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 Landsat TM 50m (Statistisches Bundesamt, 1997) False colours 0.63-0.69 0.76-0.90 1.55-1.75μm 20 km Measurement area Lindenberg experiments LITFASS 1998-2003

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

4. ‚ Mesoscale and convective organized transports (dynamical transports)  Feedback processes between dynamical transports and subgrid turbulence Dynamical effect Effects of land surface heterogeneity on atmospheric transports  Investigation of the dynamical effect and its role in the vertical energy- and momentum transport Goals SSSAM ‚ 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 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) grid: Arakawa-C 40x40, 80x80 0.25-48 km 21-31  -levels non-hydrostatic 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 1kmFOOT 0.25km u, v, w, T, q, p, u g, v g CLW, RR Soil: type, T, W u, v, w, T, q, p, u g, v g CLW, RR Soil: type, T, W

6. Treatment of heterogeneity effects for surface energy fluxes Mahrt (1996) subgrid velocity scale w fc =w * = convection velocity scale C a,eff = effective exchange coefficient (e.g. from effective z 0 ) Mosaic method Standard mosaic method: T 0, q 0, a 0 from 1D-SVAT model ‘Optimal‘ mosaic method: T 0, q 0, a 0 from sub-grid model Aggregation method modified with w *

7. 250m, L C = 4 km, V g = 2 m/s, F x = 12km Idealized simulations meadow/bare soil

8. 250m, L C = 4 km, V g = 8 m/s, F x = 12km

9. 1 km, L C = 16 km, V g = 2 m/s, F x = 48km

11. 250 m, LITFASS, V g = 2 m/s, F x = 12km, W = 60% Idealized simulations LITFASS area

12. Realistic simulations LITFASS area 17 June 1998, nesting LM7 250 m, LITFASS, v g (LM)≈14 m/s, F x = 12km, W = W(LM)

13. Idealized simulations LITFASS area Subgrid and mesoscale TKE Realistic simulations LITFASS area 17 June 1998, nesting LM7 TKE/SKE at 30m v g (LM)≈14 m/s, F x = 12 kmV g = 2 m/s, F x = 12km

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

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

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

17. H in W/m² Idealized simulations LITFASS area 250 m, F x = 2 km, v g =2 m/s250 m, F x = 250 m, v g =2 m/s

18. 250 m, F x = 2 km, v g =2 m/s H 0 -H 0,mosa in W/m²E 0 -E 0,mosa in W/m² Variance ff(30m) in m²/s²Variance T(0m) in K²

19. 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

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