災(zāi)害天氣

災(zāi)害天氣研究進展

1 災(zāi)害天氣監(jiān)測

1.1 華南云降水微物理結(jié)構(gòu)觀測和綜合分析

在2016年華南暴雨外場試驗期間，利用Ka波段云雷達(dá)、C波段連續(xù)波雷達(dá)和激光云高儀等設(shè)備，獲取了華南云降水垂直結(jié)構(gòu)綜合數(shù)據(jù)；利用X波段相控陣天氣雷達(dá)和X波段雙線偏振雷達(dá)，獲取了強對流三維結(jié)構(gòu)數(shù)據(jù)，這些數(shù)據(jù)在云降水機理研究方面得到應(yīng)用。分析了云雷達(dá)、C波段連續(xù)波雷達(dá)和激光云高儀探測能力，提出了3種數(shù)據(jù)的融合方法，形成了數(shù)據(jù)融合數(shù)據(jù)，利用這些數(shù)據(jù)分析和改進了華南夏季云降水的統(tǒng)計特征，包括云底和云底高度日變化、不同高度云發(fā)生頻次變化、不同高度云和降水分類的回波強度概率分布等（圖1）。（劉黎平，阮征，崔哲虎）

1.2 雷達(dá)成果的集成和業(yè)務(wù)應(yīng)用

（1）與中國氣象局?jǐn)?shù)值預(yù)報中心等合作，研發(fā)了適應(yīng)于雷達(dá)數(shù)據(jù)模式同化的新一代天氣雷達(dá)質(zhì)量控制軟件系統(tǒng)，通過了中國氣象局預(yù)報與網(wǎng)絡(luò)司組織的評估。同時，研發(fā)了涵蓋所有型號新一代天氣雷達(dá)（包括上海WSR-88D雙線偏振雷達(dá)）的質(zhì)量控制軟件系統(tǒng)，實現(xiàn)了全部的新一代天氣雷達(dá)質(zhì)量控制，為雷達(dá)數(shù)據(jù)同化提供技術(shù)支撐。(王紅艷，劉黎平，李豐)

（2）建立風(fēng)廓線雷達(dá)質(zhì)控軟件系統(tǒng)，在廣州市氣象局業(yè)務(wù)運行為短臨預(yù)報提供支持，該系統(tǒng)在中國氣象局氣象探測中心業(yè)務(wù)試運行，提交中國氣象局?jǐn)?shù)值預(yù)報中心進行模式試驗，并在中國氣象科學(xué)研究院業(yè)務(wù)系統(tǒng)中運行，提供面向科研的支撐（圖2）。（阮征，李豐）

（3）集成實驗室多年的雙線偏振雷達(dá)質(zhì)量控制、降水估測、相態(tài)識別、短臨預(yù)報等成果，研發(fā)了北京市氣象局X波段雙線偏振雷達(dá)數(shù)據(jù)處理和短臨預(yù)報系統(tǒng)，實現(xiàn)了試運行。(劉黎平，胡志群，王紅艷)

（4）與河南電力研究院合作，研發(fā)的新一代天氣雷達(dá)颮線和對流系統(tǒng)識別軟件系統(tǒng)成功應(yīng)用于河南、浙江和新疆電力部門。（劉黎平，王紅艷）

1.3 多種觀測設(shè)備在多個科研項目上開展的外場試驗

在“華南暴雨RDP外場試驗”和“第3次青藏高原大氣科學(xué)試驗——邊界層和對流層觀測”項目中，云雷達(dá)、激光雷達(dá)、X波段相控陣天氣雷達(dá)和C波段偏振雷達(dá)數(shù)據(jù)應(yīng)用于云降水微物理和動力結(jié)構(gòu)觀測，形成了多種遙感手段反演高原和華南對流系統(tǒng)空氣上升速度、云水/云冰/雨水/雪水的垂直廓線的反演方法。（劉黎平，胡志群）

2 青藏高原研究

2.1 青藏高原感熱、潛熱通量對湍流、對流結(jié)構(gòu)的影響

基于第3次青藏高原大氣科學(xué)試驗11個站點的觀測結(jié)果，分析了青藏高原和周邊地區(qū)大氣近地層陸面參數(shù)和湍流特征。大渦模擬試驗表明，青藏高原近地層感熱、潛熱通量可影響湍流和對流結(jié)構(gòu)，也可顯著影響對流云中液態(tài)水含量異常變化。數(shù)值模擬可揭示出青藏高原特殊的“爆米花”對流云特征可能的成因。（王寅鈞，徐祥德）

2.2 基于高原試驗獲取的高原西部自動探空觀測資料和“內(nèi)插猜估”插值方案的新資料變分同化試驗

基于高原試驗獲取的高原西部申扎、改則、獅泉河3站自動探空觀測資料，設(shè)計了“內(nèi)插猜估”探空觀測資料的插值構(gòu)造方案，并將“內(nèi)插猜估”后得到的新探空數(shù)據(jù)同化到數(shù)值模式當(dāng)中。數(shù)值試驗中降水分析結(jié)果表明，將青藏高原西部有限探空觀測數(shù)據(jù)以及經(jīng)過“內(nèi)插猜估”后的探空數(shù)據(jù)進行同化后，降水的TS評分均得到提高，其中“內(nèi)插猜估”試驗中，降水的TS評分提高更為明顯。（張勝軍，徐祥德）

2.3 青藏高原對流結(jié)構(gòu)及其與下游暴雨過程的關(guān)聯(lián)性

基于高原地區(qū)獨特情況，建立了一個新的高原對流系統(tǒng)（TCS）提取方法，從而剔除了高原卷云和卷層云的影響。對TCS的季節(jié)變化特征進行了統(tǒng)計分析，發(fā)現(xiàn)各季節(jié)高原對流對青藏高原及其下游地區(qū)降水都具有重要貢獻(xiàn)。通過暴雨過程及其前期水汽輸送通量、渦度、散度三維結(jié)構(gòu)綜合相關(guān)分析，揭示了長江流域大范圍持續(xù)暴雨發(fā)生、發(fā)展過程中青藏高原上游勢-流函數(shù)場動力系統(tǒng)三維結(jié)構(gòu)“強信號”特征。（胡亮，徐祥德）

2.4 青藏高原大氣水分循環(huán)的勢-流函數(shù)解析

基于青藏高原大地形熱力、動力效應(yīng)引起的繞流、爬流特征，采用大氣運動場的流函數(shù)與勢函數(shù)場，以更清晣地描述青藏高原熱力驅(qū)動相關(guān)聯(lián)的區(qū)域-全球多尺度環(huán)流特征。通過勢函數(shù)風(fēng)結(jié)構(gòu)揭示出青藏高原大地形區(qū)域水汽流入、流出與輻散-輻合綜合物理圖像。另外，通過流函數(shù)場剖析大氣環(huán)流動力結(jié)構(gòu)特征，以凸顯青藏高原熱力驅(qū)動下的高層反氣旋、低層氣旋性耦合環(huán)流動力結(jié)構(gòu)，并探討此類高原特殊動力結(jié)構(gòu)在大地形與大氣環(huán)流系統(tǒng)、波流相互作用中的貢獻(xiàn)，揭示高原熱力、動力過程對東亞、全球大氣水分循環(huán)的影響及其水汽交換輸送多尺度源-匯結(jié)構(gòu)（圖3）。（徐祥德）

2.5 中國東部暴雨水汽輸送結(jié)構(gòu)綜合相關(guān)模型

中國東部暴雨頻數(shù)分布狀態(tài)呈東南高頻區(qū)向西北方向的大地形邊緣帶逐步遞減，這與中國3階梯大地形與梅雨邊緣帶走向一致，其也反映出東部暴雨頻數(shù)分布與梅雨帶季節(jié)性演變、水汽輸送強弱及其與大地形動力、熱力影響等因素存在某種相關(guān)關(guān)系。研究表明了中國東部整層水汽輸送結(jié)構(gòu)及其環(huán)流型特征與中國東部暴雨極端事件發(fā)生頻數(shù)亦顯著相關(guān)。（徐祥德）

2.6 三江源區(qū)大氣的水汽來源、輸送途徑及其空間結(jié)構(gòu)特征

夏季三江源區(qū)短時輸送的水汽主要來自于青藏高原以及其西北側(cè)陸地區(qū)域，而更長時間（8～10天）的來源可追蹤到阿拉伯海和孟加拉灣等遠(yuǎn)距離海洋區(qū)域；水汽輸送通道主要有2支，第1支為沿著索馬里海到阿拉伯海的跨赤道水汽輸送，第2支為在西風(fēng)控制下從中亞乃至西亞地區(qū)向三江源區(qū)的輸送（圖4）。（陳斌）

