Comparing the spatiotemporal variation of air quality data from satellite measurements and ground monitoring station in Manila, Philippines before, during, and after the COVID-19 lockdown

The Philippines was placed under several lockdowns to limit movements and prevent the spread of the virus during the COVID-19 pandemic. The imposed restrictions reduced the transport and industrial operations, which are primary contributors of air pollution, mainly in the cities of Metro Manila. Satellite measurements of aerosol optical depth (AOD) and greenhouse gases (GHG) such as carbon dioxide (CO₂) and tropospheric ozone (O₃) can improve surface monitoring of particulate matter (PM_1,2.5,10) and GHG but this requires a better understanding of the relationship between satellite and ground monitoring data. In this study, we used the MODIS MAIAC land AOD data at 550 nm, Sentinel-5P TROPOMI O₃ data, and OCO2 X_CO2 for the satellite data over Manila, Philippines with a concurring 5-year continuous measurement of PM_1.0,2.5,10, O₃, and CO₂ from a ground monitoring station near a busy highway. This measurement coincides with the lockdown from the COVID-19 pandemic and shows how human activities can greatly affect air quality. The results show that PM values before the lockdown period have the highest values and exceed WHO limits, while the lowest values were measured after lockdown period for the whole study period. On the other hand, CO₂ and O₃ values increased. This study also shows the correlation between satellite and ground monitoring data and shows the possibility of using remote satellite data as alternative for ground air quality measurement in Manila. Overall, these findings provide supplemental information for operative policymaking to mitigate air pollution and improve air quality in highly urbanized areas.