2014年盛夏湖南两次大暴雨过程的对比分析

Simulation Study of rainstorm and flood inundation in Longxu River Basin Based on the Flood Area Model

利用NCEP1°×1°再分析资料、湖南省96个气象观测站降水资料,对2014年7月3-5日和11-17日分别出现的两次大暴雨过程从大气环流背景、水汽条件、低空急流配置等方面进行对比分析。结果表明:"7.3"暴雨是高空槽引导低涡切变东移引起的,雨强较强,但随着高空低槽东移降水快速结束;而"7.11"暴雨发生在副高边缘,由于副高一直维持在湖南上空,导致降水维持了很长一段时间。从水汽条件看,两次暴雨发生前期湖南高空都为高湿状态,最大比湿都在14g.kg^(-1)以上,比湿大值中心都位于湘西,达到18g.kg^(-1);不同的是"7.03"暴雨的水汽通道有两支,一支来源于南海,一支来源于孟加拉湾,其水汽通量散度中心强度达到-6×10^(-6)g.cm^(-2).h Pa.s^(-1),与"7.3"相比,"7.11"暴雨水汽主要来源于南海,水汽通量散度中心强度比前次弱,为-4×10^(-6)g.cm^(-2).h Pa.s^(-1)。低空急流的存在也是暴雨维持的重要条件,"7.11"暴雨的低空急流经过减弱消失再生成过程,降水也随之减弱消失再发生。低空急流的长时间维持,使得"7.11"暴雨比"7.03"暴雨的持续时间长。

Based on the return period values of area rainfall causing flood calculated by generalized extreme value distribution functions and data of daily rainfall of all the meteorological stations in Longxu River basin, flooding simulation is obtained from FloodArea model by using the return period values, data of hourly rainfall and the digital elevation model, the return period values of flooding scope and flooding depth are carried out. The results of show that there is a sharp rise of the water level at middle and lower of Longxu river basin, Ronghua hydrologic station closing to the middle of river is the deepest stimulating flooding location, with twice over 3 meters floods. According to comparing the hydrologic data, the peak of flooding depth is lagging behind 5-7 hours of rainfall peak, the simulation result of FloodArea model agrees with the fact. This indicates that the FloodArea model generates good simulation effect of flooding in Longxu river basin and it can be used in the risk evaluation and early-warning of rainstorm and flood disasters.