大氣探測與雷電防護

大氣探測與雷電防護研究進展

2010年，大氣探測所緊跟雷電監(jiān)測、預(yù)警、防護以及地基云觀測的國際研究前沿，不斷開拓創(chuàng)新，在一些關(guān)鍵技術(shù)和關(guān)鍵科學(xué)問題方面取得顯著的進步，主要成果如下。

1. 在觸發(fā)閃電回擊電流以及自動氣象站雷電防護研究方面獲得突破

閃電回擊過程是雷電防護的主要對象，回擊電流參數(shù)對雷電防護理論和標準研究以及防護產(chǎn)品檢測具有重要參考價值。大氣探測所多年來在廣東開展了人工觸發(fā)閃電試驗，并不斷提高電流測量技術(shù)。以多年電流采集數(shù)據(jù)為基礎(chǔ)，統(tǒng)計分析了閃電放電過程的回擊電流特征。結(jié)果顯示，電流峰值的幾何平均值為16.59 kA，半峰寬度的幾何平均值是21.91 μs，10%～90%平均陡度的幾何平均值為29.61 kA·μs-1，最大陡度的幾何平均值是55.89 kA·μs-1，回擊之后1 ms內(nèi)的電荷轉(zhuǎn)移為1.61 C，回擊之后1 ms的比能量為6.60×103A2·s。廣東觸發(fā)閃電試驗中的回擊電流平均而言比其他研究中報道的回擊過程要強。研究發(fā)現(xiàn)，峰值電流與10%～90%的平均陡度有一定的線性相關(guān)關(guān)系（R2=0.64），與最大陡度有較好的線性相關(guān)關(guān)系（R2=0.74），與回擊后1 ms內(nèi)的電荷轉(zhuǎn)移有強的冪函數(shù)關(guān)系（R2=0.89），與回擊之后1 ms內(nèi)的比能量有顯著的對數(shù)函數(shù)關(guān)系（R2=0.92）。此外，還觀測到一次高度觸發(fā)閃電的初始回擊過程電流（以前的報道中只有4次這樣的電流被測量，但只有2次在該階段的電流數(shù)據(jù)質(zhì)量較高而被分析），它具有較小的半峰寬度（2.12 μs），電荷傳輸（36.37 mC）和比能量（181.56 A2·s），但是其他的參數(shù)與前面統(tǒng)計的回擊過程接近。

基于觸發(fā)閃電，大氣探測所還開展了真實雷電環(huán)境中自動氣象站架空電源線和垂直信號線感應(yīng)電壓和電流的特征研究。結(jié)果發(fā)現(xiàn)，架空電源線中與回擊（電流范圍-6.67～-26.47 kA）對應(yīng)的感應(yīng)電壓脈沖峰值電流顯示出雙極性的特征。次峰和主峰的感應(yīng)電壓范圍分別為0.99～4.47 kV和-4.98～-1031 kV。脈沖持續(xù)時間111.00～155.40 μs。依據(jù)主峰之后波形恢復(fù)的形狀，脈沖可以分為慢恢復(fù)和震蕩恢復(fù)兩種類型。在風速垂直信號上對應(yīng)回擊過程的感應(yīng)電壓波形也表現(xiàn)出兩種類型，一種在主峰后有次峰，一種在主峰后無次峰，所有的主峰都呈現(xiàn)“V”形結(jié)構(gòu)。垂直信號線上感應(yīng)電壓脈沖的半峰寬度、10%～90%上升時間、10%～90%平均陡度和脈沖峰值（主峰：-0.41～-3.10 kV；次峰：46.59 ～1861.17 V）要比架空電源線上的感應(yīng)電壓脈沖小很多。感應(yīng)電壓的幅度與回擊電流的幅度沒有明顯的比例關(guān)系。通過連接電源線的電涌保護器的感應(yīng)電流范圍在-0.22～-1.64 kA，在電流脈沖之后的殘壓持續(xù)時間比在高電壓試驗中模擬記錄的殘壓時間長很多。通過這個研究，對自動氣象站遭雷擊損壞的機理有了更清楚的認識，也為自動氣象站的雷電防護提供了基礎(chǔ)參數(shù)。

高度觸發(fā)閃電（T201005）的光學(xué)照片（通道閃擊到連接電流測量設(shè)備的引雷針上）Image shot by digital camera of the lower part of the altitude triggered lightning T201005 (the channel struck to the lightning rod connected with the current measuring equipment in series).

