Analysing trends of climatic variables in Purulia district, India using non-parametric methods

Location-specific data on rainfall and temperature trends at different temporal scale is crucial for developing agricultural strategies and managing water resources in drought prone areas like Purulia, West Bengal. Therefore, the present study assessed the spatio-temporal variability of rainfall and temperature in Purulia by utilizing gridded data for 40 (1984–2023) years from India meteorological department (IMD). We employed the Mann-Kendall (MK), modified Mann-Kendall (mMK) test and Sen’s slope estimator (β) to identify the trend and magnitude of change. Furthermore, innovative trend analysis (ITA) is used to detect sub-trends of the data series. The results of MK/mMK and Sen’s slope showed a declining trend of annual rainfall (Z= -1.990, β =-7.015) and increasing trend of annual maximum (Z = 2.200, (β) = 2.021) and minimum (Z = 2.060, β = 0.015) temperature. However, variability of annual rainfall (16.03%) is higher than variability in annual temperature (maximum temperature = 2.29%, minimum temperature = 1.81%). On seasonal scale, negative trends have been observed for winter and monsoonal rainfall and positive trends for summer and post-monsoonal rainfall. While maximum and minimum temperature of the study area is dominated by increasing trends. The result of ITA is more or less similar to the MK/mMK and Sen’s slope. Additionally, Spatial mapping of Z statistics and ITA slope showed that agriculturally productive subdivisions Purulia Sadar and Manbazar are significantly vulnerable to climate variability. The findings of this study offer a suitable framework for the development of future projects since it accurately explains the variability of rainfall and temperature.