中文摘要：

根据NCEP/NCAR逐日、逐月温度资料和相对湿度资料,及长江中下游60个气象站逐日降水资料,采用趋势分析、突变检验等方法,研究了近60年来全球和北半球地表温度变化趋势,分析了温度增加前后,夏季（6～8月）对流性降水的变化特征及其部分影响因子。结果表明：近60年来,北半球年平均及夏季平均地面温度为增暖趋势,1998年为增暖突变年份;变暖后,长江中下游地区夏季对流性降水事件的发生频率呈增多趋势且强度增强;全球增暖后,对流层中、高层水汽含量呈下降趋势,对流层低层水汽含量呈上升趋势;热含量除个别月份外,在700、850、1000hPa均有明显增长;大气中不稳定性也显著增强。这些与对流性降水事件发生频率的增加和强度的增强有很好的对应关系,说明全球变暖导致的大气中水汽含量变化、湿空气热含量增加和不稳定性增强对对流性降水事件可能有重要影响。

英文摘要：

The authors analyzed the tendency of the annual and summer average surface temperatures in the Northern Hemisphere for a period covering nearly 60 years and the variation of the convective precipitation occurred in summer （June-August）. The possible causes of the variation were also researched in this article by investigating the impact factors of the convective precipitation. The analysis was based on the monthly data, daily and monthly relative humidity, temperature data of NCEP/NCAR, and the daily precipitation records of 60 selected stations in the mid-lower reaches of the Yangtze River using trend analysis and mutation testing method. The results show that for nearly 60 years the annual and summer average surface temperatures in the Northern Hemisphere have been rising with an abrupt temperatures leap in nearly 1998 so that this year can be regarded as an temperature discontinuity. With the increasing effect of global warming, both the frequency and intensity of the convective precipitation events that occurred in summer were enhanced in the reaches of the Yangtze River. In years when the temperature was higher than average, the water vapor content in the upper and middle troposphere showed a continuously decreasing trend and in the lower troposphere showed an increasing trend in July and August. Apart from a few individual years, the heat content at the 700 hPa, 850 hPa, and 1000 hPa levels had an obvious positive trend. The atmospheric instability also showed a clear tendency of strengthening. These factors have a strong correlation with the increasing frequency and intensity of the convective precipitation. It was concluded that changes in water vapor content and enhancement of heat content and atmospheric instability caused by global warming may have an important influence on the increase of convective precipitation events.