2008年河南黄淮地区暴雨过程个例分析

利用常规气象资料和NCEP资料对2008年7月22日河南黄淮地区的暴雨过程进行了分析.结果表明:这次过程是在500 hPa槽前西南气流引导下,高低空急流耦合区内西南涡沿切变线移出,弱冷空气侵入暖倒槽触发不稳定能量释放造成的.垂直螺旋度计算结果显示:中低层正垂直螺旋度中心与降水落区有很好的对应关系,大暴雨中心位于正垂直螺旋度中心附近.湿位涡演变分析发现,这次过程有"干侵入"发生,暴雨区中低层对流不稳定和对称不稳定共存,有利于降水增幅.水汽条件分析表明:这次过程的水汽源地在孟加拉湾和南海,主要是低层和近地层的水汽辐合.

Case analysis of a heavy rainfall event between Yellow River and Huaihe River area of Henan in 2008

Based on the conventional and NCEP (1°× 1°) reanalysis data, the causes of a heavy rainfall event occurred on 22 July, 2008 between Yellow River and Huaihe River area of Henan is diagnosed and analyzed. The results show that the heavy rainfall event is caused by the southwest air current in front of the trough at 500hPa, the southwest vortex moves along the lower-level shear which are located in the intersection region of the upper-level jet and the low-level jet. The cold air and the warm air inter-act between Yellow River and Huaihe River area of Henan, so the unstable energy is released and the heavy rainfall event occurs. The diagnostic results show that the movement direction and intensity transformation of the positive center of the vertical helicity at lower-level match the heavy rainfall regions quite well. The heavy rainfall center lies on the vertical helieity center. The moist potential vorticity analysis indicates that the invasion of dry-cold air from upper-level makes existing of the convectively instability with symmetric stability at lower-level in the meantime, which is advantageous to the precipitation intensity increment. The water vapor condition analysis shows that the vapors mainly come from the Bengal Bay and the South China Sea. The maximum of moisture flux locates in the lower-layer and boundary layer at low-er-level.