ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 44 Issue 4 > 2018,44(4):469-484. DOI:10.7519/j.issn.1000-0526.2018.04.001 Prev Next
Structure, Triggering and Maintenance Mechanism of Convective Systems During the Guangzhou Extreme Rainfall on 7 May 2017
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Abstract:
A very extreme rainfall event occurred on 7 May 2017 in Xintang Town, Zengcheng District of Guangzhou with maximum hourly precipitation exceeding 180 mm and 3 h rainfall exceeding 330 mm (shortly “the 5·7 extreme rainfall event”), causing severe economic damages. The rainfall process can be divided into two stages: Huadu rainfall stage and Zengcheng rainfall stage. The severe rainfall was mainly concentrated in two or three hours. The maximum minutely rainfall was high up to 5.0 mm. About 120 mm of the rain poured between 05:30 and 06:00 BT for the extreme hourly precipitation of 184.4 mm in Xintang Town of Zengcheng. Some negative lightning was observed during the Huadu rainfall stage and only several lightning occurred during the Zengcheng convection stage. Both radar reflectivity and satellite images show that the severe convective rainfall system was characterized by smallscale and rapid developing. The radar vertical profiles show the convection featured lowechocentroid warmcloud precipitation. There was remarkable spatial inconsistency between radar maximum reflectivity and minimum TBB of satellite image during the mature stages of the convection. The strong updraft was the cause of the spatial inconsistency between radar maximum reflectivity and minimum TBB. The topographic radiation cooling formed the surface cold center near Huadu. The terrain combined with largescale weak cold air blocked the northmoving warm, moist flow, and the convection was finally triggered near Huadu. The continuously transport of warm, moist air and blocking of Huadu terrain maintained the mesoscale convective system (MCS) during 01:00-03:00 BT in Huadu. The southmoving largescale weak cold air enhanced the cold pool, and pushed the MCS to move southward rapidly in 03:00-04:00 BT. The combination of southmoving MCS and local convection enhanced the convection over Zengcheng Region. The cold pool driven theory can explain the longtime maintenance and development of the MCS over Zengcheng. Both weak ambient flow and southward surface flow made the MCS slowly move during the two heavy rainfall stages. Thus, the extremely severe rainfall over Huadu and Zengcheng of Guangzhou took place.
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