Exploring the Efficiency of MERRA-2 and AIRS Datasets to Evaluate COVID-19 Effects on Carbon Monoxide Over Iraq

This study investigated the use of satellite data to observe carbon monoxide (CO) levels in Iraq during the COVID-19 pandemic. CO data from MERRA-2 (0.50°×0.625° resolution) and AIRS (1°×1° resolution) sensors were analysed alongside observations over five cities between January and June 2019-2020. The comparison aimed to assess the impact of the pandemic on air pollution by cross-referencing these datasets. Monthly surface CO levels measured by both instruments were compared across Iraq, with fluctuations examined relative to the mean CO background. Results showed the largest discrepancies in CO levels occurred in crowded urban areas, mountainous regions, and near CO sources, while minimal differences were observed over deserts and sparsely populated areas. The clear reductions revealed in CO levels in 2020 after mid-February for both AIRS and MERRA-2 instruments compared to 2019, attributed to the COVID-19 impact. Regional CO variations were smaller in pristine desert areas and larger in regions with higher CO concentrations. Due to geographic and meteorological factors and the instruments’ sensitivity to different tropospheric layers, monthly CO anomalies exhibit a seasonal cycle, peaking in January (408.55 ppbv) and reaching a minimum in June (80.89 ppbv). Despite differing sensitivities, the instruments show general consistency. Satellite observations effectively captured the spatial and temporal CO variations across the study area.