Regional Simulation of Present-day (1981–2010) Saharan Dust Aerosols using WRF-Chem

The Sahara Desert is the largest source of aeolian dust with high annual transport across West Africa, Europe, the Caribbean and United States, which affects air-quality, and poses a health risk to many communities. Global Climate Models (GCMs) are used to project future climate under different representative concentration pathway (RCP for CMIP5) or shared socioeconomic pathway (SSP for CMIP6) scenarios; however, their coarse resolution present major challenges in resolving primary dust emission over dust sources in North Africa. In this study, we drive the Weather Research and Forecasting (WRF) model coupled with Chemistry (WRF-Chem) at the lateral boundaries using reanalysis products from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the National Center for Environmental Prediction (NCEP), and model outputs from the Coupled Model Intercomparison Project Phase 6 (CMIP6) Earth System Models (ESMs) for the period of 1981 to 2010 at every 6 hours. Three CMIP6 models; the Max Planck Institute Earth System Model (MPI-ESM), the Community Earth System Model 2 (CESM2), and the third European Consortium Earth System Model (EC-EARTH) are used to drive WRF-Chem at 20 km grid spacing. Field campaigns such as the BoDEx 2005 dust experiment can provide valuable case studies to evaluate the WRF-Chem simulations. Preliminary results show WRF-Chem accurately simulates the BoDEx 2005 dust plume in terms of the intensity, location, and timing of the event, and show consistency with previous studies. We will evaluate the simulated dust in terms of the vertically integrated quantity (aerosol optical depth) against the Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging SpectroRadiometer (MISR) from 2000 to 2010, the vertical profiles against the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) from 2006 to 2010, and the surface concentration against the African Monsoon Multidisciplinary Analysis (AMMA) measurements over the Sahel from 2006 to 2010. The preliminary results so far suggest large biases in terms of the magnitude of dust concentrations during winter but less in summer. Reasons for such seasonal biases are being explored and will be presented in this conference.