三江源冬季降雪时空特征及成因分析

The Snowfall Characteristics and Cause of Formation in Winter of Three-River Headwaters Region

为研究三江源冬季降雪时空分布特征及形成机制,基于美国国家环境预测中心和美国国家大气研究中心提供的大气环流再分析资料及国家气候中心提供的1987-2016年三江源18个国家站逐日降水、平均温度资料,通过EOF分析、小波分析、合成分析等方法对三江源冬季降雪进行研究,发现北极涛动、东亚冬季风、南支槽对三江源冬季降雪有影响。研究结果表明,三江源冬季降雪空间分布表现为“东强西弱”的特征,冬季降雪整体呈减弱趋势;多雪年冷暖气流在三江源地区相汇,少雪年三江源地区被偏北气流控制;当北极涛动为正(负)位相、东亚冬季风减弱(增强)、南支槽加深(减弱)都有(不)利于三江源降雪增加。

In order to study the temporal and spatial distribution characteristics and formation mechanism of winter snowfall in the Three-River Headwaters Region,this paper is based on the atmospheric circulation reanalysis data,provided by NCEP and NCAR,and the daily precipitation and temperature data of 18 national stations in Three-River Headwaters Region from 1987 to 2016,provided by the National Climate Center.Through EOF analysis,wavelet analysis,synthesis analysis and other methods,we study the winter snowfall of Three-River Headwaters Region,and we find Arctic Oscillation,East Asian Winter Monsoon and trough in the South Branch have influence for winter snowfall of Three-River Headwaters Region.The results show that the spatial distribution of winter snowfall in Three-River Headwaters Region is strong in the east and weak in the west,and the overall winter snowfall shows a weakening trend.Cold and warm air flow converges in the Three-River Headwaters Region in snowy years,it is controlled by northerly airflow in the year of less snow.When the Arctic oscillation is in a positive phase,the East Asian Winter Monsoon weakens and Trough in the South Branch deepens,the snowfall of Three-River Headwaters Region will increase.When the Arctic oscillation is in negative phase,the East Asian Winter Monsoon strengthens and Trough in the South Branch weakens,it is not conducive to snowfall in Three-River Headwaters Region.