Simulating Indian Monsoon Rainfall over irrigation intensive regions using updated LULC and irrigation representation in WRF model

Accurate representation of land surface characteristics plays a crucial role in improving regional monsoon simulations. Recent studies demonstrate that irrigation in croplands positively influences rainfall; therefore, explicitly representing irrigated regions can lead to more accurate rainfall simulations. In this study, we employ the Weather Research and Forecasting (WRF v4.5) model to evaluate the performance of two land surface models (LSMs), Noah and Noah-MP, in simulating Southwest (SW) and Northeast (NE) monsoon rainfall over an irrigation-intensive region of India. Here, three simulations were conducted Noah, Noah-MP without irrigation, and Noah-MP with irrigation, using the National Remote Sensing Centre (NRSC) land use land cover (LULC) dataset for 2018-2019, which provides an updated representation of land cover over India. We implement the FAO irrigated fraction map, which serves as the default irrigation dataset in WRF v4.5. The model outputs were compared with the high-resolution regional reanalysis from the Indian Monsoon Data Assimilation and Analysis (IMDAA) of 12km resolution using statistical metrics such as root mean square error (RMSE) and mean bias. The results indicate that both LSMs reasonably capture the broad spatial and temporal characteristics of monsoon rainfall, albeit with varying levels of accuracy. These findings underscore the strong sensitivity of WRF rainfall simulations to both the land surface parameterization and the underlying land use representation, highlighting the importance of accurate region specific high resolution LULC data and LSMs for accurate monsoon rainfall modeling. The results demonstrate that irrigation alters land atmospheric interactions by inducing surface cooling and atmospheric moistening, which modify upper-level humidity, geopotential height, and wind patterns. These changes regulate convective activity differently across space and seasons, leading to regionally and temporally complex rainfall responses. This study provides guidance on selecting appropriate modeling schemes for irrigation-intensive, monsoon-focused simulations over the Indian region.