应用NASA MERRA再分析资料对一次高原切变线的诊断分析

利用2016年6月29—30日地面及高空常规观测资料、CMORPH融合降水资料以及时空分辨率较高的NASA MERRA 0.625°×0.5°逐3 h再分析资料,对一次高原切变线过程进行了天气动力学诊断分析。运用广义位温、广义湿位涡和涡生参数等诊断量对切变线系统的生成及其降水分布进行分析。结果显示:广义位温等值线梯度大值区与大气水汽的聚集区相对应。切变线降水的发生、发展与广义湿位涡的分布及演变有较好的对应关系,低层大气广义湿位涡的正异常大值对降水发生有一定关联。广义湿位涡正负异常值之间的零线可较好表征高原切变线的位置。广义湿位涡中心强度对切变线生成与发展有一定指示意义。涡生参数可作为高原切变线生成和加强的一个明显前兆信号。

Diagnosis analysis on a plateau shear line process based on NASA MERRA reanalysis datasets

By using the conventional ground and high-altitude observations, the CMORPH blended precipitation and the high-resolution NASA MERRA reanalysis datasets (with spatial resolution of 0.625°×0.5ånd temporal resolution of three hours), the synoptic-dynamic diagnosis were performed on the process of plateau shear line during 29-30 June 2016. The formation of the shear line and the related precipitation were analyzed by multi-physical quantities involve the generalized potential temperature, the generalized moist potential vorticity and the vortex generation parameter, etc. Results indicate that the great value area of generalized potential temperature gradient is coincident with the region where water vapor accumulated. The formation and development of shear line precipitation is connected with the distribution and evolution of generalized moist potential vorticity, and positive low-level generalized moist potential vorticity anomaly always accompanies the occurrence of precipitation. In addition, there is a close spatial relationship between the zero line of generalized moist potential vorticity and the plateau shear line, and the intensity of the generalized moist potential vorticity center may indicate the development of shear line. Moreover, the vortex generation parameter can be regarded as a significant precursory signal for the building and strength of the plateau shear line.