2.7 青藏高原與太平洋/大西洋熱力作用對北半球陸地夏季風(fēng)年際變化的協(xié)同影響

青藏高原加熱可以調(diào)整高原與太平洋之間的垂直環(huán)流，進而調(diào)節(jié)太平洋地區(qū)的凝結(jié)潛熱加熱和干絕熱加熱，導(dǎo)致該地區(qū)對流層中上層的溫度異常，最終對夏季亞洲-太平洋濤動（APO）的年際變化產(chǎn)生重要影響。夏季亞洲季風(fēng)區(qū)降水與北美中緯度降水存在顯著負(fù)相關(guān)，形成洲際間的降水異常型，而與北美季風(fēng)降水存在正相關(guān)，這種降水異常型與春夏季歐亞（包括青藏高原）和北美陸地加熱及熱帶中東太平洋海溫的異常有密切聯(lián)系。（劉舸，趙平，陳軍明）

3 暴雨研究

3.1 華南季風(fēng)降水試驗進展

災(zāi)害天氣國家重點實驗室暴雨研究團隊自2013年以來牽頭推進世界氣象組織（WMO）世界天氣研究計劃（WWRP）“華南季風(fēng)降水試驗”（SCMREX 2013—2018）研究發(fā)展項目，SCMREX旨在通過外場觀測以及物理機制和對流可分辨模擬研究提高華南前汛期強降水預(yù)報水平。其實施內(nèi)容含4個組成部分：外場觀測，資料管理，強降水事件物理機制研究，以及包括資料同化影響、模式物理過程表達(dá)方案檢驗與改進、集合預(yù)報試驗等對流可分辨數(shù)值試驗。2016年利用比2013—2015年更多的先進設(shè)備開展了華南暴雨外場觀測試驗，加密觀測期（IOP）從2017年5月1日連續(xù)運行至6月15日。已經(jīng)收集了試驗期間的業(yè)務(wù)觀測網(wǎng)和移動設(shè)備觀測資料，并納入了SCMREX資料庫。進行了SCMREX數(shù)據(jù)庫和網(wǎng)站的維護和升級，并改進了SCMREX網(wǎng)站（http://scmrec.cma.gov.cn）。SCMREX網(wǎng)站上添加了往年加密觀測期間主要強降水事件的文字描述以及雷達(dá)、衛(wèi)星、閃電等圖形，并且在機理研究、資料同化影響、模式云降水微物理過程參數(shù)化方案檢驗和改進、集合預(yù)報試驗等各方面取得了新的進展。2016年10月SCMREX首席科學(xué)家羅亞麗研究員向WMO熱帶氣象研究工作組匯報了最新進展，得到包括WMO季風(fēng)委員會主席Chie-Pei Chang教授在內(nèi)的工作組專家的高度肯定。暴雨團隊牽頭全面總結(jié)了SCMREX 2013—2015年的進展，形成的綜述性論文發(fā)表在《美國氣象學(xué)會通報》（BAMS）（羅亞麗）。

3.2 華南前汛期暴雨機理研究

暴雨研究團隊利用SCMREX獲取的最新綜合性觀測資料，研究發(fā)現(xiàn)華南前汛期沿海極端強降水是由長生命史的中尺度對流系統(tǒng)（MCS）產(chǎn)生的，這些MCS的維持時間、組織結(jié)構(gòu)、準(zhǔn)靜止等特點與前汛期的環(huán)境大氣熱動力條件密切相關(guān)：這些MCS發(fā)生在盛行的低層西南氣流中，即使沒有低空急流也能輸送足夠的水汽，華南復(fù)雜的下墊面特征（如海陸對比、海岸線附近和內(nèi)陸都分布著山脈）有利于持續(xù)的對流初生，MCS的一系列反饋作用（如，對流產(chǎn)生的冷出流邊界處常常發(fā)生連續(xù)對流初生）。圖5給出了如何基于雷達(dá)觀測和地面中尺度分析來估計中尺度冷出流邊界的厚度。分析了華南前汛期降水日變化特征，指出華南前汛期日變化存在3種傳播模態(tài)：（i）發(fā)生在華南西部上午的東傳或東南傳降水日變化模態(tài)，這種模態(tài)主要與增強的低空西南急流及其造成的低空輻合有關(guān)；（ii）發(fā)生在午后華南東部與局地暖濕環(huán)境有關(guān)的準(zhǔn)靜止模態(tài)；（iii）發(fā)生在日間沿海向內(nèi)陸傳播的與海陸風(fēng)有關(guān)的降水日變化模態(tài)，這種模態(tài)在季風(fēng)爆發(fā)后更為顯著（圖5）。（羅亞麗，寶興華，姜智娜）

3.3 我國極端小時降水研究

綜合分析自動氣象站雨量計觀測、天氣圖、組合雷達(dá)反射率等資料，利用客觀和人工判斷相結(jié)合的天氣背景識別方法，分析了從海南島至東北地區(qū)的我國東部廣大地區(qū)的極端小時降水的天氣背景。小時降水（＞0.1 mm/h）的季節(jié)變化顯示降水發(fā)生頻次和強度具有復(fù)雜的區(qū)域特征，因此采用99.9百分位定義各個臺站的極端小時降水的閾值。極端降水在華南沿海和華北平原最強，1981—2013年期間，77%的極端小時降水發(fā)生在夏季，峰值（30.4%）出現(xiàn)在7月。根據(jù)天氣背景類型將2011—2015年大約5800個極端小時降水分為4種類型：低渦／切變型、弱天氣尺度強迫型、地面鋒面型、熱帶氣旋型，它們分別占總頻次的39.1%、39.0%、13.9%和8.0%，并且具有各自不同的區(qū)域分布及日變化和季節(jié)變化特征。熱帶氣旋型在東南和華南沿海最為頻繁，深入內(nèi)陸銳減；地面鋒面型在104°E以東分布比較均勻；低渦／切變線型在四川盆地有一個顯著的高頻中心，從這個中心朝著東南和東北方向伸展出2個高頻帶；弱天氣尺度強迫型在東南、西南和華北以及東北的最東部地區(qū)發(fā)生比較頻繁。中尺度對流系統(tǒng)與更小尺度的系統(tǒng)對弱天氣尺度強迫型的發(fā)生頻次的貢獻(xiàn)相當(dāng)，但是二者發(fā)生頻次較高的地點有所差異。（羅亞麗）

3.4 我國中東部地閃統(tǒng)計特征及其與降水的關(guān)系

利用我國6年地閃觀測資料和TRMM觀測資料，對我國中東部地區(qū)的地閃時空活動規(guī)律進行了統(tǒng)計研究，并對比分析了其與降水的關(guān)系。結(jié)果表明，地閃頻次在夏季（冬季）最高（最低），且正地閃比例最低（最高）。華北地區(qū)夏季地閃頻發(fā)，而冬季地閃多發(fā)生在長江流域。最大地閃活動中心位于廣東中部地區(qū)，地閃密度達(dá)9次/（km2·a），珠江三角洲北部年平均閃電日達(dá)70天以上，其次是長江中下游地區(qū)和四川盆地及周邊地區(qū)。在地形復(fù)雜的華北地區(qū)和四川盆地及周邊地區(qū)，其西部的高山區(qū)雷暴日數(shù)大于東部平原（盆地）區(qū)，但地閃密度明顯小于后者，這與高山地區(qū)頻發(fā)的短時午后雷暴有關(guān)。地閃頻次在8月最高，而對流性降水在5月或7月達(dá)到峰值。四川盆地及其周邊山區(qū)暖季降水峰值出現(xiàn)在夜間，而除此以外的我國東部平原地區(qū)暖季降水日變化存在2個峰值，其中午后的峰值對應(yīng)著地閃頻次的峰值；而夜間到清晨的降水峰值對應(yīng)的閃電活動較少，緣于此階段層狀降水比例增大。（夏茹娣）

3.5 海南島降水時空分布規(guī)律

基于5年高分辨率地面和探空觀測資料的統(tǒng)計分析和數(shù)值試驗，開展海南島降水時空分布規(guī)律原因探究，揭示了環(huán)境條件對降水時間分布規(guī)律的影響和環(huán)境風(fēng)、地形和海風(fēng)環(huán)流對降水空間分布的綜合作用機理。結(jié)果表明，4—9月的高濕度和有效位能、低自由對流高度和弱垂直風(fēng)切變使該時期為海南島的顯著降水時期。弱環(huán)境風(fēng)速、低地形和海風(fēng)環(huán)流共同作用使得強降水容易在背風(fēng)坡海岸生成，并在不同環(huán)境風(fēng)向下產(chǎn)生不同傳播特點。（梁釗明）

3.6 華南颮線精細(xì)結(jié)構(gòu)分析

利用雙多普勒風(fēng)場反演技術(shù)，研究了2007年4月24日影響廣東省的一次颮線的形成機理和三維結(jié)構(gòu)，給出了此次颮線的三維結(jié)構(gòu)概念模型。相對風(fēng)暴的自后向前的干冷氣流從層狀云3 km的低層進入颮線；相對風(fēng)暴的自前向后的氣流從對流線中低層進入颮線內(nèi)部，在7.5 km高度分成2支氣流，一支流向前部，另一支則流向?qū)訝钤茀^(qū)。（周海光）

