初冬四川盆地霾的变化特征及其成因分析

Variation Characteristics and Cause Analysis of Haze in Sichuan Basin in Early Winter

选取NCEP/NCAR大气环流资料以及四川盆地16个地市州代表站天气现象数据,运用EOF分解、线性相关等统计方法,分析了初冬四川盆地霾的变化特征及其成因。结果表明:在年际尺度上,初冬四川盆地霾日数均表现为两种不同的分布模态,一是全区一致型,二是东西反相型。影响霾日数一致型模态的关键环流系统为,霾日数偏多(少)时,表现为AO/NAO呈负(正)位相,欧亚南部型(SEA)遥相关波列呈负(正)位相,四川盆地为高度场正(负)距平控制,受到青藏高原以北(南)偏西北风(西南风)异常影响,来自孟加拉湾的西南暖湿水汽输送较弱(强)。影响霾日数东西反相型环流系统为,霾日数东多西少(东少西多)时,呈现类似SEA型遥相关波列。降水量的减少是影响初冬四川盆地霾天气的重要气象因子,降水对大气的净化作用随着降水量的减少而减弱,造成霾天气频发。

The empirical orthogonal function(EOF)and correlation analyses are applied to NCEP/NCAR atmospheric circulation data and weather phenomenon data collected at 16 observational stations in Sichuan Basin to study the variation characteristics and caouses of haze in Sichuan Basin in early winter.The results show that on the interannual scale,the haze days in Sichuan Basin in early winter show two different distribution modes,one is the consistent type in the whole region,and the other is the east-west inverse type.The key circulation system affecting the consistent type mode of haze days is that when the number of haze days is more(less),the AO/NAO shows negative(positive)phase,the Southern Eurasian type(SEA)remote correlation wave column shows negative(positive)phase,the Sichuan Basin is controlled by the positive(negative)anomaly of geopotential at 500 hPa,and is affected by the northwestern(southwestern)wind anomaly in the northern(southern)Tibet Plateau,the southwestern warm and humid water vapor transport from the bay of Bengal is weak(strong).The east-west inversion-type circulation system affecting the number of haze days is that when the number of haze days is more in the east and less in the west(less in the east and more in the west),it shows a remote correlation wave train similar to the SEA type.The decrease of precipitation is an important meteorological cause of haze weather in Sichuan Basin in early winter.With the decrease of precipitation,the purifying effect of precipitation on the atmosphere is weakened,resulting in frequent haze weather.