010). In the different 16 wind directions, the averaged mixing ratio of CH3CCl3in 2010 was lower than those in 2009 by 1.03 ×10-12–1.68×10-12. (Yao Bo)

2.7 Influence of downward air mass transport on the variability of surface ozone at Xianggelila regional atmospheric background station, Southwest China

In situ measurements of ozone (O3), carbon monoxide (CO) and meteorological parameters were made from December 2007 to November 2009 at the Xianggelila regional atmospheric background station (28.006°N, 99.726°E, 3580 m.a.s.), Southwest China. It was found that both O3and CO peaked in spring while the minima of O3and CO occurred in summer and winter, respectively. A normalized indicator (marked as “Y ”) on the basis of the monthly normalized O3, CO and water vapor, is proposed to evaluate the occurrence of O3downward transport from the upper, O3-rich atmosphere. This composite indicator has the advantage of being less inf uenced by the seasonal or occasional variations of individual factors. It is shown that the most frequent and effective transport occurs in winter (accounting for 39% of the cases when Y is larger than 4), which makes a signif cant contribution to surface O3at Xianggelila. A 9.6×10-9increase (21.0%) of surface ozone is estimated based on the impact of deep downward transport events in winter. A case of strong O3downward transport event under the synoptic condition of a deep westerly trough is studied by a combined analysis of the Y indicator, potential vorticity, total column ozone and trajectory. Asian monsoon plays an important role in suppressing O3accumulation in summer and fall. The seasonal variation of O3downward transport, as suggested by the Y indicator at Xianggelila, is consistent with the seasonality of stratosphere-to-troposphere transport and the subtropical jet stream over the Tibetan Plateau. (Zheng Xiangdong)

2.8 Wintertime peroxyacetyl nitrate (PAN) in the megacity Beijing: The role of photochemical and meteorological processes

Previous measurements of peroxyacetyl nitrate (PAN) in Asian megacities were scarce and mainly conducted for relatively short periods in summer. Here, we present an analysis of the measurements of PAN, O3, NOx, etc. made at an urban site (CMA) in Beijing from 25 January to 22 March 2010. The hourly concentration of PAN averaged 0.70×10-9(0.23×10-9–3.51×10-9) was well correlated with that of NO2but not O3, indicating that the variations of the winter concentrations of PAN and O3in urban Beijing are decoupled with each other. Wind conditions and transport of air masses exert very signif cant impacts on O3, PAN, and other species. Air masses arriving at the site originated either from the boundary layer over the highly polluted N-S-W sector or from the free troposphere over the W-N sector. The descending free-tropospheric air was rich in O3, with an average PAN/O3ratio being smaller than 0.031, while the boundary layer air over the polluted sector contained higher levels of PAN and primary pollutants, with an average PAN/O3ratio being 0.11. These facts related with transport conditions can well explain the observed PAN-O3decoupling. Photochemical production is important to PAN in the winter over Beijing. The concentration of the peroxyacetyl (PA) radical was estimated to be in the range of 0.0014×10-12–0.0042×10-12. The contributions of reaction from the formation and thermal decomposition to PAN’s variation were calculated and found to be signif cant even in the colder period in air over Beijing, with the production exceeding the decomposition (Fig. 3). (Xu Xiaobin)

2.9 Changing characteristics of NOx and CO emission at three sites in Beijing and its surrounding areas

To study the similarity and dissimilarity in the characteristic features of the ambient NOxand CO emission in different parts of the North China Plain (NCP), we observed the mixing ratios of CO and NOxin the surface layer air at three sites in the NCP, which are over 100 km apart from each other and in the prevailing SW–NE wind directions. The three sites are China’s Meteorological Administration (CMA), the Shangdianzi station (SDZ), and the Gucheng station (GCH), representing typically the urban area of Beijing, the regional background area of the NCP, and the rather seriously polluted rural area in North China, respectively. The results of our investigation show that from June 2008 to May 2009, the annual average concentration of NOxat CMA, GCH, and SDZ were (42.4±21.8)×10-9, (26.9±15.2)×10-9, and (13.8±5.5)×10-9, respectively, and those of CO were (1.13±0.37)×10-6, (1.11±0.62)×10-6, and (0.67±0.17)×10-6, respectively. At CMA and GCH, the monthly average concentrations of NOxand CO reached the corresponding maximum in winter and minimum in summer, whereas the highest monthly average concentration of CO at SDZ was observed in June (1.03×10-6). The concentrations of NOxat CMA, GCH, and SDZ turned to be 3.4, 3.6, and 1.8 times higher in winter than those in summer, respectively. The concentrations of CO at CMA, GCH, and SDZ were 1.8, 2.9, and 0.8 times higher in winter than in summer, respectively. The average diurnal variations indicated that the CO and NOxconcentrations of SDZ decreased to their minimum around noon, about 3–4 h earlier than those of GCH and CMA, and then increased gradually till evening, in response to the impact of transported pollutants on the gas concentrations of SDZ. The above dissimilarities in the diurnal variations can probably account for the different effects of emission sources and the air-mass transport on the concentrations of pollutants at the three sites. The time series of the daily average CO and NOxconcentrations show great similarities among the sites, revealing that the characteristic features were inf uenced by the common regional pollution and similar meteorological conditions. The observation data we have gained indicate fairly high CO level in the North China Plain in summer, which was probably caused by the outdoor combustion of wheat straw in large amount (Fig. 4). (Xu Xiaobin)

2.10 Characteristics of CO at Lin,an Station in Zhejiang Province

Background CO mole fractions were continuously measured at Lian’an background station in Zhejiang Province from September 2010 to February 2012 with Cavity Ring Down Spectroscopy (CRDS) system used. The diurnal variation of CO was strongly inf uenced by anthropogenic activities with two peaks occurring at 07:00–10:00 and 19:00–20:00 (Local time). The average daily mole fraction and amplitude in summer were the lowest among the four seasons with values being (314.3±7.6)×10-9(mole fraction, the same below) and (50.1±47.9)×10-9, respectively. The seasonal variations displayed peak values during winter-spring period and valley in summer, which was roughly consistent with those observed variations at other sites located in the Northern hemisphere such as Jungfraujoch in Switzerland and Waliguan in China. However, the average mole fractions were much higher than other stations. The amplitude of monthly CO mole fractions was (286.8±19.2)×10-9. The analysis of cluster to backward trajectories and surface wind inf uence might suggest that the non-background CO mole fractions at Lin’an station were mainly affected by the emissions from the megacities and industrial areas in the N-NNE-ENE sectors. The maximum enhancements in spring, summer and winter all occurred in ENE sector, with a maximum value being (106.3±58.0)×10-9in winter. (Fang Shuangxi)

