Analysis of Rainfall Trends and Variability in Eastern Himalaya: Evidence from Sikkim

Since last century, Sikkim has witnessed substantial climatic fluctuations that can affect the local water availability, agricultural productivity, and livelihood security. Despite this growing concern, a limited study incorporated century-long datasets to explore the underlying climatic pattern of the state and often focuses only on trend analysis without applying a diverse set of statistical and spatial techniques. Hence, a comprehensive analysis has been employed to explore the long-term trend and variability of Sikkim’s yearly and seasonal precipitation patterns from 1923 to 2023.Several statistical matrices have been applied viz. Coefficient of Variation (CV), Analysis of Variance (ANOVA) and Tukey’s Honest Significant Difference (HSD) Test to analyze the intra-seasonal and inter-seasonal rainfall variability, Standardized Precipitation Index (SPI) has been used to find out wet and dry years, Precipitation Concentration Index (PCI) shows annual and seasonal rainfall distribution, Simple Moving Average method has been applied to detect long-term trend, Inverse Distance Weighted interpolation technique visualizes the spatial rainfall variation in the state. This research offers new insights into the precipitation behavior and shifting rainfall dynamics such as summer rainfall demonstrates the most significant inter-cluster difference, wet and dry events are significantly increasing in summer season, the highest variability in precipitation distribution can be observed in monsoon rain, the summer and winter rainfall is increasing, where monsoon rainfall is decreasing significantly over the region, monsoon rainfall shows significant increasing trend in Gyalshing and Mangan, where summer and winter rain is increasing at Gyalshing and Mangan. These findings can help in regional adaptation strategies, water resource management, agricultural planning, and minimize climate-related livelihood vulnerabilities, as most of the farmers of this state rely on rainfall for their irrigation purposes.