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Working Group on Numerical Experimentation - WGNE M. Blackburn 1, B. J. Hoskins 1,2, D. L. Williamson 3, Y-Y. Hayashi.

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Presentation on theme: "Working Group on Numerical Experimentation - WGNE M. Blackburn 1, B. J. Hoskins 1,2, D. L. Williamson 3, Y-Y. Hayashi."— Presentation transcript:

1 Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/ M. Blackburn 1, B. J. Hoskins 1,2, D. L. Williamson 3, Y-Y. Hayashi 4 and K. Nakajima 5 & 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 -

2 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

3 Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/ Compare idealised climates simulated by global atmospheric circulation models (AGCMs) being developed and used for numerical weather prediction and climate research. Provide a benchmark of current model behaviour. Stimulate research to understand the causes of inter-model differences arising from different models parameterization suites dynamical cores methods of coupling the two. Experiment Aims

4 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

5 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, O 3, GHG etc Symmetric SST profiles SST anomaly experiments 3KW1 1KEQ 3KEQ

6 Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/ APE Modelling Groups GroupLocationModelResolnFeatures AGU for APE Japan (consortium)AFES v.1.15T39 L48Spectral, eulerian CGAM Reading, UKHadAM3N48 L303.75º x 2.5º grid CSIRO Aspendale, AustraliaCCAM-4-12C48 L18~220km conformal cubic grid DWD Mainz, GermanyGME 29.1.1ni=64 L31~1º icosahedral-hexagonal grid ECMWF Reading, UKIFS 29r2 / 32r3T L 159 L60Spectral, semi-lagrangian FRCGC Yokohama, JapanNICAM7km L54icosahedral grid, non-hydrostatic GFDL Princeton, USAAM2p14N72 L242.5º x 2º grid (IPCC) GSFC Maryland, USANSIPP-1N48 L343.75º x 3º grid K1-Japan Japan (collaboration)CCSR/NIES 5.7T42 L20s-l moisture and cloud LASG Beijing, ChinaSAMILR42 L9Spectral, eulerian MIT Cambridge, USAMIT-gcmC32 L40~280km cubed sphere MRI Tokyo, JapanMRI/JMA98T42 L30Spectral, eulerian NCAR Boulder, USACCSM-CAM3T42 L26Spectral, eulerian UKMO Exeter, UKpre-HadGAM1N96 L381.875º x 1.25º, semi-lagrangian

7 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 Qobs Peaked Flat

8 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 ) ECMWFGSFCCSIRO Qobs – control differences

9 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 θ e 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

10 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

11 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. timestepgrid Trunc n.diffusion params. at T42

12 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)

13 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)

14 Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/ Bullet points ditto Response to SST Anomalies

15 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)

16 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

17 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

18 Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/

19 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-planetAMIP 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)

20 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 CO 2 forcing2. Ingredients of Atlantic storm-track Response to uniform or polar SST increase Kodama & Iwasaki (2009, JAS, in press) [T][T] [u][u] Brayshaw et al (2009, JAS, in press) Zonal wind 250hPa (colour) 850hPa (contour) SST (contour) Continents Rockies

21 Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/

22 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

23 Working Group on Numerical Experimentation - WGNE http://www.met.reading.ac.uk/~mike/APE/ Insolation Theoretical: sw_toai = (S 0 /π) * cos(lat) Several models are near identical, with equatorial peak S 0 / π =434.493 Wm -2 Scaling, timing, polar issues


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