[MITgcm-devel] seaice_budget_ice

[Jinlun Zhang]

Hi Martin,

Parkinson&Washington gives a very nice description about 
surface_emissivity. It lists all the components of surface heat flux, 
really an excellent paper about ice thermodynamics.

Jinlun

Martin Losch wrote:

> Thanks Jinlun,
> but then, what is the meaning of the of the term
> surface_emissivity*lwdown?
> (surface is both ice and ocean for the respective cases in budget) I  
> would have thought that the radiation that is emitted by the surface  
> is upward radiation, not downward. Or does one parameterize the  
> emitted radiation as .97*lwdown?
>
> Martin
>
> On 27 Dec 2006, at 17:51, Jinlun Zhang wrote:
>
>> 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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