Sources, sinks, and transatlantic transport of North African dust aerosol: A multi-model analysis and comparison with remote-sensing data

This study evaluates model simulated dust aerosols over North Africa and the North Atlantic from five global models that participated in the AeroCom phase II model experiments. The model results are compared with satellite aerosol optical depth (AOD) data from MODIS, MISR, and SeaWiFS, dust optical depth (DOD) derived from MODIS and MISR, AOD and coarse-mode AOD (as a proxy of DOD) from ground-based AERONET sunphotometer measurements, and dust vertical distributions/centroid height from CALIOP and AIRS satellite AOD retrievals. We examine the following quantities of AOD and DOD: (1) the magnitudes over land and over ocean in our study domain, (2) the longitudinal gradient from the dust source region over North Africa to the western North Atlantic, (3) seasonal variations at different locations, and (4) the dust vertical profile shape and the AOD centroid height (altitude above or below which half of the AOD is located). The different satellite data show consistent features in most of these aspects, however the models display large diversity in all of them, with significant differences among the models and between models and observations. By examining dust emission, removal, and mass extinction efficiency in the five models, we also find remarkable differences among the models that all contribute to the discrepancies of model simulated dust amount and distribution. This study highlights the challenges in simulating the dust physical and optical processes, even in the best-known dust environment, and stresses the need for observable quantities to constrain the model processes.JRC.H.2-Air and Climat