CORDEX Arctic Simulations: Initial Results from the Weather
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Transcript CORDEX Arctic Simulations: Initial Results from the Weather
John J. Cassano, Matthew Higgins, Alice DuVivier
University of Colorado
Wieslaw Maslowski, William Gutowski, Dennis Lettenmaier, Andrew Roberts
Project goals
Develop 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 system
Small-scale features in the atmosphere can have
large impacts on climatically important processes
such as:
Cyclone intensity / polar lows
Mesoscale features such as topographically forced winds
(Greenland tip jets)
Realistic representation of these processes is
critical for improved climate projection
Cyclone Intensity and Size
Resolution 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 human
activities 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)
WRF Tip Jet Case
Observed and Modeled Wind Speed
a)
b)
c)
d)
e)
Two Month: WRF average latent heat flux
a)
b)
c)
d)
Two Month: WRF 95th percentile latent heat flux
a)
b)
c)
d)
RACM simulations
Coupled: Regional Arctic Climate Model (RACM)
WRF – POP – CICE - VIC
Simulation from 1989 to 2002 (currently)
Atmosphere – land : WRF – Noah
CORDEX simulation from 1989 to 2009
RACM and WRF simulations forced with:
ERA-Interim IBC/LBCs
Observed sea ice
Use 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)
Sea Level Pressure
1989-2002 DJF Climatology
ERA-Interim
RACM
WRF
ERA-Interim & RACM
RACM – ERA-Interim
WRF – ERA-Interim
Sea Level Pressure
1989-2002 JJA Climatology
ERA-Interim
ERA-Interim & RACM
RACM
WRF
RACM – ERA-Interim
WRF – ERA-Interim
SLP and Sea Ice
1989-2002 JJA Climatology
ERA-Interim
ERA-Interim & RACM
RACM
RACM – ERA-Interim
RACM - NSIDC
Near Surface Temperature
1989-2002 JJA and DJF Climatology
RACM – ERA-Interim JJA
WRF – ERA-Interim JJA
RACM – ERA-Interim DJF
WRF – ERA-Interim DJF
Temperature Profiles
Northern Alaska
1989-2002 DJF Climatology
Height
RACM – ERA-Interim DJF
WRF
RACM
Temperature
Part of Russia
Height
Height
North of 80 Latitude
WRF
RACM
Temperature
WRF
RACM
Temperature
Precipitation and Snow Cover
1989-2002 DJF Climatology
RACM – ERA-Interim DJF
WRF – ERA-Interim DJF
RACM – WRF DJF
Precipitation Difference (%)
RACM – ERA-Interim DJF
WRF – ERA-Interim DJF
Snow Water Equivalent Difference (kg m-2)
RACM – WRF DJF
Conclusions
Use RASM to explore the impact of small-scale
atmospheric processes on the coupled climate system
Greenland tip jet showed large change in surface heat
fluxes with increased resolution
Care must be taken when coupling model components
Precipitation problem in early versions of RACM
Current version of RACM is stable
Errors 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 simulation
o Evaluation of baseline simulation
• Multi-decadal simulations
o Retrospective
o Future climate
o Regional simulations for CORDEX / AR5
Next Steps
• Implementation
of additional
system components
o Ice sheets
o Dynamic
vegetation
climate