Impact of transport schemes on modeled dust concentrations

A sensitivity study is performed with the CHIMERE-DUST chemistry transport model in order to evaluate the modeled mineral dust spread due to the horizontal transport scheme accuracy. Three different schemes are implemented in the model: the simple first-order UPWIND scheme, the second-order Van Leer scheme, and the third-order parabolic piecewise method (PPM) scheme. The results showed that a large part of the uncertainty in dust modeling may be due to the transport scheme only. Compared to the PPM scheme, it is shown that, over a large domain encompassing western Africa and the North Atlantic, a significant increase in the dust plume extension is locally diagnosed (+25% with Van Leer and +48% with UPWIND) and linked to a decrease in the dust maxima (-17% with Van Leer and -32% with UPWIND) to PPM. Far from the sources, hourly surface concentration differences may be up to 30 μg m^-3 in Europe, highlighting the high uncertainty of dust modeling for air quality use.