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

[Martin Losch]

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
>
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