Quantifying urban heat island and pollutant nexus over South Asian cities

Thermal comfort of urban residents under changing climate scenarios, varying near-surface aerosol loading and modified urban infrastructure is a raising concern. This is especially true for the cities in South Asia where urbanization induced change in land use, change in urban microclimate and elevated aerosol loading intensifies the frequency, intensity and impact of climate extremes. This study investigates the thermal behavior of South Asian cities, focusing on satellite retrieved geospatial databases including land surface temperature (LST), surface albedo, urban built-up, urban greenery, columnar aerosol loading and co-emitting short-lived trace gases. Spatial patterns of urban microclimate and landscape variables were explored in between heatwave periods during 2020 to 2024 to assess its attribution on the urban thermal environment. Surface urban heat island intensity was spatially correlated with multiple climate and landscape variables over two distinct Indian cities. Using NASA's ECOSTRESS and MODIS-based aerosol optical depth (AOD) data, the study analyzes seasonal and diurnal variations in LST and AOD across urban and rural areas. Urban and non-urban areas were delineated using the city clustering algorithm applied to MERIS Land Cover datasets. Significant diurnal thermal disparities are observed between urban cores and rural areas, with Lahore exhibiting the highest average SUHI (3.48°C). The nexus between urban aerosol loading and aerosol optical property with localized urban heating was explored. Notable aerosol loading disparities were identified, particularly in Lahore (range: 0.53 to 0.73). The findings highlight the critical influence of urban features and urban pollution on urban heat island dynamics across South Asian cities.