2.11 Seasonal variation of ammonia and ammonium aerosol at a background station in the Yangtze River Delta region, China

The measurement of atmospheric NH3was conducted by means of passive samplers from September 2009 to December 2010 at Lin’an regional background station located in the economically booming Yangtze River Delta (YRD) region in East China. NH4+in f ne particles was also measured in 2010 at this site. The NH3concentration ranged from 0.1×10-9to 41.8×10-9, with the annual average being (16.5±11.2)×10-9in 2010. The daily NH4+concentrations ranged from 0.02 to 19.2 μg m-3, with an annual average of (4.3±3.5) μg m-3. NH3concentrations were highest in summer and lowest in winter, showing positive correlations with agricultural activities and temperature. The highest concentrations of NH4+were in autumn coinciding with the period of active open burning of agricultural residues. The mean mass ratio of NH3/NHxis estimated to be (0.8±0.1) during 2010, indicating that NHxwas mainly inf uenced by local sources around Lin’an. The air mass back trajectory analysis suggests that both local sources and long-distance transport play an important role in the observed ammonium aerosol at Lin’an station. High NHxdeposition in this regional background station suggests the urgency of reducing NH3emission in the YRD region. (Meng Zhaoyang)

2.12 Variability, formation and acidity of water-soluble ions in PM2.5 in Beijing

Daily PM2.5and hourly water-soluble inorganic ions in PM2.5and gaseous precursors were measured during June–November 2009 at an urban site in Beijing. The average mass concentration of the total watersoluble ions was 44 μg m-3, accounting for 38% of PM2.5. Sulfate (SO42-), nitrate (NO3-) and ammonium (NH4+) were dominant ions. The summer-fall difference in seasonal average mass concentrations was smaller than 30% for SO42-, but was up to a factor of 2.0 for NO3-and NH4+. A pronounced diurnal cycle was found for most ions and gaseous precursors and could be explained by their respective sources, formation mechanisms and meteorological conditions. The average oxidation/conversion ratios for SO42-(SOR), NO3-(NOR) and NH4+(NHR) were estimated to be 63%, 15% and 15%, respectively. The low NHR value suggests that NH3was mainly from local sources, the excessive existence of which thus was not a limiting factor in the formation of NH4+. As a result, the diurnal pattern of NH4+was similar to that of SO42-to some extent, but differed signif cantly from that of NH3. Based on the estimated H+concentration and acidity purity (f ), 75% of data samples were strongly acidic and a few percentages might be alkaline. Seasonal variations in aerosol acidity and chemical forms of major ions were also brief y discussed. (Zhang Yangmei)

2.13 Chemical composition and mass size distribution of PM1 at an elevated site in central east China

Size-resolved aerosol chemical compositions were measured continuously for 1.5 year from June 2010 to January 2012 with an aerosol mass spectrometer (AMS) to characterize the mass and size distributions (MSDs) of major chemical components in submicron particles (approximately PM1) at Mountain Tai (Mt. Tai), an elevated site in central east China. The annual mean mass concentrations of organic, sulfate, nitrate, ammonium, and chloride were 11.2, 9.2, 7.2, 5.8, and 0.95 μg m-3, respectively, which are much higher than those at most mountain sites in the USA and Europe, but lower than those at the near-surface urban sites in China. A clear seasonality was observed for all major components throughout the study, with low concentration in fall and high in summer, which is believed to be caused by seasonal variations in planetary boundary layer (PBL) height, near surface pollutant concentrations and regional transport processes. Air masses were classif ed into categories impacted by PBL, lower free troposphere (LFT), new particle formation (NPF), in-cloud processes, and polluted aerosols. Organics dominated the PM1mass during the NPF episodes, while sulfate contributed most to PM1in cloud events. The average MSDs of particles between 30 and 1000 nm during the entire study for organics, sulfate, nitrate, and ammonium were approximately log-normal with mass median diameters (MMDs) of 539, 585, 542, and 545 nm, respectively. These values are slightly larger than those observed at ground sites within the North China Plain (NCP), likely due to the relative aged and well-mixed aerosol masses at Mt. Tai. There were no obvious differences in MMDs during the PBL, LFT, in-cloud and polluted episodes, but smaller MMDs, especially for organics, were observed during the NPF events. During the PBL, NPF, and polluted episodes, organics accounted for major proportions at smaller modes, and reached 70% at 100–200 nm particles in the polluted events. In cloud episodes, inorganics contributed 70% to the whole size range dominated by sulfate, which contributed 40% to small particles (100–200 nm), while organics occupied 20%, indicating that sulfate is a critical chemical component in cloud formation. Seven clusters of air masses were classified based on 72 h back-trajectory analysis. The majority of the regionally dispersed aerosols were found to be contributed from short distance mixed aerosols, mostly originating from the south with organics and sulfate as major components. Air masses from long range transport always brought clean and dry aerosols which resulted in low concentrations at Mt. Tai. AMS-PMF (positive matrix factorization) was employed to resolve organics into subtype. Oxygenic organics aerosols (OAs) occupied 49%, 56%, 51%, and 41% of OAs in the four seasons respectively, demonstrating that most OAs were oxidized in summer due to strong photochemical reactions. Biomass burning OAs (BBOAs) accounted for 34% of OA in summer, which was mainly from f eld burning of agricultural residues, and coal combustion OAs (CCOAs) accounted for 22% of OA in winter, which was from heating. (Zhang Yangmei)

2.14 Characterization of chemical components of aerosol particles in various regions over China

In order to obtain the overall chemical “picture” of the aerosol pollution in various regions of China and discuss the further direction in pollution control, we need to assess and evaluate the concentration level, chemical composition and pollution sources region-by-region in China. Features of the chemical aerosol particles in China have been obtained, based on the analysis of six major chemical components (sulfate, nitrate, ammonium, mineral aerosol, organic and elemental carbon) from ground-based observation, all of which have undergone at least one-year-long measurement. The four most hazy regions out of the nine with characteristics of synchronous changes in visibility within China are also identif ed in areas like the region to the south of Beijing (also called the Hua Bei Plain and Guanzhong Plain); mostly the East China region with Yangtze River Delta; the South China region focused on the Pearl River Delta; and also the region of Sichuan Basin. Of the total mass of PM10in China, three major components account for ～20%–38% for mineral aerosol, ～14%–24% for sulfate, and ～11%–18% for organic carbon.

The heaviest aerosol pollution was found in the Hua Bei and Guanzhong Plain regions, with the annual mean concentrations being 35–47 μg m-3of sulfate (much higher than the 13 to 18 μg m-3of urban Beijing), 28–45 μg m-3of organic carbon (about 1.8 factors higher than 19–22 μg m-3of Beijing), 19–22 μg m-3for nitrate (2 times higher than 9.9–12 μg m-3of Beijing), 14–16 μg m-3for ammonium (still one factor higher than the 6.2–8.4 μg m-3of Beijing mean concentration), and the 9.1–12 μg m-3of elemental carbon which was similar to the level of Beijing. More than 50% mass of nitrate and organic carbon is attributable to coalcombustion, and the agricultural activity is the most important source for ammonium.

