中文摘要：

利用1961-2008年中国751个地面观测站气温资料插值而成的CN05格点资料,首先分析了中国东部夏季极端高温日数变化特征。结果表明,中国东部整体夏季极端高温日数有显著增多趋势,以东北、内蒙古中东部和东南沿海增多趋势最明显,而江淮黄淮地区增多趋势最不明显甚至出现减少趋势。极端高温日数年际波动周期以2.5~3.0年为主,江淮地区以5年为主。对极端高温日数进行EOF分解的结果表明,第1典型场主要表现了极端高温日数的线性变化趋势,第2、3典型场分别表现为江淮和东北、华南和华北极端高温日数的两种南北＂偶极型＂分布特征。合成分析表明,第2典型场正＂偶极型＂对应江淮地区500 hPa位势高度正异常和东北高度负异常以及西太平洋副热带高压（简称副高）偏北偏强,负＂偶极型＂则相反;第3典型场正＂偶极型＂对应华南500 hPa位势高度正异常和华北高度负异常以及西太平洋副高偏南偏强,负＂偶极型＂则相反。偏相关分析表明,鄂霍次克海阻高与东北和东南沿海极端高温日数正相关显著,与黄淮部分地区呈显著负相关;副高脊线与华北和东北极端高温日数呈显著正相关;副高强度与东南沿海呈显著正相关。

英文摘要：

Based on the CN05 grid datasets interpolated by the temperature data from 751 observation stations in China from 1961 to 2008,the variation characteristics of extreme high temperature days over eastern China in summer（neh）were firstly studied. Results show a significant increasing trend of nehover the whole eastern China,especially in the northeast China,the eastern and middle part of Inner Mongoli and the Southeast Coast of China,however,the trend is the most insignificant in Jiang-huai and Huang-Huai areas,parts of the area even shows a decreasing trend. The interannual period is mainly between 2. 5 and 3 years in the whole eastern China while it is quasi five year in Jiang-huai area. Empirical orthogonal function（EOF）analysis of nehshows a linear trend in the first mode,while a north-south‘dipole＇pattern appears in Jiang-huai area and northeast China in the second mode,and the‘dipole＇pattern appears in south China and north China in the third mode,respectively.Composite analysis shows that a positive 500 h Pa geopotential height anomaly appears over Jiang-huai area and a negative anomaly appears over northeast China in the positive phase of the second mode,meanwhile,the western Pacific subtropical high（WPSH）is stronger and locates north relative to the climatological average field,the anomalous feature is opposite in the negative phase,respectively. And a positive 500 h Pa geopotential height anomaly appears over south China and a negative anomaly appears over north China in the positive phase of the third mode,meanwhile,the WPSH is stronger and locates south,the anomalous feature is opposite in the negative phase too. The partial correlation analysis shows a significant positive correlation between Okhotsk blocking high and nehover northeast China and the Southeast Coast,but shows a significant negative correlation over parts of Huang-huai area;the latitude of the ridge line of WPSH and nehover north China and northeast China shows a significant positive correlation;the intensity of WPSH a