[MITgcm-support] Salinity variability malfunction

[Martin Losch]

Hi Ivan,

The change in salinity depends entirely on the freshwater forcing (E-P-R, evaporation minus preciptation minus runoff). Please check out the diagnostics package, where you can control the output of dynamic variables like temperature and salinity, but also more technical quantities like salinity tendency, or the freshwater flux (“oceFWflx”) This will tell you how much change in salinity to expect given the forcing that you apply over your approximately 55days of integration.
I remember that your model area is the Sea of Azoz, right? In that case you should have considerable river runoff (it should be one of your forcing files, but I am not sure if JRA25 runoff data can be used in your area) that should affect the salinity locally at the river mounths …

Increasing vertical mixing will not help when everything is at 11 anyway, All this does is to homogenize an already homogeneous salinity profile.

Martin

> On 22 Aug 2016, at 15:56, Иван Запорожцев <zaporozhtsev.if at gmail.com> wrote:
> 
> Dear MITgcm expert!
> 
> I am a novice user of MITgcm and I would be grateful to get a piece of advice from you. 
> The task is regional modelling for real water area. Time steps for calculation are 100 s. Space step is 0.1 degree for both lon/lat. Area has approximately 50 by 20 degrees grid. Depth levels are 0.5 m wide (16 layers in depth => depth is 10 m as average). Forcing files are from JRA25. Initial temperature and salinity are set as constants (20 deg C and 11 psu). After approximately 48000 iterations (step is 100 sec) salinity changes by only 0.5 psu (from 11 psu). I have values: diffKhS=0.,
>  diffKrS=3.E-5. Then I carried out experiments changing coeffs above from 1.0E-5 to 1.0E5 and have no reasonable differences. 
> 
> Is this situation normal (it requires much more time to change constant salinity significantly)?
> Or maybe I mistakenly switched off effective usage of these coeffs?
> 
> I use the following in main data file
> 
> no_slip_sides=.FALSE.,
>  no_slip_bottom=.TRUE.,
>  viscAr=1.E-3,
>  viscAh=1.E2,
>  diffKhT=0.,
>  diffKrT=3.E-5,
>  diffKhS=0.,
>  diffKrS=3.E-5,
>  rigidLid=.FALSE.,
>  implicitFreeSurface=.TRUE.,
>  eosType='JMD95Z',
>  saltStepping=.TRUE.,
>  tempStepping=.TRUE.,
>  momStepping=.TRUE.,
>  implicitDiffusion=.TRUE.,
>  implicitViscosity=.TRUE.,
>  allowFreezing=.TRUE.,
>  exactConserv=.TRUE.,
>  useCDscheme=.TRUE.,
> 
> And the following in CPP Options
> 
> #define SHORTWAVE_HEATING
> #define INCLUDE_PHIHYD_CALCULATION_CODE
> #define INCLUDE_CONVECT_CALL
> #define INCLUDE_CALC_DIFFUSIVITY_CALL
> #undef ALLOW_BL79_LAT_VARY
> #undef ALLOW_3D_DIFFKR
> #define INCLUDE_IMPLVERTADV_CODE
> #undef ALLOW_ADAMSBASHFORTH_3
> #define ALLOW_SRCG
> #undef ALLOW_NONHYDROSTATIC
> #define ATMOSPHERIC_LOADING
> #undef EXCLUDE_FFIELDS_LOAD
> #define EXACT_CONSERV
> #undef NONLIN_FRSURF
> C#define COSINEMETH_III
> #undef  OLD_ADV_BCS
> #undef OLD_GRID_IO
> #include "CPP_EEOPTIONS.h"
> C o Include/exclude code specific to the ECCO/SEALION version.
> C   AUTODIFF or EXF package.
> C   Currently controled by a single header file
> C   For this to work, PACKAGES_CONFIG.h needs to be included!
> cph#if (defined (ALLOW_AUTODIFF) || \
> cph     defined (ALLOW_ECCO) || \
> cph     defined (ALLOW_EXF))
> cph# include "ECCO_CPPOPTIONS.h"
> cph#endif
> #endif /* CPP_OPTIONS_H */
> 
> I look forward to hearing from you.
> 
> Yours sincerely,
> Zaporozhtsev Ivan,
> Postdoctoral Research Fellow
> Murmansk State Arctic University
> 
> 
> 
> 
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