关键词: 暴雪天气, 水汽通量, 环流特征, 物理量场, 新疆

Abstract: In this paper, the circulation features and physical scalar fields of a continuous snowstorm over north Xinjiang, China during the period from January 4th to 7th, 2010 are analyzed based on the observed meteorological data and the daily 6-hour reanalyzed data of NCEP/NCAR. The results reveal that the long duration of blocking high and the stable cutoff low over the mid-high latitudes of the Northern Hemisphere provided a circulation background for the snowstorm. The cutoff low generated continuously short waves, moved back westward and then eastward, and affected the snowstorm; over the snowy area during the heavy snowy period, the strong convergence lines of northwest wind (10-16 m/s) and southeast wind (8-10 m/s) at 850-hPa were maintained, the 700-hPa was the convergence area of wind speed, and the 500-200-hPa was the divergence area. The strong convergence in lower troposphere, strong divergence in mid-high troposphere and strong upward motion were formed in the whole troposphere; water vapor was mainly transported along the southwest path, and some of it came from the northwest. There was a water vapor transport belt near 55°N, and it moved from the east to the west, then from the north and the northwest to the south and then to the southeast. The highest value of water vapor flux along this transport belt accounted nearly 1/4 of the southwest water vapor. Multi-source vapor transport was the main cause of forming the historical infrequent heavy snowstorm in north Xinjiang.

Key words: snowstorm, water vapour flux, circulation feature, physical scalar field, Xinjiang