2010年我国南方两次持续性强降水的环流特征

The Atmospheric Circulation Features of Two Persistent Heavy Rainfalls over Southern China in the Summer of 2010

通过对2010年夏季我国南方两次持续性强降水期间对流层高、中、低多个大尺度关键影响系统的时空演变特征及其影响机制的分析和比较,讨论了我国南方持续性强降水的大气环流特征。结果表明:这两次持续性强降水均出现了东亚西风带沿海低槽不断快速重建或加深,且中纬度锋区位置稳定维持,低空西南急流反复加强,且其轴线左侧的南风经向强梯度带位置相对稳定,副热带高空西风急流和南亚高压脊线及西太平洋副热带高压的纬度带位置相对稳定;相应地,在强降水带上空反复出现强烈的低层水汽辐合抬升、高层辐散抽吸及垂直上升运动发展,进而形成持续性强降水。西西伯利亚低槽的不断快速重建与加深(东移)、马斯克林高压西侧高压及马斯克林高压的不断加强东移、副热带高空西风急流的建立和维持对南方持续性强降水具有超前指示意义。强降水带位于东亚低空西南急流轴左侧南风经向强梯度辐合带、高空西风急流南侧至南亚高压脊线北侧之间的强辐散区及中层垂直上升速度大值带中。

The large scale rainstorm flooding induced by the persistent heavy rainfall in summer is the main meteorological disaster in China. Still more efforts are needed to improve the quantitative and refined forecast ability on the characteristic quantity of the persistent heavy rainfall, such as starting and ending time, drop location and the intensity of precipitation. By using daily intensive observed precipitation data and NCEP/ NCAR reanalysis data, two persistent heavy rainfalls in Southern China is analyzed and compared to investigate the spatial-temporal evolutioning features and the influencing mechanism of the large scale key influence systems, and atmospheric circulation features of the two processes are summarized as below. During the periods of persistent heavy rainfalls over Southern China in the summer of 2010, the we erly trough over coastland reformed and strengthened frequently and the mid-latitude frontal zone ma tained steadily, the low level southwest jet strengthened repeatedly and the strong gradient belt of merid nal wind on the left side of the low level southwest jet axis are relatively stable. Meanwhile the latitude stin io lo cation of the subtropical westerly jet, the ridge of South Asia high and the west Pacific subtropical high are also relatively stable in East Asia. Under the joint influences of the large scale key influence systems mentioned above, vapor convergence in the the vertical ascending m persistent heavy rainfall otlon over strengthe Southern low layer and divergence in the upper layer occurs repeatedly, and ns over the heavy rainfall belt, which leads to the formation of the China. Before the persistent heavy rainfall in Southern China, the trough in western Siberian keeps reforming and strengthening, shifting to east of Mascarene high and its western high. The subtropical upper westerly jet is also established and maintains in East Asian. The heavy rainfall belt of the persistent heavy rainfall lies in these areas. The strong gradient convergence belt of meridional wind on the left side of the low level southwest jet axis, the strong divergence zone between the south boundary of subtropical upper westerly jet and the ridge axis of South Asia high, the belt of high updraft vertical velocity in the middle layer in East Asian, the south margin of the middlelatitude frontal zone in the middle-upper troposphere, and the north boundary of the west Pacific subtropical high.