Classification and dynamic composite analysis of three kinds of high altitude cold vortex
SHEN Xinyong1,2, ZHANG Chi1, GAO Huanyan1, WANG Lin1, LI Xiaofan3
1. Key Laboratory of Meteorological Disaster, Ministry of Education/Joint International Research Laboratory of Climate and Environment Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044;
2. Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai), Zhuhai 519082;
3. School of Earth Sciences, Zhejiang University, Hangzhou 310027
Based on geographical distribution, the North China cold vortexes are divided into three categories:Northeast China Cold Vortex (120°-145°E, 35°-60°N), North China Cold Vortex (100°-130°E, 30°-45°N) and East Mongolia Cold Vortex (100°-130°E, 40°-55°N). According to NCEP/NCAR 1°×1° reanalysis datasets and daily precipitation datasets from 2000 to 2018, the cold vortex cases in 19 years are screened, the activity rules of the three kinds of cold vortexes are statistically analyzed, and the structure and precipitation characteristics of the three kinds of cold vortexes are analyzed by dynamic composite analysis method. The results show that in the 490 cases of high-altitude cold vortexes in 19 years, 2 cases are missed, and 13 cases are repeated. The remaining 475 cases can be well selected and classified, and the definitions of three types of cold vortexes are reasonable. Northeast Cold Vortex and East Mongolian Cold Vortex can occur throughout the year, while North China Cold Vortexes are not found in December and February. Northeast Cold Vortexes are found mostly in April and May, and also in March and August with less frequency. North China cold vortexes are found mostly in May and less frequently in winter. In May, June and September, there are more cold vortexes generated in east Mongolia, while there are fewer in February, March and November. Dynamic composite analysis is used to analyze the three types of cold vortices. In terms of structure, the distribution of potential height, temperature, vorticity, and isentropic potential vortices show that the average strength of the Northeast China Cold Vortex is the strongest, followed by the East Mongolia Cold Vortex, and the North China Cold Vortex is the weakest. In the period when the cold vortex intensity is the strongest, the cold vortex precipitation mainly appears in the north of the outlet area of the upper jet, with strong divergence. Due to the differences in the distribution of low-layer humidity and the intensity of moisture transport, there are differences in the location of large precipitation centers of the three types of cold vortexes. The North China Cold Vortex has the largest mean precipitation intensity, followed by the Northeast Cold Vortex, and the East Mongolia Cold Vortex has relatively weak precipitation.