Precipitation and temperature changes in eastern India by multiple trend detection methods

Abstract

The present study deals with spatial and temporal trend analysis of precipitation and temperature (1970–2004) in eastern India. Long-term trend direction and magnitude of change over time (annual and seasonal) were detected and analyzed by Mann–Kendall test, Sen's slope estimator, Least square linear regression, Spearman rank correlation and Sequential Mann–Kendall test. In addition to it, correlation analysis was also performed. Trend analysis of annual rainfall by different methods indicated similar annual trends in eastern India. North-eastern, south-eastern and western parts of eastern India indicated increasing trend, whereas the north-western, central and southern parts showed decreasing trend. A similar trend was observed by different methods in case of seasonal rainfall. During winter season, decreasing trend was observed in the central part, whereas similar results were obtained for pre-and post-monsoon in the western part. The trend during monsoon season was found similar to annual rainfall trend. Abrupt change in trend of rainfall with time was lacking in eastern India. Maximum temperature analysis indicated increasing trend in the western part for all the seasons (except in monsoon) and decreasing trend in the eastern part. On the contrary, increasing trend was observed in the eastern part and decreasing trend in the western half of the study area for all the seasons in case of minimum temperature. Significant changes were observed during monsoon season as compared to other seasons. A decreasing trend in mean temperature was observed in the central, southern and north western parts, whereas it was found to be increasing in the north-eastern, western and south-eastern parts. In majority of the eastern India region, any abrupt change of trend in temperatures with time was not clearly observed. Negative correlation between rainfall and maximum temperature was observed in the entire eastern India. Similar results were observed in case of minimum temperature (monsoon) and mean temperature (pre-monsoon and monsoon).