john j. cassano, matthew higgins, alice duvivier university of colorado wieslaw maslowski, william...
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John J. Cassano, Matthew Higgins, Alice DuVivierUniversity of Colorado
Wieslaw Maslowski, William Gutowski, Dennis Lettenmaier, Andrew Roberts
Project goalsDevelop a state-of-the-science regional
Arctic system model (RASM)
Why do we want a high resolution atmospheric model in RASM?The atmosphere forces and is forced by all other
components of the climate systemSmall-scale features in the atmosphere can have
large impacts on climatically important processes such as:Cyclone intensity / polar lowsMesoscale features such as topographically forced winds
(Greenland tip jets)
Realistic representation of these processes is critical for improved climate projection
Cyclone Intensity and SizeResolution impacts the size and intensity of cyclones
AMPS simulates lower pressure and smaller cyclones than all reanalyses
Stronger and smaller storms will impact air-sea coupling as well as impact humanactivities in polar regions
Mesoscale Features: Greenland tip jets
Topographically forced mesoscale winds can be very strong but are poorly resolved in low resolution models
These winds drive large sensible and latent heat fluxes
10 m
wind speed (2/21/07)
a) b) c)
d) e)
a) b)
c) d)
Two Month: WRF average latent heat flux
a) b)
c) d)
Two Month: WRF 95th percentile latent heat flux
RACM simulationsCoupled: Regional Arctic Climate Model (RACM)
WRF – POP – CICE - VICSimulation from 1989 to 2002 (currently)
Atmosphere – land : WRF – NoahCORDEX simulation from 1989 to 2009
RACM and WRF simulations forced with:ERA-Interim IBC/LBCsObserved sea iceUse spectral nudging of wave numbers 1 and 2
Comparison presented here will focus on 1990 to 2002
Coupling Problems: Precipitation (Jan and July 1990)
Coupling Problems: Tsfc Impacts (July 1990)
Coupling Problems: SLP Impacts (July 1990)
ERA-Interim WRF
1989-2002 DJF Climatology
RACM
RACM – ERA-InterimERA-Interim & RACM WRF – ERA-Interim
ERA-Interim WRF
1989-2002 JJA Climatology
RACM
RACM – ERA-InterimERA-Interim & RACM WRF – ERA-Interim
ERA-Interim
1989-2002 JJA Climatology
RACM
RACM – ERA-InterimERA-Interim & RACM
RACM - NSIDC
1989-2002 JJA and DJF Climatology
RACM – ERA-Interim DJF WRF – ERA-Interim DJF
RACM – ERA-Interim JJA WRF – ERA-Interim JJA
1989-2002 DJF Climatology
Temperature
Part of Russia
Temperature
North of 80 Latitude
Northern Alaska
Temperature
RACM – ERA-Interim DJF
WRFRACM
WRFRACMWRF
RACM
1989-2002 DJF Climatology
WRF – ERA-Interim DJF RACM – WRF DJF
RACM – WRF DJFWRF – ERA-Interim DJF
Precipitation Difference (%)
Snow Water Equivalent Difference (kg m-2)
RACM – ERA-Interim DJF
RACM – ERA-Interim DJF
ConclusionsUse RASM to explore the impact of small-scale
atmospheric processes on the coupled climate systemGreenland tip jet showed large change in surface heat
fluxes with increased resolutionCare must be taken when coupling model
componentsPrecipitation problem in early versions of RACM
Current version of RACM is stableErrors in coupled simulations are similar to those in
atmosphere-only simulations, with some errors reduced in the coupled simulations
Next Steps• Resolve issue with land temperature bias• Complete 20+ year fully coupled simulation
(1989 to present) baseline simulationoEvaluation of baseline simulation
• Multi-decadal simulationsoRetrospectiveoFuture climateoRegional simulations for CORDEX / AR5
Next Steps• Implementation of additional climate
system componentso Ice sheetsoDynamic
vegetation