[Ncep.list.emc.monsoondesk] Discripancy in the actual Ocean Surface temperatue and Surface temperature Seen by the Atmosphere (GFS)

Wanqiu Wang wanqiu.wang at noaa.gov
Thu Sep 25 14:07:32 UTC 2014


I think Moorthi's explanation is probably right for the differences you saw.

The ocean output contains two surface temperatures in grib files, one is 
tmpsfc and the other potdsl(lev=5).  I just checked one coupled run, the 
tmpsfc field in ocean file (ocnf) looks quite similar to the same 
variable (tmpsfc) in the atmospheric file (flxf).  But potdsl(lev=5) in 
the ocean file is warmer in the Arctic because it is the water 
temperature of the ocean top layer.

Are both of the two temperatures you plotted tmpsfc?  If so, then the 
differences are strange.


On 9/25/2014 6:43 AM, Shrinivas Moorthi wrote:
> Prajeesh,
>     I have not looked at the code and not sure how MOM treats sea ice, 
> but where sea ice exists, it is treated like land and
> the atmosphere sees sea ice skin temperature.  I assume that sst  in 
> the sea ice region should be the ice bottom temperature
> (or the sea surface temperature under sea ice.  (I am not sure if this 
> is what is done, but I am not a MOM4 expert).
> Moorthi
> On 09/25/2014 12:42 AM, Prajeesh A.G. wrote:
>> Hi all,
>> I find that, over the Sea-Ice regions, there is a large discrepancy 
>> in the Surface temperature calculated by the Ocean Model and the one 
>> which is seen by the Atmospheric model.
>> The attached figure is from a free run of our ESMv1 model (Which has 
>> MOM4p1 in place of MOM4p0 in CFSv2). In the figure left panel is the 
>> Sea Surface temperature from Ocean Model and the right panel is 
>> Surface temperature from Atmospheric (GFS) Model. The Color scales 
>> are same. It can be seen that over the Polar region the surface 
>> temperature are largely different. In the Ocean model it is between 
>> -1 to 1 degree, where as in the atmosphere it is below -4 degree 
>> (Sea-Ice region over the north pole) . We also confirmed that this 
>> discrepancy exist in our CFSv2 simulations too.
>> I think that, this discrepancy is due to the Sea-Ice thermodynamics 
>> model in the GFS. The atmospheric model see the Ocean calculated 
>> surface temperature only where there is no Sea-Ice, and where there 
>> is Sea-Ice it takes the Sea-Ice fraction and Sea-Ice depth from Ocean 
>> model and calculates the surface temperature using a Sea-Ice 
>> thermodynamics model in the GFS. I conjecture that this might account 
>> some part of the TOA energy Imbalance.
>> We would be like to hear from other users of CFSv2 on this issue.
>> *Regards..*
>> Prajeesh
>> IITM, Pune
>> India
> -- 
> Dr. Shrinivas Moorthi
> Research Meteorologist
> Global Climate and Weather Modeling Branch
> Environmental Modeling Center / National Centers for Environmental Prediction
> 5830 University Research Court - (W/NP23), College Park MD 20740 USA
> Tel:(301)683-3718

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