“神舟七号”飞船主着陆场区强对流天气的气候背景和环流条件

Climate Background and Circulation Characteristic of Severe Convective Weather Process over the Main Landing Field of Shenzhou No.7 Space Ship

利用NCEP再分析资料，对2008年8—9月内蒙主着陆场区强对流天气频发和降水异常偏多现象，研究其形成的气候背景和大尺度环流特征。结果表明：前期赤道西太平洋海表温度异常偏低、欧亚和青藏高原积雪异常偏深是其前期气候背景。极涡中心8月位于东半球和9月位于西半球。是场区前期降水偏多和后期气温偏高的原因之一。欧亚经向环流的偏强，有利于南北方冷暖空气的交汇。副热带高压偏强偏西及活跃的印缅槽为场区提供了充沛的水汽和强对流天气必要的扰动能量。中低层偏南风和偏北风在淮河以北地区汇合与维持，是场区降水异常和强对流偏多的主要原因。

Aiming at the frequent strong convectiver weather and exceptional more precipitation over Inner Mongol main landing field of Shenzhou No. 7 Space Ship in August and September 2008, the climate background and the large - scale circulation feature were analyzed based on NCEP 1°×1° reanalysis data. Result indicated that the sea surface temperature （SST） over Western Tropical Pacific from July 2007 to February 2008 was lower and snow cover over Eurasia and Qinghai - Tibet Plateau was bigger in the preceding winter and spring. The polar vortex centre was located at the Western Hemisphere in August and Eastern Hemisphere in September, which was the main reason why there was exceptionaly more precipitation in the preceding stage and higher temperature in the succeeding stage over the main landing field. The strong meridional circulation over Eurasia was beneficial to the cold and warm air convergence. The stronger and west Subtropic High and the active India - Burma trough provided the abundant water vapor and fluctuation energy for convective activity over the main landing area. The southerly and northerly wind at mid - low levels encountered and maintained over the north of Huaihe River, which was the main reason for more precipitation and more convective activity over the main landing field in August and September 2008.