salinity "overshoots"

[edith]

Hi,
I am trying to run simulation with rivers for Gulf of Riga using realistic topography.
When i add ana_psource i get several problems that i do not seam to be able to figure out:
1) salinity values get unrealistically big (initial salinity 5psu and input 0psu, i get salt values 30psu and up within first steps after starting run). overshooting values appear next to next to freshwater inflow (if i put point source in the middle of the bay it is directed opposite to fresh water).
2) model is very unstable, qbar bigger then 1 m3/s will cause immediate blow up (does not make sense with domain 220x160km big?)
3) dt bigger then 1e-03 will blow up almost immediately.

was hoping someone can give me a clue where too look for a solution. was checking different mixing but did not seam to be much different.
Can this kind of instability come from the way grid file is made? i kind of wrote a small script to make my own roms_grd.nc file and even though i have been checking it ten million times there might still be something i did not find.

I am running serial and debug. Using mpdata, k-epsilon turbulent mixing,
grid 71x118x10, horizontal resolution 1/40degrees.

AKT_BAK == 5.0d-6 5.0d-6 ! m2/s
ad_AKT_fac == 1.0d0 1.0d0 ! nondimensional
AKV_BAK == 5.0d-6 ! m2/s
ad_AKV_fac == 1.0d0 ! nondimensional
! Turbulent closure parameters.
AKK_BAK == 5.0d-6 ! m2/s
AKP_BAK == 5.0d-6 ! m2/s
TKENU2 == 0.0d0 ! m2/s
TKENU4 == 0.0d0 ! m4/s


cppdefs used are:
#define UV_ADV
#define UV_QDRAG
#define UV_COR

#define UV_PSOURCE
#define DJ_GRADPS
#define TS_MPDATA
#define MIX_GEO_TS
#define TS_PSOURCE
#undef NONLIN_EOS
#define SALINITY
#define MASKING
#define SOLVE3D
#define SPLINES
#undef AVERAGES
#define AVERAGES_AKV
#define AVERAGES_AKT
#define AVERAGES_AKS

#define SOUTHERN_WALL
#define EASTERN_WALL
#define NORTHERN_WALL

#define WESTERN_FSCHAPMAN
#define WESTERN_M2FLATHER
#define WESTERN_M3RADIATION
#define WESTERN_TRADIATION

#define N2S2_HORAVG
#define GLS_MIXING
#define CANUTO_A

#define ANA_FSOBC
#define ANA_M2OBC
#define ANA_PSOURCE

#undef ANA_GRID
#define ANA_INITIAL
#define ANA_SMFLUX
#define ANA_SRFLUX
#define ANA_SSFLUX
#define ANA_STFLUX
#define ANA_BSFLUX
#define ANA_BTFLUX
#define ANA_MASK

[austinctodd]

Hi Edith,

I had run into problems implementing point sources for rivers using realistic bathymetry a while ago. I had also made my own script for creating the grid file, and quickly found out some mistakes that I was making that caused blow-ups near my river inputs. Can you check to make sure that the depths of the grid where the land mask is applied is set to the minimum ocean depth? I was setting mine to a value consistent with "land," when really they should be set to the minimum ocean depth, then just masked out. This caused large velocities by altering the fluxes across the land/ocean cell wall.

Also, did you alter ana_psource.h for your purposes? If so, maybe it would be useful to see how ana_psource.f90 is implementing your point source.

Cheers,
Austin

[edith]

Hi Austin,
Thank you for the reply. I made that mistake too at the beginning but i already figured out my self before and now i have under mask h = 2m that is my hmin. Did you use any other way to smooth topography?

i modified ana_psource.h to have right locations for i and j. also moved it around to be sure i see what is going on. so i cant see what more could be wrong there? also have tried different Qbar. i did not modify Qshape. when i look in analytical.f90 it seams it have got the right values for a point source location and Qbar.

So i am still stuck. it has probably something to do with a way model mixes water.
What would be good advection etc to use?