ape workshop at univ. reading, 20-22 april 2005 activity of k-1 japan in ape masahiro watanabe...

APE workshop at Univ. Reading, 20-22 April 2005

Activity of K-1 Japan in APE

Masahiro Watanabe (Hokkaido University)

and

Masahide Kimoto (CCSR, University of Tokyo)

leading

The K-1 Japan project team:

Center for Climate System Research (CCSR)

National Institute for Environmental Studies (NIES)

Frontier Research Center for Global Change (FRCGC)

[email protected]


• Same atmospheric model as used for IPCC FAR• Dynamics

– T42 spectral representation– Vertical 20 layers– Semi-Lagrangian moisture / cloud water transports (Lin & Rood 1996)

• Physics:– Prognostic Arakawa-Schubert (Pan and Randall, 1998)– Prognostic cloud water for layer cloud and LSC (Le Treut & Li 1991)– K-distribution 2-stream radiation (Nakajima et al., 1995)

+ max.-random cloud overlap– Mellor-Yamada level 2 turbulent closure + moist effect (Smith, 1990)

K-1 Japan: CCSR/NIES/FRCGC AGCM ver. 5.7


Cumulus convection in the K1 model

Sensitivity to d : timescale of cloud base mass flux

1 Feb

1 Mar

1 Jan

Cloud cluster is less organized with shorter lifetime Standard value of d = 7200s = 2hr

d = 1000s d = 3600s d = 7200s


Cloud water/ice in the K1 model

Radiative budgets are sensitive to the definition of melting layer

melting layer (-25C < T < -5C)Cloud ice

Cloud water


Time mean state (precipitation)

Single ITCZ except for “Flat”

Meridional SST distribution



Precipitation in the K-1 model is moderate among APE participants

* cited from Dr. Williamson’s summary


• Main focuses in APE might be:– To evaluate the model spread due to physical

parameterization– Behavior of tropical disturbances (MJO, cloud clusters)

• Main focuses in our group are:– Behavior of the extratropical low-frequency variability (tomorrow afternoon session) – Tropical zonal mean state associated with an interaction

between the Walker and Hadley circulations (tomorrow morning “teaser”)

• Extended integrations:– Control and 3KW1 extended for 2700 days (=7.5yrs)


with a special attention to the comparison between Control and 3KW1 experiments

Tropical zonal mean states in APE

Masahiro Watanabe (Hokkaido University)

[email protected]


Mean tropical atmosphere in K1 Control & 3KW1

c.i.=0.01Pa/s


Equatorial superrotation

Suarez & Duffy (1992)

Results in two-level, dry primitive models

Saravanan (1993)

•This may not be effective in more complicated models?


Mean tropical atmosphere in Control & 3KW1


Possible Walker-Hadley interaction

• Whether we can see a sudden transition to the supper-rotating state? Is there hysteresis?

• Possible mechanisms– Meridional momentum transports

by extratropical synoptic eddies (Suarez & Duffy 1992; Saravanan 1993)

by forced tropical stationary eddies (Hoskins et al. 1999)

– Vertical momentum transports linked with the Hadley cell

• Role of moist processes


A proposal

A series of APEs (Control and 3KW1, and additionally 1KW1, 2KW1, 4KW1,….)

may be useful to test a basic dynamics of the interaction between Walker and Hadley circulations, or the superrotation problem, which might be

to revisit previous results in the two-level dry

models (e.g. Suarez & Duffy 1992; Saravanan 1993) then

to extend more recent results in aquaplanet

models (e.g. Hoskins et al. 1999; Kraucunas & Hartmann 2005)

ape workshop at univ. reading, 20-22 april 2005 activity of k-1 japan in ape masahiro watanabe...

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