In the urban areas of East, South and Northeast China, the concentration levels of aerosol chemical components were similar to that in Beijing, but in urban areas of the Sichuan Basin, the annual mean concentrations were higher than that in Beijing, exhibiting heavy aerosol pollution there. In Lanzhou of Northwest China, the urban concentrations of aerosol chemical components were also similar to that in Beijing, except for much lower concentration in elemental carbon and slightly higher concentration of nitrate observed. In the remote desert area of Northwest China, the chemical concentrations of aerosol particles were far lower than that in Beijing, so were in the Tibetan and Yunnan-Guizhou Plateaus.

Coal-combustion, motor vehicle, urban fugitive dust and agricultural activities are found to be the four major pollution sources according to the aerosol chemical composition analysis made in different regions. Therefore, the future control of atmospheric aerosol pollutants should be directed to the following: strengthening coal desulfurization in addition to the power generation industry, further reducing coal produced emissions of NOx, organic carbon and its precursor gases, and effectively reducing ammonia emissions from agricultural activity, and effectively limiting the formation of secondary aerosol, especially sulfate and nitrate. (Zhang Xiaoye)

2.15 Characteristics of PM10 and its chemical components at Mount Tai

In order to better understand the chemical components and their variations of background aerosols in the North China Plain, 64 PM10samples were collected on the top of Mount Tai from June 2010 to July 2011. The mass concentration and seasonal variations of PM10as well as its nine water soluble irons, organic carbon (OC) and elemental carbon (EC) have been analyzed. The correlation analysis of various chemical components has also been performed. The annual average mass concentration of PM10is 68.4 μg m-3, of which inorganic salt accounts for 64.8%, carbon aerosol for 17.4%. The mass concentration of inorganic salt increases gradually from the Spring Festival, reaches its peak in summer, then decreases in autumn and comes to the lowest in winter. The mass concentration of OC increases from the Spring Festival to autumn and reaches the minima in winter. Similar pattern has been found in the mass concentration of EC; however, the concentrations of EC between summer and autumn are much smaller in difference. The ratio of secondary organic carbon (SOC) to OC is above 50% for all seasons with an annual average of 58.5%. A back trajectory analysis shows that when Mount Tai is mainly inf uenced by air masses from the south and megacities, mass concentrations of PM10and its components are high; while it is mainly inf uenced by air masses from the Northwest China through long distance transport, the mass concentrations of PM10and its components are much lower. (Wang Yaqiang)

2.16 The characteristics of particle number size distribution under typical meteorological conditions at Shangdianzi regional station in Beijing

By using the instruments of Twin Differential Mobility Particle Sizer (TDMPS) system and an Aerodynamic Particle Sizer, measurements of particle number size distribution (PNSD) in the range of 3 nm–10 μm were performed at Shangdianzi regional station. Based on the dataset in 2008, the characteristics of particle number size distribution at different meteorological conditions such as dust storm, new particle formation event and fog-haze day were investigated. On the dust storm day, the air mass originated from the northwest, with high wind speed. The coarse particle number concentration increased sharply and PM10mass concentration could reach up to milligrams per cubic meter. A typical “banana shape” new particle formation event occurred when the atmosphere background was quite dry, clean and clear, with the air mass coming from the northeast. The nucleation mode particle could grow signif cantly in size to around 80 nm, which has the potential to be activated as cloud condensation nuclei. The fog-haze day usually occurred when southwest air mass arrived, with the meteorological conditions being of high humidity. The conditions favored the f ne particles (＜1 μm) for accumulation. The case study showed the PNSD on haze-fog day was dominated by the accumulation mode and higher number concentration than on a haze-fog free day. The mass concentration of PM2.5could increase by 10 times on a haze-fog day, which is mainly contributed by f ne particles. On fog-haze days, the accumulation mode particles of high number concentration were mainly transported from the urban area. Thus the study of PNSD at rural sites could also provide information for the analysis of the complex emission sources in urban areas. (Shen Xiaojing)

2.17 Column aerosol optical properties and aerosol radiative forcing during a serious haze-fog month over North China Plain in 2013 based on ground-based sunphotometer measurements

In January 2013, North China Plain experienced several serious haze events. Cimel sunphotometer measurements at seven sites over rural, suburban and urban regions of North China Plain from 1 to 30 January 2013 were used to further our understanding of spatial-temporal variation of aerosol optical parameters and aerosol radiative forcing (ARF). It is found that Aerosol Optical Depth at 500 nm (AOD500nm) during nonpollution periods at all stations was lower than 0.30 and increased signif cantly to greater than 1.00 as pollution events developed. The Angstrom exponent (Alpha) was larger than 0.80 for all stations most of the time. AOD500nmaverages increased from north to south during both polluted and non-polluted periods at the three urban sites in Beijing. The f ne mode AOD during pollution periods is about a factor of 2.5 times larger than that during the non-pollution period at urban sites but a factor of 5.0 at suburban and rural sites. The f ne mode fraction of AOD675nmwas higher than 80% for all sites during January 2013. The absorption AOD675nmat rural sites was only about 0.01 during pollution periods, while 0.03–0.07 and 0.01–0.03 during pollution and nonpollution periods at other sites, respectively. Single scattering albedo varied between 0.87 and 0.95 during January 2013 over North China Plain. The size distribution showed an obvious tri-peak pattern during the most serious period. The f ne mode effective radius in the pollution period was 0.01–0.08 μm, which was larger than that during non-pollution periods, while the coarse mode radius in pollution periods was 0.06–0.38 μm, which was less than that during non-pollution periods. The total, f ne and coarse mode particle volumes varied by 0.06–0.34 μm3, 0.03–0.23 μm3, and 0.03–0.10 μm3, respectively, throughout January 2013. During the most intense period (1–16 January), ARF at the surface exceeded ?50 W m-2, ?180 W m-2, and ?200 W m-2at rural, suburban, and urban sites, respectively. The ARF readings at the top of the atmosphere were approximately?30 W m-2in rural and ?40–60 W m-2in urban areas. Positive ARF at the top of the atmosphere at the Huimin suburban site was found to be different from others as a result of the high surface albedo due to snow cover. (Che Huizheng)

2.18 A study of the meteorological causes of a prolonged and severe haze episode in January 2013 over central-eastern China

