一次辽宁秋季暴雨天气的诊断分析

使用1.0°×1.0°NCEP再分析资料,对2006年10月21—22日深秋暴雨在天气形势分析的基础上,进行物理量诊断。结果表明:在有利的环境背景形势下,高位涡从对流层高层向低层伸展并形成湿位涡柱,引起气旋性环流与低涡环流叠加。对流层低层的湿斜压性增强,引起低层的锋区加强及垂直涡度发展,高空入侵干冷空气锲入底层,低层暖湿空气强迫抬升,使地面发展为气旋;高低空急流耦合产生上升气流,同时较强的补偿下沉运动激发上升运动加强,使次级环流加强,触发不稳定能量的释放;低空急流和超低空急流向辽宁输送暖湿空气及能量,对流层中低层形成湿柱并积聚高不稳定能量;中尺度气旋、高低空急流、湿位涡柱、次级环流上升支、地面高水汽含量湿区、高假相当位温出现的时间、强度、位置和结构决定了暴雨的时间和落区。

Diagnosis of Autumn Rainstorm in Liaoning:A Case Study

Using 1.0×1.0° NCEP reanalyzed data and based on the analysis of the synoptic situation of a rainstorm in late autumn, physical quantity diagnosis w as carried out. The results indicate that under the advantageous environmental b ackground situation, high potential vorticity extends from upper troposphere to low level and forms moist potential vorticity column, which causes the superposi tion of the cyclonic circulation and the low vortex circulation. The enhancement of moist baroclinity in the low troposphere causes the strengthening of the fro ntal zone in the low level and the development of vertical vorticity; the dry an d cold air invaded from upper level enters into the bottom layer, and the warm a nd wet air in the low level is forced to lift, which causes the surface cyclone to develop. The coupling of high and low level jet produces the upward cur stronger compensation sinking movement excites the strengthening of lifting move ment, which produces the secondary circulation and triggers the release of unsta ble energy. The low and super low level jets transport warm and wet air and ene r gy to Liaoning, so the moist air column is formed in the middle and low troposph ere and high unstable energy is accumulated. The appearance time, intensity, pos ition and structure of meso scale cyclone, high and low level jets, moist poten tial vorticity column, the rising branch of secondary circulation, the surface we t area with high moisture content and high potential pseudo equivalent temperatu re decide occurring time and falling area of rainstorm.