Spatio-Temporal Dynamics of Tropospheric Pollutants and Land Surface Temperature over Andhra Pradesh, India: A Google Earth Engine-Based Satellite Remote Sensing Study (2020–2024)

Air quality monitoring is the need of the hour in Andhra Pradesh, owing to the accelerated pace of urbanization and industrial growth in certain areas. This study undertakes a detailed spatio-temporal evaluation of six major air pollutants-carbon monoxide (CO), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), ozone (O₃), particulate matter (PM2.5 and PM10) along with Land Surface Temperature (LST) across the state for the period 2020–2024. In the current study a multi-sensor suite of satellite data was processed and analyzed using the Google Earth Engine (GEE) cloud platform, which includes Sentinel-5P for trace gases, MODIS-derived Aerosol Optical Depth (AOD) for particulate matter, and Landsat 8 for LST. The results reveal persistent pollution hotspots concentrated in the industrial corridors of Visakhapatnam-Kakinada and the urban agglomerations of Vijayawada and Tirupati, particularly for NO₂ and PM2.5. Temporal analysis indicates a significant reduction in NO₂ during the 2020 COVID-19 lockdown, followed by a gradual rebound in later years. High-resolution LST analysis distinctly delineated the Urban Heat Island (UHI) effect in major cities. A key contribution of this work is the development and application of a multi-level threat classification framework, which translates raw concentration data into an intuitive risk assessment map for each parameter. This research validates a scalable, multi-sensor approach for environmental surveillance and provides actionable, data-driven insights to support evidence-based air quality management and sustainable urban planning.