近55年湖北省涼夏氣候事件及其大氣環流特征
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Characteristics of Cool Summer Events and Atmospheric Circulation in Last 55 Years over Hubei Province
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    摘要:

    以夏季平均氣溫距平的-10倍標準差為涼夏閾值,將單站涼夏分為弱和強兩個等級,在此基礎上確定區域涼夏和全省涼夏的界定方法和等級劃分標準,區域涼夏和全省涼夏采用涼夏站數比確定。對湖北省1961—2015年的涼夏事件時空分布特征的分析結果表明:湖北省單站涼夏頻率南多北少,東多西少,鄂東南涼夏頻率最高,鄂西北最低;研究時段內全省性涼夏共發生7次(年),其中強涼夏3次(年)。涼夏事件主要發生在20世紀80年代和90年代,此后全省涼夏指數變率增大,在夏季增暖背景下,仍會發生全省性涼夏事件。利用NCEP/NCAR再分析資料,對比分析涼夏年、夏季高溫年及多雨年大氣環流背景發現:涼夏年500 hPa、100 hPa東亞沿海中緯度位勢高度距平波列均呈現為“-” 位相分布,而夏季高溫年則反之;與夏季高溫年相比,涼夏年副熱帶高壓脊線偏南約3~5個緯度,南亞高壓位置偏南約2~3個緯度;涼夏年中高緯環流多波動,呈現長波長的兩槽一脊環流背景,西風帶環流偏南;夏季多雨年我國東部自北到南500 hPa高度距平位相波列為“-+”分布,但負距平中心比涼夏年更偏西;部分年份既是涼夏年,又是夏季多雨年。另有赤道中東太平洋海溫Ni〖KG-*5〗n〖DD(-1*2〗〖HT〗^〖DD)〗o 34指數與湖北夏季氣溫異常指數呈現不顯著的滯后與同期負相關,涼夏年一般對應赤道中東太平洋暖事件。

    Abstract:

    The threshold of cool summer is defined as -10 times the standard deviation of average summer air temperature anomaly, and singlestation cool summer is divided into two intensity grades: weak cool summer and strong cool summer. On the basis of the division method for singlestation cool summer, the definition method and classification standards for regional and provincial cool summer are defined, and regional and provincial cool summer intensity are identified by the percentile rank of cool summer stations respectively. The analysis of the spatial and temporal distribution characteristics of the cool summer events in Hubei Province from 1961 to 2015 shows that the cool summer event occurred more frequently in the southern and eastern Hubei than in northern and western parts. The frequency of cool summer over the southeastern Hubei was the highest while lowest in northwestern area. There occurred 7 cool summer years across Hubei over the last 55 years, including three strong years. The cool summer events occurred mainly in the 1980 s and 1990 s. Afterwards the variability of cool summer index tends to increase after the 1980s, and the provincial cool summer events still occurred in the background of global warming. By use of the NECP/NACR reanalysis dataset, the atmospheric circulation backgrounds of the cool summer years and the warm summer years and the rainy summer years are analyzed. The wave trains of mean geopotential height anomalies at 500 hPa and 100 hPa show as negative phase spatial distribution in cool summer years in the midlatitude region of the East Asia coast, and vice versa in warm summer years. The ridge line of the subtropical high was southward by 3 to 5 latitudes in cool summer years than those in warm summer years, and the ridge line of the South Asia high was southward by 2 to 3 latitudes in cool summer years than those in warm summer years. In cool summer years, there were more circulation fluctuations in at middle to high latitudes with a circulation background of two troughs and one ridge, and southward westerlies circulation. The wave trains of mean geopotential height anomaly at 500 hPa showed a “-+” distribution in cool summer years from Northeast China to South China, but the negative anomaly center was westward. Some cool summer years were also rainy summer years. There existed contemporary negative correlation and nonsignificant lag between SST Ni〖KG-*5〗n〖DD(-1*2〗〖HT〗^〖DD)〗o 34 index of the Equatorial Middle East Pacific and the summer temperature anomaly index in Hubei Province, generally cool summer years corresponding with warm events in the Equatorial Middle East Pacific.

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洪國平,王苗,方思達.近55年湖北省涼夏氣候事件及其大氣環流特征[J].氣象科技,2018,46(2):352~360

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  • 收稿日期:2017-03-27
  • 定稿日期:2017-12-20
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  • 在線發布日期: 2018-05-02
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