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Evaluation of the Diurnal Cycle in the Atmospheric Boundary Layer Over Land as Represented by a Variety of Single-Column Models: The Second GABLS Experiment |
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| Authors: | G Svensson A A M Holtslag V Kumar T Mauritsen G J Steeneveld W M Angevine E Bazile A Beljaars E I F de Bruijn A Cheng L Conangla J Cuxart M Ek M J Falk F Freedman H Kitagawa V E Larson A Lock J Mailhot V Masson S Park J Pleim S S?derberg W Weng M Zampieri |
| Institution: | 1. Department of Meteorology, Stockholm University, Stockholm, Sweden 2. Meteorology and Air Quality Section, Wageningen University, Wageningen, The Netherlands 3. Department of Geography and Environmental Engineering, Johns Hopkins University, Baltimore, MD, USA 4. Max Planck Institute for Meteorology, Hamburg, Germany 5. CIRES, University of Colorado, Boulder, CO, USA 6. NOAA ESRL, Boulder, CO, USA 7. CNRM (National Centre for Meteorological Research)?CGAME, M??t??o-France/CNRS, Toulouse, France 8. European Centre for Medium-Range Weather Forecast, Reading, UK 9. KNMI, Royal Netherlands Meteorological Institute, De Bilt, The Netherlands 10. Science Systems and Applications, Inc., Hampton, VA, USA 11. Langley Research Center, NASA, Hampton, VA, USA 12. Departament de F??sica Aplicada, Universitat Polit??cnica de Catalunya, Manresa, Spain 13. Departament de F??sica, Grup de Meteorologia, Universitat de les Illes Balears, Ciutat de Mallorca, Spain 14. NOAA Science Center, National Centers for Environmental Prediction/Environmental Modeling Center, Camp Springs, MD, USA 15. Department of Mathematical Sciences, University of Wisconsin, Milwaukee, WI, USA 16. San Jose State University, San Jose, CA, USA 17. Japan Meteorological Agency, Tokyo, Japan 18. Met Office, Exeter, UK 19. Meteorological Research Division, Environment Canada, Dorval, QC, Canada 20. Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, CO, USA 21. U.S. Environmental Protection Agency, Research Triangle Park, NC, USA 22. WeatherTech Scandinavia, Uppsala, Sweden 23. York University, Toronto, ON, Canada 24. ISAC-CNR, Bologna, Italy |
| Abstract: | We present the main results from the second model intercomparison within the GEWEX (Global Energy and Water cycle EXperiment) Atmospheric Boundary Layer Study (GABLS). The target is to examine the diurnal cycle over land in today??s numerical weather prediction and climate models for operational and research purposes. The set-up of the case is based on observations taken during the Cooperative Atmosphere-Surface Exchange Study-1999 (CASES-99), which was held in Kansas, USA in the early autumn with a strong diurnal cycle with no clouds present. The models are forced with a constant geostrophic wind, prescribed surface temperature and large-scale divergence. Results from 30 different model simulations and one large-eddy simulation (LES) are analyzed and compared with observations. Even though the surface temperature is prescribed, the models give variable near-surface air temperatures. This, in turn, gives rise to differences in low-level stability affecting the turbulence and the turbulent heat fluxes. The increase in modelled upward sensible heat flux during the morning transition is typically too weak and the growth of the convective boundary layer before noon is too slow. This is related to weak modelled near-surface winds during the morning hours. The agreement between the models, the LES and observations is the best during the late afternoon. From this intercomparison study, we find that modelling the diurnal cycle is still a big challenge. For the convective part of the diurnal cycle, some of the first-order schemes perform somewhat better while the turbulent kinetic energy (TKE) schemes tend to be slightly better during nighttime conditions. Finer vertical resolution tends to improve results to some extent, but is certainly not the solution to all the deficiencies identified. |
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