Laboratory of Cloud-Precipitation Physics and Severe Storms, Institute of Atmospheric Physics, Chinese Academy of Sciences
为了对比分析降水过程中不同表达形式热力学变量和位涡时空分布特点，本文针对2013年7月13-14日吉林省强降水过程，利用模式输出资料对常规位温（θ）、相当位温（θe）、包含凝结概率函数的广义位温（θGao）、包含冻结概率函数的广义位温（θWang）和同时涵盖凝结过程与冻结过程（θGu）五种不同形式位温进行计算，并分析五种对应位涡（PVθ、PVθe、PVθGao 、PVθWang 、PVθGu）与降水的关系。结果表明，引入冻结概率函数的广义位温（θWang）和对应的广义湿位涡（PVθWang）与强降水的对应性更好。θWang与θGao差异集中在降水区对流层中高层5-11km，前者始终高于后者，最大差异达2.5K，说明冻结概率函数的引入扩大了广义位温的适用范围，更适合描述降水区湿大气非均匀饱和热力状态。五种位涡的差异主要在降水区上空12km以下，由θGao和θWang定义的位涡PVθGao和PVθWang的正负异常中心更为明显。相比于PVθGao，PVθWang异常值更大，差异可达±0.2PVU，这主要是由于冻结概率函数的引入增大降水区上空广义位温，促使冻结区的湿位涡异常增强
For comparison and analysis of spatial and temporal distribution characteristics among different types of thermodynamic variables and potential vorticity during precipitation process, based on a heavy rainfall occurring in Jilin Province during 13-14 July 2013, five different types of potential temperature including conventional potential temperature (θ), equivalent potential temperature (θe), generalized potential temperature containing condensation probability function (θGao), generalized potential temperature containing freezing probability function (θWang), potential temperature covering both condensation process and freezing process (θGu) were calculated with model output. Relationships between five associated types of potential vorticity (PVθ, PVθe, PVθGao, PVθWang, PVθGu) and precipitation were also analyzed. The results shows that generalized potential temperature introducing freezing probability function (θWang) and its potential vorticity (PVθWang ) have a better correspondence with heavy rainfall. The differences between θWang and θGao mainly concentrate on 5-11km in the mid-upper troposphere over rainfall region. θWang is always greater than θGao, with a maximum difference up to 2.5K, indicating that introduction of freezing probability function extends the application scope of generalized potential temperature and has a more suitable depiction for thermodynamic state of non-uniform saturated moist air over rainfall region. Differences among five types of potential vorticity are mainly under 12km over rainfall region. Positive and negative anomaly centers for potential vorticity PVθGaoand PVθWang defined by θGao and θWang are more visible. Compared with PVθGao, anomaly value for PVθWang is greater, and the differences can reach ±0.2PVU, which is due to the enhancement of generalized potential temperature over rainfall region caused by the introduction of freezing probability function, leading the abnormal enhancement of moist potential vorticity in freezing region.