Assessment of Diurnal Temperature Range and Urban Heat Island effect over megacity Delhi

Abstract

An estimate by World Urbanization Prospects suggests that by the year 2050, around 69 percent of the global population will live in the urban areas. Over the last several decades, the National Capital Region (NCR) of India has seen a significant increase in urban and built-up area. The proposed study focuses on the estimation of land use land cover over the megacity Delhi. Furthermore, the influence of these land use/land cover changes on the spatial and temporal variability of meteorological parameters is studied. For the scope of this study, Land Surface Temperature, Diurnal Temperature Range (DTR) and Urban Heat Island (UHI) effect has been assessed over the study region. For the past two decades (1997-2020), the growth in built-up areas has been observed at 140 percent. Increase of urban settlements suggests impact on radiation budget and impact on surface temperatures. This study observes increase in nighttime Land Surface Temperature by more than 1 ⁰C within 20 years span with a high heating rate of 0.0642 ⁰C/year. The diurnal temperature range also witnessed a decrease of more than 1.6 ⁰C with a decline rate 0.0739 ⁰C/year, with increasing urbanization. Urban Heat Island effect has been prominent over the study region. Increase in UHI values over 20 years can be observed from the assessment in urban canopies. Maximum UHI of more than 5 ⁰C at urban hotspots have been observed through this assessment. The impacts depicted here have major consequences for human health, energy consumption, ventilation, and air pollution.