黄河下游春季一次大暴雨过程的结构特征及落区分析

利用HLAFS资料和实况资料,对2003年4月17日至18日发生在黄河下游的一次强暴雨过程的大尺度环流背景和物理量场的结构特征进行了分析。结果表明,本次暴雨是高空冷空气、低空低压切变线和黄淮气旋外围倒槽共同影响造成的;从南海到山东的西南低空急流为暴雨区提供了充沛的水汽和能量;暴雨区850hPa上的高θse,700hPa上的强烈垂直上升运动,以及低空辐合、高空辐散是造成暴雨的有利物理量场特征。大的正涡度区位于500hPa以上,600hPa以下为强辐合区,以上则为强辐散区,这种结构配置成为暴雨发生的有利的动力机制。

Structure Characteristics and Appearance Areas of a Spring Rainstorm Process in the Lower Reaches of the Yellow River

Using the results of HLAFS and really detected data this paper analyses a strong rainstorm process on April 17-18, 2003 in the Lower Reaches of the Yellow River. The obtained results show that this rainstorm process is mainly resulted from the joint effect of high-level cold air, low-level low pressure shear line and inverted trough around Huang-huai cyclone; the low-level southwest jet from the South China Sea to Shandong Province provides abundant water-vapor and heat energy; higher 8se at 850 hPa, stronger updraft at 700 hPa. low-level convergence and high-level divergence are the main favorable and physical characters of this rainstorm process. The vertical distribution of physical characters in the rainstorm is higher positive vorticity at 500 hPa, stronger convergence and divergence over and below 600 hPa respectively, which provides dynamical mechanism for the rainstorm process.