近55年湖北省凉夏气候事件及其大气环流特征
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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:

    以夏季平均气温距平的-10倍标准差为凉夏阈值,将单站凉夏分为弱和强两个等级,在此基础上确定区域凉夏和全省凉夏的界定方法和等级划分标准,区域凉夏和全省凉夏采用凉夏站数比确定。对湖北省1961—2015年的凉夏事件时空分布特征的分析结果表明:湖北省单站凉夏频率南多北少,东多西少,鄂东南凉夏频率最高,鄂西北最低;研究时段内全省性凉夏共发生7次(年),其中强凉夏3次(年)。凉夏事件主要发生在20世纪80年代和90年代,此后全省凉夏指数变率增大,在夏季增暖背景下,仍会发生全省性凉夏事件。利用NCEP/NCAR再分析资料,对比分析凉夏年、夏季高温年及多雨年大气环流背景发现:凉夏年500 hPa、100 hPa东亚沿海中纬度位势高度距平波列均呈现为“-” 位相分布,而夏季高温年则反之;与夏季高温年相比,凉夏年副热带高压脊线偏南约3~5个纬度,南亚高压位置偏南约2~3个纬度;凉夏年中高纬环流多波动,呈现长波长的两槽一脊环流背景,西风带环流偏南;夏季多雨年我国东部自北到南500 hPa高度距平位相波列为“-+”分布,但负距平中心比凉夏年更偏西;部分年份既是凉夏年,又是夏季多雨年。另有赤道中东太平洋海温Ni〖KG-*5〗n〖DD(-1*2〗〖HT〗^〖DD)〗o 34指数与湖北夏季气温异常指数呈现不显著的滞后与同期负相关,凉夏年一般对应赤道中东太平洋暖事件。

    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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洪国平,王苗,方思达.近55年湖北省凉夏气候事件及其大气环流特征[J].气象科技,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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  • 在线发布日期: 2018-05-02
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