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 to satellite data
Winter Autumn Spring Summer
SCANDIA
AVHRR
(%)
RCA
22 km
RCA
44 km
ERA40
100 km
Jones and Karlsson

5. Cloudiness and surface radiation in RCA and ERA
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 km, 60 levels
RACMO km, 24 levels
RCA km, 24 levels
LM 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. Using cloud area fraction and scaled optical depth in the radiationCv Δz Ca
Area fraction
Cloud thickness
Optical depth
Brooks et. al.
fliq (T>273K), fice(T<273K)
Random:
Random 2:
Del Genio et. al.

13. Using cloud area fraction and scaled optical depth in the ECMWF radiation scheme
LW down (W/m2)
12 Aug Aug
Cloud fraction (%)
KNMI RADAR
ECMWF (W/m**2)
Height (km)
SW down (W/m2)
12 Aug 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 Two-layer overlap Accumulated overlap
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. September 2001 CLIWANET BBC campaign
Susanne Crewell, Henk Klein Baltink and Olivier Sievers
September 2001

23. Cabauw August 2001

24. Cabauw September 2001