[MITgcm-devel] Re: Large & Yeager 2004

[Andrea Molod]

hi patrick and martin,

i usually don't put in my 2 cents here, but the ocean
emissivity issue is usually handled on the atmosphere side
by setting it to a wavelength-dependant set of numbers that
are:

0.9788, 0.9833, 0.9819, 0.9820, 0.9835, 0.9865, 0.9886, 0.9719, 0.9719, 0.9719, 0.9719, 0.9719

for wave bands:
    band 1:   4.5 -  5.3 um
    band 2:   5.3 -  5.9 um
    band 3:   5.9 -  7.1 um
    band 4:   7.1 -  8.0 um
    band 5:   8.0 -  9.1 um
    band 6:   9.1 - 10.2 um
    band 7:  10.2 - 12.5 um
    band 8:  12.5 - 14.9 um
    band 9:  14.9 - 18.5 um
    band 10: 18.5 - 25.0 um
    band 11: 25.0 - 35.7 um
    band 12: 35.7 -  oo  um

this is from a reference called Fu and Liou (i need to look it up....)

so your 0.97 number sounds closer to this.....


and we use 0.08 for open ocean albedo - not sure of the source of this 
number.

andrea

On Mon, 18 Dec 2006, Patrick Heimbach wrote:

>
> Definitely yes.
> The "bulk formulae" are almost identical to the Large & Pond ones.
> It seems to be the "radiation formulae" that matter.
> exf has default 0.97, Large & Yeager recommend 1.
> It's a simple runtime parameter in data.exf:
> ocean_emissivity = 1.,
>
>
> On Dec 18, 2006, at 3:26 PM, Martin Losch wrote:
>
>> Patrick,
>> 
>> I have just put a run with large+yeager bulk formulae into the queue. Would 
>> it make more sense to stop that job and do, what you suggest 
>> (ocean_emissivity = 1)?
>> 
>> Martin
>> 
>> On 18 Dec 2006, at 20:52, Patrick Heimbach wrote:
>> 
>>> 
>>> Dimitris,
>>> 
>>> an update on this.
>>> Different people seem to understand different things
>>> when they talk about "bulk formulae".
>>> I undetstood the derivation of buoyancy and momentum fluxes
>>> from atmos. state involving the parameterization of the neutral
>>> transfer coefficients, their stability corrections and the like,
>>> thus deriving, taux & tauy, sensible & latent heat fluxes, evaporation.
>>> The treatment of radiation is somewhat separate, since completely
>>> decoupled from these "bulk formulae".
>>> 
>>> However, in fact it seems that this minor detail might be
>>> the only relevant part that distinguishes our current
>>> exf implementation from the Large & Yeager 2004 recommendations,
>>> i.e. they suggest ocean_emissivity to be set to 1,
>>> whereas exf has a default of 0.97
>>> (and bulkf_force a default of 0.985).
>>> 
>>> So I'll conduct another run with changed emissivity
>>> (the 3% difference should in fact have a discernable impact).
>>> 
>>> -Patrick
>>> 
>>> 
>>> 
>>> On Dec 17, 2006, at 12:26 PM, Dimitris Menemenlis wrote:
>>> 
>>>> Patrick, thank you for info re bulk formulae.
>>>> This is indeed very useful information.
>>>> Dimitris
>>> 
>>> ---
>>> Dr Patrick Heimbach | heimbach at mit.edu | http://www.mit.edu/~heimbach
>>> MIT | EAPS, 54-1518 | 77 Massachusetts Ave | Cambridge, MA 02139, USA
>>> FON: +1-617-253-5259 | FAX: +1-617-253-4464 | SKYPE: patrick.heimbach
>>> 
>>> 
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>> 
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> ---
> Dr Patrick Heimbach | heimbach at mit.edu | http://www.mit.edu/~heimbach
> MIT | EAPS, 54-1518 | 77 Massachusetts Ave | Cambridge, MA 02139, USA
> FON: +1-617-253-5259 | FAX: +1-617-253-4464 | SKYPE: patrick.heimbach
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