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Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
M. Blackburn1, B. J. Hoskins1,2, D. L. Williamson3, Y-Y. Hayashi4 and K. Nakajima5
&14 APE Modelling Groups
1. NCAS-Climate, University of Reading, UK;2. Imperial College, London and University of Reading, UK;3. National Center for Atmospheric Research, Boulder, USA;4. Kobe University, Japan;5. Kyushu University, Fukuoka, Japan
Comparison of Atmospheric GCM Simulations on a
Water-Covered Earth
- MOCA-09 J11 Climate Model Intercomparison 24 July 2009 -
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
• Experiment aims and configuration
• Participating groups and models
• Aspects of model intercomparison:
• Future plans
• Wider context
Talk outline
Tropical mean state – dependence on SST profile
Tropical variability
(Response to localised SST anomaly)
Global energy balance
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
APE Experimental Design (1)
• Complete AGCMs but idealised planet
• More constrained experiment than real-world benchmark (AMIP)
• Investigate sensitivity to tropical SST profile – with reference to theoretical limits (Held & Hou, 1980)
• Zonally symmetric forcing – unconstrained wave evolution
• Convective organisation and remote response to tropical SST anomalies
• Facilitate understanding of model differences and sensitivities
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
APE Experimental Design (2)
• No land / orography
• 8 idealised sea surface temperature (SST) distributions
• 5 symmetric SSTs span a range of tropical climates
• Local and global-scale SST anomalies
• 3-year climate (following spin-up)
• Following Neale & Hoskins (2000)
• Specified solar forcing, O3, GHG etc
Symmetric SST profiles
SST anomaly experiments
3KW1
1KEQ 3KEQ
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
APE Modelling Groups
Group Location Model Resoln Features
AGU for APE Japan (consortium) AFES v.1.15 T39 L48 Spectral, eulerian
CGAM Reading, UK HadAM3 N48 L30 3.75º x 2.5º grid
CSIRO Aspendale, Australia CCAM-4-12 C48 L18 ~220km conformal cubic grid
DWD Mainz, Germany GME 29.1.1 ni=64 L31 ~1º icosahedral-hexagonal grid
ECMWF Reading, UK IFS 29r2 / 32r3 TL159 L60 Spectral, semi-lagrangian
FRCGC Yokohama, Japan NICAM 7km L54 icosahedral grid, non-hydrostatic
GFDL Princeton, USA AM2p14 N72 L24 2.5º x 2º grid (IPCC)
GSFC Maryland, USA NSIPP-1 N48 L34 3.75º x 3º grid
K1-Japan Japan (collaboration) CCSR/NIES 5.7 T42 L20 s-l moisture and cloud
LASG Beijing, China SAMIL R42 L9 Spectral, eulerian
MIT Cambridge, USA MIT-gcm C32 L40 ~280km cubed sphere
MRI Tokyo, Japan MRI/JMA98 T42 L30 Spectral, eulerian
NCAR Boulder, USA CCSM-CAM3 T42 L26 Spectral, eulerian
UKMO Exeter, UK pre-HadGAM1 N96 L38 1.875º x 1.25º, semi-lagrangian
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
Precipitation response to SST
• Regime transition: single double ITCZ
• Transition occurs close to Qobs profile (based on tropical Pacific)
• Accurate tropical simulation of the real Earth may be particularly difficult to achieve
Control QobsPeaked
Flat
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
Precipitation (mm/day)
Temperature (K)
Omega (Pa s-1)
Rel. Humidity (%)
Zonal wind (m s-1)
ECMWF GSFC CSIRO
Qobs – control differences
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
Impacts
• Cools the tropics (deep convection over cooler SST, fixes tropical θe profile)
• Widens Hadley Cell
• Displaces the jets polewards
Qobs - control
• Large uncertainty due to transition / no-transition
• Consistency between degree of transition and strength of tropical and extratropical response
Outliers (CSIRO, LASG):
• Weak splitting of ITCZ but strong response
• Due to increase in sub-tropical precipitation?
ITCZ Regime Transition
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
Inter-tropical Convergence Zone
• When does convection break through the trade-wind inversion?
• Many interacting processes
• ITCZ location sensitive to all these processes in models
Emanuel (1994)
[ Evap – Precip ] Surface Wind ECMWF - APE control (time average)
(mm/day)Cool 30º lat.
Eq. Warm
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
Hydrological Cycle: NCAR model
Williamson (2008)
Precipitation: contributions to resolution dependence, T42 / T85
params.
timestep grid
Truncn. diffusion
params.at T42
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
Tropical Wave Spectra (control)
Log-power of symmetric modes of equatorial precipitation (10°N - 10°S average)
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
Tropical Wave Spectra (ECMWF)
• Recent model includes major convection changes (cy32r3, November 2007)
• Precipitation organised strongly in equatorial waves
• MJO for Qobs?see Bechtold et al (2008)
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
• Global energy balance unknown
• Mean ~15 Wm-2 down
• TOA imbalance goes into ocean (fixed SST)
• TOA spread >30 Wm-2
• Dominated by cloud (fraction + reflectivity)
• Compensation of land / ocean biases for real-Earth global balance?
Global Energy Balance (control)
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
• Currently completing diagnostic analysis & writing papers
• Special Issue of J. Met. Soc. Japan (published 2010)
• APE Atlas – comprehensive intercomparison plots (online)
• Data archive made public (~end 2009)
APE – Status & Plans
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
• Comparison of climate and NWP models in idealised configuration
• Wide variety of behaviour despite idealised setting
• Transition from single to split ITCZ close to Earth-like SST profile
• Tropical wave spectrum not converged at typical climate resolutions
• Large uncertainty in global energy balance (compensating biases?)
• “Correct” behaviour unknown, but reveals uncertainties
• Augment with single-model sensitivity + constrained experiments
• Addition to the experimental hierarchy
• Use as a process-study test-bed
• Talks in M10 Tropical Circulation (MOCA-09 week 2)
APE – Conclusions / Context
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
Evaluation of Atmospheric GCMs- an experimental hierarchy -
1D / 2D idealised flows
Dynamical core
Idealised moist core Aqua-planet AMIP
•Full complexity GCM
- unique dynamics
- unique moist parameterizations
•Difficult to isolate reasons for differences
•Aqua-planet idealises the planet, not the model!
•Dry dynamics
- linear relaxation to climatology
- Rayleigh friction boundary layer
•Unrealistic sensitivities?
•Aim for
- single idealised moist parameterization
- minimal complexity to represent processes
•Use in all dynamical cores
•Sensitivity of a moist atmosphere to dynamical formulation
•Frierson et al (2006,2007)
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
Use as a Process-Study Test-bed• Idealised configurations useful for process studies
• Main use of the Held-Suarez Dynamical Core
• Aqua-Planet examples:
1. Partition response to CO2 forcing 2. Ingredients of Atlantic storm-track
Response to uniform or polar SST increase
Kodama & Iwasaki (2009, JAS, in press)
[T]
[u]
Brayshaw et al (2009, JAS, in press)
Zonal wind
250hPa (colour)
850hPa (contour)
SST (contour)
Continents
“Rockies”
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
• Large spread in albedo
• Due to cloud – both fraction + reflectivity
• e.g. UKMO, MRI high albedo but low fraction
Global Energy Balance
Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/
Insolation
• Theoretical: sw_toai = (S0/π) * cos(lat)
• Several models are near identical, with equatorial peak S0/ π =434.493 Wm-2
• Scaling, timing, polar issues