Study of aerosols over the southern region of Pakistan using satellite, reanalysis and model data

This study examines aerosol measurements using the Copernicus Atmospheric Monitoring Service (CAMS) model and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data products. Aerosol Optical Depth (AOD) exhibit a strong seasonal cycle, with peak values in July and lowest values in November and December. The characterization of AOD provided by CAMS reveals significant seasonality in the monthly mean AOD of dust (DU), sea-salt (SS), and sulfate (SU), with peaks in June and July. In contrast, AOD of black carbon (BC) and organic matter (OM) show minimal seasonal variation. An increasing temporal trend is observed in BC AOD and SU AOD, whereas the AOD of OM remains relatively constant over the study period. The AODs for BC, OM, and SU are notably lower in the year 2020, which experienced a global lockdown due to the COVID-19 pandemic, reducing anthropogenic aerosol emissions. The comparison of MODIS and CAMS AODs shows a good correlation, with a regression line slope of 0.46 and a correlation coefficient of 0.65. Seasonal comparisons between MODIS and CAMS AOD indicate stronger correlations in winter and autumn, with correlation coefficients of 0.63 and 0.72, compared to summer and spring, where the coefficients are 0.40 and 0.39, respectively. The comparison of root mean square error and mean absolute error show that the CAMS and MODIS data are in good agreement during autumn and winter than spring and summer. Additionally, the root means bias value show that CAMS AOD overestimates MODIS AOD in autumn and underestimates in other seasons.