This paper employs meteorological observation data from surface and high-balloon stations, China Meteorological Administration (CMA) model T639 output data, NCEP reanalysis data, PM2.5observations and modeled HYSPLIT4 trajectory results to study the meteorological causes, including large-scale circulation and planetary boundary layer features, which led to the extended haze episode on January 6–16, 2013 in central-eastern China. It discusses the possible impact of pollutants transported from southern Hebei Province on Beijing. The results show that: (1) the re-adjustment of atmospheric circulation from a longitudinal to a latitudinal model provides a valuable interpretation of the large-scale circulation background to the haze episode experienced in the metropolitan regions of Beijing, Tianjin, Hebei and their surrounding regions; (2) the regional atmospheric stratif cation of the planetary boundary layer is stable and the mixing height is low, suppressing air turbulence in the planetary boundary layer and providing favorable meteorological conditions for the formation of haze; and (3) the southwesterly jet stream with wind speeds of 6–11 m s-1at a height of 850–950 hPa and the below-700 m air mass trajectory tracking established using the HYSPLIT4 model interdependently suggest a transport of pollutants from southern Hebei Province to Beijing at 850–950 hPa. (Wang Hong)

2.19 Aerosol optical properties under the condition of heavy haze over an urban site in Beijing, China

In January 2013, several serious haze pollution events happened in North China. Cimel sunphotometer measurements at an urban site in Beijing (Chinese Academy of Meteorological Sciences—CAMS) from 1 to 30 January 2013 were used to investigate the detailed variation of aerosol optical properties. It is found that Angstrom exponents were mostly larger than 0.80 when aerosol optical depth values were higher than 0.60 in the urban region of Beijing during January 2013. The aerosol optical depth (AOD) in the urban region of Beijing remained steady at approximately 0.40 before the haze happened and then increased sharply to more than 1.50 at 500 nm with the onset of haze, which suggests that the f ne mode AOD is a factor of 20 of the coarse-mode AOD during a serious haze pollution event. The single scattering albedo was approximately 0.90±0.03 at 440, 675, 870 and 1020 nm during the haze pollution period. The single scattering albedo at 440 nm as a function of the f ne-mode fraction was relatively consistent, but it was highly variable at 675, 870 and 1020 nm. Except on January 12 and 18, all the f ne-mode particle volumes were larger than those of coarse particles, which suggested that f ne particles from anthropogenic activities made up most of the haze. An analysis of aerosol type classif cation showed that the dominant aerosol types can be classif ed as “mixed”and “urban/industrial (U/I) and biomass burning (BB)” categories during the heavy haze period of Beijing in January 2013. The mixed category occurrence was about 31%, while the U/I and BB was about 69%. (Che Huizheng)

2.20 Aerosol optical properties retrieved from a Prede skyradiometer over an urban site in Beijing, China

SKYNET is an international research network of ground-based Prede sky radiometers for the observation and monitoring of aerosol-cloud-radiation interactions in the atmosphere. The algorithm developed by SKYNET is SKYRAD.pack, which can be used to process the measurement data by Prede instruments. In this study, the latest SKYRAD.pack software (Version 5.0) has been used to retrieve the aerosol optical properties measured by a SKYNET Prede sky radiometer over an urban site in Beijing, China. Continuous data have been processed over a two-year period, and inversion products, including aerosol optical depth (AOD), ?ngstr?m exponent (α), volumes of different aerosol particle size distributions, and single-scattering albedos (SSA), have been analyzed. AOD values were found to vary from 0.11 (5th percentile) to 1.14 (95th percentile) with a median of 0.34 at 500 nm, and the maximum and minimum seasonal α values in Beijing were 1.05±0.36 in summer and 0.82±0.39 in spring. SSA values are higher in summer and spring with a similar value of 0.96±0.03, but lower in winter with a value of 0.93±0.04 at 500 nm. Aerosol particles in Beijing clearly demonstrated bimodal size distributions throughout the year: there were coarser particles in spring and finer particles in summer. The α values increased with AOD, indicating that f ne particles play an important role in the optical properties of aerosols in Beijing. Dust type aerosol occurrence accounted for 4.1%, 5.1%, 0.5%, and 1.2% of all measurements data in spring, summer, autumn, and winter, respectively, according to the dust criteria threshold (α＜0.47 and SSA400nm?SSA1020nm＜0.018). (Che Huizheng)

2.21 A multi-source observation study of the severe prolonged regional haze episode over eastern China in January 2013

By employing visibility observation of PM10, SO2and NO2concentration, MODIS AOD at 550 nm, CARSNET AOD at 440 nm, and CALIPSO extinction coefficient at 532 nm, we studied the air pollution condition of a severe haze episode occurring on 6–16 January 2013 over eastern China. It is found that this severe pollution episode of large area haze was accompanied with low visibility, high PM10and AOD in eastern China. The most polluted regions are the Jing-Jin-Ji and its closely neighboring ones including central and southern Hebei, western Shandong and northern Henan provinces. The haze pollutants were spread to the offshore area of from 125°E to the east of China, and even affected the whole ocean surface to the west of 140°E. The PM10variation trend shows a strong linkage among the big cities in Jing-Jin-Ji, and their closely surrounding cities, indicating the possible inter-transport of pollutants among them. The suburban areas of megacities suffered the similar serious pollution to the urban regions during this severe haze episode. Most aerosol pollutants concentrated in boundary layers of below 1500 m vertical height, in particular, the vertical heights of 100–800 m above the ground which are most intensive. (Wang Hong)

2.22 Column-integrated aerosol optical and physical properties at a regional background atmosphere in North China Plain

The AERONET level 2.0 data at Xinglong station from February 2006 to July 2011 were used to characterize the aerosol optical and physical properties, including temporal variability, aerosol absorption, classif cation and properties under dust and haze conditions. The annual mean aerosol optical depth (AOD) and extinction Angstrom exponent (EAE) are 0.28±0.30 and 1.07±0.38, respectively. The seasonal variations of AOD440nmare higher in spring (0.40±0.3) and summer (0.40±0.42) than in autumn (0.20±0.22) and winter (0.19±0.21). The EAE is low in spring (0.96±0.43) and high in summer (1.22±0.38). The EAE is ～1.25 with an absorption Angstrom exponent (AAE) of ～1.0–1.5 at Xinglong station, which indicates that the dominant type is mixed aerosol (accounting for 88.2% at AAE＞1.0). Almost all of the dust observations occurred in spring. The volume concentrations of both f ne and coarse mode particles increase with increasing AOD. In spring, the increase of coarse particles is greater than that of f ne aerosols; however, the reverse phenomenon is observed for other seasons. The high AOD at Xinglong station could be associated with the growth of f ne mode aerosols and the addition of coarse mode particles. This background station is not only impacted by dust aerosols from northwest China and south Mongolia but also inf uenced by long-range transport of anthropogenic aerosols from southern urban and industrial regions. The mean AOD was 1.49 on the dust day, while AOD was 1.10 on the haze day. The mean EAEs were 0.09 and 1.43 on dust and haze days, respectively. (Che Huizheng)