觸發(fā)閃電(T200804)在采集器前端產(chǎn)生的通過SPD的殘壓和感應(yīng)電流Waveforms of residual voltage and induced current produced by return strokes of T200804 through the SPD at the front of the acquisition device

2. 基于觸發(fā)閃電對地閃定位系統(tǒng)的探測效能進行了初步評估

閃電定位系統(tǒng)（LLS）是目前最主要的雷電監(jiān)測手段，在雷電預(yù)警以及雷電防護等工作中起著重要的作用，但其性能指標大多基于理論分析，客觀檢驗工作一直比較缺乏。人工觸發(fā)閃電由于時間地點確定，電流可測，在閃電定位系統(tǒng)的效能客觀評估方面具有自身的獨特優(yōu)勢。大氣探測所利用廣東從化人工觸發(fā)閃電近距離光電觀測的部分數(shù)據(jù)，分析了廣東電網(wǎng)閃電定位系統(tǒng)對人工觸發(fā)閃電事件及其回擊過程的探測效率和探測精度。結(jié)果表明，對于14次包含有回擊過程的人工觸發(fā)閃電事件，閃電定位系統(tǒng)共探測到13次，探測效率約為93%（即13/14）；對于能夠利用觀測資料確認的62次回擊過程，閃電定位系統(tǒng)共探測到26次，探測效率約為42%；參與定位的站數(shù)≥3個的回擊記錄有24次，其中有21次回擊過程屬于接地點已知的地面觸發(fā)閃電事件，閃電定位系統(tǒng)對這些回擊過程接地點位置的平均定位誤差約為760 m；對于其中9次有雷電流直接測量結(jié)果的回擊過程，閃電定位系統(tǒng)雷電流峰值反演結(jié)果的相對誤差約為14%。

3. 深入認識了雷暴活動中的特殊放電——袖珍云閃的特征，并在臺風閃電活動特征研究方面取得初步進展

袖珍云閃（CID）是近年來大氣電學(xué)研究的一個熱點，大氣探測所利用位于廣州從化和重慶兩地的VLF/LF多站閃電探測系統(tǒng)觀測到的CID，全面分析了CID不同于常規(guī)地閃和云閃的多方面的性質(zhì)，并重點比較了正CID和負CID兩者之間的差異。主要得到了以下幾方面結(jié)論：CID能夠產(chǎn)生非常大的電場變化，總體上比地閃回擊產(chǎn)生的電場變化更大；負CID產(chǎn)生的電場變化總體上又比正CID大；CID的發(fā)生具有一定的孤立性，這種孤立性主要指在CID發(fā)生之前有其他放電事件的概率非常小。而正CID與負CID相比，前者更有可能引發(fā)其他的放電事件。CID產(chǎn)生的低頻輻射在地面與電離層之間會發(fā)生反射，反射信號被測站記錄到就形成電離層反射脈沖，利用反射脈沖和原脈沖之間的時間差關(guān)系，發(fā)展了一種對CID實現(xiàn)三維定位的新方法，該方法能夠?qū)^大范圍內(nèi)的CID實現(xiàn)較為準確的三維定位，利用這一點計算了大量正、負CID的放電高度，發(fā)現(xiàn)正CID主要發(fā)生于7～15 km，而負CID主要發(fā)生于15～18 km。CID與雷暴強度之間存在著一定的聯(lián)系，總的來看，CID頻數(shù)隨著雷暴的增強有一定的增多趨勢。通常情況下雷暴過程主要產(chǎn)生正CID，但隨著雷暴的增強，負CID的比例也有增大的趨勢。綜合以上正CID與負CID之間的差異，可以認為負CID是一種更為特殊的放電事件。