4 臺風(fēng)研究

4.1 海溫對熱帶氣旋（TC）加強的影響

利用1988—2014年北大西洋熱帶氣旋（TC）最佳路徑資料及全球再分析資料研究發(fā)現(xiàn)，TC所處的海溫不僅決定TC最大可能強度（MPI），還決定了TC最大可能加強速度（MPIR），海溫和MPIR之間存在指數(shù)關(guān)系。研究發(fā)現(xiàn)，隨著海溫增加，TC的加強速度和MPIR也增大，當(dāng)海溫大于27 ℃時，MPIR隨海溫增加迅速增大。而且，TC的加強速度在高海溫低垂直切變的區(qū)域會更大，這也說明雖然海溫可以決定MPIR，但是實際的TC加強速度還受著環(huán)境因素的影響，比如環(huán)境垂直風(fēng)切變。本項研究不僅提出了很好的臺風(fēng)加強研究思路，同時也為業(yè)務(wù)預(yù)報提供了較好的理論依據(jù)。（徐晶，王玉清）

4.2 西北太平洋高空冷渦（UTCL）對熱帶氣旋（TC）活動的影響

利用中國氣象局最佳路徑資料與全球再分析格點數(shù)據(jù)，對2000—2012年西北太平洋熱帶氣旋（TC）及其間高空冷渦（UTCL）的活動以及它們的相互關(guān)系進行統(tǒng)計分析。結(jié)果表明，346個TC中73%在其生命史存在UTCL活動，其中21%與UTCL中心相對距離小于15經(jīng)/緯距，即二者可能發(fā)生相互作用。進一步分析發(fā)現(xiàn)，該距離內(nèi)UTCL對TC運動和強度變化均存在一定影響。與整個太平洋TC運動狀況相比，盡管UTCL的存在從整體上并沒有增加TC移向的突變比例，但對于特定方位角和相對距離，UTCL對TC運動的影響是顯著的，比如5經(jīng)/緯距內(nèi)TC易發(fā)生突然左折。UTCL對強度變化的影響主要發(fā)生在TC的發(fā)生和初期發(fā)展時期，當(dāng)二者進入相互作用距離，在12 h內(nèi)約45%的TC強度增強，38%維持，僅有17%強度減弱。增強TC主要位于UTCL的南側(cè)，減弱主要位于其北側(cè)。對于TC強度的迅速變化，迅速加強（RI）容易在UTCL東東南象限和南西南象限發(fā)生。TC迅速減弱（RW）的樣本則大多出現(xiàn)在UTCL的西側(cè)（圖6）。（李英，魏娜，張大林）

5 雷電研究

5.1 青藏高原閃電活動與對流云結(jié)構(gòu)的關(guān)系

基于自主研制的地基全天空云觀測系統(tǒng)觀測并分析了高原日喀則地區(qū)的云量、云狀等分布特征，發(fā)現(xiàn)日喀則地區(qū)的云量和云狀都呈現(xiàn)明顯的季節(jié)分布?；赥RMM衛(wèi)星降水特征（PFs）資料，分析了高原產(chǎn)生閃電的對流云和沒有產(chǎn)生閃電的云結(jié)構(gòu)特征及差異性。研究表明，產(chǎn)生閃電的PFs的面積比無閃電發(fā)生的PFs的面積要大一個量級。高原東北部（青海地區(qū)）產(chǎn)生閃電的PFs尺度普遍在1400 km2以上。高原東南部（中心29°N、97°E附近）產(chǎn)生閃電的PFs尺度最小，極小值在500 km2以下。高原上產(chǎn)生閃電的PFs的云高要比沒有產(chǎn)生閃電的PFs的云高2～4 km。高原上產(chǎn)生閃電的PFs的云頂高度在中南部最高，可到12 km以上，藏南附近區(qū)域最低，低于10 km。高原產(chǎn)生閃電的PFs的20 dBz最大高度與分布于喜馬拉雅山以南的平原相當(dāng)?shù)孕?，?0 dBz的最大高度大于喜馬拉雅山以南地區(qū)。產(chǎn)生閃電的PFs的平均閃電密度在高原的西部和東北部地區(qū)較大。（張義軍，鄭棟，呂偉濤，孟青，楊俊，姚雯，馬穎，王飛）

5.2 特種觀測資料同化及雷電災(zāi)害天氣系統(tǒng)的監(jiān)測預(yù)警方法

（1）利用水汽混合比與閃電頻數(shù)、霰混合比的經(jīng)驗關(guān)系式，建立了SAFIR3000全閃輻射源資料與相對濕度的經(jīng)驗關(guān)系，并在WRF-3DVar同化系統(tǒng)中實現(xiàn)對全閃定位資料的連續(xù)循環(huán)同化。利用基于WRF-Electric模式搭建的雷電活動短時預(yù)報平臺，連續(xù)開展2個汛期的雷電活動預(yù)報試驗，并對試驗結(jié)果進行初步檢驗。初步完成利用雷電臨近預(yù)警系統(tǒng)與中尺度起放電模式相耦合實現(xiàn)0～12 h雷電預(yù)報方法的方案設(shè)計，以彌補原有僅靠外推算法時效性短的缺陷，進而提升雷電的預(yù)警預(yù)報效果（圖7）。（徐良韜，姚雯，張榮）

（2）對10次中尺度對流系統(tǒng)雷達(dá)和地閃數(shù)據(jù)的綜合分析發(fā)現(xiàn)，層云地閃首次回?fù)綦娏鞣逯低ǔＲ笥趯α鞯亻W首次回?fù)舻碾娏鞣逯怠釉频亻W一般在最大反射率核心（≥30 dBz）分布在3～6 km高度的區(qū)域邊緣或者圍繞該區(qū)域接地。這一區(qū)域的反射率特征與回波亮帶特征具有一致性，表明亮帶區(qū)域的電荷結(jié)構(gòu)對層云閃電的激發(fā)或者傳播可能具有重要影響。這一結(jié)果為研究亮帶和層云地閃之間的關(guān)系提供了一個重要證據(jù)，也為層云地閃預(yù)警方法的研究提供了一條理論依據(jù)（圖8）。（王飛）

5.3 閃電初始階段特征與雷暴結(jié)構(gòu)的時空配置關(guān)系

進一步完善了低頻電場變化探測陣列（LFEDA）的方法和技術(shù)，并在廣東進行了閃電活動觀測試驗，獲取了大量雷暴過程的閃電放電探測數(shù)據(jù)，初步完成了對LFEDA的性能評估?；谖挥贚FEDA站網(wǎng)內(nèi)的人工觸發(fā)閃電的評估表明其具有良好的探測性能，對觸發(fā)閃電和回?fù)舻奶綔y效率分別達(dá)到了100%和95%，平均定位誤差達(dá)到102 m。將雷暴演變過程中LFEDA的三維總閃定位結(jié)果與雷達(dá)回波結(jié)合也表明LFEDA具有可靠的探測能力。此外，基于LFEDA數(shù)據(jù)分析了一次云閃個例和一次地閃個例先導(dǎo)過程的通道發(fā)展特征，獲得了與通道發(fā)展的一些相關(guān)參量，這些分析表明LFEDA具有描述閃電三維通道的能力。

研究分析了一次超級單體組合體過程的閃電起始特征。發(fā)現(xiàn)閃電起始位置主要被霰、干雪、小雹和冰晶4類粒子主導(dǎo)，對應(yīng)的閃電起始占總閃電的比例分別為44.3%、44.1%、8.0% 和3.0%。在南部超級單體發(fā)生龍卷的階段，與霰粒子對應(yīng)的閃電起始主導(dǎo)超級單體的主體區(qū)域以及它的右側(cè)和前側(cè)；與干雪對應(yīng)的閃電起始主導(dǎo)前側(cè)云砧、右側(cè)云砧和后側(cè)云砧的外圍區(qū)域；與小雹對應(yīng)的閃電起始則主要集中在上升氣流區(qū)的周圍，更偏向主上升氣流區(qū)的前側(cè)。高密度的閃電起始對應(yīng)差分反射率弧的位置和右側(cè)云砧的區(qū)域。平均閃電起始高度的分布呈現(xiàn)自后側(cè)向前側(cè)和自右側(cè)到左側(cè)逐漸降低的趨勢，同時，從閃電起始位置高度分布范圍看，其最大范圍出現(xiàn)在上升氣流區(qū)的前側(cè)。研究表明，起始自前側(cè)云砧區(qū)域的閃電尺度最大，然后是那些起始自上升氣流區(qū)前側(cè)和接近差分反射率弧的區(qū)域。研究支持了關(guān)于電荷口袋的概念，并進一步推測在右側(cè)云砧區(qū)的電荷口袋分布量最大和最為緊湊，所有導(dǎo)致該區(qū)域頻繁的閃電起始，但對應(yīng)閃電尺度小，閃電起始的垂直范圍淺薄。（鄭棟，張陽，張義軍，孟青，張文娟，徐良韜，黃治鋼）