2.23 Dust aerosol drives upward trend of surface solar radiation during 1980–2009 in the Taklimakan Desert

Long-term trend of surface solar radiation (SSR) in the Taklimakan Desert (TD) during 1980–2009 and its relationship with total cloud cover (TCC), low cloud cover (LCC), water vapor content (WVC) and aerosol optical depth (AOD) were investigated. Annual mean SSR has increased by 1.21 W m-2decade-1. Upward SSR trends were observed in seasons except winter. TCC, LCC and WVC have increased while, however, AOD and occurrences of severe dust storms have decreased, which indicates that it is dust aerosol rather than cloud cover and water vapor drive long-term upward trend of SSR in the TD. (Che Huizheng)

2.24 Study of aerosol optical properties based on ground measurements over Sichuan Basin, China

The characteristics of aerosol optical depth (AOD) and ?ngstr?m exponent as well as the relationship between the AOD and particulate matter (PM10), were measured and analyzed at the Chengdu station over the Sichuan Basin in China from February 2007 to December 2009. High monthly AODs were observed in March, August and December, while a low value was observed in October. Monthly variations in ?ngstr?m exponent were opposite to that of AODs in March and August. The averaged PM10showed a significantly seasonal variation with a peak in winter. There is a complicated (not linear) positive correlation between total AOD and near-surface PM10. Three typical cases under the conditions of dust and haze were studied, and the results show that the AODs on the dust days were largest while minimum AODs occurred on haze days. On the contrast, the ?ngstr?m exponent distributions among three weather conditions were opposite to that of AODs. The 3-day back-trajectory analysis indicates that the origin of the air masses largely affects the aerosol optical properties over the Sichuan Basin. (Che Huizheng)

2.25 Analysis of global distribution characteristics of cloud microphysical and optical properties based on the CloudSat data

The global distribution and seasonal variation of the cloud physical characteristics (including the cloud liquid and ice water content, liquid and ice water path, the effective radius, etc.) and cloud optical parameters (the cloud optical depth, etc.) were analyzed with the CloudSat 2B data from January 2007 to December 2010. The results show that the distribution of ice water paths is mainly over the North America, South America, Africa, Australia and the South Asia, as well as the Pacif c, Atlantic and Indian Ocean, with the highest values reaching 600 g m-2or more. In the vertical direction, the high values of ice water content are located near the height of 8 km over the equatorial regions and from 4 to 8 km over the middle latitude regions. The high values of liquid water paths are located over the Pacif c Ocean, the Indian Ocean and the mid and low latitudes of Atlantic. In the vertical direction, the value of liquid water content decreases with height. The ice effective radius reaches its maximum of over 200 μm near the surface at high latitudes, while having a maximum of over 80 μm at the height of 4–8 km in the equatorial region and at the height of 2–4 km in the mid-latitude. The liquid effective radius is large at the boundary layer under 1 km, with a value of over 12 μm. The total cloud optical depth is below 40 around the globe, with largest values located in the vast middle and high latitudes as well as over the oceans off the west coasts of low-latitude continents. Large cloud optical depths are concentrated below the boundary layer. The distribution of the cloud optical depth is closely linked to cloud amount, which is in good spatial accordance with the former, and also to cloud water content, and cloud effective radius. (Wang Zhili)

2.26 Validation of Aura Microwave Limb Sounder (MLS) water vapor and ozone prof les over the Tibetan Plateau and its adjacent region during boreal summer

We present validation studies of MLS V2.2 and V3.3 water vapor (WV) and ozone profiles over the Tibetan Plateau (Naqu and Lhasa) and its adjacent region (Tengchong) respectively by using the balloon-borne Cryogenic Frost point Hygrometer and Electrochemical Concentration Cell ozonesonde. Coincident in situ measurements were selected to compare the MLS V2.2 and V3.3 WV and ozone prof les for understanding the applicability of the two version MLS products over the region. MLS V2.2 and V3.3 WV prof les respectively show their differences within (2.2±15.7) % (n=74) and (0.3±14.9) % (n=75) in the stratosphere at and above 82.5 hPa. Accordingly, at 100 hPa, the altitude approaching the troposphere height, differences are within (9.8± 46.0) % (n=18) and (23.0±45.8) % (n=17), and they are within (21.5±90.6)% (n=104) and (6.0±83.4)% (n=99) in upper troposphere. The differences of MLS ozone are within (-11.7±16.3) % (n=135, V2.2) and (15.6±24.2) % (n=305, V3.3) at and above 82.5 hPa. At 100 hPa, they are within (-3.5±54.4) % (n=27) and (-8.7±41.6) % (n=38), and within (18.0±79.1) % (n=47) and (34.2±76.6) % (n=160) in the upper troposphere. The relative difference of MLS WV and ozone profile is significant in oscillation and scattering at upper troposphere and lower stratosphere partly due to the stronger gradients of WV and ozone concentrations here as well as the linear interpolation of sounding data for the inter-comparison. At and below 70 hPa, the relative differences of MLS ozone are signif cantly larger over Lhasa during the Tibetan Plateau “ozone valley” season, which is also the Asian summer monsoon period. The MLS ozone differences over the three sites are similar in their vertical distributions during that period. A simple linear correlation analysis between MLS and sounding prof les indicates that the sensitivity of MLS prof le products is related to concentrations at each pressure level. The MLS V3.3 product sensitivity is slightly improved for WV at and above 82.5 hPa, whereas it is not for ozone. The possible factors contributing to the differences of the MLS prof le products of WV and ozone are discussed. (Zheng Xiangdong)

3 Model development and implementation, the impacts of atmospheric compositions on climate, weather, and human health

3.1 Air quality forecasts and assessment of control measures during APEC

With the climate forecasting results and the CMA operational air quality (AQ) forecast model CUACE, the AQ trends and detailed forecasts were carried out. One month before the APEC, we provided the day to day variation trend for the APEC period to capture the main pollution episodes. Ten days before the APEC, high resolution forecasts were obtained for the proper Beijing and the APEC meeting venue in Huairou district. With the same CUACE model and observational results, the impacts of pollution reduction control measures were also assessed. It is shown that the control measures had reduced the PM2.5by 35% and NO2by 33% in Beijing City, contributing to the “APEC Blue”. It is found that the local contribution by Beijing City to the overall control impacts was 83%–89%, where the outside contribution was only 11%–17%, due to the weak southerly winds during the APEC period. Spatially, the most eff cient control measures were those taken within a circle of 300 km around Beijing and the contribution of vehicle control measures outside Beijing was not signif cant. The reduction at the point sources outside Beijing contributed about 9% of the reduced PM2.5in Beijing. (Gong Shanling, Liu Hongli)

3.2 Improvement of cloud microphysics in the aerosol-climate model BCC_AGCM2.0.1_CUACE/ Aero, evaluation against observations, and updated aerosol indirect effect

