Investigating Urban Signatures to Monsoon Modification over the National Capital Region (NCR), Delhi

As cities around the world are growing at a rapid pace, the need to understand their impact on the regional to local climate has become more crucial. The potential for urban-rainfall modification has been reported in several studies where urbanisation has a notable impact on cloud development and rainfall modification. Urban settlements are more affected by rainfall than rural areas. Localised circulation patterns, the topography of the region and micro-scale systems induced by Land-Use Land-Cover (LULC) can modify regional flows to produce unique patterns in the urban region. National Capital Region (NCR) - Delhi, the second biggest urban settlement globally, reported an almost ~20 fold increase in urban and built-up areas in past decades. NCR urbanisation during the past few decades caused a corresponding increase up to 3-5 and 2-4 K in values of LST and T2m, respectively, while a decrease in the magnitude of surface winds up to 2 m s-1 was noted. This study attempts to assess the spatio-temporal characters and decadal changes of monsoonal features in detail. NCR Delhi exhibits a reduction in rainfall in the recent period when compared with the 1987-96 decade. The study reveals that the precipitation reduction is alongside the weakening of the monsoon winds over the region. India Meteorological Department (IMD) daily gridded rainfall data, ERA-5 re-analysis is used for vertical profile and spatial analysis of wind distribution, Land Surface Temperature observation (LST) retrieved from the Terra platform of Moderate Resolution Imaging Spectroradiometer (MODIS-Terra), and rainfall measurement from Global Precipitation Measurement (GPM) missions - Integrated Multi-satellite Retrievals for GPM (IMERG) observations are utilized for the analysis and rainfall patterns studied.