5.4 雷暴上升運動與起電和放電活動關(guān)系的模擬

利用一個三維起電放電數(shù)值模式，研究了上升運動與雷暴中主要的起電活動和放電活動的關(guān)系。結(jié)果發(fā)現(xiàn)，上升運動在對閃電活動的發(fā)展（在此以閃電活動中和電荷率表征）起到主要促進作用的同時，還對閃電活動的增強起著抑制作用。上升運動有利于非感應(yīng)起電活動的發(fā)生，但過強的上升運動則不利于非感應(yīng)起電效率的進一步提高。模擬個例中具有較高起電效率的非感應(yīng)起電活動基本發(fā)生在上升速度小于20 m/s的上升運動區(qū)內(nèi)。此外，上升速度中心的高度在閃電活動的多數(shù)時間里與反轉(zhuǎn)溫度的高度基本保持一致，可以用來區(qū)分霰粒子非感應(yīng)起電獲得不同極性電荷區(qū)域的分界。（王飛）

5.5 雷電重大災(zāi)害天氣系統(tǒng)的動力過程和演變規(guī)律

利用多種觀測資料和高分辨率數(shù)值模式，對2個發(fā)生在不利大尺度背景下的局地雷暴過程進行研究，重點分析了觸發(fā)過程。研究表明，北京地區(qū)周邊雷暴系統(tǒng)的冷池出流、局地地形和北京城市復(fù)雜下墊面特征等均會對局地雷暴的發(fā)生產(chǎn)生重要影響。對2015年7月中旬京津冀地區(qū)持續(xù)性夜間雷雨天氣開展了初步分析，發(fā)現(xiàn)傍晚到夜間的低層上升運動更強，水汽輸送和輻合更充分，層結(jié)更不穩(wěn)定，均有利于降水在傍晚和夜間發(fā)生。對多雨多閃、多雨少閃和少雨多閃等3類事件的背景環(huán)流合成分析表明，多雨多閃和多雨少閃事件均發(fā)生在高層有異常正輻散、中層槽和低層有西南氣流輸送水汽的背景下，而少雨多閃事件主要是由山區(qū)地面加熱作用引起，中高層天氣尺度強迫較弱；多雨多閃事件的環(huán)境場擁有相對高的對流有效位能（CAPE）和LI以及較小的對流抑制能量（CIN），而多雨少閃事件多發(fā)生在夜間，CAPE和CIN值較?。簧儆甓嚅W事件發(fā)生在相對中等強度的CAPE和0～6 km垂直風(fēng)切變環(huán)境場中。

明確了超級單體中閃電起始對應(yīng)水成物粒子類型、閃電起始密度、高度、垂直范圍等特征。構(gòu)建了閃電起始特征與超級單體結(jié)構(gòu)的關(guān)系模型。發(fā)現(xiàn)大、小電流地閃氣候活動在自身特性和時空分布上存在顯著差異性，這種差異性隨季節(jié)和下墊面而變化。（張大林）

5.6 雷電物理過程研究、雷電探測技術(shù)發(fā)展和外場觀測試驗

繼續(xù)開展廣東閃電綜合觀測試驗，在人工觸發(fā)閃電實現(xiàn)、放電過程精細(xì)化觀測、雷暴的全閃探測以及雷電物理過程研究等方面獲得了顯著進展。（1）成功人工觸發(fā)閃電13次，觸發(fā)閃電成功率約72%，無論是觸發(fā)次數(shù)還是成功率，都保持了較高的水平。（2）發(fā)展了連續(xù)干涉儀精細(xì)化定位技術(shù)，建設(shè)了3天線陣列的觀測系統(tǒng)，實現(xiàn)了觸發(fā)閃電和自然閃電全放電過程通道發(fā)展的高時間分辨率、精細(xì)化描繪。（3）進一步完善了閃電低頻電場探測陣列并開展觀測，獲取了6—11月從化地區(qū)雷暴過程的云閃、地閃及NBE事件的脈沖放電信息，實現(xiàn)了閃電放電通道初步可分辨的全閃三維定位。此外，開展了高原地區(qū)低頻電場探測陣列的站點考察，并完成2個子站的建設(shè)。（4）獲得了對先導(dǎo)始發(fā)先驅(qū)脈沖、不規(guī)則先導(dǎo)發(fā)展特征及物理過程的新認(rèn)識，并發(fā)現(xiàn)了大電荷轉(zhuǎn)移過程M分量、連續(xù)電流及回?fù)舻南嚓P(guān)性。（5）廣州高建筑物雷電觀測大幅提升了先導(dǎo)過程的高速光學(xué)觀測能力及不同強度的電磁場輻射信號的完整記錄能力，得到了先導(dǎo)梯級發(fā)展的精細(xì)化特征，給出了負(fù)極性地閃連接過程中下行負(fù)先導(dǎo)和上行連接先導(dǎo)的2種基本的連接行為（圖9）。（呂偉濤，張陽，鄭棟，張義軍，姚雯，馬穎，黃治鋼，徐良韜，齊奇）

6 模式關(guān)鍵技術(shù)和再分析資料研究

6.1 天氣氣候一體化模式關(guān)鍵技術(shù)研究

在模式動力框架方面，在廣泛調(diào)研當(dāng)今國際趨勢的基礎(chǔ)上，建立了正二十面體網(wǎng)格生成器，并基于該網(wǎng)格建立了球面平流方程求解器和淺水方程求解器；在正二十面體網(wǎng)格上建立了正定的兩步保形平流方案，測試顯示該方案目前可以很好地運行于正二十面體網(wǎng)格，計算效果與之前在經(jīng)緯度網(wǎng)格上的效果相當(dāng)。在物理過程方面，為改善該耦合模式中大氣頂輻射收支不平衡問題，引入一個新的云輻射方案（BCC_RAD），顯著改善了大氣頂輻射收支的平衡狀況，并顯著改善東亞層云區(qū)冷季短波云輻射強迫的模擬。在模式耦合技術(shù)方面，本年度基于美國國家大氣研究中心（NCAR）的CESM模式以及耦合器CPL7，替換大氣和海洋分量模式，逐步建立一個新分量的海-陸-氣-冰耦合系統(tǒng)，由此掌握高分辨率耦合模擬的耦合技術(shù)； 實現(xiàn)耦合模式和MPI-M水文模式耦合，徑流通過水文模塊進入海洋，完成了全球水量循環(huán)的閉合，模式具備氣候系統(tǒng)模式所需的完備分量。在耦合模式同化方面，基于中國氣象科學(xué)研究院現(xiàn)有的耦合氣候系統(tǒng)模式版本，引進了中國科學(xué)院大氣物理研究所發(fā)展的EnOI-IAU同化方法，基于耦合模式同化海洋溫鹽廓線資料（弱耦合同化），并開展了年代際氣候預(yù)測回報試驗（圖10～11）。（張祎，陳昊明，容新堯，李建）

6.2 東亞區(qū)域大氣再分析攻關(guān)任務(wù)

完成了東亞區(qū)域大氣再分析系統(tǒng)搭建并進行初步測試。對2014年7月進行了試驗（不同化觀測資料），并進一步優(yōu)化模式參數(shù)組合。開展了2014年6—8月的模擬，并基于模擬結(jié)果進行了背景誤差協(xié)方差的統(tǒng)計計算和與默認(rèn)背景協(xié)方差矩陣初步的對比。完善了同化流程，開展了再分析同化試驗。為了突出東亞區(qū)域再分析特色，開展關(guān)鍵資料的分析研究，即對未參加國際交換的探空資料、地基GPS/Met、衛(wèi)星導(dǎo)風(fēng)、雷達(dá)資料等資料進行了同化試驗。結(jié)合觀測試驗開展觀測試驗資料同化試驗，通過與高原試驗項目的聯(lián)合開展了高原試驗資料同化試驗并完成1個月資料的同化運行；通過與華南季風(fēng)觀測試驗團隊的合作，基于華南觀測試驗資料開展了模式云物理過程的比對與優(yōu)化。（梁旭東，尹金方，陳鋒，劉英，何會中，周海波，郝世峰）

7 信息網(wǎng)絡(luò)支撐

完成中國氣象科學(xué)研究院重點工作“科研數(shù)據(jù)共享平臺”項目建設(shè)，在此基礎(chǔ)上整合了華南季風(fēng)降水試驗數(shù)據(jù)共享網(wǎng)站和第3次青藏高原大氣科學(xué)試驗項目網(wǎng)站。2016年汛期開始向中國氣象科學(xué)研究院內(nèi)部用戶開放使用。承擔(dān)完成了網(wǎng)絡(luò)信息安全檢查工作10多項，完成了院網(wǎng)站掛標(biāo)和集約化網(wǎng)站群建設(shè)。升級和擴容了高性能存儲系統(tǒng)，增強了數(shù)據(jù)服務(wù)的支持能力。完成中國氣象科學(xué)研究院信息系統(tǒng)運維管理與技術(shù)支持，保證對外服務(wù)網(wǎng)站全年無安全事故（圖12）。（高梅，張文華，李斌，李豐，趙盛華，朱孔駒）

