First results from the Aqua-Planet Experiment

intercomparison

Mike Blackburn, Brian HoskinsUniversity of Reading

David WilliamsonNational Center for Atmospheric Research

Peter GlecklerProgram for Climate Model Diagnosis and Intercomparison

Richard NealeNOAA-CIRES Climate Diagnostics Center

APE Modelling Groups

http://www.met.reading.ac.uk/~mike/APE/

Working Group on Numerical Experimentation - WGNE

http://www.met.reading.ac.uk/~mike/APE/

Working Group on Numerical Experimentation - WGNE

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 Cycle 29r2 TL159 L60 Spectral, semi-lagrangian

FRCGC Yokohama, Japan NICAM 7km L54 icosahedral grid, non-hydro.

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

MGO St. Petersburg, Russia MGO-gcm T30 L14 Spectral

MIT Cambridge, USA MIT-gcm C32 L40 ~280km cubed sphere

NCAR Boulder, USA CCSM-CAM3 T42 L26 Spectral, eulerian

UKMO Exeter, UK pre-HadGAM1 N96 L38 1.875º x 1.25º grid, s-lagrangian

http://www.met.reading.ac.uk/~mike/APE/

Working Group on Numerical Experimentation - WGNE

The Experiment

• Complete GCMs but idealised planet

• More constrained experiment than real-world benchmark (AMIP)

• Facilitate understanding of model differences and sensitivities

• 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)

Symmetric SST profiles

Latitude

SS

T (

degC

)

SST anomaly experiments

3KW1

1KEQ 3KEQ

Zonal Average Hydrological CyclePrecipitation (mm/day)

Evaporation (mm/day)

different scale

http://www.met.reading.ac.uk/~mike/APE/

Working Group on Numerical Experimentation - WGNE

Hydrological Cycle: NCAR model

Courtesy of David Williamson, NCAR

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/

Working Group on Numerical Experimentation - WGNE

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.SST

Eq. Warm SST

Tropical Variability (precipitation)

average 5ºN-5ºShttp://www.met.reading.ac.uk/~mike/APE/

Working Group on Numerical Experimentation - WGNE

(mm/day)

http://www.met.reading.ac.uk/~mike/APE/

Working Group on Numerical Experimentation - WGNE

Observations + Theory

Observed variability (OLR)

• Hierarchy of convective organisation

Tim

e

Time-longitude section of transient OLR averaged between the equator and 5N from May to July in 1980. (Nakazawa, 1988)

Zonal Wavenumber

Fre

quen

cy (

CP

D)

UKMO_n96 sym. spectrum (precip)

Observed sym. spectrum (OLR)

Images from Yoshi-Yuki Hayashi; Yukiko Yamada; NOAA CDC

Wider SST maximum in tropics

Stronger SST gradient : displaced poleward

Response of zonal climate to SST

qobs-control

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

cntl

qobs

latitude

SS

T (

degC

)

http://www.met.reading.ac.uk/~mike/APE/

Working Group on Numerical Experimentation - WGNE

Storm-track statistics

• Tracking of storm features using 6 hourly sea-level pressure

• NCAR model for all 8 SSTs

Courtesy of Kevin Hodges, ESSC, Reading

Mean Intensity

latitude

Pre

ssur

e an

omal

y (h

Pa)

Track Density

latitude

Num

ber

per

mon

th in

5º

radi

us

peakcntlqobsflatcntl5n1keq3keq3kw1

Zonal speed

Zon

al s

peed

(m

s-1)

latitude

http://www.met.reading.ac.uk/~mike/APE/

Working Group on Numerical Experimentation - WGNE

Storm-track statistics

• Tracking of storm features using 6 hourly sea-level pressure

• 6 models for “flat” SST

Courtesy of Kevin Hodges, ESSC, Reading

Track Density

latitude

Num

ber

per

mon

th in

5º

radi

us

Mean Intensity

latitude

Pre

ssur

e an

omal

y (h

Pa)

http://www.met.reading.ac.uk/~mike/APE/

Working Group on Numerical Experimentation - WGNE

Low Frequency Variability

• Significant zonal wavenumber m=5 in 3-year means

• Slow propagation, c = 1.7ms-1

• Significant correlation with annular mode variability

Courtesy of Masahiro Watanabe,

Hokkaido University. GRL 32, L05701. (2005)

1-point correlation maps: 10-day low-pass surf. pressure

EOFs of 10-day low-pass streamfunction =0.3

Ref 51.6N

Global Energy Balance

APE control experiment:

3 year averages +

temporal variability

Net flux (toa; surface)

sw_dn TOA sw_up

sw TOA lw

http://www.met.reading.ac.uk/~mike/APE/

Working Group on Numerical Experimentation - WGNE

http://www.met.reading.ac.uk/~mike/APE/

Working Group on Numerical Experimentation - WGNE

Summary

• APE is useful to test model changes

• Complex, difficult to understand - despite constrained setup

• Documenting a wide variety of model behaviours (not converged?)

• Attempts to understand sensitivities in individual models

• Additional experiments needed to understand model differences (eg fixed radiation to remove feedbacks)

• Diagnostic focus: Mean state: model/SST differences; tropical theory; maintenance Tropical wave activity Diurnal cycle Mid-latitude variability & storm-tracks

• Issues: Reference solution is unknown Expect resolution convergence with parameterizations?