关键词: 秋冬季暴雨, 成因分析, 垂直螺旋度

Abstract: Based on NCEP/NCAR's 1°×1° global assimilation data, systematic analysis data, ground station data and Doppler radar observation data, the autumn heavy rainfall process in Hunan on 10-13 November 2015 is analyzed. The results show that the heavy rainfall process is the most widespread and longest lasting heavy rainfall process in autumn 2015, mainly occurring in southern Hunan. Ural ridge strengthened eastward trough in the bay of Bengal, high ground north strengthened, and extended to the southwest, the continuous supply of cold air southward to the southern region, due to the low pressure system makes the pressure not north of the bay of Bengal to move rapidly from southwest, and the formation of air forces in Southern Hunan confrontation over the favorable circulation environment for the rainstorm occurrence and maintenance; The left front rainstorm area is located in the low level jet axis, southwest warm air from the bay of Bengal and the cold air from the north to South intersection, the formation provides moisture and dynamic conditions for convergence steady rise of the heavy rainfall,which 850 hPa is the main source of regional water vapor transport the rainfall; The heavy rainfall is mainly in stability,the characteristics of unstable stratification are different from those of typical summer rainstorms are different. The energy front area is stronger, and the front wind is stronger than the south wind. The rainstorm process is post frontal precipitation. The change of the positive helix center has a good indication for the change of the ground cyclone center and the occurrence of heavy rainfall.

Key words: autumn and winter rainstorm, genetic analysis, vertical helicity