NUMERICAL SIMULATION OF HARMATTAN DUST OVER WEST AFRICA USING A FINE RESOLUTION WEATHER MODEL

Abstract

This study investigated the ability of the Weather Research and Forecasting model coupled with the Chemistry (WRF-Chem) model using the GOCART dust scheme in capturing the spatial and temporal distribution of a severe dust storm which occurred from 5th – 14th March, 2006 over West Africa at 30 km and 10 km model resolution. The period coincides with the African Multidisciplinary Monsoon Analysis (AMMA) Special Observing Period (SOP) which produced the Aeronet Robotic Network (AERONET) data used as one of the observation datasets. From the 5th March, a dust storm started to form in northern Algeria, which propagated south (and to the west and east) over the following days. An intense dust haze was transported southward over the Gulf of Guinea thereby generating an Aerosol Optical Depth (AOD) greater than 4 over Nigeria. Qualitative and quantitative characterization between observations and WRF-Chem simulations demonstrate the WRF-Chem model efficiency to simulate the spatial and temporal distribution of harmattan dust over West Africa. We discovered that the WRF-Chem modeled AOD under estimated the AOD from AERONET as a result of all other aerosols integrated into it. Five different sizes of dust particles were simulated and it was also discovered that dust particles of sizes 1.4 μm, 2.4 μm and 4.5 μm are more prevalent among other sizes from the raised and transported dust over West Africa