Space-Based Earth Observations on Hotspots of Atmospheric NO₂ over India Using Google Earth Engine: An Open-Source Cloud Platform

The atmospheric nitrogen dioxides (NO₂) play an important role in tropospheric chemistry and climate change. The present study focused on utilizing the space based atmospheric NO₂ observations and investigated variability in hotspots of NO₂ concentration using Google Earth Engine over Indian regionThe predominant variability in NO₂concentrations (~ 2-2.3 × 10¹⁶ molecules/cm²)is observed over Indo Gangetic Plain region(IGP). Over the Indian region forest fire hotspots were identified using MODIS/FIRMS data and highest number of forest fires was observed during the premonsoon. Lightning FlashRate (LFR)/ Lightning Flash Density (LFD) was estimated using Lightning Imaging Sensor (LIS) data on-board on Tropical Rainfall Measuring Mission (TRMM). Highest LFR is observed during monsoon season with values levelling between 120 to 180 Flashes yr^− 1km^− 2 while the lowest is observed during the post monsoon season with values ranging between 40 and 100 Flashes yr^− 1km^− 2during the years 2012–2014. Results indicated that Lightning Flash Rate is spatially correlated well with the hotspots of tropospheric NO₂ concentration with correlation coefficients varying between 0.5 and 0.9 during monsoon.The present study also investigated the relationship between the lightning density, tropospheric NO₂ concentration over the persistent NO₂ hotspot regions. Further, a case study was examined over the Punjab and Haryana regions during 2019–2021 post-monsoon period for the active stubble burning in accordance with the severity classes and the burnt area was estimated. Moderate and High Severity is seen in different region of Punjab for almost all the years considered for analysis (during October-November).