A two-moment cloud microphysical scheme, which predicts both the mass and number concentrations of cloud droplets and ice crystals, is implemented into the aerosol-climate model BCC_AGCM2.0.1_CUACE/ Aero. The model results for aerosols, cloud properties, and meteorological fields are evaluated, and the anthropogenic aerosol indirect effect (AIE) is estimated. The new model simulates more realistic aerosol mass concentrations and optical depth as compared with the former version using a one-moment bulk cloud microphysical scheme. The global annual mean column cloud droplet number concentration (CDNC) from the new model is 3.3×1010m-2, which is comparable to the 4.0×1010m-2from satellite retrieval. The global annual mean cloud droplet effective radius at the cloud top from the new model is 8.1 μm, which is smaller than the 10.5 μm from observation. The simulated liquid water path (LWP) in the new model is signif cantly lower than that in the former model. In particular, the annual mean LWP is lower in the new model by more than 100 g m-2in some mid latitude regions, hence more consistent with satellite retrievals. Cloud radiative forcing and precipitation are improved to some extent in the new model. The global annual mean radiation budget at the top of the atmosphere is -0.6 W m-2, which is considerably different from the value of 1.8 W m-2in the former model. The global annual mean anthropogenic AIE is estimated to be -1.9 W m-2without a lower bound of CDNC being imposed, whereas it is reduced signif cantly when a higher lower bound of CDNC is prescribed. (Wang Zhili)

3.3 Primary assessment of the simulated climatic state by a coupled aerosol-climate model BCC_ AGCM2.0.1_CAM

With the coupled model system of the second generation Global Circulation Model of the National Climate Center (BCC_AGCM2.0.1) and Canadian Aerosol Model (CAM), the simulation of five typical aerosols (sulfate, black carbon, organic carbon, soil dust, and sea salt) and possible effects on the modeled climate are discussed. The results show that in general, the coupled system simulates the five aerosols reasonably well, and there are obvious improvements in that for sulfate, dust, and sea salt aerosols compared to the original monthly mean aerosol data used in BCC_AGCM2.0.1. The climatic statistics simulated by the coupled system mainly agree well with observational/reanalyzed data, and are a little better than the monthly mean aerosol data in terms of the total cloud amount, land surface temperature, and precipitation. The enhanced representation of dust and sea salt improves the simulation of net solar radiation at the top of the atmosphere in the Sahara Desert and mid-latitude ocean in the Southern Hemisphere, which directly affects the land surface temperature. The cloud feedback above the tropical ocean caused by the change in an aerosol scheme not only alters radiation but also markedly inf uences precipitation. (Wang Zhili)

3.4 Effects of emission-sources reduction at different time points on PM2.5 concentration over Beijing

The Model-3 Community Multi-scale Air Quality (CMAQ) modeling system with a high resolution inventory data over Beijing-Tianjin-Hebei area was used to investigate the effects on PM2.5concentrations over Beijing of emission-sources reduction, the rates of which were the same but the 5 time points of which were different: 4 days, 3 days, 2 days, 1 day and 0 day in advance of the most polluted day. Simulations were made for a representative air pollution episode (Feb 7th–16th, 2012), in which Feb 13th was found to be the most polluted day. The results show that the PM2.5concentration was likely to decline more signif cantly if emissionsources reduction measures were taken before the most polluted day than were taken on the most polluted day. In addition, the earlier emission-sources reduction measures were taken, the more signif cantly the PM2.5concentration would decline. Reducing emission-sources 1 day, 2 days, 3 days ahead of the most polluted day led to the reduction of the peak value of PM2.5concentration at the Haidian station by 23%, 31%, and 39%, and in urban Beijing by 22%, 30%, and 38%, respectively. However, as the number of days ahead of the most polluted day (Feb 13th) to take reduction measures increased further, the additional decrease of the peak PM2.5concentration became smaller, thus the emission-sources reduction became less effective. The peak PM2.5concentration would decrease by 40% and 39% at Haidian station and urban Beijing if the reduction measures were taken 4 days before the most polluted day, which shows almost no improvement compared with those taken 3 days in advance. Similar results were obtained from simulations for another pollution episode (Jan 11th–20th, 2012). For controlling severe air pollution, both reduction costs and benef ts should be considered. Our study indicates that the most effective way of emission-sources reduction is to take reduction actions 2–3 days ahead of a possible severe pollution event, the timing of which can be obtained from meteorological condition prediction. In this way, a substantial decrease of the peak PM2.5concentration can be achieved with less cost for implementing the reduction measures. (An Xingqin)

3.5 Research on the application of the NASA/Goddard Long-Wave Radiative Scheme to the GRAPES_Meso model

The National Aeronautics and Space Administration (NASA)/Goddard Long-Wave Radiative Scheme is integrated into the Global/Regional Assimilation and Prediction System Mesoscale (GRAPES-Meso) model in this study. One month of simulation experiments conducted in China and its nearby areas are compared with the corresponding National Centers for Environmental Prediction (NCEP) reanalysis data recorded in April 2006. The results show that the distribution of the clear-sky outgoing long wave radiation f ux (OLRC) at the top of atmosphere and downward long wave radiation f ux at ground (GLWC) of 24-h and 48-h forecasts by using the GRAPES Meso model are in good agreement with the NCEP reanalysis data. The monthly average percentage error of the OLRC of these forecasts is within -10% and 10%. Although the monthly average percentage error of the GLWC is slightly larger than that of the OLRC, both are within a reasonable and acceptable range. The comparison study of the daily averaged anomaly correlation coeff cient and standard error of these f uxes of the two forecasts show that the monthly averaged anomaly correlation coeff cients of the OLRC and the GLWC of the 24-h forecast are 0.96 and 0.98 respectively, and that the monthly averaged standard errors are 24.54 W m-2and 27.23 W m-2respectively. Those of the OLRC and the GLWC of the 48-h forecast are 0.95 and 0.98 and 22.43 Wm-2and 27.64 W m-2respectively. Overall, the daily averaged anomaly correlation coeff cients of the OLRC and the GLWC of both 24-h and 48-h forecasts are above 0.93, and the daily standard error is within 31 W m-2. Moreover, the correlation of the GLWC and the NCEP reanalysis data is stronger than that of the OLRC, whereas the standard error of the OLRC and the NCEP reanalysis data is smaller than that of the GLWC. A comparison of the long wave radiative schemes of the rapid radiative transfer (RRTM) and the NASA/Goddard models reveals that the forecasting by the two schemes is essentially identical. The results of OLRC and the GLWC show that NASA/Goddard long wave radiative scheme may be appropriate for application to the GRAPES_Meso model. (Wang Hong)

3.6 Direct effect of tropospheric aerosols on stratospheric climate

Satellite data are used to be compared with WACCM-3 model results. It is found that model results have a very good consistency with satellite data in such areas: central Africa, the Arabian Peninsula, Indian subcontinent, and most of China; however, in southern central Africa, Caribbean, Europe and the Americas, the model results are low. In short, model results can well reproduce the global distribution of aerosols, and there still exist numerical differences in some areas.

