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RCA and CLIWANET results Ulrika Willén, Rossby Center SMHI, Norrköping Sweden

RCA and CLIWANET results Ulrika Willén, Rossby Center SMHI, Norrköping Sweden. The RCA model Cloud vertical distribution Subgrid Overlap (& radiation) Overlap (&radiation). RCA – SMHI HIRLAM. 106*114, 44km, L24 - climate run New land surface scheme - not in HIRLAM

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RCA and CLIWANET results Ulrika Willén, Rossby Center SMHI, Norrköping Sweden

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  1. RCA and CLIWANET results Ulrika Willén, Rossby Center SMHI, Norrköping Sweden • The RCA model • Cloud vertical distribution • Subgrid Overlap (& radiation) • Overlap (&radiation)

  2. RCA – SMHI HIRLAM • 106*114, 44km, L24 - climate run • New land surface scheme - not in HIRLAM • Clouds and condensation: Rasch-Kristjánsen and Kain-Fritsch • Turbulence: TKE dry variables – CBR scheme • Radiation: Savijärvi and Sass plus modifications by Räisienen etc.

  3. Cloud fraction and radiation in RCA Cloud fraction (Slingo 1987): High (> 400hPa) - RH thresholds mid (750hPa< p <400hPa) – RH thresholds Low (surface p < 750 hPa) – RH thresholds, ω and Γ SW: H2O and O3 explicitly (O2 and CO2 implicitly). Cloud absorption and transmission (cloud water, cloud fraction, Reff). Aerosols constant correction factors LW: clear-sky gaseous emission, H2O explicitly, (CO2, O3, CH4, N2O, CFC’s empirical). Cloud emission (cloud water, Tcloud base, cloud fraction, Reff)

  4. Cloudiness in RCA and ERA compared tosatellite data Winter Autumn Spring Summer 1993-2000 SCANDIA AVHRR (%) RCA 22 km RCA 44 km ERA40 100 km Jones and Karlsson

  5. Cloudiness and surface radiation in RCA and ERA ERA RCA44 SCANDIA LW SW OBS RCA44 ERA Jones and Karlsson

  6. Change of cloud overlap in RCAO • RCAO coupled run had too much ice. Changing from maximum to maximum-random overlap reduced ice cover and improved SST’s Maximum LW Error (RCA-OBS) Maximum–Random Sea ice area Döscher et al 2001

  7. BBC campaign of CLIWANET August and September 2001 Susanne Crewell, Henk Klein Baltink and Olivier Sievers Models ECMWF 50 km, 60 levels • RACMO 18 km, 24 levels • RCA2 18 km, 24 levels • LM 7 km, 35 levels Observations at Cabauw 35 GHz KNMI cloud radar 95 GHz GKSS cloud radar CT75K lidar ceilometer SW and LW surface fluxes

  8. Cloud vertical structure Cabauw August 2001 Cabauw September 2001

  9. New cloud fraction scheme for RCA3… Slingo C=f(RH, ω, Γ) Xu Randall C=f(RH, TCW) Cabauw July 2004 Cabauw January 2004 Ewan O’Connor

  10. Cloud thickness and layer frequency distributions M Haeffelin 2% 8% 24% 48% 18%

  11. Cloud volume and cloud area fraction Cabauw September 2001 maximum random random minimum 2-range gates K=2 Brooks et. al. fliq (T>273K), fice(T<273K) Random: Random 2: K=6 K=16

  12. Brooks et. al. fliq (T>273K), fice(T<273K) Random: Random 2: Using cloud area fraction and scaled optical depth in the radiation Cv Δz Ca Area fraction Cloud thickness Optical depth Del Genio et. al.

  13. Using cloud area fraction and scaled optical depth in the ECMWF radiation scheme LW down (W/m2) 12 Aug 13 Aug Cloud fraction (%) KNMI RADAR ECMWF (W/m**2) Height (km) SW down (W/m2) 12 Aug 13 Aug ECMWF Observed (W/m**2) Time (days) 12 & 13 August 2001, Cabauw

  14. 2-layer cloud overlap Cabauw September 2001

  15. Accumulated cloud fraction - overlap Cabauw September 2001 Maximum Maximum-Random M-R gradient Random Minimum

  16. Cloud overlap matrix Cabauw September 2001 Two-layer overlap Accumulated overlap

  17. Cloud overlap matrix Cabauw September 2001

  18. Mean value of overlap matrix CLIWANET and CLOUDNET

  19. Cloud overlap and radiation 12 August 2001, Cabauw Cloud fraction (%) LW down (W/m2) RADAR Height (km) Observed Maximum M-R Random SW down (W/m2) RCA Height (km) Time (hrs) Time (hrs)

  20. Julklappslista – Xmas list… • Vertical profiles of humidity, temperature and total cloud water • Ozone, effective radius and optical depth of aerosols

  21. Cabauw August 2001

  22. CLIWANET BBC campaign Susanne Crewell,Henk Klein Baltink and Olivier Sievers September 2001

  23. Cabauw August 2001

  24. Cabauw September 2001

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