[MITgcm-devel] seaice_budget_ice

[Jinlun Zhang]

Hi Martin,
0.97 is surface emissivity.
Jinlun

Martin Losch wrote:

> Hi Jinlun, Dimitris,
>
> Please forgive me, if I am confused about all these constants:
> I am currently trying to implement some radiation-bulk formulae that  
> estimate lwdown from air and ocean temperature, humidity, because  
> apparently for the Arctic the reanalysis fields for lwdown (and  
> swdown) are not very good (this is what my Arctic specialists Gerdes,  
> Karcher, Kauker, Koeberle tell me). The seaice-pkg has some remains  
> of the original Parkinson&Washington bulk formulae in it, which is  
> close to what we want to have for the Arctic (for comparison  
> reasons), so I want to understand what the individual contributions are.
> So: What is the 0.97? ice emissivity? why then have .97*lwdown, if  
> lwdown is not affected by the surface? Or is it some sort of albedo  
> for long wave radiation? What variable name should I give to this  
> number?
>
> Martin
>
> On 27 Dec 2006, at 07:23, Dimitris Menemenlis wrote:
>
>> Martin, why do you think that emissivity is already part of  lwdown?  
>> My understanding of the NCEP and ERA fields is that lwdown  and 
>> swdown are radiation fields prior to any interaction with sea  
>> surface, as opposed to lwnet and swnet, which include interaction  
>> with sea surface.  A more serious issue is potentially the lack of  
>> realism of the representation of atmospheric boundary layer  
>> processes, especially in NCEP reanalysis, which is the older of the  
>> two.
>>
>> A second comment is that by default we bypass the  
>> seaice_budget_ocean bulk formulae and instead use that of pkg/exf.
>>
>> Dimitris
>>
>>> Whatever forcing one uses, make sure 0.97 is not used twice. Jinlun
>>> Martin Losch wrote:
>>>
>>>> Hi there,
>>>> why is lwdown (now lwdownLoc) mulitplied by 0.97 in  seaice_budget_ice
>>>> (formerly budget)? This looks awfully like some ocean surface   
>>>> emissivity,
>>>> which is already part of lwdown if I am not mistaken.  (the same  
>>>> is true
>>>> for seaice_budget_ocean, also formerly budget.)
>>>> I think that this is wrong.
>>>> Martin
>>>
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>
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-- 

Jinlun Zhang
Polar Science Center, Applied Physics Laboratory
University of Washington, 1013 NE 40th St, Seattle, WA 98105-6698

Phone: (206)-543-5569;  Fax: (206)-616-3142
zhang at apl.washington.edu
http://psc.apl.washington.edu/pscweb2002/Staff/zhang/zhang.html