圖1 2016年7月10日在廣東龍門觀測的回波強度的時間高度圖：(a)Ka波段云雷達(dá)（CR）、C波段調(diào)頻連續(xù)波（FMCW）垂直觀測雷達(dá)（CVPR）和激光云高儀（CEIL）融合的回波強度；(b)剔除雜波后的回波強度；(c)融合數(shù)據(jù)的資料來源。（(a)(b)中黑點為激光云高儀觀測的云底，(c)中藍(lán)色和黃色分別表示云雷達(dá)和C波段調(diào)頻連續(xù)波垂直觀測雷達(dá)觀測數(shù)據(jù)，紫色為雜波）Fig. 1 Time-height cross-sections of reflectivity on 10 July 2016 in Longmen, Guangdong: (a) the merged reflectivity from Ka band cloud radar, C band frequency modulated continuous wave (FMCW) vertical pointing radar (CVPR) and a laser ceilometer(CEIL); (b) reflectivity after removing clutters; (c) data resources of reflectivity. The black dots in (a) and (b) indicate the CEIL-derived cloud-base heights. In (c), data from CR and CVPR, and clutters are shaded in blue, yellow and purple, respectively

圖2 風(fēng)廓線雷達(dá)質(zhì)控軟件系統(tǒng)及同化試驗結(jié)果Fig. 2 Wind prof ler radar (WPR) data quality control (QC) scheme and numerical assimilation experiment

圖3 青藏高原熱力驅(qū)動區(qū)域-全球水分循環(huán)多尺度特征Fig. 3 Regional to global multi-scale characteristics of the heat-induced atmospheric water tower over the Tibetan Plateau

圖4 夏季（6－8月）到達(dá)三江源空氣塊診斷的E-P場Fig. 4 The summer seasonal mean (July-August) of E-P calculated using all air parcels reaching the TRHR

圖5 2015年5月20日5個時刻汕尾S波段雷達(dá)的PPI圖（其中：(a～e)為仰角1.5°的徑向風(fēng)速度，黑色圓圈代表距地高度250 m、500 m、750 m和1000 m；(f～j)為仰角2.5°的雷達(dá)回波反射率，黑色圓圈代表距地高度600 m、1000 m和2000 m。黑色虛線框為關(guān)鍵區(qū)，棕色虛線表示根據(jù)地面自動站觀測估計的中尺度邊界的大致位置)Fig. 5 PPI analysis of Shanwei S-band radar at 5 selected times on 20 May 2015: (a-e) the radical velocity at 1.5° elevation(m s-1), with the black circles denoting the height of 250 m, 500 m, 750 m and 1000 m MSL, respectively; (f-j) the reflectivity at 2.5° elevation (dBz), with the black circles denoting the height of 600 m, 1000 m and 2000 m MSL, respectively, with the black rectangle box representing the control region with extreme accumulated rainfall, the brown dashed lines representing the approximate locations of the surface mesoscale boundary based on the surface observations

圖6 12 h加強(a)和12 h減弱(b)熱帶氣旋（TC）中心相對于高空冷渦（UTCL）中心（0點）空間分布（黑色點顯示快速增強/減弱TC位置）Fig. 6 The spatial frequency distribution of TCs within a 15° distance from the composite UTCL center during the subsequent (a)12 h intensifying, (b) 12 h weakening. Black dots denote the locations of TCs experiencing rapid intensity changes

圖7 觀測和模擬的6 h閃電活動分布Fig. 7 The observed and simulated 6-hour accumulated lightning

圖8 雷達(dá)組合反射率與對流地閃（白色實心●）、層云-對流地閃（○）和層云地閃(×)的接地位置（a）及圖（a）中黃色實線位置的雷達(dá)反射率垂直剖面（b）Fig. 8 (a) Composite radar reflectivity, overlain with the return stroke points of CCGs (white dots), SCCGs (○) and SCGs (×); (b)Vertical reflectivity prof le along the yellow segment in (a)

圖9 連續(xù)干涉儀甚高頻定位結(jié)果（左）、LFEDA低頻定位結(jié)果（右）和下行先導(dǎo)圖像（下）Fig. 9 VHF location of continuous INTF (left), LF location of LFEDA (right) and image of downward leader (below)

圖10 氣候模式模擬的全球平均大氣頂凈能量收支（從左至右分別為27個參加CMIP5的模式及CAMS_CSM和采用BCC_RAD方案的CAMS_CSM的結(jié)果）Fig. 10 Global annual mean residual energy (unit: W/m2) at the model top in 27 CMIP5 models and CAMS_CSM with different radiation schemes

圖11 觀測(HadISST，紅色)和同化（藍(lán)色）的Nino3海溫指數(shù)Fig. 11 Observed (HadISST, red) and assimilated (blue) Nino3 index

圖12 氣象科研數(shù)據(jù)共享平臺Fig. 12 Meteorological scientific and research data sharing platform

Advances in Severe Weather Research

1 Severe weather monitoring technology

1.1 Observation and analysis of microphysical structures of cloud and precipitation over South China

To improve our understanding of the cloud and precipitation properties in South China, the field campaigns were carried out by Chinese Academy of Meteorological Sciences (CAMS). Vertical structures of nonprecipitating and precipitating clouds，3D structures of strong convective precipitations have been observed with X-band phased array radar and X-band polarization radars, a K-band solid-state transmitter cloud radar (CR), a C-band frequency modulated continuous wave (FMCW) vertical pointing radar (CVPR)and a laser ceilometer (CEIL) in Guangdong Province, China. The observational abilities of CR, CVPR radars and CEIL were examined to construct merged cloud-precipitation radar dataset that can be used to analyze statistically the vertical characteristics of clouds and precipitations in South China, including valid rate of observations, cloud-base and cloud-top height estimates and reflectivity distributions (Fig.1). (Liu Liping，Ruan Zhen, Cui Zhehu)

1.2 Integration and operational application of outcomes from radar

(1) The software system of new-generation operational radar data quality control (QC) for radar data assimilation was developed by LaSW, CAMS, in cooperation with the Numerical Weather Prediction Center of CMA, which passed the evaluation organized by Department of Forecasting and Networking of CMA. The radar data QC system for all types of radar in CMA was also developed and used in radar data assimilation.(Wang Hongyan, Liu Liping, Li Feng)

(2) The Wind Profiler Data Quality Control System (WPDQCS) is operated in the Guangzhou Meteorological Bureau to provide support for nowcasting, with its test run in the Meteorological Observation Center of CMA to give the support for GRAPES-MESO data assimilation experiment. It is also operated in the operation system of CAMS to provide support for scientific research (Fig. 2).(Ruan Zhen, Li Feng)

(3) The Beijing Meteorological Bureau dual linear polarization radar processing and nowcasting software systems were developed and used in operational test to realize radar data QC, QPE, hydrological distinguish and nowcasting. (Liu Liping, Hu Zhiqun, Wang Hongyan)

(4) The software systems for squall and convective warning were used in Henan, Zhejiang and Xinjiang electrical power bureaus, in cooperation with Henan electrical power institute. (Liu Liping, Wang Hongyan)

1.3 Field experiment on cloud and precipitation in scienti fic projects

In the Southern China Monsoon Rainfall Experiment (SCMREX) that was endorsed by the World Meteorological Organization (WMO) as a Research Demonstration Project (RDP) of the World Weather Research Programme (WWRP), and the Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX-Ⅲ),cloud radar, lidar, X-band phased array radar and C-band dual linear polarization radar were used to observe the microphysical and dynamical structures in clouds and precipitation over the Tibetan Plateau and South China. The vertical motion, cloud water/cloud ice/precipitation/snow contents were documented, the diurnal variations of several important cloud properties were analyzed, including cloud top and base, cloud depth,cloud cover, number of cloud layers, and their vertical structures, during summertime over the Tibetan Plateau and South China. (Liu Liping, Hu Zhiqun)

2 Research on weather over the Tibetan Plateau

2.1 The effects of surface sensible heat flux (H) and latent heat flux (LE) on the structures of

convection and turbulence over the Tibetan Plateau (TP)

Based on results from 11 flux sites during the Third Tibetan Plateau (TP) Atmospheric Scientific Experiment (TIPEX-Ⅲ), land surface parameters and the turbulence characteristics of the atmospheric surface layer over the TP and surrounding regions were analyzed. The large eddy simulations (LES) illustrate that H and LE in the surface layer can have an effect on the structures of convection and turbulence, which also have great impact on the anomalous variations of the liquid water content (LWC) in convective clouds over the TP.The simulations reveal the possible cause of the formation of the special “popcorn clouds” over the TP. (Wang Yinjun, Xu Xiangde)

2.2 Design of a new so-called “interpolation guess” scheme based on the limited automatic sounding observational data on western plateau obtained from the TIPEX-Ⅲ, and its use in data assimilation

A new interpolation scheme of the “interpolation guess” method was designed using the automatic sounding observational data at Shenzha, Gaize, Shiquanhe stations on western plateau from TIPEX-Ⅲ (the Third Tibetan Plateau Atmospheric Scientific Experiment), and more sensitivity experiments were conducted to evaluate the effect on the numerical simulations after all these new data were assimilated into the numerical model. The numerical simulation results indicate that the Threat Score (TS) for the simulated rainfall in the numerical experiments with both the automatic sounding observation only at three stations and with the new data after the “interpolation guess” method has been higher than that in the control experiment without data assimilation, with the improvement of the TS in the experiment with the new method being more obvious than that in the experiment with the original method. (Zhang Shengjun, Xu Xiangde)

