Subject: ccm3 in coupled AOGCM.
From: Wei Cheng (cheng@obelix.rsmas.miami.edu)
Date: Tue Jan 06 1998 - 20:36:08 MST
Dear colleagues,
I am wondering if any of you have some experiences with CCM
in coupled AOGCMs.
I have been using CCM3 (standard version except T21 resolution)
in a coupled ocean-atmosphere general circulation model. The model
has settled into a quite robust mean climate state after
the first few years' initial adjustment and the model climate
reproduces most of the basic features of the observed climate.
The biggest discrepancy between model climate and reality is the
warmer(higher)-than-observed tropical and subtropical eastern Pacific
SST(rainfall) field. There is a double ITCZ straddling the equator in the
annual mean plot of precipitation. Further looking into the
seasonal cycle of precipitation tells this is mainly due to the fact
that in northern winter to spring (JAN to MAY), ITCZ across the Pacific
persists around 10S and dumps excessive rain in the eastern subtropical
Pacific. Meanwhile the trade winds collapse and the eastern upwelling
weakens. This is similar to what is operating in an ElNino event, except
that, it happens year after year. We haven't figured out what triggers
this permanent ENSO and why the model, unlikely the reality, doesn't
recover from this warm state.
For those of you who also use CCM in coupled modeling, may I ask: do you
meet with a similar problem in your experiments and do you know what
could possibly cause this problem? Or if you don't have this problem,
you know what makes your model behave well?
I am looking forward to hearing from you and would highly appreciate
any of your comments.
Good luck with every one's work.
Wei cheng
university of Miami/RSMAS/MPO
wcheng@rsmas.miami.edu
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