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Grid scale parameterization of topographic effects on radiation

Grid scale parameterization of topographic effects on radiation. Matteo Buzzi, Mathias W. Rotach and Marco Arpagaus MeteoS wiss. Overview. Introduction The topographic problem General aspects Topographic parameters Parameterization scheme Corrections factors

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Grid scale parameterization of topographic effects on radiation

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  1. Grid scale parameterization of topographic effects on radiation Matteo Buzzi, Mathias W. Rotach and Marco Arpagaus MeteoSwiss

  2. Overview • Introduction • The topographic problem • General aspects • Topographic parameters • Parameterization scheme • Corrections factors • Corrected surface radiation components • Case studies • Summary, conclusions and outlook Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  3. The problem: shortwave radiation . Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  4. The problem: thermal downward radiation 4 esT eff 4 esT 4 esT Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005 slope slope

  5. Introduction • NWP mesoscale models resolution tends to the order of magnitude of 1 km: topographic effects become important • Topographic shadowing (horizon, sun elevation) • Slope angle • Slope aspect • Sky view (horizon) • aLMo radiation scheme (Ritter and Geleyn,1992): surface radiation is computed on horizontal surfaces, topographic effects are not considered • Idea: try a simple approach with correction factors for surface radiation components Müller and Scherrer (2005) Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  6. Overview • The topographic problem • Introduction • Topographic parameters • Parameterization scheme • Corrections factors • Corrected surface radiation components • Case studies • Summary, conclusions and outlook Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  7. Topographic parameters: slope aspect (7 km) Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  8. Topographic parameters: slope aspect (2 km) Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  9. Topographic parameters: slope angle (7 km) Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  10. Topographic parameters: slope angle (2 km) Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  11. Overview • The topographic problem • Introduction • Topographic parameters • Parameterization scheme • Correction factors • Corrected surface radiation components • Case studies • Summary, conclusions and outlook Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  12. Sky view factor: 7 km Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  13. Sky view factor: 2 km Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  14. 2004-12-11 08 UTC (7 km) Correction factor for direct radiation radiation on horizontal surface  radiation on inclined and oriented surface Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  15. 2004-12-11 08 UTC (2 km) Correction factor for direct radiation SE slope increased radiation Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005 Shadowing NW slope

  16. 2004-12-11 12 UTC (7 km) Correction factor for direct radiation Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  17. 2004-12-11 12 UTC (2 km) Correction factor for direct radiation Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  18. 2004-12-11 15 UTC (7 km) Correction factor for direct radiation Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  19. 2004-12-11 15 UTC (2 km) Correction factor for direct radiation Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  20. Direct solar radiation Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005 Müller and Scherrer (2005)

  21. Diffuse downwelling solar radiation Reduced sky view Reflections by adjacent areas Assumptions: • Diffuse downwelling radiation considered isotropic • Adjacent areas have the same upwelling diffuse radiation Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005 Müller and Scherrer (2005)

  22. Thermal downwelling radiation Reduced sky view Radiation from adjacent areas Assumptions: • fac = ratio of the upwelling thermal radiation of a grid-point and its adjacent points (at higher elevation): considers a horizontal length scale (7 or 4 km), a mean slope angle (sky view) and a mean vertical temperature lapse rate (6.5°C/1000m) Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005 Modified from Müller and Scherrer (2005)

  23. Overview • Introduction • Topographic parameters • Parameterization scheme • Correction factors • Corrected surface radiation components • Case studies • 2004-12-11: aLMo 3.15, 7 km and 2 km • 2003-06-22: aLMo 3.15, 7 km and 2 km • Summary, conclusions and outlook Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  24. Results: 7 km, 2004-12-11 00 UTC +09 Surface temperature difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  25. Results: 7 km, 2004-12-11 00 UTC +12 Surface temperature difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  26. Results: 7 km, 2004-12-11, grid-point Correction factor NET solar radiation Surface temperature Sensible heat flux at the surface Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005 corrected control

  27. Results: 7 km, 2004-12-11, grid-point Correction factor NET solar radiation Surface temperature Snow amount Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005 corrected control

  28. Results: 2 km, 2004-12-11 00 UTC +09 Surface temperature difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  29. Results: 2 km, 2004-12-11 00 UTC +12 Surface temperature difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  30. Results: 2 km, 2004-12-11 00 UTC +14 Total cloud cover difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  31. Results: 2 km, 2004-12-11 00 UTC +12 10 m wind vectors difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005 corrected control

  32. Results: 7 km, 2003-06-22 00 UTC +08 Surface temperature difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  33. Results: 7 km, 2003-06-22 00 UTC +12 Surface temperature difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  34. Results: 2 km, 2003-06-22 00 UTC +08 Surface temperature difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  35. Results: 2 km, 2003-06-22 00 UTC +12 Surface temperature difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  36. Results: 2 km, 2003-06-22 00 UTC +12 Total cloud cover difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  37. Results: 2 km, 2003-06-22 00 UTC +14 Total cloud cover difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  38. Overview • Introduction • Topographic parameters • Parameterization scheme • Correction factors • Corrected surface radiation components • Case studies • Summary, conclusions and outlook Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  39. Summary and conclusions • The Müller and Scherrer (2005) scheme for topographic effects on radiation has been implemented into the aLMo • Some sensitivity case studies have been carried out • The impact of the topographic effects (shadowing, slope angle, slope aspect and sky view) is substantial at high resolution • Some significant indirect impacts (feedbacks) even at 7km: related to snow melt, stability (turbulence) and low clouds • Higher impact during the winter time due to sun elevation and snow conditions • Significant secondary effects on clouds cover at 2km • Surface thermal changes at high resolution have also secondary effects on thermal circulation Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  40. Outlook • Next step: systematic validation with observations • Extension of the domain to the entire aLMo operational domain (7 km and 2 km) and start test suite • Compare implementation results with the sub-grid-scale version of the Müller and Scherrer (2005) scheme (differences in preprocessor) • Indirect effects (feedbacks) on clouds and stability (turbulence) have to be further investigated • How to solve the problem of clouds at high resolution? Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  41. Thank you very much for your attention! matteo.buzzi@meteoswiss.ch

  42. Implementation into the LM • Preprocessor: prior to model integration • Computes corrections factors (time dipendent) + sky view factor (time indipendent) and save results in binary file • LM reads the correction factors (parallelized) • Corrections take place in the fesft.incf radiation subroutine • In spectral loop for solar radiation (direct and diffuse) • After the spectral loop for thermal radiation: the two components (up and down) have to be recomputed from the thermal radiation balance, corrected and added to a new radiation balance Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  43. Topography: 7 km Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  44. Topography: 2 km Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  45. The problem: clouds at high resolution Model: no cloud cover Reality: cloud cover Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  46. Results: 2 km, 2003-06-22 00 UTC +12 10 m wind vectors difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005 corrected control

  47. Results: 2 km, 2004-12-11 00 UTC +12 Total cloud cover difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  48. Results: 7 km, 2003-06-22 00 UTC +14 Surface temperature difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  49. Results: 7 km, 2004-12-11 00 UTC +15 Surface temperature difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

  50. Results: 7 km, 2003-08-07 00 UTC +15 Surface temperature difference Matteo.buzzi@MeteoSwiss.ch COSMO Meeting, WG 3, 20.09.2005

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