2.3 The correlation between Tibetan Convective Systems (TCS) and the hard rain over its downstream regions

A new definition of TCS was introduced to exclude the effects of cirrus and cirrostratus over the Tibet.Based on the new definition, 2032 TCSs were selected and analyzed to study their seasonal variation. The result shows that TCSs play an important role in precipitation over the Tibetan Plateau and its adjacent regions in all four seasons. By analyzing the three-dimensional structure of the water vapor flux, vorticity and divergence prior to and during the heavy rainfall events, the upstream “strong signals” related to heavy rainfall events were revealed. (Hu Liang, Xu Xiangde)

2.4 The use of potential/stream function to analyze the water vapor cycle over the Tibetan Plateau

Based on the understanding of climbing and deflective flows caused by large topography of the Tibetan Plateau (TP) and the “midair heat island” thermal-driven divergence-convergence structure, the kinetic fields were decomposed into stream function and potential function fields. The atmospheric water tower over the TP can be clearly depicted from the water vapor flux and its regional-to-global multi-scale characteristics can be analyzed. The wind vectors of potential function can portrait the regional water vapor fluxes into and out of the TP and their three-dimensional physical diagram. Meantime, the wind vectors of the stream function can anatomically reflect the dynamic structure of the atmospheric circulation, particularly the anticyclonic-aloft-cyclonic-beneath coupled kinematic structure. With this analysis framework, we examined the dynamic structure caused by the TP topography, its unique atmospheric circulation, and the wave- flow interaction. We further illustrated impact of the dynamic and thermodynamic processes over the TP on the regional-to-global water vapor cycle and the sink and source of the multi-scale transport of water vapor (Fig. 3). (Xu Xiangde)

2.5 The integrated model of moisture transport in heavy rainfall in eastern China

The spatial distribution of summer rainstorm frequency in eastern China is higher in the southeast and lower in the northeast, which is very similar to the distribution of the “staircase” topography. The similarity in the pattern of the three-step staircase topography and the rain bands suggests a strong link between the rainstorm frequency and seasonal migration of Meiyu, moisture transport by monsoonal flow, dynamic and thermodynamic influence of large-scale topography. It is showed that column-integrated moisture transport and moist flow pattern in the summer over eastern China yield great in fluence on the frequency of extreme rainstorms. (Xu Xiangde)

2.6 The Three-River Headwaters Region moisture sources, pathways and its spatio-temporal structure

The major moisture sources contributed to the Three-River Headwaters Region (TRHR) summer water vapor with relatively short transport timescales (less than 7 days) are mainly originated from the Tibetan Plateau and its northwestern regions, while the moisture transport with longer timescale (8–10 days) could be tracked back from the long-distance oceanic regions, particularly the Bay of Bengal and Arabian Sea. There are two moisture channels: One is related to the moisture located in the southern Indian Ocean crossing the equator nearby the Somalian coastal region; another stems from the central and western Asia (Fig. 4). (Chen Bin).

2.7 Collaborative influences of the Tibetan Plateau and the Pacific/Atlantic on the interannual variations of the land monsoon in the Northern Hemisphere

The Tibetan Plateau (TP) heating can modulate the vertical circulations between the Tibetan Plateau and the Pacific, and therefore regulates the condensation latent heat and dry adiabatic heat over the Pacific, which leads to mid-upper-tropospheric temperature anomalies in situ and ultimately affects the interannual variability of the summer Asian-Pacific Oscillation (APO). The precipitation over the Asian monsoon region was significantly and negatively correlated with that over the mid-latitudes of North America, and was positively correlated with that over the North American monsoon region, constituting an intercontinental contrasting Asian-North American (CANA) precipitation anomaly pattern. The CANA precipitation anomaly pattern was closely related to the land heating of Eurasian (including the Tibetan Plateau) and North America and sea surface temperature (SST) anomalies in the tropical central and eastern Pacific during spring and summer. (Liu Ge, Zhao Ping, Chen Junming)

3 Heavy rainfall research

3.1 Progress of the South China Monsoon Rainfall Experiment

Since 2013, the Heavy Rainfall Research Group at LaSW/CAMS has been leading the South China Monsoon Rainfall Experiment (SCMREX), a unique program for improving heavy rainfall forecasts over South China during the pre-summer rainy season through field campaigns and research on physical mechanisms and convection-permitting modeling, which was endorsed by the World Meteorological Organization (WMO) as a Research Demonstration Project (RDP) of the World Weather Research Programme (WWRP). The SCMREXRDP (2013–2018) consists of four major components: Field campaign, database management, studies on physical mechanisms of heavy rainfall events, and convection-permitting numerical experiments including impact of data assimilation, evaluation/improvement of model physics, and ensemble prediction. During 1 May–15 June 2016, the SCMREX-2016 intensive observing period (IOP) ran continuously with more portable instruments than those participated in the 2013–2015 IOPs. All the datasets from the operational network and portable instruments have been collected and archived in the SCMREX database with both hardware and data management being upgraded. The SCMREX website (http://scmrex.cma.gov.cn) is also improved in this year with description and images (radar, satellite, and lightning) of major heavy rainfall events during the previous IOPs being added. Moreover, new results are achieved by the studies on physical mechanisms of heavy rainfall, impact of radar data assimilation on QPF, improvement of model cloud microphysics schemes,and development and evaluation of convection-permitting ensemble forecast system. In October 2016, Chief Scientist of SCMREX RDP, Dr. Luo Yali, made a progress report at the WMO Tropical Meteorological Research Working Group Meeting, which was highly praised by the experts at the meeting including the chair of the WMO Monsoon Panel, Prof. Chie-Pei Chang. The progress of SCMREX during 2013–2015 is summarized in a paper that is published in theBulletin of American Meteorological Society. (Luo Yali)

3.2 Studies on heavy rainfall during the pre-summer rainy season

Utilizing the newest, comprehensive observations collected during the SCMREX IOPs, studies by the Heavy Rainfall Research Group suggest that extreme daily rainfall in South China during the pre-summer rainy season was produced by long-lived MCSs with a line alignment of convective cells that favored persistent and large rainfall accumulation over the same region. The characteristics of the extreme-rain-producing MCSs during SCMREX that led to heavy rainfall (duration, organizational patterns, and quasi-stationary behavior) appear to be attributable to the characteristics of the environmental dynamic and thermodynamic conditions during the pre-summer rainy season. Namely, these systems occurred in prevailing low-level southwesterly monsoonal flows providing sufficient moisture, even without the presence of an LLJ, over the complex underlying surfaces in South China (e.g., land/sea contrast, and mountains near the coasts and inland facilitating continuous convective initiation), and within a series of feedbacks from MCSs (i.e., convectively generated cold out flow boundaries where continuous convective initiation usually takes place), as discussed by Wang et al. (2014) and Wu and Luo (2016). As an example, Fig.5 shows how we estimate the depth of a mesoscale cold outflow boundary based on radar observations combined with surface mesoscale analysis.The diurnal cycle of rainfall (DCR) over South China during the pre-summer rainy season is also examined.Three propagating modes accounting for the pre-summer DCR are found: (i) An eastward- or southeastwardpropagating mode occurs mostly over southwestern China that is associated with the enhanced transport of warm and moist air from tropical origin and the induced low-level convergence; (ii) A quasi-stationary mode over the east of South China appears locally in the warm sector with weak-gradient flows; (iii) An inland propagating mode occurs during the daytime in association with sea breezes along the southern coastal regions,especially evident throughout the post monsoon-onset period (Fig. 5). (Luo Yali, Bao Xinhua, Jiang Zhina)

3.3 Synoptic analysis of extreme hourly precipitation in China

Synoptic situations associated with extreme hourly precipitation over the extensive eastern China from Hainan Island to Northeast China are investigated using rain gauge data, weather maps, and composite radar reflectivity data, with both objective and subjective approaches to identify the types of synoptic patterns.Seasonal variations of hourly precipitation (0.1 mm h-1) suggest complicated regional features in the occurrence frequency and intensity of rainfall. The 99.9th percentile is thus used as the threshold to define the extremehourly rainfall for each station. The extreme rainfall is the most intense over the southern coastal areas and the North China Plain. About 77% of the extreme rainfall records occur in summer with a peak in July (30.4%)during 1981–2013. Nearly 5800 extreme hourly rainfall records during 2011–2015 are classified into four types according to the synoptic situations under which they occur: The tropical cyclone (TC), surface front,vortex/shear line, and weak-synoptic forcing. They contribute 8.0%, 13.9%, 39.1%, and 39.0%, respectively,to the total occurrence and present distinctive characteristics in regional distribution and seasonal or diurnal variations. The TC type occurs most frequently along the coasts of Southeast and South China and decreases progressively toward inland China; the frontal type is distributed relatively evenly in the east of 104°E; the vortex/shear line type shows a prominent center over the Sichuan Basin with two high-frequency bands extending from the center southeastward and northeastward, respectively; the weak-synoptic type occurs more frequently in Southeast, Southwest, and North China, and in the easternmost area of North China. Occurrences of the weak-synoptic type have comparable contributions from mesoscale convective systems and smallerscale storms with notable differences in their preferred locations. (Luo Yali)

