Co-variance nexus between ultraviolet index and tropospheric ozone during COVID-19 lockdown over megacities of India

Abstract Worldwide spread out of COVID-19 in a short-time has brought a significant decline of road traffic, tourist flow and industrial ventures. During this emergency period, the restricted human dealings with nature have appeared as blessing for health of the total environment. The variation of atmospheric O3 may modulate the range of UV index (UVI) at any region of the earth. The objective of the study is to examine the alteration of UV index over the megacities of India with respect to tropospheric O3 level modification during COVID-19 lockdown. The spatiotemporal data of UVI, over the major megacities of India (New Delhi, Mumbai, Kolkata, and Chennai) have been extracted from Tropospheric Emission Monitoring Internet Service. The monthly average surface ozone concentration throughout the time frame of 2019 and 2020 has been obtained from NASA Earth Observatory (NEO) hub. The meteorological or environmental data (temperature in °C, gust in km/h, wind speed km/h, relative humidity in %, air pressure in mb and cloud cover in okta) of four selective megacities of India (Kolkata, Chennai, Delhi, Mumbai) during and pre lockdown period have been acquired from world weather online. The descriptive statistical applications i.e. standard deviation, standard errors and K-means clustering have been done through standard statistical software. The result shows that the four major megacities in India namely New Delhi, Mumbai, Kolkata and Chennai have experienced the vibrant diminution in terms of the concentration of UV index with slightly increasing the tropospheric O3 level during the lockdown phase. In the meantime, the prominent reduction of NOx during the lockdown period decreases the titration impact to O3 and this mechanism helps to revitalize the ozone concentration level. The uniqueness of the current study is highlighted the ground reality regarding reduction of UV index and amplification of tropospheric O3 concentration during lockdown phase. This study definitely assists to make new environmental policy, act and law for recover the health of the total environment.