ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 39 Issue 11 > 2013,39(11):1402-1412. DOI:10.7519/j.issn.1000-0526.2013.11.003 Prev Next
Analysis on the Heavy Rainfall Events Triggering Two Severe Mountain Torrent Geological Hazards in Guangxi
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Abstract:
Based on conventional observation data, satellite cloud imagery, radar detection data and the rainfall data of automatic weather stations etc., comparative analysis on the meteorological conditions for the two severe mountain torrent geological hazards occurred during 27-28 June 2010 and 20-22 May 2012 in northwest Guangxi was done. The results showed that: (1) The torrential rainfall occurs in the northwest of Guangxi with a maximum precipitation >350 mm. The maximum precipitation of mesoscale rain clusters is larger than >100 mm·h-1 in the processes and over 70 mm·h-1 in the hazard areas. The concentrated rainfall period is in 02:00-06:00 BT. The disasters begin in the late night, and occur in the area with maximum precipitation and fragile geological conditions, where different geological conditions correspond to different disasters. The severe weather has characteristics with small range, concentrated rainfall periods, intensity rainfall and triggers serious disasters. (2) The heavy rainfall is caused by circulation background with two ridges and one trough at 500 hPa in Eurasian Region and ridge line of South Asia high throughout Guangxi over at 200 hPa accompanied with active monsoon cloud system. The weather systems with upper trough or vortex and surface dry line or frontal indicate a vortex type storm. (3) The variation of upper air elements is the temperature decreases before the rainfall but rises after it. Unstable energy and stratification, low level convergence, middle and low level vortex, ascending motion of the whole atmosphere layer, high temperature and humidity, and strong convergence of water vapor are characteristics of the physical quantities. (4) Generation and mergence of convective cloud clusters on the satellite cloud images have implications to heavy rainfall. The rainstorm occurs in the developing stage of the clouds, and the TBB value less than 200 K can be used as an indicator to the severe precipitation. Train effect produced by low centroid of radar echoes and the effect of topography are important factors for the heavy rainfall. Strong vertical motion due to low level convergence and upper level divergence is conducive to the development and maintenance of the severe convection.
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