Aerosol Optical Depth over the Middle East and North Africa region in CMIP6 Models: Climatology, Variability, and Trends

Abstract This study evaluates the aerosol optical depth (AOD) distribution in the Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations over the Middle East and North Africa (MENA) region. The CMIP6 outputs are first validated against available moderate resolution imaging spectroradiometer and multiangle imaging spectroradiometer satellite observations and Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2) reanalysis over the 2003–2014 period. The climatological annual AOD fields across the 16 CMIP6 models range between 0.2 to 0.8, in agreement with the satellite observations (0.2 to 0.6). The regionally averaged climatological AOD from the satellite observations over the MENA region is 0.35, while it ranges between 0.15 and 0.50 in the CMIP6 models. A multi-model mean (MME) was constructed as the average of the five best CMIP6 models, selected based on the correlations with observations (> 0.8), and other robust statistical metrics. The MME reproduces the AOD seasonal cycle and its interannual variations over the MENA. The observed positive trends (summer and annual) over the AP, and negative trends (winter) over the North African regions, are well captured. Furthermore, the MME generally reproduces the regional meteorological factors responsible for the AOD trends, albeit with a few discrepancies.