中文摘要：

利用我国35°N以北地区333个测站46年逐日地面观测总云量、低云量、降水量和温度资料,系统地研究了该地区云和降水的空间分布特征,用趋势分析方法分析了各区内的总云量、低云量及降水量的变化趋势。结果表明,我国35°N以北地区东部总云量、低云量呈明显减少趋势,而西北区西部略有增加。降水量表现出西北区西部及东北区西部呈增加趋势,而东部呈减少趋势,其中西北区东部、华北和东北区东部近年来降水量明显减少,呈干旱化趋势。分析总云量和低云量与温度和降水量之间的相关,发现总云量与温度呈负相关;而低云量与气温呈弱的正相关,与降水量呈较显著的正相关。总云量是制约我国北方温度变化的重要因素,而低云量则是影响降水的主要因素。

英文摘要：

The spatial and temporal characteristics of the cloud cover over six regions of Northern China are systematically investigated based on the daily data of cloud cover and precipitation at 333 observation stations in the region to the north of 35°N from 1960 to 2005.The correlation between the total cloud and low cloud covers with the precipitation is discussed.Linear variational trends of the total cloud and low cloud covers and precipitation from 1960 to 2005 were analysed.The results show that： The cloud cover decrease in the east of Northern China and increase in the northwest China;precipitation in the northwest and northeast of China increase in the region to the north of 35°N and reduce trend in the east;precipitation in the northwest and northern part of northeast of China obvoiusly increase in the recent years,which appears drought trend.Analysis on the correlation between cloud cover with precipitation and temperature show that there is a significant negative correlation between the total cloud and low cloud covers with temperature.It is found that correlation between the low cloud cover and temperature is positive,but notable positive correlation with precipitation.This indicates that the total cloud cover maybe is a important factor to restrict the change of temperature in the Northern China,while the low cloud cover is an important factor of precipitation.