Atmospheric dust modeling from meso to global scales with the\ud online NMMB/BSC-Dust model � Part 2: Experimental campaigns\ud in Northern Africa

摘要

The new NMMB/BSC-Dust model is intended\udto provide short to medium-range weather and dust forecasts\udfrom regional to global scales. It is an online model\udin which the dust aerosol dynamics and physics are solved\udat each model time step. The companion paper (P�©rez et al.,\ud2011) develops the dust model parameterizations and provides\uddaily to annual evaluations of the model for its global\udand regional configurations. Modeled aerosol optical depth\ud(AOD) was evaluated against AERONET Sun photometers\udover Northern Africa, Middle East and Europe with correlations\udaround 0.6â��0.7 on average without dust data assimilation.\udIn this paper we analyze in detail the behavior of\udthe model using data from the Saharan Mineral Dust experiment (SAMUM-1) in 2006 and the Bod�©l�© Dust Experiment (BoDEx) in 2005. AOD from satellites and Sun photometers, vertically resolved extinction coefficients from lidars and particle size distributions at the ground and in the\udtroposphere are used, complemented by wind profile data\udand surface meteorological measurements. All simulations\udwere performed at the regional scale for the Northern African\uddomain at the expected operational horizontal resolution of\ud25 km. Model results for SAMUM-1 generally show good\udagreement with satellite data over the most active Saharan\uddust sources. The model reproduces the AOD from Sun\udphotometers close to sources and after long-range transport,\udand the dust size spectra at different height levels. At this\udresolution, the model is not able to reproduce a large haboob\udthat occurred during the campaign. Some deficiencies\udare found concerning the vertical dust distribution related to\udthe representation of the mixing height in the atmospheric\udpart of the model. For the BoDEx episode, we found the\uddiurnal temperature cycle to be strongly dependant on the\udsoil moisture, which is underestimated in the NCEP analysis\udused for model initialization. The low level jet (LLJ) and\udthe dust AOD over the Bod�©l�© are well reproduced. The remaining negative AOD bias (due to underestimated surface\udwind speeds) can be substantially reduced by decreasing the\udthreshold friction velocity in the model.