Simulation tests indicate that the changes of stratospheric temperature are neither caused by changes of stratospheric short-wave radiation nor decided by the changes of long-wave radiation. It is not the main reason of the tropospheric aerosol effect on the stratospheric temperature, the changes of temperature are caused by dynamic processes, the change of the long wave radiative heating rate is in response to temperature changes. The stratospheric chemical, dynamic and radiation processes are tightly coupled together. The stratospheric chemical process is of vital importance to the effect of the tropospheric aerosols on stratospheric climate. The stratospheric chemical process has different effects in different seasons and different regions. Polar and highaltitude regions are considered to be mostly affected. In addition, the stratospheric chemical process also has a great inf uence to the upper stratosphere.

Planetary wave propagation changes make the stratospheric climate change: Stratospheric temperature, and wind f eld. Stratospheric ozone and radiation and dynamic processes are closely linked and inf uence each other. The temperature and wind changes then inf uence the concentration of ozone. Polar and high-altitude regions are considered to be mostly affected and impact on high southern altitude is greater than that on high northern altitude. The temperature variation could reach 10 K at most, while zonal wind variation could reach 12 m s-1and ozone mixing ratio could decline for 0.8×10-6at most at 20 hPa in the lower Antarctic stratosphere. In most other areas the temperature change does not exceed 1 K. (Liu Yu)

3.7 Study on impact of city emission and transport on greenhouse gases background observation at Shangdianzi station, Beijing

In-situ measurements of Carbon dioxide (CO2) and several halogenated greenhouse gases (HFC-134a, PFC-218 and HCFC-22) were chosen for case study. We did a statistical analysis and calculation of concentration anomalies and loadings from each wind direction, discussing impact of city emission and transport on greenhouse gases background observation at Shangdianzi station in different seasons. In the study period, the ratio of background concentration of CO2was about 21.2%. The difference between nonbackground concentration and background concentration was (3.7±1.3)×10-6due to local and city emission and transport. Anomalies and loadings of HFC-134a and PFC-218 ref ected differences in source characteristics of these two compounds. The seasonal trend of HCFC-22 was in consistency with the emission pattern of refrigerant. (Yao Bo)

3.8 Retrieve emission of SF6 in China using FLEXPART

SF6is one of long-lived halogenated greenhouse gases and listed as the restricted emission species in“Kyoto Protocol”. Along with the rapid economic development, SF6emission in China is increasing, which attracts attention in the world. For the traditional “bottom-up” method for SF6emission estimation, the required highly accurate and timely updated emission factors and activity data constitute a bottleneck. This paper presents the results on the estimation of SF6emissions in China for the year 2009 by using the Laprange particle dispersion model of FLEXPART and based on the in-situ measurement data obtained from the Shangdianzi regional atomspheric background station (SDZ). The preliminary estimations of SF6emissions in China for the year 2009 is 1.25×103(0.53×103–1.97×103) t, which is similar to the results reported by other studies in the literature. Compared to the a-priori emission, the retrieved emission boasts an improved correlation coefficient which increases from 0.37 to 0.43 and an improved root-mean-square (RMS) which decreases by 2.64 %. (An Xingqin)

3.9 Satellite observed aerosol effect on warm cloud properties under different meteorological conditions over eastern China

By taking meteorological conditions into account, this paper studies aerosol indirect effect on summertime warm clouds over the Yangtze River Delta (YRD) and East China Sea (ECS). The observed aerosol and cloud data are from MODIS/Aqua Level 2 datasets, and meteorological variables are from NCEP Final Analyses Operational Global Analysis datasets. To minimize meteorological effect on statistical analyses of aerosolwarm cloud interaction, several meteorological variables such as cloud top pressure (CTP), relative humidity (RH), pressure vertical velocity (PVV) and lower tropospheric stability (LTS) are considered in this study. Results show that cloud droplet radius (CDR) decreases with increasing aerosol optical depth (AOD) over ECS, while increases with increasing aerosol abundance over YRD. By taking CTP and RH into account, aerosol effects on cloud fraction (CF) are investigated. When aerosol loading is relatively small, CF is found to increase more sharply over YRD than over ECS in response to aerosol enhancement regardless of RH conditions. Therefore, we argue that the horizontal extension of cloud is prone to be driven by aerosol rather than meteorological conditions. Meanwhile, a joint correlative analysis of AOD-CF and AOD-CTP reveals that CTP effect on AOD-CF is not signif cant, indicating CTP makes little contribution to observed AOD-CF relationship. Constrained by lower LTS and pressure vertical velocity (750 hPa), CDR variation in response to AOD is analyzed. In general, CDR tends to decrease as aerosol increases over both ECS and YRD under stable conditions (higher LTS value). In contrast, CDR positively responds to aerosol over land under unstable conditions. Dynamically, CDR has stronger effects on the ascending motion than on the sinking motion with the same aerosol loading over both land and ocean. The reason can be partially explained by the phenomenon that updrafts favor the growth of cloud droplets. Overall, the observed cloud variations can be extremely diff cult to be attributed to aerosol particles alone due to dynamical and thermodynamical processes in cloud systems. (Guo Jianping)

3.10 Diurnal variation and inf uential factors of precipitation from surface and satellite measurements in Tibetan Plateau

Some new features concerning the diurnal variation of precipitation over the Tibetan Plateau (TP) are revealed from rainfall data acquired by a network of rain gauge stations and estimated by the Climate Precipitation Center Morphing (CMORPH) technique during the summer of 2010 and 2011. Maxima in precipitation amount and frequency are associated with the afternoon-to-evening precipitation regime as recorded at approximately 60% of the stations in the network. CMORPH data also capture this pattern, but miss the late morning peak that occurs at some stations. The timing of maximum occurrence agrees well with the diurnal cycle of synoptic conditions favoring the development of precipitation over this area. There is no distinct west-to-east propagation of the diurnal cycle, implying that the diurnal cycle is more driven by local effects than by large-scale circulation. It turns out that the diurnal cycle in precipitation frequency depends largely on topography and landscape. The geographical transition in precipitation peaking is distinct from hilly regions (daytime peak) towards lakes and valleys (evening-to-nocturnal peak). Stations located in mountainous regions (valleys) tend to experience more precipitation in either late morning or early afternoon (late afternoon or evening). Overall, precipitation amount shows a similar topographic dependence, as does the precipitation frequency, suggesting that local-scale effects, such as the mountain valley circulation effect, have a great impact on the diurnal variation in precipitation when large-scale dynamical processes are weak. A possible mechanism for the non-uniform diurnal cycle of precipitation over the TP is proposed. The major conclusion is that plateau-scale synoptic systems, as well as local circulation systems caused by the complex topography, should be taken into account when the diurnal variation in precipitation over the TP is determined. (Guo Jianping)

