Abstract. Numerical models that combine weather forecasting and atmospheric chemistry are here referred to as chemical weather forecasting models. Eighteen operational chemical weather forecasting models on regional and continental scales in Europe are described and compared in this article. Topics discussed in this article include how weather forecasting and atmospheric chemistry models are integrated into chemical weather forecasting systems, how physical processes are incorporated into the models through parameterization schemes, how the model architecture affects the predicted variables, and how air chemistry and aerosol processes are formulated. In addition, we discuss sensitivity analysis and evaluation of the models, user operational requirements, such as model availability and documentation, and output availability and dissemination. In this manner, this article allows for the evaluation of the relative strengths and weaknesses of the various modelling systems and modelling approaches. Finally, this article highlights the most prominent gaps of knowledge for chemical weather forecasting models and suggests potential priorities for future research Published by Copernicus Publications on behalf of the European Geosciences Union. J. Kukkonen et al.: A review of operational, regional-scale, chemical weather forecasting models in Europedirections, for the following selected focus areas: emission inventories, the integration of numerical weather prediction and atmospheric chemical transport models, boundary conditions and nesting of models, data assimilation of the various chemical species, improved understanding and parameterization of physical processes, better evaluation of models against data and the construction of model ensembles.

Verification of two months, April and May 1997, of 48-h mesoscale model simulations of the atmospheric state around Greenland are presented. The simulations are performed with a modified version of The Pennsylvania State University-National Center for Atmospheric Research fifth-generation Mesoscale Model (MM5), referred to as the Polar MM5. Global atmospheric analyses as well as automatic weather station and instrumented aircraft observations from Greenland are used to verify the forecast atmospheric state. The model is found to reproduce the observed atmospheric state with a high degree of realism. Monthly mean values of the near-surface temperature and wind speed predicted by the Polar MM5 differ from the observations by less than 1 K and 1 m s Ϫ1 , respectively, at most sites considered. In addition, the model is able to simulate a realistic diurnal cycle for the surface variables, as well as capturing the large-scale, synoptically forced changes in these variables. Comparisons of modeled profiles of wind speed, direction, and potential temperature in the katabatic layer with aircraft observations are also favorable, with small mean errors. The simulations of the katabatic winds are found to be sensitive to errors in the large-scale forcing (e.g., the large-scale pressure gradient) and to errors in the representation of key physical processes, such as turbulence in the very stable surface layer and cloudradiation interaction.

Satellite images occasionally show the existence of mesocyclones (MCs)

The katabatic wind system over the Greenland ice sheet is studied using simulations of the hydrostatic Norwegian Limited Area Model (NORLAM) and measurements of an instrumented aircraft. The structure and the dynamics of the katabatic wind over the ice sheet are investigated for a case study of the aircraft-based experiment KABEG (Katabatic wind and boundary layer front experiment around Greenland) in the area of southern Greenland in April/May 1997. Monthly mean structures and individual contributions of the momentum budget integrated over the boundary layer are examined for one winter month. The NORLAM is able to simulate realistically the structures of the katabatic wind system in the lowest 400 m. The comparison with KABEG aircraft measurements for a katabatic wind case with strong synoptic forcing shows good agreement for the momentum budget terms. The pure katabatic force represents the main mechanism for the boundary layer wind field, but a considerable influence of the large-scale synoptic forcing is found as well. Acceleration components from the NORLAM forecasts are also presented for the whole month of January 1990. The monthly mean fields show significant regional differences because of different inversion strengths and synoptic forcings. In particular, Southeast Greenland is influenced by transient synoptic cyclones and the associated cloud patterns. All other areas of the slopes of the Greenland ice sheet are characterized by a downslope katabatic acceleration. The pressure gradient force over the northwestern part of the Greenland ice sheet points in the direction of the local katabatic force, which explains the relatively strong monthly mean near surface winds over the ice. Over the southwestern and northeastern parts of Greenland, however, no significant synoptic support of the katabatic winds is present, and the synoptic pressure gradient is even opposed to the katabatic force in some regions.

This article reviews interactions and health impacts of physical, chemical, and biological weather. Interactions and synergistic effects between the three types of weather call for integrated assessment, forecasting, and communication of air quality. Today's air quality legislation falls short of addressing air quality degradation by biological weather, despite increasing evidence for the feasibility of both mitigation and adaptation policy options. In comparison with the existing capabilities for physical and chemical weather, the monitoring of biological weather is lacking stable operational agreements and resources. Furthermore, integrated effects of physical, chemical, and biological weather suggest a critical review of air quality management practices. Additional research is required to improve the coupled modeling of physical, chemical, and biological weather as well as the assessment and communication of integrated air quality. Findings from several recent COST Actions underline the importance of an increased dialog between scientists from the fields of meteorology, air quality, aerobiology, health, and policy makers.