Abstract
Abstract. Three detailed meteorological case studies are conducted with the global and regional atmospheric chemistry model system ECHAM5/MESSy(→COSMO/MESSy)n, shortly named MECO(n). The aim of this article is to assess the general performance of the on-line coupling of the regional model COSMO to the global model ECHAM5. The cases are characterised by intense weather systems in Central Europe: a cold front passage in March 2010, a convective frontal event in July 2007, and the high impact winter storm "Kyrill" in January 2007. Simulations are performed with the new on-line-coupled model system and compared to classical, off-line COSMO hindcast simulations driven by ECMWF analyses. Precipitation observations from rain gauges and ECMWF analysis fields are used as reference, and both qualitative and quantitative measures are used to characterise the quality of the various simulations. It is shown that, not surprisingly, simulations with a shorter lead time generally produce more accurate simulations. Irrespective of lead time, the accuracy of the on-line and off-line COSMO simulations are comparable for the three cases. This result indicates that the new global and regional model system MECO(n) is able to simulate key mid-latitude weather systems, including cyclones, fronts, and convective precipitation, as accurately as present-day state-of-the-art regional weather prediction models in standard off-line configuration. Therefore, MECO(n) will be applied to simulate atmospheric chemistry exploring the model's full capabilities during meteorologically challenging conditions.
Highlights
This third part of a series of articles about the newly developed 1-way on-line coupled global and regional chemistry model system MECO(n) is dedicated to its meteorological evaluation. Kerkweg and Jockel (2012a) describe the connection of the Modular Earth Submodel System (MESSy, Jockel et al, 2005, 2010) to the limited-area weather prediction and climate model of the COnsortium for Small-scale MOdeling (COSMO, Doms and Schattler, 1999; COSMOCLM, Rockel et al, 2008) resulting in the limited-area atmospheric chemistry model COSMO/MESSy
As this study considers specific meteorological situations, the climate model EMAC has been nudged to the “observed” meteorology, i.e. to the same ECMWF analysis data set that is used for the generation of the initial and boundary data of the off-line simulations
For chemistry applications the entire capability of the MECO(n) system is clearly evident, as to our knowledge only this system can provide fully consistent boundary conditions for regional chemistry applications
Summary
This third part of a series of articles about the newly developed 1-way on-line coupled global and regional chemistry model system MECO(n) is dedicated to its meteorological evaluation. Kerkweg and Jockel (2012a) describe the connection of the Modular Earth Submodel System (MESSy, Jockel et al, 2005, 2010) to the limited-area weather prediction and climate model of the COnsortium for Small-scale MOdeling (COSMO, Doms and Schattler, 1999; COSMOCLM, Rockel et al, 2008) resulting in the limited-area atmospheric chemistry model COSMO/MESSy. Since potential applications of this model system are in the area of chemical weather prediction, air pollution studies, and the interpretation of chemical observations during field experiments, the question arises, how accurately the COSMO/MESSy model, on-line coupled to the global climate chemistry model EMAC, captures specific meteorological events, compared to the classical setup, where COSMO is driven off-line by meteorological data from a global model forecast or analyses. To address this question, we investigate simulations of three meteorologically diverse cases: 1.
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