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[1] Inclusion of mineral dust radiative effects could lead to a significant improvement in the radiation balance of numerical weather prediction models with subsequent improvements in the weather forecast itself. In this study the radiative effects of mineral dust have been fully incorporated into a regional atmospheric dust model. Dust affects the radiative fluxes at the surface and the top of the atmosphere and the temperature profiles at every model time step when the radiation module is processed. These changes influence the atmospheric dynamics, moisture physics, and near-surface conditions. Furthermore, dust emission is modified by changes in friction velocity and turbulent exchange coefficients; dust turbulent mixing, transport, and deposition are altered by changes in atmospheric stability, precipitation conditions, and free-atmosphere winds. A major dust outbreak with dust optical depths reaching 3.5 at 550 nm over the Mediterranean region on April 2002 is selected to assess the radiative dust effects on the atmosphere at a regional level. A strong dust negative feedback upon dust emission (35-45% reduction of the AOD) resulted from the smaller outgoing sensible turbulent heat flux decreasing the turbulent momentum transfer from the atmosphere and consequently dust emission. Significant improvements of the atmospheric temperature and mean sea-level pressure forecasts are obtained over dust-affected areas by considerably reducing both warm and cold temperature biases existing in the model without dustradiation interactions. This study demonstrates that the use of the proposed model with integrated dust and atmospheric radiation represents a promising approach for further improvements in numerical weather prediction practice and radiative impact assessment over dust-affected areas.Citation: Pérez, C., S. Nickovic, G. Pejanovic, J. M. Baldasano, and E. Ö zsoy (2006), Interactive dust-radiation modeling: A step to improve weather forecasts,

Published by Copernicus Publications on behalf of the European Geosciences Union. A. Baklanov et al.: Online coupled regional meteorology chemistry models in EuropeAbstract. Online coupled mesoscale meteorology atmospheric chemistry models have undergone a rapid evolution in recent years. Although mainly developed by the air quality modelling community, these models are also of interest for numerical weather prediction and regional climate modelling as they can consider not only the effects of meteorology on air quality, but also the potentially important effects of atmospheric composition on weather. Two ways of online coupling can be distinguished: online integrated and online access coupling. Online integrated models simulate meteorology and chemistry over the same grid in one model using one main time step for integration. Online access models use independent meteorology and chemistry modules that might even have different grids, but exchange meteorology and chemistry data on a regular and frequent basis. This article offers a comprehensive review of the current research status of online coupled meteorology and atmospheric chemistry modelling within Europe. Eighteen regional online coupled models developed or being used in Europe are described and compared. Topics discussed include a survey of processes relevant to the interactions between atmospheric physics, dynamics and composition; a brief overview of existing online mesoscale models and European model developments; an analysis on how feedback processes are treated in these models; numerical issues associated with coupled models; and several case studies and model performance evaluation methods. Finally, this article highlights selected scientific issues and emerging challenges that require proper consideration to improve the reliability and usability of these models for the three scientific communities: air quality, numerical meteorology modelling (including weather prediction) and climate modelling. This review will be of particular interest to model developers and users in all three fields as it presents a synthesis of scientific progress and provides recommendations for future research directions and priorities in the development, application and evaluation of online coupled models.

[1] A long Saharan dust event affected the western Mediterranean in the period 12-28 June 2002. Dust was present mainly between 1-and 5-km height affecting most parts of the Iberian Peninsula and reaching western/central Europe. Intensive backscatter lidar observations over Barcelona (Spain) and Sun photometer data from two stations (El Arenosillo, Spain, and Avignon, France) are used to evaluate different configurations the Dust Regional Atmospheric Modeling (DREAM) system. DREAM currently operates dust forecasts over the Mediterranean region (http://www.bsc.es/projects/earthscience/ DREAM/) considering four particle size bins while only the first two are relevant for long-range transport analysis since their life time is larger than 12 hours. A more detailed bin method is implemented, and two different dust distributions at sources are compared to the operational version. Evaluations are performed at two wavelengths (532 and 1064 nm). The dust horizontal and vertical structure simulated by DREAM shows very good qualitative agreement when compared to SeaWIFS satellite images and lidar height-time displays over Barcelona. When evaluating the modeled aerosol optical depth (AOD) against Sun photometer data, significant improvements are achieved with the use of the new detailed bin method. In general, the model underpredicts the AOD for increasing Å ngström exponents because of the influence of anthropogenic pollution in the boundary layer. In fact, the modeled AOD is highly anticorrelated with the observed Å ngström exponents. Avignon shows higher influence of small anthropogenic aerosols which explains the better results of the model at the wavelength of 1064 nm over this location. The uncertainties of backscatter lidar inversions (20-30%) are in the same order of magnitude as the differences between the model experiments. Better model results are obtained when comparing to lidar because most of the anthropogenic effect is removed.Citation: Pérez, C., S. Nickovic, J. M. Baldasano, M. Sicard, F. Rocadenbosch, and V. E. Cachorro (2006), A long Saharan dust event over the western Mediterranean: Lidar, Sun photometer observations, and regional dust modeling,

Abstract. We provide an atmospheric aerosol characterization for North Africa, Northeastern Atlantic, Mediterranean and Middle East based on the analysis of quality-assured direct-sun observations of 39 stations of the AErosol RObotic NETwork (AERONET) which include at least an annual cycle within the 1994-2007 period. We extensively test and apply the recently introduced graphical method of Gobbi and co-authors to track and discriminate different aerosol types and quantify the contribution of mineral dust. The method relies on the combined analysis of theÅngström exponent (α) and its spectral curvature δα. Plotting data in these coordinates allows to infer aerosol fine mode radius (R f ) and fractional contribution (η) to total Aerosol Optical Depth (AOD) and separate AOD growth due to fine-mode aerosol humidification and/or coagulation from AOD growth due to the increase in coarse particles or cloud contamination. Our results confirm the robustness of this graphical method. Large mineral dust is found to be the most important constituent in Northern Africa and Middle East. Under specific meteorological conditions, its transport to Southern Europe is observed from spring to autumn and decreasing with latitude. We observe "pure Saharan dust" conditions to show AOD>0.7 (ranging up to 5), α<0.3 and δα<0 corresponding to η<40% and R f ∼0.13 µm. Small pollution particles are abundant in sites close to urban and industrial areas of Correspondence to: S. Basart (sara.basart@bsc.es) Continental and Eastern Europe and Middle East, as well as, important contributions of biomass burning are observed in the sub-Sahel region in winter. These small aerosols are associated to AOD<1, α>1.5 and δα∼−0.2 corresponding to η>70% and R f ∼0.13 µm. Here, dust mixed with fine pollution aerosols shifts the observations to the region α<0.75, in which the fine mode contribution is less than 40%.