中文摘要：

基于1980-2010年共31年NCEP再分析资料和华北地区地面台站资料,采用百分位阈值法研究了华北地区夏季极端高温天气事件的时空特征,并对其环流成因进行了分析.结果表明,1980-2010年华北地区极端高温日数和极端高温事件发生时的日平均、最高温度都有明显的增加趋势,其中极端高温日数的增加趋势尤为显著,线性趋势系数达到0.261,通过了0.01的显著性水平检验.空间分布上,近10年华北地区的极端高温日数显著增加,并且北部地区增加大于南部,极端高温多发区由20世纪80年代的“南多北少”向目前的“北多南少”分布态势转变；合成分析的结果表明,在华北地区极端高温日数偏多年,副高势力较强,且西伸脊点偏西,中高纬度地区为两高一低型,造成华北地区极端高温日数偏多的大气环流系统是其中偏东的深厚大陆高压,此系统强度大且在对流层低层势力尤为强盛,位势高度异常在850 hPa上超过5 gpm.

英文摘要：

Based on the daily data at 84 stations of North China and the NCEP/NCAR reanalysis data from 1980 to 2010, temporal and spatial characteristics of extreme high temperature events （EHTE） in summer were studied by using the centesimal threshold value method. The formative circumfluent background was also analyzed and the results show that, during 1980-2010 the number of days or mean/maximum of the EHTE increased significantly, and especially the days of the EHTE increased significantly with a linear trend coe℃ient of 0.261 in North China. As for the space distribution, the period of increased EHTE was focused particularly on the recent ten years, and the days of the EHTE increased more in the north than in the south parts of Northern China. Thus the distribution of the days of the EHTE changed from a ’more in the south and less in the north’ state to an opposite situation. A composite analysis showed that the western Pacific subtropical high was stronger with a westward ridge point, two high pressures and one low pressure systems located in the middle and high latitude. The eastern high pressure of the two was the circulation system that caused more EHTE in Northern China. This system was especially strong in the lower layers of the troposphere. For example, at 850 hPa the value of the geopotential height anomaly was above 5 gpm.