Spatiotemporal Variability of Extreme Monsoon Precipitation Across Major Indian Urban Clusters

The rapid rate of urbanization across the Indian subcontinent is currently transforming the way the built environment and natural weather patterns interact, especially during the monsoon season. In this respect, we have analyzed long term variability in extreme monsoon precipitation within major urban clusters to assess the impact that dense settlements may apply to the frequency and intensity of heavy rainfall. High resolution observational data for several decades are used to isolate hydrological trends confined to urbanized zones only, beyond large regional signals onto the city scale. This, in turn, provides an opportunity to investigate whether the expanding footprint of cities is amplifying extreme weather events and quantifies heterogeneity due to such changes across diverse geographic contexts. Our analysis exposes a complex and non-uniform landscape of precipitation changes, challenging the notion of a universal increase in rainfall intensity. Instead of having a monotonic increase in all cities, we find significant spatial divergence in the way in which extreme monsoon spells are experienced over urban areas. These contrasting patterns suggest that local urban factors modulate the stability and moisture dynamics of the monsoon differently. This heterogeneity therefore implies that the impact of urbanization on rainfall is not linear but instead highly dependent upon local geographic and atmospheric interactions. The findings thus emphasize the need to use multi-source observations to capture city specific deviations, and to do so in order to enable more hybrid modeling approaches to predict the environmental extremes for the management of flood risks in rapidly developing metropolitan regions.