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THE EFFECT OF THE SURFACE CHARACTERISTICS ON THE DICE RESULTS SEEN BY THE MESONH MODEL

THE EFFECT OF THE SURFACE CHARACTERISTICS ON THE DICE RESULTS SEEN BY THE MESONH MODEL M. A. Jiménez, P. Le Moigne and J. Cuxart. DICE workshop, 14-16 October 2013, Exeter (UK). DIurnal land/atmosphere Coupling Experiment (DICE) CASES – 99 experiment: 23-26 October 1999

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THE EFFECT OF THE SURFACE CHARACTERISTICS ON THE DICE RESULTS SEEN BY THE MESONH MODEL

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  1. THE EFFECT OF THE SURFACE CHARACTERISTICS ON THE DICE RESULTS SEEN BY THE MESONH MODEL M. A. Jiménez, P. Le Moigne and J. Cuxart DICE workshop, 14-16 October 2013, Exeter (UK)

  2. DIurnal land/atmosphere Coupling Experiment (DICE) CASES – 99 experiment: 23-26 October 1999 released May 2013, preliminary results October 2013 Photograph taken at the CASES-99 experiment (Southern Great Plains, USA)

  3. MODEL PARTICIPANTS

  4. Stage 1a Atmosphere- SCM Surface - prescribed H, LE, RN, LST Stage 1b Atmosphere - prescribed T,wind,q at 55m T,wind,q at 10m Surface - SURFEX ISBA (3 layers) Stage 2 Stage 3 Atmosphere- SCM Surface - SURFEX As Stages 1a and 1b but prescribing 12 different forcings (SCM and SURFEX) SCM + SURFEX (coupling)

  5. INITIAL CONDITIONS WIND LSM - INITIAL CONDITIONS (evolution of T, q and wind during the simulated period) T Q SCM - INITIAL PROFILES (sounding at 12 LT, 1900 UTC) wind speed (m/s) potential temperature (K) specific humidity (g/kg)

  6. SCM: MesoNH model (Lafore et al., 1998) Turbulence (Cuxart et al., 2000), length scale (Bougeault and Lacarrere 1989) Radiation (ECMWF code called every time-step) Kessler microphysical scheme (vapor, cloud water and rain) Time step (300s for SCM and 20s for coupled runs) Vertical grid (Cuxart et al., 2007): 85 levels (3m resolution at lower levels, gradual stretching) LSM: SURFEX (Masson et al., 2013) ISBA 3 layers Land use: Ecoclimap at 1km resolution (Masson et al., 2003) 50% great plains crops and 50% rockies grassland total vegetation fraction over the pixel = 0.73 root depth = 1.5m and total depth = 2m leaf area index = 1.46 CLAY=0.24, SAND=0.38 from Harmonized World Soil Database (HWSD) at 1km resolution

  7. SURFACE ENERGY BUDGET (W/m2) H LE INT INT TURB RAD Steeneveld et al 2006 RN G

  8. TIME SERIES observations in green * the wind speed is well captured * differences in T of 4-5K during day/night but CPL match better to the observations * CPL run too humid → large LE T2m (K) M10m (m/s) Q2m (kg/kg)

  9. SCM – STAGE 1B SCM + SURFACE – STAGE 2 LLJ well captured-> large-scale advection CPL run too humid

  10. SCM – STAGE 1B SCM + SURFACE – STAGE 2 H smaller LE larger T colder (lower levels) H larger LE smaller T warmer (lower levels)

  11. SENSITIVITY TESTS

  12. RN (W/m2) TESTING THE SURFACE SCHEME observations in red, equivalent to SCM SENSIBLE HEAT FLUX (W/m2) LATENT HEAT FLUX (W/m2) SCM = root depth SCM = bare soil

  13. TESTING THE SCM model LE SCM results (1b) agree with SURFEX results (1a) SCM = bare soil RN H SCM = root depth

  14. TESTING THE SCM model * no impact on the wind speed * impact on the T and q * q(bare ground) similar to obs. observations in blue 2m temperature (K) 10m wind speed (m/s) 2m specific humidity (kg/kg)

  15. SENSITIVITY TESTS vertical resolution (SCM, Stage 1b only) default: 85 levels (3m at lower levels) test: 60 levels (10m at lower levels)

  16. SENSITIVITY TESTS vertical resolution 60 levels 85 levels (DICE) potential temperature (K) wind speed (m/s) 1-2 K difference

  17. Stage 3a results (SCM) 12 forcings as stage 1b RN H LE hight & low values hight & low values

  18. Preliminary resultsStage 1b (near surface evolution) 20m 55m

  19. Preliminary resultsStage 1b (potential temperature)

  20. SUMMARY 1) SCM vs CPL * CPL is giving larger LE and smaller H than SCM * CPL has more specific humidity than SCM 2) reducing the percentage of vegetation * Improve LE and H become closer to observations * As a test case, bare ground soil is taken but this is far from the reality... 3) reducing the root depths to a more realistic values * Improve H and LE is closer to observations * more realistic case, by default the root depth is too high 4) vertical grid mesh * importance to properly reproduce the surface layer characteristics

  21. DICE site EASY CASE! surface and tower observations (model validation) clear-skies, flat, homogeneous, … SURFACE CHARACTERISTICS in the model covered by dry vegetation But still difficult for models … (introduce the concept of died vegetation)

  22. ACKNOWLEDGEMENTS RESEARCH PROJECT CGL2012-37416-C04-01 JAE-DOC contract

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