Spatial and temporal trend analysis of rainfall in eastern India

Abstract

A study on annual and seasonal (winter, pre-monsoon, monsoon, and post-monsoon) trend analysis of Rainfall at the spatial and temporal scales had been carried out during 1901 to 2017 for Eastern states of India. Non-parametric statistical techniques viz. Mann-Kendall (MK) test with Sen’s slope estimator, and Pettitt Mann-Whitney (PMW) test had been carried out to examine the annual and seasonal trends at 5% level of significance. The results of the nonparametric tests showed statistically significant increasing trends in annual and monsoon season for minimum rainfall in West Bengal and statistically decreasing trend was found in annual, winter and monsoon season for Bihar and Jharkhand. Rainfall in Odisha show significant decreasing trend in winter. The rate of change of the rainfall obtained from Sen’s slope estimator was found to be higher in annual (1.56 mm/year) and lower average decreasing trend in seasonal rainfall. The most probable year of changes in the rainfall were occurred in between 1918-1977. In conclusion, it was clear that the magnitude of the rainfall trend is highest in monsoon season and variability is greater in winter season.