Evaluation of dust extinction and vertical profiles simulated by WRF-Chem with CALIPSO and AERONET over North Africa

Abstract

In this study, the Weather Research and Forecasting model with Chemistry (WRF-Chem) is applied to compare the simulated dust content and extinction coefficients from the Goddard Chemistry Aerosol Radiation and Transport (GOCART), the Air Force Weather Agency (AFWA) and University of Cologne (UoC) dust emission scheme available in WRF-Chem. The observations made by the AErosol RObotic NETwork (AERONET) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) are used to assess the model performance during the summer of 2006 over northern Africa. The results highlight that all the three schemes reproduce broadly the observed spatiotemporal distribution of dust content and extinction profile over northern Africa. However, differences exist in extent and intensity between the three emissions schemes and observations. All the three dust emission schemes reproduce the daily variation of the major dust events observed from the AERONET stations over northern Africa but failed to capture correctly the spatial distribution of the maximum zones of observed dust content by CALIOP. It is found that the simulated dust extinction profiles overestimate broadly the observation from CALIPSO in terms of vertical extent and magnitude over northern Africa. Our results reveal significant differences between the three schemes (GOCART, AFWA, and UoC). These differences between the schemes could be related to the calculation of the threshold wind speed in each scheme, which indicating the necessity to continue improving these dust emission schemes in the WRF-Chem model to better reduce uncertainties in the representation of dust plumes.