3.4 Characteristics of cloud-to-ground lightning and its relationship with rainfall over central and eastern China

The cloud-to-ground (CG) lightning climatology and its relationship with rainfall over central and eastern China are examined, using 32 million CG lightning flashes data and TRMM (Tropical Rainfall Measuring Mission) measurements during a 6-year period of 2008–2013. Results show substantial spatial and temporal variations of flash density across China. Flash counts are the highest (lowest) in summer (winter) with the lowest (highest) proportion of positive flashes. CG lightning over North China is more active only in summer,whereas in winter CG lightning is more active only in the Yangtze River Valley. The highest CG lightning density exceeding 9 and more than 70 CG lightning days yr-1are found in the northern Pearl River Delta region, followed by the Sichuan Basin, the Yangtze River Delta and the southeastern coast in order. Lowerflash-density days occur over mountainous regions due to the development of short-lived afternoon storms,while higher-flash-density days, typically associated with nocturnal thunderstorms, appear over the North China Plain and Sichuan Basin. The highest CG lightning flashes take place in August whereas monthly convective rainfall peaks in May or July. Flash rates during the warm season are typically maximized in the afternoon hours in coincidence with a convective rainfall peak except for Sichuan Basin and its surrounding mountainous areas where a single late-night convective rainfall peak dominates. Much less lightning activity corresponds to a late night to morning rainfall peak over plains in eastern China due to the increased proportion of stratiform rainfall during that period. (Xia Rudi)

3.5 Characteristics of the temporal and spatial distributions of precipitation over Hainan Island

The causes of the temporal and spatial distributions of precipitation over Hainan Island, including the influences of environmental conditions on the temporal distribution of precipitation and the combined effect of synoptic winds, orography and sea-breeze circulation on the spatial distribution of precipitation,are investigated and discussed, based on the statistical analyses of 5-year high-resolution surface and sounding observations and numerical experiments. The results show that the high humidity and convective available potential energy (CAPE), unstable atmospheric stratification, low free convection level (LFC) and weak vertical wind shear associated with southwesterly during April–September lead to large amounts of precipitation over Hainan Island, along with the beneficial effect of sea-breeze front’s (SBF’s) convergence tendency under weak synoptic wind conditions. Pronounced precipitation is apt to occur over the leeward side of the mountain under the in fluences of weak synoptic winds, low mountain and sea-breeze circulation.Moreover, different propagation features are shown for precipitation depending on different synoptic wind directions. (Liang Zhaoming)

3.6 Analysis of the detailed structure of the squall line over South China

Based on dual-Doppler weather radar retrieved wind, the mechanism and 3D structure of the squall line on 24 April 2007 in Guangdong Province were analyzed. The conceptual model of the squall line was also developed. In the wide trailing stratiform region, the rear-to-front cold in flow enters the squall line below the altitude of 3 km. The storm-relative front-to-rear warm flow enters the squall line from the lower and middle level of the leading edge. Above 7.5 km height, part of the front-to-rear in flow moves forward and part of the in flow slopes gradually into the trailing stratiform region. (Zhou Haiguang)

4 Typhoon research

4.1 The relationship between sea surface temperature and maximum potential intensi fication rate of tropical cyclones over the North Atlantic

An empirical relationship between sea surface temperature (SST) and the maximum potential intensification rate (MPIR) of tropical cyclones (TCs) over the North Atlantic is developed based on best track TC data and observed SST during 1988–2014. Similar to the empirical relationship between SST and the maximum potential intensity (MPI) of TCs previously documented, results from this study show a nonlinear increasing trend of MPIR with SST. That is the IR showing a general increasing trend with increasing SST as well with a more rapid increasing trend with higher IR when SST is greater than 27 ℃.The analysis shows that about 29% of Atlantic TCs reach 50% of their MPIR, and only 6% reach 80% of their MPIR at the time when they are at the lifetime maximum intensification rate. Moreover, a TC tends to have a larger intensification rate during its lifetime when it is located in a higher SST region and lower VWS, indicating that SST is not only critical for TC IR but also determines the MPIR. In addition, a theoretical basis for the MPIR has also been provided based on a previously constructed simplif ed dynamical system for TC intensity prediction, and the theoretical result is well in agreement with the observational f tted MPIR with longer data records over a wide range of SST. (Xu Jing, Wang Yuqing)

4.2 A statistical analysis of the relationship between UTCL and tropical cyclone track and intensity change over Western North Paci fic

The geographical and temporal characteristics of upper tropospheric cold lows (UTCLs) and their relationship with tropical cyclone (TC) track and intensity changes over the Western North Pacific (WNP)during 2000–2012 are examined using the best track TC data and global meteorological re-analysis data. An analysis of the two datasets shows that 73% of 346 TCs coexist with UTCLs, and 21% of them coexist with TCs within an initial cut-off distance of 15o, within which interactions could occur. By selecting those coexisted systems within this distance, we find possible in fluences of UTCLs on TC track and intensity changes,depending on their relative distance and on the sectors of UTCLs where TCs are located. Results show that the impact of UTCLs on TC directional changes are statistically insignificant when averaged within the 15o radius.However, left-turning TCs within 5o distance from the UTCL center tend to occur abrupt turnings. Results also show that TCs seem to interact with an UTCL during their early development stages. Intensifying (weakening)TCs are more distributed in the southern (northern) sectors of UTCLs. In addition, rapid intensifying TCs take place in the east-southeastern and south-southwestern quadrants of UTCLs, whereas rapid weakening cases appear in the western semicircle of UTCLs (Fig. 6).(Li Ying， Wei Na, Zhang Dalin)

5 Lightning research

5.1 Study on the relationship between lightning activity and structure of convective clouds in Qinghai-Tibet Plateau

Based on the observation of the home-grown Total-Sky Cloud Imager, the cloud cover and cloud type over Shigatse are analyzed and found to change with seasons. Meanwhile, the dataset of Precipitation Features(PFs) derived from the observation of TRMM satellite is introduced to study the structures of clouds with lightning and without lightning over the Tibet Plateau. The area of PFs with lightning is an order of magnitude larger than that of the PFs without lightning. The horizontal area of PFs with lightning is generally above 1400 km2over the northeastern plateau, while the minimum is below 500 km2over the southeast (centered near 29°N, 97°E). Over the plateau, cloud height of PFs with lightning is 2?4 km higher than that of PFs without lightning. The maximum cloud height of PFs with lightning is over southern-central plateau with the value above 12 km, and minimum height is less than 10 km near the southern Tibetan region. The maximum height of 20 dBz radar reflectivity over the plateau is similar and slightly smaller than that over the plain to the south of Himalaya region, but the maximum height of 40 dBz radar reflectivity over the plateau is higher than that over the plain. PFs with lightning over western and northeastern plateau have larger mean lightning density than in other regions. (Zhang Yijun, Zheng Dong, Lü Weitao, Meng Qing, Yang Jun, Yao Wen, Ma Ying, Wang Fei)

5.2 Assimilation of special observation data and research on detecting and forecasting methods for severe thunderstorms

(1) The empirical relationship between flash rate, water vapor mixing ratio and graupel mixing ratio was used to adjust the model relative humidity, which was then assimilated using the three-dimensional variation data-assimilation method in WRF-3DVar system in cycling mode with 10 min intervals. A short-range lightning prediction platform was constructed based on the WRF-Electric model. Two flood season prediction experiments were carried out and the prediction results were preliminarily assessed. The basic scheme which blended the Lightning Nowcasting and Warning System (CAMS_LNWS) and mesoscale numerical weather prediction was designed to improve the 0?12 hour lightning prediction (Fig. 7). (Xu Liangtao, Yao Wen, Zhang Rong)

(2) Based on the comprehensive analysis on the data of radar and lightning from 10 mesoscale convective systems (MCSs), it has been found that the first return stroke currents of stratiform cloud-to-ground (CG)lightning flashes are usually greater than that of convective lightning flashes. Most of stratiform CG lightning flashes strike the ground under the verge of or around the area in stratiform region of MCS, where the reflectivity core (≥30 dBz) locates in the height range of 3?6 km. This characteristic of reflectivity core is consistent with that of brightband. It suggests that the charge structure of the stratiform region with brightband may have an important in fluence on initiation or propagation of stratiform lightning. This result provides a vital evidence for research of the relationship between stratiform lightning and brightband and a theoretical basis for the development of stratiform CG lightning warning (Fig. 8). (Wang Fei)

5.3 The temporal and spatial relationship between the initial characteristics of lightning and the thunderstorm structure

The location method and technology of lightning Low-Frequency Electric-f led Detection Array (LFEDA),which is running in Guangdong with the aim to detect the lightning activity in three-dimensions, were furtherimproved. Based on LFEDA, we conducted the lightning observational experiment, obtained good data and then investigated the performance of LFEDA and obtained some preliminary results. The LFEDA shows a fine performance in the location of the triggered lightning flashes (TLFs) which were carried out in the inner of the network of the LFEDA, with the detection efficiency for TLFs and return strokes being 100% and 95%,respectively, and the average location error being 102 m. The combination of the three-dimensional locations of the total lightning during the evolution of thunderstorms with the radar echo also support the reliable performance of LFEDA. In addition, two examples including an intra-cloud lightning and the leader of a cloudto-ground lightning are exhibited, while some parameters associated with the initial propagation of channels are also counted according to the location data. The analysis proves that LFEDA is capable of describing the three-dimensional channel of lightning to some extent.

