A COMPARATIVE STUDY ON CHARACTERISTICS AND THERMODYNAMIC DEVELOPMENT MECHANISMS OF TWO TYPES OF WARMSECTOR HEAVY RAINFALL ALONG THE SOUTH CHINA COAST

作者：苗春生,杨艺亚,王坚红,李萍

摘要：Warm-sector heavy rainfalls along the south China coast from April to June during 2009-2014 can be divided into two main types based on their low-level circulations. Type I is the southerly pattern with meridional convergence line at the west of the Pearl River estuary, which is formed by the convergence of southeasterly, southerly, and southwesterly flows. Type II is the southwesterly pattern with a latitudinal convergence line at the east of the Pearl River estuary, which is formed by the convergence of westerly and southwesterly flows. Statistics on 6-hourly heavy rainfall events indicates that, during the afore-mentioned 6 years, there were on average 73.2 occurrences of the southerly pattern and 50.3 occurrences of the southwesterly pattern per year. After the onset of summer monsoon in the South China Sea, the occurrence frequencies of both patterns increase remarkably. The synthetic diagnosis of pattern circulation shows that, at 500 h Pa, for the southerly pattern, there is a broad warm high ridge, and a temperature ridge is behind the high ridge, which causes an obvious warm advection at the high ridge area. There is no frontal region. For the southwesterly pattern, the circulation is a weak trough with a temperature trough behind it. The position of the frontal region is near Yangzi River, and the south China coast is in the warm-sector of the frontal region. At the vertical cross-section of each of the two categories of heavy rainfall, there is a strong vertical motion center stretching to 400 hPa, where the convergence layer in the rainfall region is deep and with several vertical convergence centers overlapping one another. Both types of heavy rainfalls are with abundant water vapor, accompanied with deep convective instability energy layers, and with strong release of latent heat caused by condensation of water vapor. The release of latent heat leads to the warming-up and stretching of the air column, thus strengthens deep convergence and vertical velocity upward. There is a stronger latent heat-rel

发文机构：Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key Laboratory of Meteorological Disaster Center for Monsoon System Research Liaoning Meteorological Observatory School of Marine Sciences

关键词：warm-sectorheavyrainfalltheconvergencelineatlowlevelTHERMODYNAMICdevelopingmechanismnumericalsimulationLATENTheat

分类号： P47[天文地球—大气科学及气象学]