隨著閃電探測技術(shù)的發(fā)展，越來越多的試驗和研究開始關(guān)注熱帶氣旋中的閃電活動。利用全國閃電監(jiān)測網(wǎng)獲取的地閃定位資料，大氣探測所初步分析了1999—2010年登陸我國廣東地區(qū)的33個熱帶氣旋的閃電活動時空分布特征。研究發(fā)現(xiàn)，不同強度熱帶氣旋閃電活動存在差異，成熟臺風閃電活動存在明顯徑向分布特征：閃電主要發(fā)生在200～500 km的外雨帶區(qū)域，60～200 km的內(nèi)雨帶區(qū)域閃電活動較少，臺風中心至60 km的眼壁區(qū)域則又呈現(xiàn)出閃電活動的密集區(qū)。內(nèi)雨帶具有層狀云結(jié)構(gòu)特性，具有較高的正地閃比例。眼壁閃電對臺風強度及其變化具有一定指示作用，臺風中心風速快速增大時，眼壁閃電爆發(fā)，閃電爆發(fā)幾小時后中心風速達到極大值、中心氣壓最低。臺風眼壁閃電的爆發(fā)，預(yù)示著臺風將快速增強，對臺風對流結(jié)構(gòu)及其變化具有重要指示作用。利用多普勒雷達和TRMM衛(wèi)星觀測資料，研究了臺風Molave（0906）閃電活動的時空變化與臺風對流結(jié)構(gòu)的演變關(guān)系，對臺風不同區(qū)域的對流結(jié)構(gòu)和水凝物粒子分布進行了對比。結(jié)果表明，外雨帶比內(nèi)雨帶具有更強烈的反射率因子和上升氣流，相同反射率值達到的高度，外雨帶高于內(nèi)雨帶。云水、可降水、云冰和可降冰4種水凝物粒子的密度值和高度分布，外雨帶明顯大于內(nèi)雨帶。

正、負袖珍云閃CID的高度分布（正CID主要出現(xiàn)在7～15 km高度，負CID主要出現(xiàn)在15～18 km高度）Height distribution of the CIDs, (Positive CIDs mainly occur at the height of 7-15 km while negative CIDs mainly occur at the height of 15-18 km)

臺風“莫拉菲”（0906）閃電活動和雷達回波疊加圖Overlay of lightning activities and radar reflectivity of Typhoon Molave

4. 雷電監(jiān)測預(yù)警系統(tǒng)平臺獲得進一步完善和推廣，并服務(wù)于上海世博會的氣象保障

2010年，大氣探測所進一步完善了雷電監(jiān)測和臨近預(yù)警系統(tǒng)平臺，針對雷電業(yè)務(wù)的需求，改進雷電臨近預(yù)警算法，并更新了平臺下雷電實時監(jiān)測系統(tǒng)、雷電監(jiān)測分析系統(tǒng)、雷電臨近預(yù)警系統(tǒng)以及雷電預(yù)警產(chǎn)品評估系統(tǒng)的功能。新平臺在2010年汛期的雷電預(yù)警業(yè)務(wù)中發(fā)揮了重要作用，全天候向中國天氣網(wǎng)提供雷電監(jiān)測預(yù)警公共服務(wù)產(chǎn)品。更新后的雷電臨近預(yù)警系統(tǒng)在北京、湖北、湖南、青海等地開展了運行試驗，大氣探測所同步提供技術(shù)支持。以此為基礎(chǔ)，2010年10月16—17日在成都開展了第4期的雷電臨近預(yù)警技術(shù)交流會，對各地典型雷暴天氣過程的預(yù)警預(yù)報進行分析和交流，有效提高了雷電預(yù)警的服務(wù)能力。同時還對改進后的雷電臨近預(yù)警系統(tǒng)進行了應(yīng)用推廣培訓(xùn)，對升級情況和操作進行了詳細的介紹。

針對上海世博會對雷電預(yù)警的要求，大氣探測所先期對雷電臨近預(yù)警系統(tǒng)進行了必要的算法升級，升級后的雷電臨近預(yù)警系統(tǒng)CAMS_LNWS運行穩(wěn)定、界面友好，能夠快速生成0～1 h雷電發(fā)生概率、重點區(qū)域雷電發(fā)生概率以及雷電活動區(qū)域移動趨勢等產(chǎn)品，為上海市氣象局雷電預(yù)警信號的發(fā)布提供重要參考。在雷電臨近預(yù)警系統(tǒng)參與上海世博會服務(wù)期間，大氣探測所研究人員全程跟蹤，提供不間斷的技術(shù)支持，為世博會氣象保障做出了自己的貢獻。

