ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 35 Issue 11 > 2009,35(11):17-28. DOI:10.7519/j.issn.1000-0526.2009.11.003 Prev Next
Distribution and Diurnal Variations of the MCS over SichuanChongqing Area and YangtzeHuaihe River Basin During the Summer of 2007
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Abstract:
The extremely heavy rainfall, persistent rainfall and severe convective weather events occurred frequently over SichuanChongqing Area and YangtzeHuaihe Riv er Basin during the summer of 2007. Based on the FY2C TBB (equivalent temperat ure of black body) dataset during 28 June-26 July 2007, the 570 MCSs (mesoscale convective systems) with life-cycle greater than 3 hours were investigated over the former two areas and adjacent areas (25°～38°N,100°～130°E). There were four activeMCS areas: the area from the western Sichuan Province to nort hwestern Yunnan Province, the eastern Sichuan Province and Chongqing City, the e astern YunnanGuizhou Plateau and the area from northern Guangxi Zhuang Autonom ous Region to Dongting Lake and the YangtzeHuaihe River Basin（YHRB）, and the re were three minor activeMCS areas over the YHRB activeMCS area. The modal duration of the total MCSs and those over SichuanChongqing Area were approxima tely 3～5 hours, but the modal duration of the MCSs over YangtzeHuaihe River B a sin was about 5～8 hours. The MCSs were classified as three types by the time sc a le of MCS: the first type of MCS has a life cycle of 3～5 hours， the life cycle of the second MCS type is 6～11 hours and the life cycle of the third MCS type ≥12 hours. The trigger mechanisms of the three MCS types were different: the fi r st and second MCS type could occur inside and outside the mean location of the W est Pacific subtropical high, and their occurrence, development and movement wer e obviously influenced by the mesoscale weather systems and may be related to th e factors such as topography and mesoscale convergence lines; the third MCS type occurred outside the mean location of the West Pacific subtropical high, and it s occurrence, development and movement were obviously influenced by the larges cale synoptic systems. The diurnal variations of the three MCS types were also o bviously different. The peaks of the three MCS types all occurred in the afterno on. However, the first MCS type had no obviously nocturnal occurrence, but the s econd and third MCS type had a nocturnal occurrence characteristic. The most act ive peak of the first and second MCS type was both in the afternoon, but the mos t active peak of the third MCS type was after midnight (about 18UTC). Both the M CSs over SichuanChongqing Area and YangtzeHuaihe River Basin had multiple ac tive periods in a whole day, but the active periods of the MCSs over two areas w ere different. Finally, two typical MCSs causing heavy rainfall and one longdu ration MCS were presented.
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