Abstract
This study aims to evaluate dust impact on climate parameters over the Sahel region by RegCM3 regional model during 2006. Indeed, aerosols are one of the main uncertainties in climate models. The aerosol optical depth (AOD) derived from RegCM3 model has been validated with various observed datasets. The aerosol sources are identified over North Algeria and East of Sahel (Bodele depression). Discrepancies are noted when considering dust temporal and spatial distribution. Dust season extends between March and October, with two peaks of AOD recorded in March (spring) and June (summer). The dust vertical distribution showed that the mineral aerosol layer is located between 850 hPa and 300 hPa (1.5 km to 7 km). The RegCM3 model simulates fairly well the transport in the upper layers, especially in the Saharan Air Layer (SAL) during the summer. However, RegCM3 simulates poorly the transport and sedimentation of particles in the lower layers (below 2 km). The investigation of dust radiative impact shows a general cooling. The maximum of radiative forcing is located around 18°N - 20°N, with values of about -80 W/m2 in June - August (JJA) and -40 W/m2 at the surface during March - May (MAM). This study also showed the indirect effect of dust with a decrease in precipitation about -0.7 mm/day around 15 - 20°N during the rainy season.
Highlights
Annual Seasonal and Daily Pattern of Dust We begin by showing in Figure 2, the annual average of aerosol optical depth (AOD) obtained with models (RegCM3 and Global Ozone Chemistry Aerosol Radiation and Transport (GOCART)) and by two radiometers on orbit (MODIS and Multi-Angle Imaging Spectro Radiometer (MISR)) in 2006
These maximum are located between 15 and 20 ̊N latitude and longitude about 8 ̊W according to RegCM3; GOCART and MISR locate these sources in the band 15 ̊N 18 ̊N and 15 ̊E
The dust is located in the lower layers (1 - 2 km) in the dry season and in the Saharan Air Layer (3 - 5 km) during the boreal summer
Summary
The African continent is not well equipped in terms of measurement tools for assessing the climate and its evolution. It is the continent where climate change impacts are felt the most (drought in 1970). To better understand and study the variations of climate over Africa, the use of regional climate models is of great importance. These types of models have the advantage of using fine resolutions and taking into account local meteorological processes
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