5. 統(tǒng)計多年雷電災(zāi)害數(shù)據(jù)，對我國雷災(zāi)特點有進一步認識

全國雷電災(zāi)害發(fā)生事故排序圖（a）和全國雷電災(zāi)害人員傷亡排序圖（b）The rank of each province in the number of lightning-related damages (a) and the rank of each province in the number of lightningrelated casualties (b) in China

利用1997—2010年全國雷電災(zāi)害數(shù)據(jù)庫資料，分析研究了我國雷電災(zāi)情的時空分布等特征。我國雷電災(zāi)害多發(fā)生在南部地區(qū)和東部沿海地區(qū)，7—9月是雷災(zāi)多發(fā)季節(jié)。從年際變化上，1997—2007年雷電災(zāi)害呈上升趨勢，2008年后有所下降。每百萬人每年雷擊死亡率和受傷率分別為0.31和0.28，且傷亡人數(shù)以農(nóng)村居多。為了揭示我國不同區(qū)域雷擊致人傷亡的易損度，采用閃電密度、人員傷亡頻數(shù)、人口數(shù)和區(qū)域面積4個指標進行聚類分析，給出我國雷擊致人傷亡的6類風險區(qū)劃結(jié)果。結(jié)果表明，廣東、上海和海南為1類地區(qū)，雷擊致人傷亡易損度特征值高達每萬平方公里6.89人；內(nèi)蒙古、新疆和西藏為易損度最低的6類地區(qū)，每萬平方公里人員傷亡0.14人，分類結(jié)果較好地反映了雷擊致人傷亡事件的區(qū)域易損度特征。

6. 雷電光、電、磁探測設(shè)備研制和應(yīng)用實現(xiàn)較大突破

光、電、磁信號是雷電發(fā)生過程中所產(chǎn)生的最基本特征參量，其有效探測已經(jīng)成為雷電物理以及防護研究的必備手段。大氣探測所緊跟雷電光、電、磁探測技術(shù)的前沿動態(tài)，總結(jié)了以往探測中存在的問題，針對光電磁探測設(shè)備的集成化及自動化，在探測平臺集成及應(yīng)用方面進行了研究和開發(fā)，其主要成果集中在以下幾個方面：（1）研制開發(fā)了雷電光輻射探測裝置和光觸發(fā)裝置，成功獲得了閃電絕對光強和相對光強參量，實現(xiàn)了基于閃電光輻射信號特征的設(shè)備同步觸發(fā)。（2）研制開發(fā)了雷電電場變化和三維磁場探測裝置，獲得了電場變化和三維磁場數(shù)據(jù)，實現(xiàn)了電場變化設(shè)備的標定。（3）研制開發(fā)了雷電集成化電磁場探測平臺，并進一步集成了光輻射場的探測功能，成功獲得了閃電光電磁信號的同步觀測信息，實現(xiàn)了光、電、磁信號的自動同步測量，提高了獲取數(shù)據(jù)的一致性。（4）基于雷電的電、磁集成化探測，研制開發(fā)了多功能單站閃電探測定位系統(tǒng)，成功獲取了閃電電磁信號波形和閃電定位結(jié)果，實現(xiàn)了波形獲取和定位輸出一體化，能夠同時滿足科研和業(yè)務(wù)的雙重需求。

多功能單站探測定位系統(tǒng)及其顯示界面Multifunctional single-station lightning detection system and the display interface

