RCA and CLIWANET resultsUlrika Willén, Rossby Center SMHI, Norrköping Sweden

• The RCA model

• Cloud vertical distribution

• Subgrid Overlap (& radiation)

• Overlap (&radiation)

• 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.

RCA – SMHI HIRLAM

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)

Cloud fraction (Slingo 1987):

High (> 400hPa) - RH thresholds

mid (750hPa< p <400hPa) – RH thresholds

Low (surface p < 750 hPa) – RH thresholds, ω and Γ

Cloud fraction and radiation in RCA

Cloudiness in RCA and ERA compared to satellite data

Winter Autumn Spring Summer 1993-2000

(%)SCANDIA

AVHRR

RCA44 km

ERA40100 km

RCA22 km

Jones and Karlsson

Cloudiness and surface radiation in RCA and ERA

RCA44

LW SW

RCA44

OBS

SCANDIA

Jones and Karlsson

ERA

ERA

Maximum

Maximum–Random

Change of cloud overlap in RCAO

Döscher et al 2001

• RCAO coupled run had too much ice. Changing from maximum to maximum-random overlap reduced ice cover and improved SST’s

Sea ice area

LW Error (RCA-OBS)

ModelsECMWF 50 km, 60 levels RACMO 18 km, 24 levels RCA2 18 km, 24 levels LM 7 km, 35 levels

•

August and September 2001

Susanne Crewell, Henk Klein Baltink and Olivier Sievers

BBC campaign of CLIWANET

Observations at Cabauw35 GHz KNMI cloud radar95 GHz GKSS cloud radar

CT75K lidar ceilometer SW and LW surface fluxes

Cabauw September 2001Cabauw August 2001

Cloud vertical structure

Ewan O’Connor

Slingo C=f(RH, ω, Γ) Xu Randall C=f(RH, TCW)

Cabauw January 2004 Cabauw July 2004

New cloud fraction scheme for RCA3…

M Haeffelin

2%

8%

24%

48%

18%

Cloud thickness and layer frequency distributions

Cloud volume and cloud area fraction

maximum random random minimum 2-range gates

K=2

K=6

K=16

Brooks et. al.fliq (T>273K), fice(T<273K)

Random:

Random 2:

Kva CC 11

211 va CC

11 11 v

fa CeC

Cabauw September 2001

vvC

3/2va CC

vvva Cz 3/13/2

vva CCCz

va CCz

va z

aC

Brooks et. al.fliq (T>273K), fice(T<273K)

Random:

Random 2:

Kva CC 11

211 va CC

11 11 v

fa CeC

Using cloud area fraction and scaled optical depth in the radiation

Del Genio et. al.

Δz

Ca

Cv

Area fraction

Cloud thickness

Optical depth

12 & 13 August 2001, Cabauw Time (days)

KNMI RADAR

ECMWF

Observed (W/m**2)

Cloud fraction (%)

Hei

ght (

km)

LW down (W/m2)12 Aug 13 Aug

EC

MW

F (W

/m**

2)

SW down (W/m2)12 Aug 13 Aug

Using cloud area fraction and scaled optical depth in the ECMWF radiation scheme

minmax )1( CCCobs

ranobs CCC )1(max

0exp zz

Cabauw September 2001

2-layer cloud overlap

Cabauw September 2001

Maximum

Maximum-Random

M-R gradient

Random

Minimum

Accumulated cloud fraction - overlap

Cabauw September 2001

Cloud overlap matrix

Two-layer overlap

Accumulated overlap

),(max 1,1,1MAXii

MAXi AaA

1

11,1,1 1

),(max1)1(1

i

iiMRi

MRi a

aaAA

)1(*)1(1 1,1,1RANii

RANi AaA

),1(min 1,1,1MINii

MINi AaA

.)1(*)1(1

1

),(max1)1(1

11,1

11

11,1

,1

iigradMR

ii

iii

iigradMRigradMR

i

aaAa

aaa

aaA

A

MINi

MAXi

MinMaxi AAA ,1,1,1 )1(

0

exp)1( 0

,1,100

,1

zz

AAA RANi

MAXi

HIi

Cloud overlap matrix

Cabauw September 2001

CLIWANET and CLOUDNET

Mean value of overlap matrix

12 August 2001, Cabauw

Cloud overlap and radiation

Time (hrs)

RADAR

RCA

Time (hrs)

SW down (W/m2)

ObservedMaximumM-RRandom

Cloud fraction (%)

Hei

ght (

km)

Hei

ght (

km)

LW down (W/m2)

• Vertical profiles of humidity, temperature and total cloud water

• Ozone, effective radius and optical depth of aerosols

Julklappslista – Xmas list…

Cabauw August 2001

CLIWANET BBC campaign

Susanne Crewell, Henk Klein Baltink and Olivier Sievers

September 2001

Cabauw August 2001

Cabauw September 2001