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Overview of GABLS achievements as relevant for LOCO Bert Holtslag Thanks to Bob Beare,

Overview of GABLS achievements as relevant for LOCO Bert Holtslag Thanks to Bob Beare, Joan Cuxart, Gunilla Svensson and many others…. GEWEX Atmospheric Boundary Layer Study: Towards a better representation of the Atmospheric Boundary Layer in Weather and Climate models

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Overview of GABLS achievements as relevant for LOCO Bert Holtslag Thanks to Bob Beare,

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  1. Overview of GABLS achievements as relevant for LOCO Bert Holtslag Thanks to Bob Beare, Joan Cuxart, Gunilla Svensson and many others… GEWEX Atmospheric Boundary Layer Study: Towards a better representation of the Atmospheric Boundary Layer in Weather and Climate models www.met.wau.nl/gabls.html

  2. Example:Mean model bias for the 2 meter temperaturein present winter climate (30 years)Courtesy,Geert Lenderink, KNMI Also impact on diurnal cycle

  3. Mean model difference in 2 meter temperature for January 1996 using two different stabilty functions in ECMWF model (Courtesy A. Beljaars)

  4. State of the Art for stable boundary layers Large bias and sensitivity to model formulation (at least over Land and Ice!) Operational models typically like enhanced mixing What can we learn from fine-scale modeling (LES)? How do operational models compare?

  5. GABLS first inter comparison case Simple shear driven case (after Kosovic and Curry, 2000) Prescribed surface cooling 0.25 K/h (over ice) for 9 hours to quasi- equilibrium; no surface and radiation scheme Geostrophic wind 8 m/s, latitude 73N

  6. Mean potential temperature of LES modelsafter nine hours of cooling Significant spread in results, but convergence at highresolution (Sensitivity to sub-grid model) Beare et al, 2005

  7. Comparison of Single-Column Models with LES (Cuxart et al, 2005) GABLS 1D Intercomparison Resolution (most) operational models is set to 6.25 m!

  8. Momentum Fluxes Heat Fluxes

  9. a (u ms-1) ’Ekman spirals’ (Svensson+Holtslag, 2005) LES Operational Research-Meso Research

  10. Boundary-layer height and surface angle LES consistent with Cabauw data!

  11. Why do Operational Models need Enhanced Mixing? To prevent ‘runaway’ surface cooling To have sufficient ‘Ekman pumping’ To compensate for model errors However, Atmospheric Boundary Layer pays the price!

  12. Summary First model intercomparisonLarge variation among 1D models, but all operational models show too strong mixing!Details in Turbulence Schemes do matter!8 papers are currently acceptedfor special issue in Boundary Layer Meteorology, to appear in 2005/6

  13. Second GABLS model intercomparison experiment About 20 models by 15 groups Coordinated by Gunilla Svensson Department of meteorology, Stockholm university

  14. Intercomparison of 1D models on basis of CASES99 for a period of 2.5 days (focus on PBL) Prescribed surface temperature Also same initial conditions and forcings for wind and humidity

  15. Potential temperature Preliminary Results +24 h forecasts

  16. Potential temperature Preliminary Results +36 h forecasts

  17. Potential temperature Preliminary Results +48 h forecasts

  18. Wind speed Preliminary Results +24 h forecasts

  19. Wind speed Preliminary Results +32 h forecasts

  20. Wind speed Preliminary Results +36 h forecasts

  21. Wind speed Preliminary Results +40 h forecasts

  22. Friction velocity

  23. Sensible heat flux

  24. Boundary-layer height

  25. What next in GABLS? Further analysis and intercomparison of the 1D models for CASES99 (Diurnal Cycle) Intercomparison of LES and 1D models for specific stable cases Coupling of models to Land Surface But HOW and by WHOM?

  26. Theme 1: Stable boundary layers -Experience with coupled land/atmosphere models for stable boundary layers in other regions of the world -Ideas for parameterizations that specifically aim at a proper representation of the land/atmosphere couplingGert Jan SteeneveldExperiences with the (coupled) boundary-layer modelling of the three day-night period in CASES99Break Zbig SorbjanParameterizations of very stable boundary layers, derived from CASES99Joan CuxartMesoscale simulations of Stable Boundary LayersBob BeareLarge Eddy Simulations of an evening transition

  27. Theme 2: Coupled boundary layer experiments and feedbacks-Observational means for diagnosing land-atmosphere interaction-SCM experiments with cloud and pbl feedbacks for other places in the world -Ideas for parameterizations that specifically aim at a proper representation of the land/atmosphere coupling Michael EkSCM experiments at CabauwAnne McCabeModeling the stable boundary layer and the role of land surface heterogeneityFrank BeyrichSome recent results on land/atmosphere interaction and ABL structure over the LITFASS areaFred Bosveld and Peter BaasClassification of low level jets at Cabauw

  28. Thanks to all the participating scientists within GABLS (about 50) and our colleagues for providing inputs, model runs, advice, et cetera

  29. Int. turb Fully turb Non- turb Example: Results with a 1D high resolution ABL model fully coupled to Land Surface for 3 different nights using dynamic forcings and local surface characteristics Steeneveld, van de Wiel, Holtslag, 2005 (J.Atmos. Sci, in press)

  30. Int. turb Fully turb Non- turb

  31. Int. turb Fully turb Non- turb

  32. Wind and temperature profiles

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