两次副热带高压北侧暖锋暴雨动力热力诊断

Diagnosis of Dynamic and Thermal Mechanisms of Two Rainstorm Processes by the Warm Front Frontogenesis North of the Subtropical High

使用常规观测资料、自动气象站降水量以及NCEP FNL再分析资料,对黑龙江省两次副热带高压(简称副高)北侧暖锋暴雨过程(简称"0801"和"0803"过程)进行动力热力机制诊断分析。结果表明,两次暖锋暴雨过程,均有台风活动,造成副高西伸北抬,副高外围的西南低空急流向北输送大量高动量的暖湿空气。两次暴雨过程与高低空急流关系密切,"0803"过程中高低空急流均更强,暴雨区位于高低空急流耦合形成的垂直次级环流的上升支。"0801"过程,暴雨发生前大气对流不稳定,辐合抬升及次级环流上升气流的共同作用触发对流,促使不稳定能量释放,形成强降水。"0803"过程,暴雨期间大气对流稳定,锋区中层的CSI有利于降水强度的增强及维持,锋面强度更大,由锋面辐合抬升形成的上升运动范围更广,造成更大范围的强降水天气。在暴雨区上空由于凝结潜热释放而引起广义位温高值区向下伸展,强暖平流促使中低层湿斜压性显著增大,利于暖锋锋生。水汽散度通量和水汽垂直螺旋度能够较好地描述强降水过程,强降水区与水汽散度通量正值区及水汽垂直螺旋度负值区相对应。

Based on the conventional meteorological observational data,automatic observational precipitation and 1°×1° NCEP FNL reanalysis data of time resolution of 6 hours interval,two heavy rain processes occurred on 1 August 2017 and 2-3 August 2018 in Heilongjiang province by the warm front frontogenesis north of the subtropical high are diagnosed with dynamic diagnosis method and synoptic method. The major conclusions are as follow:There are typhoons during the two warm front rainstorm,which cause the position of subtropical high to the west and north. The southwest low level jet outside the subtropical high transports a large amount of warm moist air with high momentum to the north. The two rainstorm processes are closely related to the high and low air jet. In the process of "0803",the low-altitude jet stream is stronger,and the rainstorm area is located in the ascending branch of the vertical secondary circulation formed by the coupling of low-altitude jet stream and low-altitude jet stream. Before the rainstorm,the atmosphere is characterized by convective instability. The interaction of convergence uplift and secondary circulation updraft triggers convection and releases unstable energy,resulting in heavy precipitation. During the process of "0803",the atmosphere is shown as convective stability during the rainstorm. The condition symmetry instability of the middle layer in the frontal region is beneficial to the enhancement and maintenance of precipitation intensity. In this process,the frontal intensity is greater,and the upward movement formed by frontal convergence is broader,resulting in heavy precipitation in a larger range. The release of latent heat of condensation over the rainstorm area will cause the generalized high potential temperature region to extend downward,and the wet baroclinic property of the middle and lower layers will increase significantly. The moisture divergence flux and the moisture vertical helicity can well describe the process of heavy precipitation. The strong precipitation area corresponds to the positive region of the moisture divergence flux and the negative region of the moisture vertical helicity.