新疆北部冬季降水异常成因

Causes of Winter Precipitation Anomalies in Northern Xinjiang

利用1960—2004年天山山区及以北地区(新疆北部)38个气象站日降水量和NECP/NCAR逐日4次再分析资料,分析了新疆北部11,12月和1月降水异常的环流和水汽特征。结果表明:冬季斯堪的纳维亚环流型(SCA环流型)与新疆冬季降水异常密切联系;11月水汽输送量最大,1月最小,西风气流输送水汽多少决定降水异常;降水异常偏多时,新地岛以东北冰洋、西伯利亚和阿拉伯海向中亚地区水汽输送异常,高纬度地区和低纬度地区向中亚地区输送水汽汇合后沿西风气流进入新疆,而非来自地中海和里海水汽源地;降水偏少时,里海以东随西风气流向新疆水汽输送减弱。关注SCA环流型活动以及西伯利亚和阿拉伯海向中亚地区水汽输送异常对冬季降水预测具有一定意义。

There is steady and thick snow cover in Tianshan Mountains and its north area（northern Xinjiang） in the cold winter.Snowfall has important impacts on crop surviving the winter,livestock feeding and drinking, traffic and transfer,ice-snow resources replenishment.With economic development,the impacts of winter precipitation anomalies become more and more important.To further understand the mechanism of winter precipitation anomalies,the inter-seasonal characteristics of circulations,water vapor（WV） transfer, income and expenses of WV are analyzed.Using daily rainfall data of 38 stations in northern Xinjiang and NCEP/NCAR daily reanalysis dataset from 1960 to 2004,the characteristics of circulation,WV transfer, income and expenses of WV for November,December and January precipitation anomalies in northern Xinjiang are investigated,as well as contributions from circulations and WV anomalies respectively on the whole WV transfer anomalies.The results show that Scandinavian（SCA） pattern plays a leading role on monthly precipitation anomalies in winter of Xinjiang.WV transfer quantity（WVTQ） is the largest in November, and smallest in January.West and east boundaries are charged with the dominating importing and exporting borderline of WV respectively for every level,and net WV earning quantity presents an obvious increasing trend every month.During the months with abundant precipitation,more WVTQ along westerly over middle-Asia comes from Arctic Ocean,Siberia and Arab Sea respectively rather than from regions of Mediterranean Sea and Caspian Sea.WVTQ along westerly of east to Caspian Sea reveals weakening in less precipitation months.For winter precipitation prediction,the east-west oscillations of the upper-level jet stream over north Atlantic and the corresponding the baroclinic eddies resulting in SCA pattern activity is very important,and WV transfer anomalies coming from Arctic Ocean,Siberia and Arab Sea areas should also be highly concerned.