[CF-metadata] new named fields for ocean

From: Stephen Griffies <Stephen.Griffies>
Date: Tue, 13 Jan 2009 09:42:06 -0500

Hi,

This email discusses the issue of why there are extra heat fluxes in
ocean models with an open water budget, relative to ocean models that
artificially close their water budget (i.e., ocean models employing a
virtual tracer flux). I originally thought it best to have this
discussion off-line, but some contacted me asking to continue online...

Stephen


Stephen Griffies wrote:
> Karl and Jonathan,
>
> 1/ Regarding pressures: Jonathan, I am fine keeping the original names.
> I will report back to the list with this point.
>
> 2/ Regarding the temperature fluxes: Jonathan, I am again happy
> returning to the names that we originally came up with. More generally,
> here are some comments...
>
> The issue of heat fluxes associated with the transfer of mass or volume
> across the ocean boundary is a relatively new issue for CMIP. Indeed,
> from my understanding, GFDL was perhaps amongst only one or two other
> coupled models in AR4 that considered material transport across the
> ocean surface associated with E-P+R. Delworth etal (2006) discussed the
> point in its heat budget discussion. The remaining coupled models have a
> closed water budget for the ocean (i.e., use virtual tracer fluxes). We
> are not interested in retaining virtual tracer fluxes, and so had to
> consider the implications of opening up the ocean to mass transport with
> the atmosphere and land. Doing so adds this extra heat transfer term. We
> wish to have a means for CMIP5 to record this term. It is clearly
> written in the WGOMD report that virtual flux models will record zero
> for this heat.
>
> To reiterate what we have already said: the transport of material
> substance (water) across the seawater boundary has an associated
> transfer of tracer mass. Correspondingly, there is a transfer of
> tracer, including heat, since the water carries a nonzero temperature
> and nonzero tracer concentration. For many cases, the water is fresh,
> so it only carries a heat. But some river models are being considered
> that carry tracer concentration. If we remove water (e.g., through
> evaporation), then we remove heat. The heat transfer associated with
> phase changes is in ADDITION to the heat associated with mass transport.
>
> Most modelers consider rain falling into the ocean to enter at the SST,
> as well as the water evaporating to be at the SST. But how one
> specifies the tracer concentration or temperature of the water
> transferred across the boundary is not relevant to the discussion. All
> I wish to have is the total amount of heat transferred to/from the ocean
> with the water mass, referenced to 0C.
>
> As Karl noted, atmospheric models generally do not carry a temperature
> for the moisture. But this present limitation of the atmospheric models
> should not force us to shut down the ocean's water cycle. That decision
> would lead us back to virtual tracer fluxes, which are not desirable
> from an oceanographic perspective. Atmospheric modelers inform me that
> the non-conservation associated with not carrying temperature of their
> moisture is small, so I should quit bothering them with this issue...
>
>
> Steve
>
Received on Tue Jan 13 2009 - 07:42:06 GMT