From: bhatt@meeker.ucar.edu (Uma Bhatt)
Message-Id: <199410281539.JAA04626@meeker.ucar.EDU>
Subject: re: CCM1 air-sea fluxes tuning
To: ccm-users@ncar.ucar.edu (ccm users group)
Date: Fri, 28 Oct 94 9:39:21 MDT
This is a response to Ilya Rivin's question about CCM1 air-sea fluxes tuning.
There are discrepencies between the observed and the CCM1 surface fluxes. But
presently all climate models have their problems. We just need to try to
diagnose the problems and deal with then the best that we can and work towards
improving future models. Because of the multitude of feedbacks in the atmosphere
fixing one problem ends up worsening another aspect of the model. Anyways...
One way to deal with this in coupled models is to use (I will say the dirty
words) 'flux corrections'. They were formalized at the Max Planck Institute in
Hamburg by Sausen et al. (1988). The ocean model is forced with daily values
from a control run of CCM1. Each day the flux needed to match the ocean model
temperature and the control run ocean temperature (the bottom boundary
condition) is calculated. This calculation is repeated using multiple years
of CCM1 control runs and an average flux correction is obtained. From this
tuning procedure you obtain an annual cycle of daily flux corrections
(at each gridpoint) which are added to the surface flux forcing in the
coupled simulation. This procedure can be used for both heat and salt
corrections.
The flux corrections are due to both atmosphere and ocean model
deficiencies. We have coupled a variable depth mixed-layer model of
the North Atlantic to CCM1. This model represents vertical processes and
therefore neglects currents. The flux corrections account for
the mean transport of heat due to ocean currents (which is substantial in
the atlantic) and the errors in the CCM1 surface fluxes.
I can send you details about what we did if you are interested.
Uma Bhatt
bhatt@imzadi.meteor.wisc.edu