Analysis of the Causes of Precipitation by Two Similar Typhoons Landing in Western Guangdong
Large-scale sustained heavy precipitation were brought about to south China before and after the landing in western Guangdong by two similar typhoons,Utor(coded 1311)and Chaba(coded 2203),and the causes were analyzed.The results are shown as follows.(1)The two typhoons were combined with the most powerful Southwest Monsoon of the respective years.The strong monsoon kept transferring water va-por to the typhoon circulation through low-level southwest jet streams,supplying sufficient water vapor to Guangdong and making the water vapor strongly convergent over there.(2)The secondary circulation gener-ated by the two typhoons after landing was conducive to the maintenance and enhancement of the precipitati-on in the Yunwu Mountain area in western Guangdong,and provided favorable dynamic conditions for the occurrence of extreme heavy precipitation in this region.(3)The strong ascending motion transferred the low-layer convection instability to the upper layer,leading to the thickening of the convectively unstable lay-er,and the weakening with the altitude of pseudoequivalent potential temperature advection also enhanced the local convective instability.Together,the two led to the long-time maintenance of atmospheric instability stratification in the Guangdong region.
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