Flash initiations within a supercell cluster during 10–11 May 2010 in Oklahoma were investigated based on observations from the Oklahoma Lightning Mapping Array and the Norman, Oklahoma, polarimetric radar(KOUN). The flash initiations at positions dominated by graupel, dry snow, small hail and crystals accounted for 44.3%, 44.1%, 8.0% and 3.0% of the total flashes, respectively. During the tornadic stage of the southern supercell in the cluster, flash initiations associated with graupel occupied the main body, the right flank and the forward flank of the supercell, while those associated with dry snow dominated the outskirts of the adjacent forward anvil, right anvil and rear anvil. The flash initiations associated with small hail were concentrated around the main updraft, particularly toward its front side. Highly dense flash initiations were located in the regions overlying the differential reflectivity (ZDR) arc and right anvil. The average initial height of the flashes decreased gradually from the rear to the front and from the right to the left flanks, while the height range over which initiations occurred reached a maximum at the front of the updraft. The flashes that were initiated in the adjacent forward anvils were the largest on average, followed by those in the regions ahead of the updraft and near the ZDR arc. This study supports the concept of charge pockets and further deduces that the pockets in the right anvil are the most abundant and compact due to the frequent flash initiations, small-sized flashes and thin layers including flash initiations. (Zheng Dong, Zhang Yang, Zhang Yijun, Meng Qing, Zhang Wenjuan, Xu Liangtao, Huang Zhigang)

5.4 Model study on the relationship between the updraft and the charging and discharging processes in thunderstorms

Using a 3D charging-discharging numerical model, the relationship between the updraft and the charging and discharging processes in thunderstorms was analyzed. The results show that the enhancement of updraft restricts the strengthening of lightning activity (here represented by the neutralized charge rate of lightning flashes per minute) while the promoting effect of updraft to lightning activity is still dominant as observations. In the simulation case, the non-inductive charging process with high charging efficiency always occurs within or near the updraft region with the updraft speed less than 20 m s-1. In addition, the height of updraft core agrees with the height of reversion temperature roughly in most of lightning activity. It can be used to separate the regions within which graupel is charged with opposite polarity through the non-inductive charging process. (Wang Fei)

5.5 Dynamical processes and structural evolution in severe thunderstorms

The developments and especially convective initiation (CI) of two local severe storms over the Beijing metropolitan region under unfavorable larger-scale conditions are examined using various observations and high-resolution model simulations. Results reveal that the important roles of the UHI effects, mountain morphology, and convectively generated pressure perturbations in determining the CI location and timing of isolated thunderstorms during the summer months. An analysis of larger-scale environments associated with high rainfall rates and high frequency of cloud-to-ground (CG) lightning flashes (HRHL), high rainfall ratesand low frequency of CG lightning flashes (HRLL), and low rainfall rates and high frequency of CG lightning flashes (LRHL) shows that the upper-level jet with anomaly divergence on its right side and the western Pacific subtropical high were favorable for HRHL and HRLL events. The horizontal wind shear and convective instability in the lower troposphere were important for the three categories of events, but their intensities were the weakest in LRHL events. Front activities related closely only to HRHL events. For events with high lightning activities, the lower atmosphere was warmer and wetter than its surrounding areas. Thunderstorm events with high frequency of flash needed better lifting condition, while HRLL events needed small convective inhibition. LRHL events also needed small 0?6 km vertical wind shear and HRHL events needed large CAPE.

Observational and modeling studies are performed to confirm the types of precipitation particles of lightning initiation, and the associated density, altitude and vertical extent in supercell thunderstorms. A conceptual model was developed to describe the relationship between the characteristics of lightning initiation and vertical structures of the supercell storms. It is also found that the climatology of CG lightning activity with strong or weak electric currents differs significantly in their own characteristics and spatio-temporal structures, depending upon the season and underlying surface conditions. (Zhang Dalin)

5.6 Research of lightning discharge process, development of lightning detection technology and conduction out field experiment

During Guangdong Comprehensive Observation Experiment on Lightning Discharge (GCOELD),significant progress in success rate of artificial triggered lightning, detailed observations of lighting discharge process, observations of total flash in thunderstorm and research on lightning physical mechanism has been gained. The specific progress is as follows. (1) The numbers and success rate of triggered lightning are 13 and 72%, respectively, both reaching relatively high levels. (2) Continuous interferometer is developed for detailed positioning of lightning channel, and the corresponding system consisting of a three antenna array is set up, which helped to describe the process of lightning discharge in a detailed and high time-resolution way.(3) We have made a further improvement of LFEDA (Low Frequency Electric-field Detection Array), with which, from June to November, acquired different impulse information during intra-cloud lightning, cloud to ground lightning and NBE events in Conghua. By analyzing these acquired data, we made it possible to get a preliminary 3-dimension positioning result for the total flash. Besides, we have investigated several installation sites for LEFDA in the plateau area, and also built 2 substations for testing. (4) A new sight was built for the development of irregular impulse and precursor impulse related to the initiate of leaders; at the same time, the relevance between M-component and continuous current in large charge transfer progress was discovered. (5)We have significantly improved the optical observation ability for the high-speed leader development process and the ability to record the completed electromagnetic radiation field signals of different magnitudes as well.Due to these updates, we revealed the detailed characteristics of leader development process, meanwhile displayed the two basic connection modes for the downward negative leaders and upward connecting leaders in negative cloud to ground flashes (Fig. 9). (Lü Weitao, Zhang Yang, Zheng Dong, Zhang Yijun, Yao Wen, Ma Ying, Huang Zhigang, Xu Liangtao, Qi Qi)

6 Model and reanalysis data

6.1 Research on weather-climate uni fied model

After the survey of the current international trend of dynamical core development, we selected the icosahedral mesh as the basis of dynamical core development. An icosahedral mesh generator and solvers ofthe transport and shallow water equations are developed. A conservative Two-step Shape-Preserving Advection Scheme (TSPAS) is generalized on the icosahedral mesh. Results show that this scheme works well in such an unstructured grid. The performance is comparable to the previous prototypes on the rectangular mesh.For model physical parameterization, a new correlated k-distribution radiation scheme (BCC_RAD) was incorporated to improve the radiation energy imbalance at the top of model atmosphere (TOA). Results show that the TOA residual energy is greatly reduced, and the shortwave cloud radiative forcing over East Asia is also improved by using BCC_RAD scheme. Based on the NCAR CESM model and the coupler CPL7 and replacing the atmospheric and oceanic components, we developed a new coupled system with new atmosphere,ocean, land and ice components, which allow us to master the high-resolution coupled simulation technique.The MPI-M hydrological model was incorporated into the coupled model to achieve the runoff into the ocean,thus close the global water cycle and the model emerges as a complete climate system model. Based on the previous version of the coupled model, we introduced the EnOI-IAU assimilation scheme developed by LASG/IAP to assimilate the observed temperature and salinity prof le data (weakly coupled assimilation) and perform decadal climate prediction experiments (Fig. 10?11). (Zhang Yi, Chen Haoming, Rong Xinyao, Li Jian)

6.2 Program for tackling key problems in East Asia regional atmospheric reanalysis data

The system for East Asia regional atmospheric reanalysis data has been built and some preliminary tests were made. Based on the system, long term simulations from June to August in 2014 were accomplished,and a background error (BE) covariance matrix was built based on the simulations. Besides, the new BE was compared with the default BE which is given by the Gridpoint Statistical Interpolation (GSI) system.In addition, the assimilation structure is optimized, and a series of assimilation tests for East Asia regional atmospheric reanalysis data have been launched. In order to show the characteristics of the East Asia regional atmospheric reanalysis data, the key datasets of sounding, GPS/Met, satellite, radar observations, which are not included in the GTS (Global Telecommunication System), were assimilated. A lot of data assimilation experiments were launched by combining the data with field experiments. A whole month experiment was carried out by introducing the data from the third Tibetan Plateau Atmospheric Scientific Experiment(TIPEX-Ⅲ). The cloud microphysical properties over South China have been investigated, and the East Asia regional atmospheric reanalysis data system has been optimized using the observations from the South China Monsoon Rainfall Experiment (SCMREX). (Liang Xudong, Yin Jinfang, Chen Feng, Liu Ying, He Huizhong,Zhou Haibo, Hao Shifeng)

7 Information network support

Upon completion of the CAMS,s keystone project “Scientific research data sharing platform”, we have integrated the South China Monsoon Rainfall Experiment (SCMREX) data sharing website and the third Tibetan Plateau Atmospheric Scientific Experiment website, in use since the 2016 rainy season. We have also completed more than 10 information security check jobs. Building Intensive website group upgraded and expanded high capacity storage system to improve data service support. We have completed the operational maintenance, management and technical support of the CAMS,s information system, ensuring zero security issues (Fig.12). (Gao Mei, Zhang Wenhua, Li Bin, Li Feng, Zhao Shenghua, Zhu Kongju)