7. 地基云自動化觀測技術(shù)和系統(tǒng)開發(fā)取得顯著進展

“地基云自動化觀測關(guān)鍵技術(shù)研究和系統(tǒng)研制”是中國氣象科學(xué)研究院基本科研業(yè)務(wù)費重點項目，其目標是研制具有我國自主知識產(chǎn)權(quán)的地基云自動化觀測系統(tǒng)，建立綜合應(yīng)用可見光數(shù)字云圖和云底高度測量結(jié)果的地基云自動化觀測技術(shù)和方法，開發(fā)穩(wěn)定可靠的軟硬件系統(tǒng)，為實現(xiàn)地基云的全面自動觀測奠定堅實的基礎(chǔ)。項目通過3年的實施，截止2010年已取得如下成果：(1) 解決了地基全天空云觀測軟硬件系統(tǒng)的關(guān)鍵技術(shù)問題，包括攝像單元兩種遮光結(jié)構(gòu)的設(shè)計與實現(xiàn)以及地基全天空云圖自動曝光控制的實現(xiàn)。研發(fā)出的樣機經(jīng)歷了野外試驗的檢驗，能夠長期穩(wěn)定可靠地運行，自動獲取全天空可見光云圖并計算得到總云量。(2) 建立了基于自適應(yīng)閾值、局部閾值插值以及混合閾值等的云檢測算法，提升了云檢測的準確度；建立了一個初步的標準云圖數(shù)據(jù)庫和多種云圖特征提取算法，并開發(fā)了基于內(nèi)容的數(shù)字云圖檢索系統(tǒng)，為下一步開展云狀識別方法研究奠定了基礎(chǔ)。(3) 開發(fā)了多套專用軟件，如魚眼圖像校正軟件、云狀人工識別分類軟件、數(shù)字云圖檢索軟件等，為順利開展地基全天空云觀測試驗、建立云圖數(shù)據(jù)庫以及進行云檢測和云狀識別方法研究等提供了條件。

項目組開發(fā)的地基全天空云觀測系統(tǒng)在北京市觀象臺、廣東省從化市氣象局、廣東省陽江市氣象局和中國氣象科學(xué)研究院開展了較長時間的觀測試驗，積累了豐富的地基云圖資料。在2010年WMO第8屆國際探空儀系統(tǒng)對比試驗中，地基全天空云觀測系統(tǒng)提供了相應(yīng)的產(chǎn)品，得到了較好的應(yīng)用。

架設(shè)在北京市觀象臺的地基全天空云觀測系統(tǒng)設(shè)備和部分結(jié)果示例The TCI device installed in the Beijing Meteorological Observatory and some sample results

Atmospheric Detection and Lightning Protection

Advances in Atmospheric Sounding and Lightning Protection Researches

In 2010, the Institute of Atmospheric Sounding kept close in step with the international research front of the lightning monitoring, warning and protection and ground-based automatic cloud observation, kept on exploring and innovating, and made great progress in some key technologies and scientif c points, which is summarized as follows.

1. Obtain a major breakthrough in the research of return stroke currents of triggered lightning and the lightning protection of the automatic weather station

The return stroke process of lightning discharge is the primary object of lightning protection. The parameters about the return stroke currents of lightning are of great value for the research on the theory and standard of lightning protection and the testing of the lightning protection products. The Institute of Atmospheric Sounding has conducted the Artif cially Triggering Lightning Experiment in Guangdong for many years and constantly advanced the current measurement technology. Based on the current data, the characteristics of the return stroke currents were investigated. The geometric mean (GM) value of the peak value current (IPeak) was 16.59 kA, the half-peak width (tHPW) was 21.91 μs, the 10%～90% risetime (t10%～90%) was 0.45 μs, the 10%～90% average gradient (G10%～90%) was 29.61 kA μs-1, the maximum gradient (GMax) was 55.89 kA μs-1, the charge transfer in 1 ms after the beginning ofthe return strokes (Q1ms) was 1.61 C, and the action integral in 1 ms after the beginning of the return strokes (AI1ms) was 6.60×103A2s. The RSs in GCOELD were, on average, stronger than those reported by other authors referenced in this study. The peak value current had a general good linear relation with G10%～90%(determination coefficient (R2=0.64), a good linear relation with GMax(R2=0.74), a strong power function relation with Q1ms(R2=0.89), and an excellent logarithmic function relation with AI1 ms (R2=0.92). Additionally, the current of the initial-stage return stroke (ISRS) of an altitude TLF was analyzed (as we know, only four ISRSs were reported in previous studies, of which, only two were investigated with their high-quality current waveforms) and found to have small tHPW(2.12 μs), charge transfer (36.37 mC) and action integral (181.56 A2s), but was similar to other RSs for all other parameters.

