High-resolution simulation of a major West African dust-storm: comparison with observations and investigation of dust impact
Simulation haute résolution d'une tempête de poussière majeure d'Afrique de l'Ouest : comparaison avec des observations et investigation de l'impact de la poussière
Kocha, Cécile ; Lafore, Jean-Philippe ; Tulet, Pierre ; Seity, Yann
This study focuses on the radiative impacts of dust on the thermodynamics and dynamics of a major Saharan dust-storm that occurred between 7 and 15 March 2006. The implementation of a dust module within the convective-scale operational model AROME permitted a 10-day simulation at high resolution (5 km) over a large domain (6.530°N; 3°W33°E). The model is able to represent most of the life cycle of this dust-storm and of the principal dust sources. According to the comparison with a complete and comprehensive set of measurements obtained within the framework of the AMMA field campaign in 2006, the simulation succeeds in representing the main thermodynamic and radiative features of the storm both qualitatively and quantitatively. As compared with a simulation without the dust, the coupling with the dust module provides signatures of the storm that are in better agreement with radiation and temperature observations. The intense heating in the core of the dust plume (more than 2°C) resulted in a large vertical dipole of potential vorticity anomaly with higher values at low levels and weaker values at mid levels, either in the lower and the upper part of the dust plume respectively. This shows that the coupling with dust reinforces the intensity of the cold extratropical outbreak with more ascent at the cold front, more cyclonic convergence near the surface, and more anticyclonic divergence aloft. Also, the subsidence is increased at the rear of the outbreak with more northerly winds. A major result is the acceleration of the easterly along-front flow (∼3 m s−1) at low levels and in the African Easterly Jet, increasing the emission of dust and its westward long-range transport. Copyright © 2011 Royal Meteorological Society
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