影响哈密降雪异常的大气环流及水汽输送特征

利用1960—2020年哈密市6个气象站降雪观测数据及NCEP再分析资料，对哈密市降雪的时空分布特征及降雪异常年的大气环流和水汽特征进行了分析，结果表明：哈密市降雪中部多南北少，降雪日数12月最多，降雪量11月最多；降雪量和降雪日数总体呈增加趋势，但主要在2010年前增加，之后减少；降雪以小雪为主，大雪以上量级降雪较少。降雪偏多时，高层偏西急流增强，急流区北扩，中层伊朗副高加强北抬，极锋锋区南压，脊前低槽南下东移；低层风速增大，出现风向辐合和气旋性切变，地面锋面气旋加强，水汽输送增大，低层水汽含量多。降雪偏少时，高层急流偏弱，急流轴南移，中层西风气流控制，极锋锋区偏北，新疆脊东移，冷空气偏北，低层风速辐散增强，北方气旋偏北偏弱，水汽输送量小，水汽含量也少。

Characteristics of Atmospheric Circulation and Water Vapor Transport Affecting Snowfall Anomaly in Hami

Based on the snowfall observation data of six meteorological stations in Hami from 1960 to 2020 and NCEP reanalysis data, the temporal and spatial distribution characteristics of snowfall in Hami and the characteristics of atmospheric circulation and water vapor in snowfall abnormal years is analyzed. The results show that there are more snowfall in the middle of Hami, and less in the North and south. The most snowfall days in December and the most snowfall in November. The snowfall volume and snowfall days generally showed an increasing trend, but mainly increased before 2010 and then decreased. The snowfall is mainly light snow, and the snowfall above heavy snow is less. When there is more snowfall, the west jet strengthens at high-level, and the jet area expands to the north. The Iran Subtropical High strengthens to the north, the polar front area is to the south, and the low trough in front of the ridge moves to the south and east. The wind speed in the lower level increases, wind direction convergence and cyclonic shear appear, the cyclone on the ground front strengthens. The water vapor transport increases, and the water vapor content in the lower layer is more. When there is less snow, the jet at high-level is weak, the jet axis moves south. The Iran Subtropical High is weakened, the polar front area is north, the Xinjiang Ridge moves east, the cold air is north, the low-level wind speed divergence is enhanced, the northern cyclone is weak to the north, the water vapor transport capacity is small, and the water vapor content is small.