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Distribution and Spatiotemporal Variations of Deep Convective Clouds over China During the Warm Season

CHEN Guochun~(1,2) ZHENG Yongguang~2 XIAO Tiangui~1 1 Chengdu University of Information Technology,Chengdu 610225 2 National Meteorological Center,Beijing 100081  
Based on the nearly-twelve-year hourly geostationary satellite multi-channel(IR1,IR2 and water vapor channels) digital infrared image dataset,the distribution and spatiotemporal variations of deep convective clouds over China and its vicinity during the warm season(March -October) from 1996 to 2008 (lacking 2004 data,part data missing) are analyzed,and comparative analysis is conducted on the distribution of thunderstorm days and the density distribution of lightning obtained from low-orbit satellites.In this paper,TB_(ir1)≤-52℃(Infrared 1-channel brightness temperature),TB_(ir1)-TB_(ir2)3 K(Infrared 2- channel brightness temperature),and TB_(ir1)-TB_(wv)≤8 K(water vapor channel brightness temperature) are used to identify the deep convetive clouds.The results show that:There are four active regions of deep convective clouds during the warm season,i.e.,the middle-east of Qinghai-Tibetan Plateau,South China and Northeast of Yunnan-Guizhou Plateau,Xinjiang Ili River Valley and its surrounding area,and the most parts of Zhejiang-Fujian-Jiangxi regions;Overall,deep convective clouds over summer(June-August) are the most active;in spring(March-May) followed by;the autumn(September-October) are the least;The geographical distribution of deep convective clouds in different seasons is significantly different;The feature of diurnal variations of deep convective clouds has a significantly difference in different seasons and regions;Autumn diurnal variation is the least significant;As spring sunset time is earlier than the summer,in general,the diurnal variation of deep convective clouds in the spring is earlier than the summer peak hours;Deep convective clouds in the middle-east of Qinghai-Tibetan Plateau,Guangdong and Guangxi hills and the Zhejiang and Fujian hilly regions are of the single peak diurnal variation;At Sichuan Basin,the deep convective clouds often have nocturnal occurrence;In spring and summer,the diurnal variations of deep convective clouds are of bimodal type in Jianghuai region,which may be related to the region more closely related to MαCS;Thermal convections in the eastern part of Qinghai-Tibetan Plateau are active;In Guangdong and Guangxi hills,Sichuan Basin,and Jianghuai region it is not only very active heat convection,but other weather systems(such as typhoons,Meiyu front,etc.) to trigger and maintain the convection are also very active in summer.
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