Sensitivity of Modeled Dynamics to Atmosphere and Ocean Resolution in CESM

Aurthors, NCAR CGD

CESM using CAM5-SE coupled to POP2 at high (hr) and standard (sr) resolutions• hr atmosphere, hr ocean: ne-120 (~0.25 deg), t-12 (~0.1deg)• hr atmosphere, sr ocean: ne-120 (~0.25 deg), gx1v6 (~1.0 deg)• sr atmosphere, sr ocean: ne-30 (~1.0 deg), gx1v6 (~1.0 deg)

Motivation

oSurface temperature reaches quasi-equillibrium in hr atm, hr ocn & sr atm, sr ocn; hr atm, sr ocn still warming

oTOM EF > 0 and trending down for all. End of run: hr atm, hr ocn (~0.3Wm-2) < sr atm, sr ocn (~0.5Wm-2) < hr atm, sr ocn (~0.6Wm-2)

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Experiment Descriptions

Summary and discussion

hr a

tm, h

r ocn

Surface Temperature

hr a

tm, s

r ocn

sr a

tm, s

r ocn

TOM Energy Flux Pot. Temp Anom from IC

Transient Behavior

SST (obs. HadISST 1999-2008)

hr a

tm, h

r ocn

hr a

tm, s

r ocn

sr a

tm, s

r ocn

Precip (obs. GPCP 1979-2009)

oC mm day-1

Annual Mean Bias

oC

Obs

erva

tions

Surface Stress (obs. ERS 1992-2000)

mm day-1 Nm-2

Nm-2

oGlobal mean and rms SST bias is...oPrecipitation biases...oWind stress...

ENSO Variability

still drifting at surface!

hr a

tm, h

r ocn

hr a

tm, s

r ocn

sr a

tm, s

r ocn

Nino 3.4 Power Spectra

Gray - HadISST

Ann SST EQ Pacific

Obs

erva

tions

oCSLP CI: 2hPa

SST Climatology

DJF Comp. SST, Tair, SLP

o hr atm, hr ocn has better depiction of SST compared to hr atm, sr ocn & sr atm, sr ocn o ...and better zonal SST gradient compared to sr atm, sr ocn

decr

ease

d oc

n re

s

decr

ease

d oc

n &

atm

os re

s

decr

ease

d at

mos

res

Red – Reynolds and Smith

o Shape and amplitude of Nino 3.4 power specra in hr atm, hr ocean resembles obs - hr atm, sr ocn & sr atm, sr ocn have too much variance and are too periodico SLP tele-connection amplitude is degraded compared to hr atm, sr ocn & sr atm, sr ocn however reasons are unclear

Winter Mean MLD Bias (obs. Reynolds and Smith)

m