AEROSOL OPTICAL DEPTH (AOD) VARIATION OVER HARYANA DUE TO LOCKDOWN AMID COVID-19 AS AN INDICATOR OF AIR QUALITY Dharmendra Singh, Chintan Nanda Haryana Space Applications Centre (HARSAC) related to the air pollutants and pollution driven problems those are having potential to affect both human and environment however, the same is limited due to geographically limited observation of aerosols [7]. For the qualitative ground based measurements of AOD, a network of ground sun-photometers worldwide Aerosol Robotic Network (AERONET) has been established. Based on the AERONET measurements it has been observed that the annual averaged AOD exceeds the global background levels by 4–5 times [8]. AOD is important variable that indicates air quality of a region. Various other ground based observations systems are available for AOD measurement however with large coverage area, receptivity of measurements and relatively of lower cost satellite based AOD can be efficiently used for air quality monitoring over Haryana. There have been numerous studies done on AOD characterization based on satellite based measurements [8; 9; 10; 11; 12]. MODIS AOD parameter is substantially validated regionally and globally and has been used for aerosol studies [9]. There are two different algorithms used to retrieve aerosol properties over land and over ocean and these algorithms are improved in day by day manner [10]. A comprehensive description of the MODIS aerosol retrieval algorithms can be found at MODIS aerosol science team publications [11]. AOD have also been found to be highly correlated with PM2.5. Thus reduction in AOD may be conformed from the analysis of PM2.5 concentration over the same geographical region. Taking this, the current study has been taken up to assess the variations in AOD and PM2.5 due to COVID-19 driven lockdown. 2. MATERIAL AND METHODOLOGY 2.1 Study Area Haryana state is situated in north-central India and bounded within the latitude of 27.64258158 to 30.90568992 and longitude of 74.46724953 to 77.53797611 (Figure 1) with geographical area 44,212 sq. km. 170 ABSTRACT Air quality is an important parameter related to the human health. Aerosol Optical Depth (AOD) is an important variable that indicates column integrated particulate matter in the air and used for air quality assessment. Thus in the current study AOD derived from Moderate Resolution Imaging Spectroradiometer (MODIS) at a spatial resolution of 3 km have been used as an indicator of air quality. Results indicate that the AOD concentration has decreased by 35% during the lockdown period in the month of April 2020 as compared to the years 2016 to 2019 in the same month. This indicates that the air quality was improved during the lockdown amid COVID-19 over the Haryana state. The same was conformed from the reduction of Particulate Matter (PM2.5) concentration by 68% during the lockdown period as compared to the year 2019 for NCR region of Haryana. Index Terms— Satellite data, AOD, Air Pollution, Pandemic, NCR Districts Haryana 1. INTRODUCTION Air pollution is a major environmental risk to health caused about 7 million deaths in 2016 [1] and 137 million at risk in United State [2]. Global data shows that 9 out of 10 people breathe air containing high levels of pollutants [3]. The air Pollution problem in India is a serious issue as it has 21 world`s most polluted cities in a list of 30 cities made by IQair [4]. Indians face 2 million premature deaths every year due to air pollution. In 2017 alone 1.24 million deaths which contributes 12.5% of the total deaths, were attributed to air pollution [5]. Air pollution not only affects human health but also the socioeconomic conditions. Under the NCAP (a central scheme for pollution reduction) it is decided to reduce the pollution level by 20 to 30% in 102 most polluted cities by the year 2025 considering 2019 as base year which may increase the life expectancy of all Indians by 1.3 years [6]. Aerosols (minute particles suspended in the atmosphere and represented by AOD) are indicators of pollutants levels and may provide required information © IEEE 2021. This article is free to access and download, along with rights for full text and data mining, re-use and analysis. InGARSS 2020 2020 IEEE India Geoscience and Remote Sensing Symposium (InGARSS) | 978-1-7281-3114-6/20/$31.00 ©2020 IEEE | DOI: 10.1109/InGARSS48198.2020.9358971