Using the triggered lightning as a tool, the Institute of Atmospheric Sounding also do a piece of research on the characteristics of the induced voltage and current generated by triggered lightning on an overhead power line and on the vertical signal line of an automatic weather station (AWS). Pulses of induced voltage on the overhead power line corresponding to the return strokes with the peak currents ranging from -6.67 to -26.47 kA showed bipolar features. Sub-peaks and main peaks ranged from 0.99 to 4.47 kV and from –4.98 to –10.31 kV, respectively, and pulse durations ranged from 111.00 to 155.40 μs. The pulses were classified into two types according to the shape of the recovering waveform following the main peaks: slow-recovery type and oscillating-recovery type. The induced voltage waveforms corresponding to the return strokes on the vertical signal line of wind speed were also of two types: with and without a sub-peak after the main peak. All the main peaks were “V” shaped. Values of halfpeak widths, 10%–90% risetimes, 10%–90% average gradients, and peaks of pulses (main peaks, –0.41 to –3.10 kV; sub-peaks, 46.59 to 1861.17 V) on the vertical signal line were much smaller than those of pulses on the overhead power line. The amplitudes of the induced voltage were out of proportion with the amplitudes of the return stroke currents. The peaks of induced currents through the surge protection device (SPD) embedded on the power line ranged from –0.22 to –1.64 kA. The duration of residual voltage after the end of the current pulses was longer than that recorded in high-voltage experiments. Through this study, we got a better understanding on the mechanism of the AWS being destroyed by lightning. The results provided basic parameters for the research of the AWS’s protection from lightning.

2. Estimate the performance of the cloud-to-ground lightning location system by using the triggered lightning as the real source

Lightning location system (LLS), as the main tool for lightning monitoring, plays an important role in lightning warning and lightning protection. However, the performance index of LLS is always determined by theoretical analysis, there being less testing based on an objective method. Artificial triggered lightning, with its clear triggering time and location and measurable current, is of unique advantages in objectively estimating the performance efficiency of the LLS. Utilizing the near-distance optical and electrical observation of the triggered lightning, the Institute of Atmospheric Sounding tested the detection efficiency and detection accuracy of the LLS operated by the electricity department of Guangdong. The results show that the LLS detected 13 of 14 triggered lightning f ashes, the detection eff ciency of the LLS on lightning f ash being calculated to be about 93%. For the 62 return stroke processes determined by the observation data, only 26 of them were detected by the LLS, the detection efficiency on the return stroke being about 42%. A total of 24 of 62 return stroke processes were detected by 3 or more sensors of the LLS. By comparing the detection data of the LLS with the real location of a total of 21 return stoke processes, the average location error of the LLS was found to be about 760 m. The LLS showed a relative error of 14% in the inversion of the current peak value, by comparing with the current data measured in the base of 9 return stroke channels.

3. Get a deep understanding on the characteristics of a kind of special discharge in the thunderstorms —compact intracloud discharges, and make some progress in the study on the lightning activities in typhoons

Compact intracloud discharge (CID) is a hot research topic of atmospheric electricity in recent years. On thebasis of a large amount of CIDs recorded by VLF/LF lightning location networks in Guangzhou and Chongqing, the Institute of Atmospheric Sounding analyzed the multiple characteristics of CIDs that are different from regular intracloud and cloud-to-ground lightning. Differences between +CIDs and –CIDs were specially investigated. There were conclusions in following respects: CIDs produce very large electric field changes, which are generally larger than that produced by return strokes. Compared with +CIDs, –CIDs generally produce larger electric f eld changes. CIDs are usually isolated with other discharge processes, which means that CIDs rarely follow other discharge processes. Compared with –CIDs, +CIDs have much higher possibility to be the initiation processes of regular discharge processes. Low frequency radiation signals produced by CIDs can be ref ected between the ground and the ionosphere and can produce ionospheric reflection pairs. Using the time differences between the reflection signals and the original signals of CIDs, a new method for determining 3D locations of CIDs are developed. This method can accurately determine 3D locations of CIDs in a large area. With this method, discharge heights of large amounts of both polarities of CIDs are computed, and it is found that +CIDs mainly occur at a height of 7～15 km while –CIDs mainly occur at a height of 15～18 km. There are certain relationships between CIDs and convective strength. CID rate generally increases with convective strength. Thunderstorms usually produce much more +CIDs than –CIDs, but the percentage of –CIDs increases as the convective strength increases. The above differences between +CIDs and –CIDs are comprehensively analyzed, and –CID is considered to be a more special type of discharge.

