Analysis of rainfall epochs in changing climate of Kangsabati river basin, India

Climate change directly or indirectly impacts the global atmosphere composition, which poses major environmental concern. The implications of climate change show noticeable change in rainfall patterns and onset worldwide. Prior knowledge of information of rainfall data is vital for many applications. In the present study, the onset, withdrawal, and duration of monsoon period have been studied for Purulia and Ranibandh locations in the Kangsabati river basin area for the period 2015 to 2022. The observed data were analysed and compared with the model data of CMIP6 GCM’s for 4 scenarios. Statistical parameters such as probability density function (PDF), Cumulative Distribution Function (CDF), Coefficient of determination (R2), and Root Mean Square Error (RMSE) were employed to evaluate the precision of matching between observed and modelled rainfall data. For onset, withdrawal, and duration of monsoon period, under 4 scenarios of Shared Socioeconomic Pathways (SSPs), highest R2 values range between 0.46 and 0.75 for CanESM5, EC-Earth3-veg and ACCESS-CM2 for Purulia and Ranibandh locations. For the duration of monsoon period between onset and withdrawal, R2 value of 0.54 and 0.46 has been observed for CanESM5-SSP370 and ACCESS_CM2-SSP126 for Purulia and Ranibandh respectively. On the other hand, for Purulia and Ranibandh, the lowest RMSE values has been observed for the model CanESM5, EC-Earth3-veg and ACCESS-CM2 for onset, withdrawal and monsoon period. The study identifies CanESM5, EC-Earth3-veg, and ACCESS-CM2 as the top-performing CMIP6 GCM models for accurately simulating monsoon dynamics onset, withdrawal, and monsoon length – in the Kangsabati basin, specifically in Purulia and Ranibandh locations. With these best performing models on projecting the precipitation for 2023 to 2100 for Purulia and 2022 to 2100 for Ranibandh, a very negligible shift has been observed in the onset and withdrawal periods. Overall, this study contributes to our understanding of rainfall patterns and monsoon dynamics, offering valuable insights for both climate modelling and water resource management in the region.