Abstract: A study has been carried out to analyze the annual and seasonal spatial patterns of trends in mean maximum temperature (MMAX), mean minimum temperature (MMIN) and diurnal temperature range (DTR = MMAX-MMIN) in India during 1961-2010. Additionally, we analyzed the spatial dependence of DTR trends on the low cloud cover (LCC) and number of rainy days (NRD). The study has revealed uneven changes in DTR across regions and time of the year in India. All India averaged annual MMAX and MMIN are increasing at the rate of 0.05 °C/decade but there is no trend in annual DTR. Seasonal averaged MMAX and MMIN are increasing for all seasons except MMIN in monsoon. But country averaged seasonal DTR is decreasing for winter and post monsoon mainly due to higher increases in MMIN or lesser decreases in MMAX, increasing for monsoon mainly due to higher increases in MMAX or lesser decreases in MMIN and showing no trend for summer during the period of study. Spatially, both MMAX and MMIN have increased all over India with the exception of northeastern region. However, DTR trends show a distinct contrast between northern and southern half of India. The amplitude of increase of MMIN compared to MMAX is high over north causing significant decrease in DTR. However, the amplitude of increase in MMAX compared to MMIN is high enough to cause significant increase in DTR in southern half of India. Stations in Western Himalayas show significant increase in DTR in all seasons except monsoon. MMAX trends in the Indo-Gangetic plains are significantly decreasing. The correlation analysis reveals that LCC and NRD are responsible for explaining much of the variance in DTR over India during the study period. Furthermore, local factors like land-use change, deforestation, urbanization, anthropogenic aerosols may also have contributed to the overall trends in DTR.
Keywords: Climate change, Maximum temperature, Minimum temperature, Diurnal temperature range, Low cloud cover, Rainy days, Trends, Correlation
