Embed Size (px)
Citation preview
Theimpactofsuper-parameterizationontheS2Sforecastskill
CristianaStan,DavidStraus,MichaelFennessy andDanPaolino
GeorgeMasonUniversity,USA
WhatisSuper-Parameterization(SP)?ProposedbyGrabowski(2001)andKhairoutdinov andRandall(2001)
IllustrationbyMikeShibao (UCAR),basedonimageryfromCMMAP
ModelsandExperiments
CCSM4 SP-CCSM4
Atm/Res CAM4/FV09 SP-CAM/F09CRM/3km
Land/Res CLM4/1 deg CLM41deg
Ocean/Res POP/1deg POP/1deg
Se-ice/Res CICE4/ 1deg CICE4/1deg
Levels 26 30
OceanandSeaIce Atm.andLand
November1
October2700Z
October2800Z
October2900Z
October3000Z
October3100Z
NMMEHindcasts1982- 2008
Initialconditions:CFSRHindcast length:12months
MJOForecastSkill
ObservationsCCSM
SP-CCSMObservationsCCSM
SP-CCSM
MJOForecastSkill
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29
Days
Correlation
CCSM
SP-CCSM
0
0.5
1
1.5
2
2.5
3
3.5
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29
Days
RMSE
CCSM
SP-CCSM
-25
-20
-15
-10
-5
0
5
10
15
20
25
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29
days
PhaseError
CCSM
SP-CCSM
initialpoint
November 1984CCSM OBS SP-CCSM
U850
OLR
CCSM
initialpoint
SP-CCSM
initialpoint
November 1996CCSM OBS SP-CCSM
OLR
CCSM
initialpoint
SP-CCSM
U850
Euro-Atlantic Sector Clusters
Thesign reversalisnotacodingerror
North Pacific Clusters
Varianceratio
SP-CCSM:0.733
ERA-I:0.726
CCSM:0.821
Varianceofzonalwindat300-mb
CCSM ERA-I SP-CCSM
zonalwavenumbers>3andperiods<10days
Summary• Theexplicitrepresentationofcloudprocessesthroughsuper-
parameterizationhasanimpactontheforecastskilloftheintraseasonalvariabilitypredictedbyanocean-atmosphereclimatemodel
• Theanomalycorrelationinthesuper-parameterizedmodelishigherandthelossofskillisslowerthanintheconventionally-parameterizedmodel
• TheforecasterroroftheMJOphaseissmallerinthesuper-parameterizedmodel
• TheuncertaintiesininitialconditionsareimportantfortheMJOforecastskill
• ThepatternandsignificanceoftheweatherregimesintheEuro-AtlanticandNorthPacificsectorsaresensitivetothecloudparameterization
