Time series trend analysis of rainfall and temperature over Kolkata and surrounding region

Studies of temperature and rainfall long-term variability in the context of climate change are important, particularly in regions where rainfed agriculture is predominant. Long-term trends of temperature and rainfall have been determined for Kolkata, India (a tropical region) using gridded monthly data from the Global Precipitation and Climate Centre (GPCC v. 7) with 0.5 degrees x 0.5 degrees resolution for the period 1901 to 2014. Precipitation concentration index, coefficient of variation, and rainfall anomaly have been calculated and Palmer drought severity index has been analyzed. Furthermore, the Mann-Kendall test and Sen's slope estimate have been used to detect time series trend. Annual temperature and rainfall have increased at a rate of 0.0082 degrees C yr-1 and 0.03 mm yr-1, respectively. Most months show statistically significant increasing trends for temperature and rainfall. Rainfall with high precipitation concentration index (16-20) has been observed for the period 1951-1975 and 1976-2000. The number of years with dry conditions has increased. However, the intensity of dryness is very close to zero. The information from this study will be helpful for farmers to plan for resilient farming.