宁夏高温气候特征及其大气环流异常分析

利用宁夏24个气象观测站1960-2009年逐日最高气温观测资料和NCEP／NCAR再分析高度场资料,分析了宁夏高温日数的空间分布及年际、年代际变化趋势,并对高温异常对应的大气环流背景进行了分析。结果表明,宁夏中北部地区高温相对多发,大武口和同心为两个高发中心;7月高温出现频率最大;1971、2000、2001年和2005年为高温日数最多的4个年份,而1962、1979年和1989年没有高温日出现;宁夏高温日数在20世纪90年代中期发生了年代际突变,1997年以来宁夏平均高温日数较1996年以前增加了3.4倍。高温日数的年际、年代际异常对应中高纬度大范围大气环流异常,即从西欧到白令海峡的大范围地区中高层高度异常场波列分布。亚洲中高纬度经向环流弱,高纬度冷空气不易南下,宁夏高温日数偏多。高温日数偏少年经向环流强,有利于北方冷空气南下。

Analysis of High Temperature Climatic Characteristics in Ningxia and Atmospheric Circulation Anomaly

Based on the daily maximum temperature data from 24 meteorological stations in Ningxia during 1960-2009 and the NCEP/NCAR reanalysis geopotential height data,the spatial distribution,inter-annual and inter-decadal variation trends of high temperature days in Ningxia,and the corresponding atmospheric circulation anomaly were analyzed.Results showed that the frequency of appearing high temperature was relatively high in mid-north area of Ningxia with Dawukou and Tongxin as two high frequency centers,and the highest frequency occurred in July.The number of high temperature days was most in 1971,2000,2001 and 2005,and no occurred in 1962,1979 and 1989.Inter-decadal abrupt change of high temperature frequency occurred in the middle 1990s,and the average annual days with high temperature in Ningxia during 1997-2009 increased to 4.4 times that during 1960-1996.The inter-annual and inter-decadal anomalies of high temperature frequency are associated with wide range atmospheric circulation anomalies,namely a wave train distribution of high-level height anomaly field in a wide range from western Europe to the Bering Strait.If the meridional circulation in middle and high latitude of Asia is weak,the days with high temperature in Ningxia are most.On the contrary,if the meridional circulation is strong and the north cold air moves southward easily,the days with high temperature in Ningxia are less.