With the development of lightning detection technology, more and more f eld experiment and research began to focus on lightning activities in tropical cyclones. Using cloud-to-ground lightning data from the national lightning detection network, the Institute of Atmospheric Sounding analyzed the temporal and spatial lightning activities in thirty-three tropical cyclones making landfall in Guangdong, China. The results show that characteristics of lightning activities varied in tropical cyclones with different intensity. A distinct radial variation in flash density was observed , with a maximum in the outer rainbands (200 to 500 km from the center), a light flash density in the inner rainbands (60 to 200 km from the center) and weak maximum in the eyewall (60 km from the center). The precipitation structure of inner rainband is similar with stratiform cloud and the ratio of positive flashes is the highest in the three regions. The inner core lightning is predictive to the typhoon’s intensity and its change. When the central wind speed increases, the eyewall lightning bursts. After several hours of the outbreaks of eyewall lightning, the central wind speed reaches the maxima. Therefore, an outbreak of lightning in the core region might indicate the imminent intensification of tyhoon, and has precisive value of typhoon’s convective structure and its change. With Weather Surveillance Radar and TRMM satellite data, the relationship between lightning activities and precipitation structure was examined for Typhoon Molave (0906) and an important piece of evidence for the convective structure in the inner and outer rainbands was provided. Results showed that the outer rainbands had higher radar reflectivity and updraft than the inner rianbands. The region of the same reflectivity in the outer rainbands reached a higher altitude. Vertical hydrometeor profiles in both rainbands were calculated and showed a higher cloud and precipitation ice density and located height in the outer rainbands, which indicated a higher ice particle content in the melting region. The knowledge of lightning activities in landfalling typhoons will be quite useful to landfalling typhoon forecasters.

4. The system platform of lightning monitoring and warning is further improved and serve for the weather service at Shanghai World Expo

In 2010, the Institute of Atmospheric Sounding further perfected the construct of the lightning monitoring and lightning nowcasting and warning system platform, advancing the algorithm and updating the function of the lightning real-time monitoring system, lightning detection and analysis system, lightning nowcasting and warning system (CAMS_LNWS) and evaluation system of lightning warning products, which commonly comprised the platform. The new platform had played an important role in the operation of lightning warning in the flood season in 2010, providing the public product of lightning monitoring and warning to the “Weather China” website withoutany break. Under the technical assistance coming from the Institute of Atmospheric Sounding, the updated CAMS_ LNWS was tested in Beijing, Hubei, Hunan, Qinghai and many other provinces. Based on the testing, the Institute of Atmospheric Sounding conducted the phase 4 seminar sessions on lightning nowcasting and warning technology in Chengdu from 16 to 17 October 2010. The participants at the seminar sessions analyzed and exchanged their knowledge on the warning and prediction of the lightning activities and thunderstorms in their working places. After that, the researchers of the Institute of Atmospheric Sounding detailedly introduced the improvement and testing of the new-version CAMS_LNWS and trained the participants to master the operation of the CAMS_LNWS. The newversion CAMS_LNWS was f nally distributed to the participants for the further application in other meteorological bureaus and other departments who were concerned about the lightning activities.

In order to meet the requirements of the Shanghai World Expo for lightning warning, the Institute of Atmospheric Sounding updated the algorithm of the CAMS_LNWS in advance. The updated CAMS_LNWS, with stable running, friendly interface and fast computing capabilities for the products of 0～1 hour lightning probability, lightning probabilities in key locations and the moving trend of the lightning activities, contributory to that, Shanghai Meteorological Bureau released the lightning warning sign for the World Expo. During this process, the researcher of the Institute of Atmospheric Sounding devoted themselves to the weather service at Shanghai World Expo by being fully involved to provide sustaining technical assistance.

