华南前汛期广东暴雨分区动力特征及特大暴雨分析

依据2009－2013 年华南地区72 测站逐日降水资料，利用 REOF方法、合成分析等方法，分析华南前汛期（4-6 月）暴雨时空特征。结果表明：暴雨降水量占总降水量34.6%，年暴雨日数170天以上。REOF方法分析获得华南前汛期5个暴雨模态区, 其中广东两模态区中心荷载强于其余3个区,降雨更多,雨强更大。合成分析显示，广东北部暴雨区受西风带系统影响为主, 暴雨中尺度系统为气旋及变形场锋生。沿海暴雨区受副热带系统控制为主,中尺度系统主要为低空急流,输送气旋式切变和旋转涡度,及低空速度辐合, 并提供自海上来的充沛水汽，造成沿海区暴雨远强于北部区。 近5 a前汛期广东24 h累积降雨量大于200mm的大暴雨有14次，均发生在沿海暴雨模态区。两区暴雨机制分别为西风带中尺度低值系统锋生降水,和副热带系统暖区登陆地形作用降水。海温SST方面沿海暴雨区环境较北部暴雨区具有更大平均水汽潜热量,含更充沛水汽。而感热场反映沿海暴雨区从下垫面吸收更多热能量,更有利于不稳定暴雨过程维持与加强。对2010 年6 月9 -12 日广东沿海上川岛持续性特大暴雨分析显示，东北阻塞高压强盛与副热带高压西伸北进势均力敌配置,水汽通道和水汽通量散度輻合异常强盛, 湿位涡湿正压项和湿斜压项均构成有利于垂直涡度增长环境, 这些因子维持了特大暴雨过程。

Dynamics characteristics of rainstorm division in Guangdong province and analysis of a severe rainstorm process

According to daily precipitation data from 72 weather stations in the South China area during 2009 to 2013, temporal and spatial characteristics of heavy rainstorms from April to June (pre-summer flooding period) were analyzed by methods of a REOF and a component analysis. The results show that the heavy rainstorm rainfall accounts for 34.6% of total rainfall and the number of annual rainstorm days is over 170 days. By the EOF analysis, the 5 modes of rainstorm area are obtained. Two modes in Guangdong province have higher coefficients than the other modes and have abundant rainfall and stronger rainfall intensity. Using the component analysis, it is found that the rainstorm area in the north of Guangdong province is influenced by westward wind belt system, and mesoscale system of rainstorm is cyclone and deformation field frontogenesis; rainstorm area in the coast of Guangdong province is controlled by subtropical high system, and mesoscale system of rainstorm is low level jet that transfers cyclone shear wind and rotates vorticity to the area and also provide ample moisture from sea surface, so it causes stronger rainstorm in the coast than in the north. There are 14 severe rainstorm (rainfall >200mm) events during pre-summer flooding season in the recent 5 years in Guangdong province, and all of them happened in the coast. Dynamic mechanisms of heavy rainstorm in both areas are different. It is westerlies mesoscale and deformation frontogenesis in the north, while it is subtropical high warm jet system landing and clambering up the coastal land in the coast. SST of off shore provides more latent heat, higher moisture and more active thermal convection environment in the coast than in the north, while sensible heat field show that rainstorm area in the coast could absorb more thermal energy, which is favorable to maintain and strengthen unstable rainstorm process. Analysis of the continue severe rainstorm at Shangchuan island of Guangdong on June 9-12, 2010 suggests that northeast blocking high and subtropical high that extends to west and moves to north both are of similar intensity, so are water vapor flux and convergence of flux divergence. Aslo, barotropic and baroclinic moisture potential vorticity all together are favorable to vertical vorticity development. The above factors are responsible for maintaining the heavy rainstorm process at Shangchuan island of Guangdong province.