[MITgcm-support] more KPP blues, maybe related?

[Martin Losch]

Chris,

I was about to write an email. I think I have localized the problem, 
but I haven't fixed it. It doesn't have anything to do with KPP but 
with the equation of state. And as usual, I am to blame for all the 
trouble:
The problem only occurs with I use
eosType='MDJWF',
so the super-duper new, latest, fantastic EOS by McDougall et al. 
(2003), but it's not the equation of state itself but probably alpha 
(in find_alpha), that's wrong. And since find_alpha/beta is only called 
from somewhere within kpp_routines.F and nobody ever uses MDJWF 
together with KPP (probably nobody every uses MDJWF to begin with, 
there's no test case for it), nobody has ever had the problem. I am 
glad that I am only responsible for my loss of time.

I'll try to fix the problem (it's probably just a wrong coefficient or 
so) and then you can decide when or if I can check it in.

Martin

On Monday, October 27, 2003, at 02:15  PM, Chris Hill wrote:

> Martin,
>
>  Could you put your setup on-line at MIT (if its not already there)
> somewhere? There are a couple of other coarse resolution KPP issues 
> that
> people have found here (though not of the 30-40 day blow up sort). It
> would be good to get Dimitris to take a quick look at the various 
> setups
> people have while he is here this week.
>
> Thanks,
>
> Chris
>
>
>
>> -----Original Message-----
>> From: mitgcm-support-bounces at mitgcm.org
>> [mailto:mitgcm-support-bounces at mitgcm.org] On Behalf Of Martin Losch
>> Sent: Monday, October 27, 2003 3:29 AM
>> To: mitgcm-support at mitgcm.org
>> Subject: Re: [MITgcm-support] more KPP blues, maybe related?
>>
>>
>> Hi again,
>>
>> I have made this mistake with the downward solar radiation, but
>> unfortunately, this does not appear to be my real problem. I
>> checked my
>> input fields again, and I had another look at FFIELDS.h where I had
>> already appreciated the ranges provided. I use net shortwave
>> radiation
>> (netsw) now. My fields are all in the proper ranges: (with Qnet =
>> latent+sensible+netlw+netsw, that's the default for
>> global_ocean.90x40x15, Qsw=netsw)
>> -225 < Qnet < 442, FFIELDS.h says: Typical range: -250 < Qnet
>> < 600 -321 < Qsw < 0, FFIELDS.h says: Typical range: -350 <
>> Qsw < 0 and here may be the problem: -9 < Qnet-Qsw < 550
>> which I think is what I should use for surfQFile
>> together with surfQswFile
>>
>> As far as I understand, I can use either
>> surfQFile = Qnet
>> or
>> surfQFile = Qnet-Qsw
>> surfQswFile = Qsw
>> I actually tried the combination
>> surfQfile = Qnet
>> surfQswFile = Qsw
>> which doesn't make any sense to me because netsw is included
>> twice. But
>> only when I use surfQFile = Qnet alone (without surfQswFile)
>> the model
>> remains stable. The other two combinations above with KPP
>> blow up after
>> 30-45 days. It must be something really stupid, like a scale
>> factor of
>> 1000 somewhere, because the effect is so drastic.
>>
>> Also, when I turn off KPP in data.pkg, then the model appears to be
>> stable with
>> surfQFile=Qnet-Qsw; surfQswFile=Qsw;
>>
>> I am still hoping for a miracle.
>>
>> Martin
>>
>>
>> On Sunday, October 26, 2003, at 05:28  PM, Dimitris Menemenlis wrote:
>>
>>>>> For SHORT_WAVE_HEATING input "Qsw" I use downward solar
>> flux (with
>>>>> oposite sign) which may be wrong (now I am almost sure
>> it's wrong).
>>>
>>> Martin, if you are using a relatively recent version of the
>> code, have
>>> a
>>> look at definitions at beginning of FFIELDS.h (or
>> exf_fields.h if you
>>> are using pkg/exf).  For each input field there is a
>> typical range of
>>> values.
>>>
>>> For global_ocean.90x40x15 experiment you need to use "net shortwave
>>> radiation", which is different from "downward shortwave radiation",
>>> and which is provided separately by NCEP.
>>>
>>> Note that if you are using pkg/exf, then you can specify either net
>>> (swflux) or downward (swdown) shortwave radiation, and the
>> model will
>>> convert as needed:
>>>
>>> c--   Compute net from downward and downward from net longwave and
>>> c     shortwave radiation, if needed.
>>> c     lwflux = Stefan-Boltzman constant * emissivity * SST - lwdown
>>> c     swflux = - ( 1 - albedo ) * swdown
>>>
>>> Hope this helps.
>>>
>>> One last thing, there is a small but finite chance that sign
>>> convention for Qnet and Qsw may change for release 2.  So
>> make sure to
>>> take a look at FFIELDS.h and at exf_fields.h when you
>> download release
>>> 2.
>>>
>>> D.
>>>
>>> --
>>> Dimitris Menemenlis <menemenlis at jpl.nasa.gov>
>>> Jet Propulsion Lab, California Insitute of Technology
>>> MS 300-323, 4800 Oak Grove Dr, Pasadena CA 91109-8099
>>> tel: 818-354-1656;  fax: 818-393-6720
>>>
>>> _______________________________________________
>>> MITgcm-support mailing list
>>> MITgcm-support at mitgcm.org
>>> http://dev.mitgcm.org/mailman/listinfo/mitgcm-support
>>
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