[1] Mineral dust aerosols play an important role in the climate system. Coupled climateaerosol models are an important tool with which to quantify dust fluxes and the associated climate impact. Over the last decade or more, numerous models have been developed, both global and regional, but to date, there have been few attempts to compare the performance of these models. In this paper a comparison of five regional atmospheric models with dust modules is made, in terms of their simulation of meteorology, dust emission and transport. The intercomparison focuses on a 3-day dust event over the Bodélé depression in northern Chad, the world's single most important dust source.Simulations are compared to satellite data and in situ observations from the Bodélé Dust Experiment (BoDEx 2005). Overall, the models reproduce many of the key features of the meteorology and the large dust plumes that occur over the study domain. However, there is at least an order of magnitude range in model estimates of key quantities including dust concentration, dust burden, dust flux, and aerosol optical thickness. As such, there remains considerable uncertainty in model estimates of the dust cycle and its interaction with climate. This paper discusses the issues associated with partitioning various sources of model uncertainty.

Dust plays a vital role in climate and biophysical feedbacks in the Earth system. One source of dust, the Bodé lé Depression in Chad, is estimated to produce about half the mineral aerosols emitted from the Sahara, which is the world's largest source. By using a variety of new remote sensing data, regional modeling, trajectory models, chemical analyses of dust, and future climate simulations, we investigate the current and past sensitivity of the Bodé lé . We show that minor adjustments to small features of the atmospheric circulation, such as the Bodé lé Low-Level Jet, could profoundly alter the behavior of this feature. Dust production during the mid-Holocene ceased completely from this key source region. Although subject to a great deal of uncertainty, some simulations of the 21st century indicate the potential for a substantial increase in dust production by the end of the century in comparison with current values. mineral aerosol ͉ regional climate model ͉ low-level jet

The Bodélé depression (Northern Chad) is believed to be the single largest source for the Saharan dust transported over the Atlantic Ocean, especially that emerging in the Gulf of Guinea in boreal winter. During the Bodélé Dust Experiment 2005 (BoDEx 2005), which was performed in February–March 2005, a severe dust event was observed and some of its main characteristics (surface wind, dust concentrations, radiation) were recorded. This paper tests the capability of a mesoscale model coupled online with a dust production model (DPM) to reproduce the small scale features associated to this dust event. These simulations clearly show that a spatial resolution of 10 km × 10 km is required to reproduce satisfactorily the observed surface winds and the main characteristics of the dust plume.

Abstract. The potentiality of dust particles to mix with sulphate over Tropical Africa and the Atlantic Ocean is investigated by combining a meso-scale meteorological model with a dust production model and an SO2 emission database. This mixing process study is based on a qualitative approach where the reactivity of dust is estimated from its calcite content, which is the main mineral known to be reactive with sulphur species. We are presenting a 1-month simulation (January 1993). Our results show that the regions Northern Egypt and Libya (NEL), Western Sahara (WS) and Sahel (S) are the major sources of dust plumes. The simulated dust loading is in agreement with the measured data close to the African coasts. The Mediterranean and Maghreb regions are highly influenced by European sources of sulphate, for which the simulated concentrations are consistent with the observed trends. This simplified study identifies two zones that favour the mixing process between dust and sulphate: 1. the Eastern Mediterranean basin due to the concomitance of high concentrations of dust and sulphate and 2. the North-Eastern Atlantic Ocean due to the high amount of calcite in the ejected dust which is very reactive. Thus, we assume that the coating process takes place mainly in these regions and the sulphate-coated dust found on the other side of the Atlantic Ocean (Caribbean and American coasts) is principally due to this phenomenon.