3.11 Precipitation and air pollution at mountain and plain stations in North China: Insights gained from observations and modeling

We analyzed 40-year datasets of daily average visibility (a proxy for surface aerosol concentration) and hourly precipitation at seven weather stations, including three stations located on the Taihang Mountains in North China during the summertime. There was no signif cant trend in summertime total precipitation at almost all stations. However, light rain decreased, whereas heavy rain increased as visibility decreased over the period studied. The decrease in light rain was seen in both orographic-forced shallow clouds and meso-scale stratiform clouds. The consistent trends in observed changes in visibility, precipitation, and orographic factor appear to be a testimony to the effects of aerosols. The potential impacts of large-scale environmental factors, such as precipitable water, convective available potential energy, and vertical wind shear, on precipitation were investigated. No direct link was found. To validate our observational hypothesis about aerosol effects, Weather Research and Forecasting (WRF) model simulations with spectral-bin microphysics at the cloud-resolving scale were conducted. Model results conf rmed the role of aerosol indirect effects in reducing the light rain amount and frequency in the mountainous area for both orographic-forced shallow clouds and meso-scale stratiform clouds and in eliciting a different response in the neighboring plains. The opposite response of light rain to the increase in pollution when there is no terrain included in the model suggests that orography is likely a signif cant factor contributing to the opposite trends in light rain seen in mountainous and plain areas. (Guo Jianping)

3.12 The transport and deposition of dust and its impact on phytoplankton growth in the Yellow Sea

Observed surface PM10mass concentrations and weather records, satellite-derived aerosol and ocean color data, dust simulations, and a backward trajectory analysis were used to investigate a severe dust storm episode during 19–22 March 2010 and its impact on phytoplankton growth in the Yellow Sea. The observed PM10concentrations and weather records show that heavy dust pollution occurred along the transport pathway. The high MODIS AOD regions were consistent with the simulated high dust emission and deposition ones. Based on the CALIPSO satellite observations, the high dust aerosol layer was below 2 km above ground, indicating the dust transported to the sea was centered within the lower layer. The model simulation estimated that the total deposition f ux over the southern Yellow Sea during 19–22 March 2010 was about 1.5 g m?2. Consequently, the chlorophyll a concentration was calculated to have increased four-fold. Ten to thirteen days later, a phytoplankton bloom occurred. The iron deposited by the severe dust episode could have increased the chlorophyll a concentration in the southern Yellow Sea by 10%–68%. Our results suggest that severe dust storms containing readily bioavailable nutrients may enhance phytoplankton growth in the southern Yellow Sea. (Wang Hong)

3.13 Wet deposition of acidifying substances in different regions of China and the rest of East Asia: Modeling with updated NAQPMS

The traditional way to study Sources-Receptor Relationships (SRRs) of wet deposition is based on sensitivity simulation, which has weakness in dealing with the non-linear secondary formation pollutants (e.g. ozone and nitrate). An on-line source tracking method has been developed in the Nested Air Quality Prediction Modeling System (NAQPMS) coupled with the cloud-process module for the f rst time. The new model can not only quantify the total volume of the sulfate, nitrate and ammonium wet deposition with more accuracy, but also trace these acidic species to their emitted precursors. Compared with previous studies, our result clearly shows: (1) East China and Central China, which are the two primary export regions, have 15%–30% and 10% effect on wet deposition in other areas, respectively; (2) Besides the above two regions, the total acid deposition in Southwest and Northeast China has reached or exceeded the critical loads under the environmental conditions of the two regions (Fig. 5). (Xu Xiaobin)

3.14 Combined effects of 1-nitropyrene and 1,2-naphthoquinone on cytotoxicity and DNA damage in A549 cells

With human lung epithelial A549 cells treated with 1-nitropyrene (1-NP), viability was measured by MTT assay; lactate dehydrogenase (LDH) leakage was determined to evaluate the cellular membrane injury; DNA damage was detected with comet assay; reactive oxygen species (ROS) generation was measured with f uorescent probe. The combined toxic effects of 1-NP and 1,2-naphthoquinone (1,2-NQ) on A549 were also evaluated. 1-NP caused a significantly concentration-dependent and time-dependent viability decrease. The LC50for 24 h and 48 h were 5.2 μmol L-1and 2.8 μmol L-1, respectively. DNA damage and intracellular ROS levels were also increased signif cantly through a dose-dependent manner after exposure to 1-NP. The LDH leakage was not signif cantly changed. Compared with the groups treated with 1-NP alone, the viability and LDH leakage were not changed signif cantly in combined-treated groups with 1-NP and 1,2-NQ. However, the DNA damage and ROS levels were signif cantly reduced in the combined-treated groups compared with the groups treated with 1-NP alone. These results suggest that 1-NP may mediate the genotoxic and cytotoxic effects through ROS generation and pretreatment with 1,2-NQ, and may inhibit the ROS generation induced by 1-NP, thereby reducing the DNA damage in A549 cells. (Li Yi)

3.15 Airborne quinones induce cytotoxicity and DNA damage in human lung epithelial A549 cells: The role of reactive oxygen species

Ambient particulate matter (PM) is associated with adverse health effects. Quinones present in PM are hypothesized to contribute to these harmful effects through the generation of reactive oxygen species (ROS). However, whether the ROS induced by quinones is involved in mediating DNA damage as well as other biological responses in pulmonary cells is less well known. In this study, the toxic effects of fve typical airborne quinones, including 1,2-naphthoquinone, 2-methylanthraquinone, 9,10-phenanthrene-quinone, 2-methyl-1,4-naphthoquinone, and acenaphthenequinone, on cytotoxicity, DNA damage, intra-cellular

calcium homeostasis, and ROSgeneration, were studied in human lung epithelial A549 cells. Anantioxidant N-acetylcysteine (NAC) was used to examine the involvement of ROS in adverse biological responses induced by quinones. The quinones caused a concentration-dependent viability decrease, cellular LDH release, DNA damage, and ROS production in A549 cells. 1,2-Naphthoquinone, but not the other four quinones, increased intracellular calcium (Ca2+) levels in a dose-dependent manner. These toxic effects were abolished by administration of NAC, suggesting that ROS played a key role in the observed toxic effects of quinones in A549 cells. These results emphasize the importance of quinones in PM on the adverse health effects of PMs, which has been underestimated in the past few years, and highlight the need, when the effects on health and exposure management are evaluated, to always consider their qualitative chemical compositions in addition to the size and concentration of PMs. (Li Yi)