Urbanization-Driven Modifications to Pre-Monsoon Thunderstorm Rainfall over Delhi: Insights from Long-Term Observations and High-Resolution WRF Simulations

Abstract

Urbanization strongly influences local weather patterns, particularly during pre-monsoon thunderstorms, by altering precipitation distribution and intensity. This study conducts a long-term climatological analysis of pre-monsoon thunderstorm rainfall over Delhi using observational datasets and reanalysis products to explore spatial and temporal trends, as well as the role of urbanization in shaping the storm behaviour. The current results indicate that urbanization over Delhi tends to amplify convective activity, especially along the city’s boundary regions. Rainfall patterns also show a spatial shift, with higher accumulations often occurring downwind of the urban core, indicating a clear urban influence on thunderstorm-induced precipitation. This effect has been investigated using high-resolution numerical simulations conducted through the WRF model. For this purpose, multiple thunderstorm events between 2008 and 2020 are selected for detailed analysis. Key land surface and atmospheric parameters, viz., latent and sensible heat fluxes, vertical velocity, long-range moisture transport, and precipitation efficiency, are examined. Simulated results imply that incorporating updated Land Use Land Cover (LULC) data significantly improves the model performance in simulating the thunderstorm-generated precipitation and related land–atmosphere interactions. This improvement stems from a more accurate representation of urban expansion, leading to better estimates of heat fluxes, moisture availability, and boundary layer dynamics. Consequently, the model could capture the urban-induced modifications to convection, moisture convergence, and storm-related characteristics more realistically, reducing biases. Thus, the study offers an improved insight into how urbanization reshapes thunderstorm-induced rainfall over a megacity like Delhi.