unexpected cold water

[guyz]

hello every one, i am freshman to ROMS, and I am trying to do some simulation of coastal upwelling. Few days ago I did a simulation, unexpected cold water shows up in my result.
about my configuration:
a rectangular study area with four open boundaries,
no heat flux, uniform wind stress blowing westward,
flat bottom with 75m depth.
and my cpp file

#define SALINITY
#define SOLVE3D
#define UV_ADV
#define UV_COR
#define TS_DIF2
#define UV_VIS2
#define NONLIN_EOS
#undef MY25_MIXING
#define GLS_MIXING
#undef ANA_VMIX


/**************Numerical schemes options *********/

#define TS_U3HADVECTION /* */
#define TS_C4VADVECTION /* */
#define DJ_GRADPS
#define MIX_S_UV
#define MIX_ISO_TS
#define CURVGRID
#define MASKING
#undef SPLINES


#undef SCORRECTION
#undef QCORRECTION
#ifdef QCORRECTION
#undef ANA_SMFLUX
#undef ANA_STFLUX
#undef ANA_SSFLUX
#endif


/************* Bottom boundary conditions ***********************/

#define UV_LDRAG
#define ANA_BTFLUX
#define ANA_BSFLUX

/************ Tides ********************************************/
# undef SSH_TIDES
# undef UV_TIDES
# undef ADD_FSOBC
# undef ADD_M2OBC


/************* Lateral boundary conditions *********************/

# define SOUTH_TRADIATION
# define EAST_TRADIATION
# define WEST_TRADIATION
# define NORTH_TRADIATION


# undef SOUTH_TNUDGING
# undef EAST_TNUDGING
# undef WEST_TNUDGING
# undef NORTH_TNUDGING



# define EAST_FSCHAPMAN
# define SOUTH_FSCHAPMAN
# define WEST_FSCHAPMAN
# define NORTH_FSCHAPMAN


# define EAST_M2FLATHER
# define SOUTH_M2FLATHER
# define WEST_M2FLATHER
# define NORTH_M2FLATHER

# define EAST_M3RADIATION
# define SOUTH_M3RADIATION
# define WEST_M3RADIATION
# define NORTH_M3RADIATION

# define EAST_M3NUDGING
# define SOUTH_M3NUDGING
# define WEST_M3NUDGING
# define NORTH_M3NUDGING

i do not know any more information need to be given.
attached is surface temperature, the unexpected cold water are circled using black circle.

can anyone tell me the reason causing the unexpected cold water

[kate]

You have both radiation and nudging for the M3 fields. I have always used the same for T, and provided some value for the outside. Otherwise, what is it going to use when it thinks there is inflow in the radiation condition? Do you have some external values you can provide? It might help.

[guyz]

You have both radiation and nudging for the M3 fields. I have always used the same for T, and provided some value for the outside. Otherwise, what is it going to use when it thinks there is inflow in the radiation condition? Do you have some external values you can provide? It might help.

Dear kate， many thanks for you reply.

I have both radiation and nudging for T too, but i think the expected cold water maybe come from the nudging effect, so i turn it off, but the cold water are still there.

i am not clear about "provided some value for the outside", do you mean the boundary condition？ in my configuration, both the boundary conditon （T and S）and inintial condition come from the same data file