2004年渝北川东大暴雨环流及其非绝热加热特征

Circulation of a Persistent Heavy Rain and Its Diabatic Heating Characteristics over the North of Chongqing and the East of Sichuan in 2004

2004年9月上旬渝北川东发生了一次持续性大暴雨天气过程,造成了极为严重的局地洪涝灾害。应用国家气象中心实时加密观测降水资料,结合多卫星微波反演的降水资料及高分辨NCEP/NCAR再分析资料,通过对西南低涡等主要影响系统的分析,揭示暴雨次天气尺度环流特征,探讨高层非地转平流风分量与暴雨落区的关系,比较第1暴雨阶段(9月2日)和第2暴雨阶段(9月3日)大气非绝热加热的差异,发现前者以稳定性降水为主,后者则为显著的对流性降水。北方弱干冷空气和南方水汽输送在西南低涡暴雨持续和发展中具有重要作用。

In September 2004, a persistent heavy rain occurs in the north of Chongqing and the east of Shichuan Province, it causes severe floods in some areas. The real time intense precipitation data provided by National Meteorological Center, multi-satellite microave inversed precipitation data and high resolution NCEP/NCAR reanalysis data sets are used. Based on the analysis on the main influence systems to the southwest low eddy, the heavy rain character of subsynoptic scale circulation is illuminated, the relationship between the high level ageostrophic wind component and the area of rainfall are discussed. Comparing the atmospheric diabatic heating of the first heavy rain period （September 2） with that of the second heavy rain period （September 3）, it is not difficult to find that the first rainstorm appears as stable rainfall and the second rainstorm obviouslyappears as convectional rainfall. Some cold air current coming from the north and the vapor transported from south are the indispensable facts in the occurrence and development of southwest low eddy rainstorm. The main results include the potential mechanism of heavy rain and its thermodynamic characteristics. Evidence suggests that the maximal heavy rains occur during the night, and CMORPH （climate prediction center morphing method） precipitation intensities are more than 18 mm. h^-1 and 22 mm. h^-1 respectively. The structure of meridional circulation presents subsynopitic scale cyclone triggered by precipitation locating over southern part of Sichuan. It appears near the right side of the high level jet exit region, and it brings the ageostrophic wind over the southern area. It is found that the position of heavy rain target region is consistent with ageostrphic center, and the convective systems of southwest low eddy become into MCC. Analysis of apparent heat source （Q1） and moist sink （Q2） show that the strong atmosphere diabatic heating centers are in the north of Chongqing and the east of Sichuan during heavy rain stages. It＇s also confirmed that dry cold air from the north and water vapour transported from the south have remarkable effect in this process. The vertical structure of Q1 and Q2 have the same features, two peaks indicate the precipitation with stability characteristics in the first heavy rain stage, and single peak with convection precipitation in the second heavy rain stage. Diabatic heating intensities are 10.7 K. d^- 1 and 7.0 K.d^-1 respectively. Studies indicate the vertical transfer term has an important role in Q1 and Q2, whereas the local variation term plays a little role and is balanced by the advection term.