“神舟七号”飞船主着陆场区强对流天气的大尺度环流特征

利用NCEP 1°×1°再分析资料，研究2008年8—9月内蒙主着陆场区强对流天气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、欧亚和青藏高原积雪与河套以北地区降水关系密切。极涡中心8月位于东半球、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、纬向环流的偏强，有利于南北方冷暖空气的交汇。副高异常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。中低层偏南风距平和偏北风距平在淮河以北地区汇合与长时间维持，是场区降水异常和强对流偏多的主要原因。

Large-scale Circulation Features of Severe Convention Process for the Main Landing Field of "Shenzhou No.7"

The climate background and large-scale circulation features of the strong convection weather happened over the main landing field in Inner Mongolia in August and September of 2008 were investigated by the use of NCEP1°×1° reanalysis data. The results indicated that the sea surface temperature of western equator Pacific in the earlier stage and the snow cover of Eurasia and Qinghai-Tibet Plateau are related closely with precipitation in north of Hetao. In the main landing field, the precipitation is more in the earlier stage and the temperature is higher in the latter stage, Which is partly due to the polar vortex centre located at Western Hemisphere in August and eastern Hemisphere in September. The strong zonal and meridional circulation of Eurasia is in favor of the North and South air junction. Subtropical high to be abnormally strong and by west, and combined with the active India-Burma trough, provide the abundant water vapor and the essential perturbation energy for strong convection weather; the precipitation and strong convection above normal on the field arise primarily from the junction of low-middle souther anomaly and norther anomaly at the north of Huaihe River as well as its persistence.