The Impact of Covid-19 Lockdown on the Urban Micro-Climate of Major Coastal vs Inland Cities of India

The climatic or meteorological characteristics over a city is significantly influenced by the city dynamics resulting in evolution of a typical micro-climatic condition enveloping the city and peripheral region. The shrinkage and expansion of the urban boundary layer depends on the dimension, design and functioning of a city and its physiographic setup. The lockdown that was enforced for varying durations globally to restrict the Covid-19 pandemic gave an extraordinary opportunity to understand the urban micro-climatic systems with substantially reduced urban operations. Therefore, the present study aims to evaluate the nature of temperature and precipitation conditions for 6 major cities in India, primarily accentuated by the urban fabric and design; during the strict as well as phased lockdown period in India (April – June, 2020). The principal objective of the study is to determine if moderation in transportation as well as commercial and industrial activities which are considered as the backbone of a metropolitan, can regulate the micro-climatic system it emanates. A comparative analysis has been attempted between the three coastal (Mumbai, Chennai, Kolkata) and three inland (Delhi, Hyderabad, Bangalore) cities to gather an understanding of the impact-magnitude, the sea has on urban meteorology. Meteorological reanalysis, satellite as well as in-situ Automatic Weather Station data products have been used for the analysis and validation of results. During the month of April when the lockdown was most stringent, there was an evident improvement in air quality with decrease in the concentration of PM2.5, PM10 and AOD (Aerosol Optical Depth) for all the cities in a range of 30 – 60 percent. To examine the direct and indirect impact of the decreased levels of air pollution on the shortwave as well as longwave radiation responsible for creating the UHI effect as well as abnormal rainfall intensity; the air temperature, land surface temperature (LST) and total amount of rainfall received by the individual cities on a daily as well as hourly basis have been considered. The study reveals that there is notable difference in LST and air temperature in the inland cities during the said period in comparison to the previous years, with relative decrease in both minimum and maximum temperature and significant increase in the number of days with lower temperatures. The pattern of high intensity rain events which is typical to intensive urbanization also experienced definite transformation in Bangalore and Delhi even during the phased lockdown period. However, the modification in all these meteorological parameters were observed to be relatively less significant in case of the coastal cities which solidifies the prominence of coastal influence in such metropolis. Therefore, the study concludes that the rapid strengthening of urban micro-climate and its consequences can be mitigated by implementing strategic reduction in core urban activities, especially for cities without external physiographic influence.