Performance of the CORDEX-SA Regional Climate Models in Simulating Summer Monsoon Rainfall and Future Projections over East India

The Indian summer monsoon rainfall (ISMR, June–September) is an important factor in agricultural planning and the Indian economy. The ISMR over East India (EI: Chhattisgarh-Bihar-Jharkhand-Odisha) is particularly significant, and it can have an impact on the country's average ISMR. The current study examined projected changes in ISMR over EI with two emission scenarios, RCP4.5 and RCP8.5, for near (2017–2040) and far-future (2041–2070) projections using a set of ten CORDEX-SA Regional Climate Model (RCMs). To begin, the performance of raw and bias-corrected ISMR over EI outputs from ten CORDEX-SA RCMs was compared to a high-resolution (0.25° × 0.25°) gridded rainfall analysis dataset from the India Meteorological Department (IMD) over the hindcast period (1971–2005). Following that, bias-corrected results were used to calculate ISMR projections over EI for the near and distant futures. Most RCMs, according to the findings, can imitate the spatial pattern of ISMR across EI but are restricted in their ability to capture actual magnitudes. Notably, RCM prediction skill increased greatly after employing various bias-correction approaches, the quantile mapping (QQM) bias-correction technique outperformed other current conventional bias correction methods, and the QQM technique was employed for ISMR future projections using RCP4.5 and RCP8.5 emission scenarios. The analysis of ISMR projections over EI reveals that there will be more deficit rainfall years in the short term while more excess rainfall years in the far future.