Abstract
Abstract. The new NMMB/BSC-Dust model is intended to provide short to medium-range weather and dust forecasts from regional to global scales. It is an online model in which the dust aerosol dynamics and physics are solved at each model time step. The companion paper (Pérez et al., 2011) develops the dust model parameterizations and provides daily to annual evaluations of the model for its global and regional configurations. Modeled aerosol optical depth (AOD) was evaluated against AERONET Sun photometers over Northern Africa, Middle East and Europe with correlations around 0.6–0.7 on average without dust data assimilation. In this paper we analyze in detail the behavior of the model using data from the Saharan Mineral dUst experiment (SAMUM-1) in 2006 and the Bodélé 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 troposphere are used, complemented by wind profile data and surface meteorological measurements. All simulations were performed at the regional scale for the Northern African domain at the expected operational horizontal resolution of 25 km. Model results for SAMUM-1 generally show good agreement with satellite data over the most active Saharan dust sources. The model reproduces the AOD from Sun photometers close to sources and after long-range transport, and the dust size spectra at different height levels. At this resolution, the model is not able to reproduce a large haboob that occurred during the campaign. Some deficiencies are found concerning the vertical dust distribution related to the representation of the mixing height in the atmospheric part of the model. For the BoDEx episode, we found the diurnal temperature cycle to be strongly dependant on the soil moisture, which is underestimated in the NCEP analysis used for model initialization. The low level jet (LLJ) and the dust AOD over the Bodélé are well reproduced. The remaining negative AOD bias (due to underestimated surface wind speeds) can be substantially reduced by decreasing the threshold friction velocity in the model.
Highlights
Mineral dust emitted from arid and semi-arid areas is one of the most important sources of atmospheric aerosol mass and significantly impacts the Earth’s climate system
We show a four hour model average aerosol optical depth (AOD) which coincides with the passage of the satellite over the region, i.e. between 11:00 and 15:00 UTC, the modeled surface dust concentration at 12:00 UTC, a combined map of MODIS DB and Terra AOD, the OMI AOD, the modeled 10 m wind speed, and the SeaWiFS and MSG RGB image at 12:00 UTC
4.1.2 Aerosol optical depth In Figs. 8 and 9 we show the comparison of AOD between eight stations and NMMB/BSC-Dust for the period 16–22 May 2006
Summary
Mineral dust emitted from arid and semi-arid areas is one of the most important sources of atmospheric aerosol mass and significantly impacts the Earth’s climate system. In Perez et al (2011), we evaluated monthly and annual means of the global configuration of the model against the AeroCom dust benchmark dataset for the year 2000 including surface concentration, deposition and aerosol optical depth (AOD), as well as the daily AOD variability in a regional domain at high resolution covering Northern Africa, Middle East and Europe against the AErosol RObotic NETwork (AERONET) (Holben et al, 1998) AOD for the year 2006. At the global scale the model lies within the top range of AeroCom dust models in terms of performance statistics for surface concentration, deposition and AOD In this contribution, we use the data from two field experiments: SAMUM-1 (Heintzenberg, 2009) and BoDEx (Washington et al, 2006a), complemented by in-situ remotesensing data and satellite retrievals to evaluate and analyze the behavior of the model in Northern Africa.
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