5. Count the years of lightning disaster data and get a further understanding of the characteristics of lightning disasters in China

According to the data of National Lightning Hazards Database from 1997 to 2010, spatial and temple distribution of lightning disasters in China were analyzed. The southern and eastern costal areas have more frequent lightning disasters, and the disasters mainly occur in summer months from July to September. Lightning-related damages have increased in the period from 1997 to 2007 and then began to decrease since 2008. The national fatalities and injuries per million people per year are 0.31 and 0.28 respectively, and rural people suffer the most. In order to reveal the vulnerability of lightning stroke which leads to injuries and deaths in different regions, four indexes—lightning density, casualties frequency, population, and regional areas are used to evaluate the vulnerability by lightning stroke and provide six different kinds of risk zones which lead to injuries and deaths in China. Guangdong, Shanghai and Hainan pertain to vulnerability evaluation extreme high areas. In these areas, the vulnerability reaches up to 6.89 people for every ten thousand square kilometers. Inner Mongolia, Xinjiang and Tibet belong to vulnerability evaluation the lowest areas, there are only 0.14 people injured and dead for every ten thousand square kilometers. The result of classif cation is appropriate, and preferably ref ects regional vulnerability evaluation characteristics of the events in which the lightning stroke causes people’s casualties.

6. Development and application of the compositive detection device of lightning optical, electrical, and magnetic signals are achieving great progress

The signals of optical strength, electric field and magnetic field are the fundamental characteristic parameters of lightning process. The detection has become a necessary step for the research on lightning physics and protection. Following the frontier of optical, electrical and magnetic detection of lightning and summarizing the problem occurring in previous detection, the Institute of Atmospheric Sounding focused much on the integration of the detection platform and its application. The main research content and results are as follows: (1) The apparatus for the detection of optical radiation and the device using optical radiation to trigger the acquisition of other signals were developed. Based on this apparatus, the absolute and relative optical strength produced by lightning discharges was obtained, and multiple signals were synchronously collected with the optical radiation serving as the triggering source. (2) The data of the electric field changes and the 3D magnetic field associated with the lightning discharge, which were observed by the newly designed electric f eld change mill and 3D magnetic f eld sensor, were successfully obtained. Meanwhile, the electric field change mill was standardized for the real value but relativevalue. (3) The detection device of optical radiation was integrated into the platform of electromagnetic f eld to form a new comprehensive observation system, which made contributions to the synchronous collection of the multiple signals produced by lightning and the high degree of consistency among the different signals. (4) On the basis of the system integrating electric and magnetic devices, a new multifunctional single-station lightning detection system, by which the electromagnetic waveform was synchronously obtained and the location of the cloud-to-ground lightning was successfully completed. Furthermore, the results were output at the same time, which served for the requirements of both the research and operation.

7. Techniques and system development of ground-based automatic cloud observation have obtained striking progress

The project “Study on the key techniques of ground-based automatic cloud observation and development of system” was funded by the key project of basic research fund of Chinese Academy of Meteorological Sciences. Its goal is to manufacture an automated ground-based cloud observing system with independent intellectual property rights, establishing a ground-based cloud observation technique and method by integrating the visible light digital cloud image and cloud-base height, developing of stable and reliable hardware and software systems, and to lay a solid foundation for accomplishing a comprehensive automated observing of the ground-based cloud. Through three years of implementation, the project mainly achieved the following results by 2010: (1) Some key technical problems have been solved for ground-based cloud observing hardware and software systems, including the design and actualization of two kinds of light-shelter schemes for the camera unit, the accomplishment of automatic exposure control for achieving ground-based total-sky cloud images. The developed prototype has experienced some field tests, which can be long-term stable and has a reliable operation, automatically capturing the totalsky cloud images and calculating total cloudage. (2) Several cloud detection algorithms have been researched, including adaptive threshold, local threshold and hybrid threshold, which enhanced the accuracy of cloud detection. A preliminary standard cloud image database and several cloud feature extraction algorithms have been established and a content-based digital cloud images retrieval system has been developed, which will lay the foundation for future cloud type identification. (3) Several sets of special software have been developed, including fisheye image correction, cloud type identif cation and classif cation of artif cial, digital cloud image retrieval software, etc. These works provide convenient conditions for carrying out ground-based total-sky cloud observation experiments, establishing cloud image database, developing of cloud detection and cloud type identif cation methods.

The ground-based total-sky cloud imager (TCI), developed by the project team, has carried out a long-time observing experiments in the Beijing Meteorological Observatory, Conghua Meteorological Bureau, Yangjiang Meteorological Bureau and Chinese Academy of Meteorological Sciences, and accumulated a wealth of groundbased cloud images.In the 8th WMO international radiosonde comparison experiments, TCI provided the corresponding product and got a preferable application.