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Grid scale parameterization of topographic effects on radiation

Explore the impact of topographic parameters on surface radiation with correction factors and case studies. Contact Matteo Buzzi for insights and summaries.

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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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