Spatial trends in rainfall seasonality: a case study in Jharkhand, India

This study aims to analyse the seasonality of rainfall for Jharkhand State, India over the period of the last 102 years. Rainfall seasonality index and individual seasonality index values were calculated, and trend analysis was performed on yearly data for the individual seasonality index, using the Mann-Kendall test, the sequential Mann-Kendall test and Sen's slope method (also known as the Theil-Sen estimator). The value of the mean individual seasonality index varied from 0.815378 to 0.977228, which indicates that rainfall in Jharkhand is markedly seasonal, with a long dry season. The results of the Mann-Kendall trend test revealed a significant decreasing trend in individual seasonality index over Deoghar, Dumka, Godda, Pakaur and Sahebganj; however, the magnitude of this trend was found to be close to negligible. This decreasing trend could have a pronounced effect on agricultural activities.