Post on 01-Feb-2016
description
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