Correlation Analyses between Interannual Changes of Cloud Cover and Surface Air Temperature in Ningxia in Recent 40 years

The interannual and interdcadal changes and their correlation relations of air temperature,total-and low-cloud covers have been analysed,utilizing the observed data of the surface air tempernture and 24 stations over Ningxia in recent 40 years.The results show that the mean temperature increase in wavy way in Ningxia in recent 40 years,especially after 1990′s on wards.The interannual changes of air temperature in arid region of middle Ningxia is larger;in Guyuan region,lesser.Since 1951,the annual mean tatal cloud cover in Ningxia gradully decrease.the decreasing tendency of low cloud cover is more obvious than that of the total cloud cover,but the cloud cover in Ningxia has increased after 2000. The correlation analysis indicates that there is a negative relation between annual mean air temperature and total and low cloud covers in Ningxia and they have passed the test of the significant level at 0.01 and the low cloud cover has a more significant relation with the temperature.There is a obvious positive relation between precipitation and total and low cloud cover.Meanwhile,the relation coefficents between the total and low cloud cover in different regions and seasons of Ningxia and the air temperature and precipitation have obvious differences.