Variability and Changes in Cloud Cover Over India During 1951–2010

Abstract

Utilizing 195 surface meteorological stations data, changes in annual and seasonal total cloud cover over India were analyzed for the period 1951–2010. There is a general decrease in mean total cloud cover over most of India but an increase in the Indo-Gangetic plains and north-east India. Long-term mean total cloud cover over India has seasonal variations with the highest cloud cover (69.1 %) in monsoon and the lowest cloud cover (25.8 %) in winter season. The annual mean total cloud cover shows significant decreasing trend of −0.44 % per decade, mainly contributed by the monsoon season where declining rate is −0.93 % per decade. Out of the total number of stations showing decreasing trends, 59, 38, 48, 58 and 33 % of the stations show significant decrease in total cloud cover for annual, winter, summer, monsoon and postmonsoon, respectively. Trends with larger magnitudes are occurring over Central India. Spatially, the seasonal patterns of trends in total cloud cover confirm the annual patterns in most cases. The relationship of total cloud cover variability with related meteorological parameters such as diurnal temperature range and numbers of rainy days is physically consistent during the period of study.