“97.12”高原暴雪过程中尺度热量和水汽收支诊断

应用非静力模式MM5V2对1997年12月（简称：97．12”）一交高原暴雪过程进行控制模拟试验。利用其输出资料以及热量和水汽收支方程，对这次暴雪过程进行了热量及水汽收支诊断。视热源（Q1）和视水汽汇（Q2）的诊断结果表明：Q1和Q2垂直积分的正值区分布形势相似且较强，并与地面降雪带的分布一致，因而，此次过程的Q1、Q2主要是由水汽凝结和潜热解释决定的。Q1在对流层为加热层，对流层上层相对为冷层，是暴雪发生发展的主要热力机制。Q1、Q2区域平均的垂直廓线峰值非常相近，该峰值区正是水汽凝结层，它与水汽输送带的水汽凝结变干有关。视水汽汇Q2与视热源Q1具有相近的垂直廓线，表明“97．12”暴雪过程中非对流性凝结降水起决定因素。这些结果为改进和发展用于模拟和预报高原暴雪的中尺度数值模式模拟系统提供了一些物理依据。

Diagnosis of Heat and Moisture Budgets of a Case of Storm Snow over the Plateau during December of 1997

The heat and moisture budgets of a storm snow over the Plateau during Dec.of 1997are diagnosed by using the output data from control simulation,the non hydrostatic mesoscale model MM5V2 of PSU/NCAR,and the equations of heat and moisture budgets.The diagnostic results for the apparent heat source ( Q 1) and apparent moisture sink ( Q 2) indicate that the positive vertical integrations of the Q 1 and Q 2 are stronger,and their distribution trend is similar,which also accord with the bands of the storm snow.So,the Q 1 and Q 2 of this case is the results of the condensation of vapor and the release of latent heat.An important thermodynamics mechanism of the genesis and development of the storm snow is that apparent heat sources Q 1 is warm in the middle troposphere and relative cool in the upper troposphere.The peak value area of the area averaged vertical profiles of the Q 1 and Q 2 is close,this area is just the level of the condensation of vapor,it is concerned to the drying of the condensation of vapor in transpot belts of vapor.Apparent heat sources Q 1 and apparent moisture sink Q 2 have the same vertical profile which shows that the no convective condensation precipitation is the main factor in the storm snow event.These results provide physical basis for improving and developing meso scale numerical models used to simulate and forecast the storm snow over the Plateau.