1961-2018年新疆区域高温变化与环流和海温关系

Heatwave changes and the potential causes in Xinjiang from 1961 to 2018

利用1961—2018年4—9月新疆气象台站实测日最高气温资料、NCEP再分析资料以及大西洋海温资料,对新疆区域高温(≥35℃)的日数、初终日、强度等变化特征及与高空环流、大西洋海温关系进行了分析。结果表明:在气候“增暖增湿”背景下新疆高温日数显著增多。在这一情势下,高温的极端性在增多、增强,表现在极高温(T_(max)≥40℃)发生的日数占比显著增多,一般高温(37℃>T_(max)≥35℃)发生的日数占比呈下降趋势;极高温站数增多,北扩至北疆偏北的阿勒泰地区。全疆高温日初日呈提前、高温日终日呈推后态势,高温日在春季、初秋增多成为高温变化的显著特征。新疆高温日数的增多趋势与高空异常环流密切相关,当赤道大西洋海表温度偏高将有利于南亚高压控制巴尔喀什湖至蒙古国区域,使得新疆区域高温日数偏多。

Given the background of global warming,heatwave changes have attracted considerable attention:High temperature events not only cause severe drought,which greatly harms ecological vegetation and agricultural production,but also have a substantial effect on the production activities of water conservancy,industrial and mining enterprises,and human health:Xinjiang is one of the areas in China with a high incidence of extreme high temperature,and there have been frequent extreme high temperature events in this area in recent years:These events in Xinjiang have the characteristics of a wide range of influence,long duration,high outbreak intensity,and an early start and a late finish:The daily maximum temperature data are used to ascertain the heatwave changes in Xinjiang based on the quality-controlled station data from April to September of 1961 to 2018:Moreover,the NCEP reanalysis data and the sea surface temperature observations are employed to understand the potential reasons for heatwave changes:We have taken the temperature from 1981 to 2010 as the climatic mean:Our findings reveal that there was a significant increase in the number of heatwave days in Xinjiang under the local warming and wetting climate:This increase was more pronounced for extreme heatwaves(T_(max)≥40°C),whereas we found a decreasing trend for the occurrence of moderate heatwaves(37°C>T_(max)≥35°C):We found that the first heatwave is beginning earlier than previously(mid-April at the earliest),and the last heatwave is finishing later than before(late September at the latest):The increase of heatwave is most pronounced in April;however,it makes a limited contribution to the total heatwave change:In North Xinjiang,the abrupt transition occurs earlier than does that in South Xinjiang:We further show that there is a strong correlation between circulation changes and the heatwave days in Xinjiang:When the 200 hPa geopotential height over Balkhash Lake and its surrounding areas is higher(lower)than normal,the number of heatwave days in Xinjiang is larger(smaller):The variation of 200 hPa geopotential height over Balkhash Lake and its surrounding areas can be traced back to anomalies in the sea surface temperature(SST)in the equatorial Atlantic:The South Asian High would control a larger area,from Balkhash Lake to Mongolia,when the equatorial Atlantic SST is higher,which could result in more heatwave days in Xinjiang:As the reasons for the delay of the initial high temperature of some stations with reduced high temperature days in Xinjiang and the mechanism of influence of SST on high temperature events in Xinjiang remain unclear,the above problems require further study.