DIURNAL ASYMMETRY OF SURFACE-TEMPERATURE TRENDS OVER INDIA

Diurnal asymmetry of the recent surface warming, reported for several continental areas, is believed to be related to changes in cloudiness, humidity, atmospheric circulation patterns, winds and soil moisture. This paper presents linear trend analyses of maximum and minimum tempe rature data at 121 stations in India during the period 1901-87. While the mean temperature trends over India are similar to the global and h emispheric trends, there are marked differences in their diurnal manif estation from those reported for other areas. The increase in the mean temperatures over India is almost solely contributed by the maximum t emperatures, with the minimum temperatures remaining practically trend less, leading to an increase in the diurnal range of temperatures. The se trends do not show any significant urban or altitude bias. There ar e some differences in the trends on smaller spatial and temporal scale s, but the increase of maximum temperature is predominant over a major part of India, particularly in winter and post-monsoon seasons.