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Treatment of S mall S cale Land S urface Heterogeneity for A tmospheric M odelling (SSSAM)

Treatment of S mall S cale Land S urface Heterogeneity for A tmospheric M odelling (SSSAM). Günther Heinemann (1) and Michael Kerschgens (2). 1 Meteorologisches Institut der Universität Bonn, Auf dem Hügel 20, 53121 Bonn

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Treatment of S mall S cale Land S urface Heterogeneity for A tmospheric M odelling (SSSAM)

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  1. Treatment of Small Scale Land Surface Heterogeneity for Atmospheric Modelling(SSSAM) Günther Heinemann (1) and Michael Kerschgens (2) 1 Meteorologisches Institut der Universität Bonn, Auf dem Hügel 20, 53121 Bonn 2 Institut für Geophysik und Meteorologie der Universität zu Köln, Kerperner Str. 13, 50923 Köln Regional Evaporation at Grid / Pixel Scale over Heterogeneous Land Surfaces

  2. Effects of land surface heterogeneity on atmospheric transports False colours 0.63-0.69 0.76-0.90 1.55-1.75μm Landsat TM 50m (Statistisches Bundesamt, 1997) Measurement area Lindenberg experiments LITFASS 1998-2003 20 km

  3. Scharmützelsee °C FOOT 250m (20km, 80x80) idealized FOOT simulation LITFASS 1998 17 June, 11 UTC F=Falkenberg L=Lindenberg W=Wulfersdorf H=Herzberg K=Forst Kehrigk Isamp=2

  4. Effects of land surface heterogeneity on atmospheric transports • Mesoscale and convective organized transports (dynamical transports)  Feedback processes between dynamical transports and subgrid turbulence Dynamical effect Goals SSSAM  Investigation of the dynamical effect and its role in the vertical energy- and momentum transport • Development of averaging strategies for vertical transports on the scale of weather forecast and regional climate models (Grid / Pixel Scale)

  5. Non-hydrostatic numerical model FOOT3DK grid: Arakawa-C 40x40, 80x80 0.25-48 km 21-31 -levels non-hydrostatic parameterizations: Vegetation and soil moisture: ISBA, Noilhan and Planton (1989) turbulent fluxes: SL: Louis (1979) PBL: prognostic TKE closure subsurface heat flux: 2 layer model radiation (two-stream) moist convection (Tiedke, 1989, modified Sogalla and Kerschgens, 2001) input data: initial fields: LM (7km) synthetic data Idealized simulations for idealized inhomogeneities and for the Lindenberg area: T/q profiles for 17 June 1998, idealized geostrophic forcing Realistic simulations for the Lindenberg area LM 7km FOOT 1km FOOT 0.25km u, v, w, T, q, p, ug, vg CLW, RR Soil: type, T, W u, v, w, T, q, p, ug, vg CLW, RR Soil: type, T, W

  6. Treatment of heterogeneity effects for surface energy fluxes Mahrt (1996) wfc=w*= convection velocity scale subgrid velocity scale Ca,eff = effective exchange coefficient (e.g. from effective z0) Aggregation method Aggregation method modified with w* Mosaic method Standard mosaic method: T0, q0, a0 from 1D-SVAT model ‘Optimal‘ mosaic method: T0, q0, a0 from sub-grid model

  7. Idealized simulations meadow/bare soil 250m, LC = 4 km, Vg = 2 m/s, Fx = 12km

  8. 250m, LC = 4 km, Vg = 8 m/s, Fx = 12km

  9. 1 km, LC = 16 km, Vg = 2 m/s, Fx = 48km

  10. Idealized simulations LITFASS area 250 m, LITFASS, Vg = 2 m/s, Fx = 12km, W = 60%

  11. Realistic simulations LITFASS area 17 June 1998, nesting LM7 250 m, LITFASS, vg(LM)≈14 m/s , Fx = 12km, W = W(LM)

  12. Subgrid and mesoscale TKE TKE/SKE at 30m Idealized simulations LITFASS area Realistic simulations LITFASS area 17 June 1998, nesting LM7 Vg = 2 m/s, Fx = 12km vg(LM)≈14 m/s , Fx = 12 km

  13. Non-linear effects for area-averaged surface fluxes Energy balance Area average 1D

  14. Dependence on averaging scale Realistic simulations LITFASS area 17 June 1998, nesting LM7 250 m, LITFASS, vg(LM)≈14 m/s, W = W(LM) Average 9-17 UTC

  15. Idealized simulations LITFASS area 250 m, LITFASS, Vg = 2 m/s, W = 60% Average 9-17 UTC

  16. Idealized simulations LITFASS area 250 m, Fx = 250 m, vg=2 m/s 250 m, Fx = 2 km, vg=2 m/s H in W/m² H in W/m²

  17. 250 m, Fx = 2 km, vg=2 m/s 250 m, Fx = 2 km, vg=2 m/s E0-E0,mosa in W/m² H0-H0,mosa in W/m² Variance T(0m) in K² Variance ff(30m) in m²/s²

  18. Summary Method: FOOT3DK simulations (resolution down to 250m) idealized and realistic surfaces and synoptic forcings (LITFASS98) Assessment of the dynamic effect for averaging methods (mosaic and aggregation) for scales of 10-20 km - dependence on the scale/structure of the heterogeneity - mosaic method yields good results for wind speeds exceeding 4 m/s • Scale dependence of area-averaged surface fluxes caused by non-linear effects • sub-grid TKE (SKE) • radiation and clouds • surface temperature and soil moisture

  19. Outlook Lindenberg experiment LITFASS 2003 EC Profiles Precip. Precip./G Scintillometer

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