[MITgcm-support] Shortwave radiation

Martin Losch Martin.Losch at awi.de
Fri Sep 11 04:06:19 EDT 2009

Hi Georges,

it looks like you are using the exf pkg with the bulk-formulae enabled:
in EXF_OPTIONS.h there is a flag ALLOW_BULKFORMULAE. If that's turned  
on the heat fluxes are computed from air-temperature, humidity, wind  
etc. and shortwave radiation is prescribed.
If you don't prescribe air-temperatures, then the model uses atemp=0  
(in Kelvin!), so you get latent and sensible heat fluxes based on a  
temperature difference on the order of 280K (you could call this a  
bug, because there is no warning for this). Just for fun, you could  
diagnose these fluxes (I think they are called EXFhs, EXFhl in the  
diagnostics package), these fluxes should be enormous.

If you want to use only sw-radiation and set the remaining heat flux  
to zero, then you should set all corresponding flags in EXF_OPTIONS.h  
to undefined (there is a table in pkg/exf/EXF_OPTIONS.h, that gives an  
overview of what happens when ...) and recompile.


On Sep 10, 2009, at 10:09 PM, Georges Djoumna wrote:

> Dear all,
> I'am running a simulation with constant shortwave radiation (200 W/ 
> m2) and wind speed (.56 m/s) using the exf package. The water  
> temperature is increasing quadratically at the surface and linearly  
> below the surface until the solution blows up. If I add the air  
> temperature, the solution behaves well.  Does anyone has already  
> face this type of problem? I'am looking for suggestions in other to  
> figure out what is the source of the problem.
> Thanks.
> Dr. Georges Djoumna
> Post Doctorate Fellow
> Faculty of Mathematics
> Department of Applied Mathematics
> University of Waterloo
> Office MC 5135
> Waterloo, Ontario
> Canada N2L 3G1
> E-mail        :  gdjoumna at math.uwaterloo.ca
> Office Phone  :  1 519 888 4567 Ext 36648
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