Abstract:

During the winter of 2021/2022, the low SST (Sea Surface Temperature) in the equatorial Middle Eastern Pacific Ocean led to low temperature and increased precipitation in Guizhou Province. But the number of freezing days was generally lower, showing a phased distribution characteristic of weak in the early stage and strong in the later stage. Based on the daily observation data of 84 national meteorological stations in Guizhou Province, the reanalysis data of NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) and the SST data of NOAA (National Oceanic and Atmospheric Administration), the causes of freezing stages characteristics were analyzed from the aspects of SST field, height field, wind field, temperature field and water vapor condition. The results show that the southern branch frontal zone of the upper level was generally weak in the early stage and strong in the later stage, which provided a favorable large-scale circulation background for the freezing stage characteristics of Guizhou Province. After January 26, 2022, the stable maintenance of shear line in lower troposphere, and the abnormal strong of northerly airflow, which made the 0 ℃ isotherm moved southward obviously. At the same time, with the continuous enhancement of the southerly airflow, the water vapor convergence in the lower troposphere is also rapidly enhanced, and the unstable stratification and ascending motion of the low-level convergence and mid-level divergence were maintained, which provided favorable water vapor conditions for the stage characteristics of freezing in Guizhou Province. In the temperature field, the warm layer was relatively deep in the early stage, and the cold air was weak in the early stage and strong in the later stage, which provided favorable temperature conditions for the characteristics of freezing in Guizhou Province. However, due to the absence of the inversion layer in the whole winter, the intensity of the 3 regional freezing processes was relatively weak.

Key words: southern branch frontal zone, freezing, stage characteristics, climate anomalies

摘要：

2021/2022年冬季，赤道中东太平洋海温偏低，导致贵州省气温偏低、降水偏多，但凝冻日数总体偏少，呈前期偏弱后期偏强的阶段性分布特征。利用贵州省84个国家气象观测站逐日观测资料、NCEP/NCAR（National Centers for Environmental Prediction/National Center for Atmospheric Research）再分析资料以及NOAA（National Oceanic and Atmospheric Administration）海温资料等，分别从海温场、高度场、风场、温度场和水汽条件等方面对凝冻阶段性特征成因进行分析。结果表明：高层南支锋区总体呈前期偏弱后期偏强，为贵州省凝冻阶段性特征提供了有利的大尺度环流背景。2022年1月26日之后，对流层低层切变线稳定维持、偏北气流异常强盛使0 ℃等温线南压明显。同时随着偏南气流持续增强，对流层低层水汽辐合也迅速增强，并维持低层辐合中层辐散的不稳定层结和上升运动，为贵州省凝冻阶段性特征提供了有利的水汽条件。温度场上，前期暖层较为深厚，冷空气势力前期偏弱后期偏强，为贵州省凝冻阶段性特征提供了有利的温度条件。但由于整个冬季无逆温层存在，导致3次区域性凝冻过程强度均偏弱。

关键词: 南支锋区, 凝冻, 阶段性特征, 气候异常