河西走廊东部冬季降雪特征分析

Analysis of Winter Snowfall East of the Hexi Corridor

本文利用河西走廊东部5个地面气象观测站1960—2011年冬季的逐日降雪观测资料，运用统计分析、Morlet小波和Mann—Kendall法分析了河西走廊东部冬季降雪的气候变化特征，最后利用1982—2012年NCEP时间间隔为6h的1°×1°格点资料研究该地冬季降雪的环流特征以及用相关分析方法进一步分析了影响冬季降雪的大气环流。其结果表明：由于受海拔高度、地理位置以及天气系统的影响，河西走廊东部降雪日数和降雪量总体分布从东南向西北递减。河西走廊东部冬季降雪量具有明显的日变化，夜间雪量大于白天，降雪日数北部平原区的峰值主要出现在1月份，而南部山区的峰值主要出现在2月份。河西走廊东部冬季降雪日数和降雪量近52a来都出现增加趋势，主要存在5～6a和9～10a的周期反映，都出现了突变，但突变年份不同，其降雪的典型环流形势为西北气流型、西风气流型、西南气流型，其影响机制相同，都需要较好的水汽条件和一定的冷空气。

Snowfall has advantages and disadvantages east of the Hexi Corridor as it can result in cattle starvation and death, traffic accidents, relieve agricultural drought and provide people with precious water resources. Here, snowfall east of the Hexi Corridor was analyzed using daily snowfall data in winter from December to February across five stations from 1960-2012. NCEP reanalysis gridded data spacing at 6 h at 1°× 1° from 1982-2012 was also analyzed to study snowfall circulation features. The results show that the spatial distribution of snowfall declines from southeast to northwest because of altitude, geographical position and weather; many of the snowfall days occurred in the southern mountain area of Wushaoling and much of the snowfall was in the southern mountain area of Gulang. The majority of events were concentrated in February, and radiation cooling at night resulted in night snowfall and accounted for 55.8% of events. We found an increasing trend in the number of snowfall days and snow amount over the last 52 years at 0.53 d/10a and 0.51 mm/10a; there were vibration periods of 6-7a, 9~10a of snowfall days and snowfall amount and abrupt years in 1974 and 1979 for snowfall days and snowfall amount. The typical circulation situation of snowfall is a northwest airflow pattern, west airflow pattern, southwest airflow pattern east of the Hexi Corridor. The majority was a northwest airflow pattern, followed by a southwest airflow pattern; the least was a west airflow pattern. Correlation coefficients showed good positive interrelations between winter snowfall with temperature and relative humidity.