storm surge problem

[wjlee]

Hello all.!

I'm trying to predict storm surge using 3D ROMS.
To predict storm surge, I run the ROMS twice.
First,I run ROMS putting TIDE(TPXO6) in as a forcing.
======================================
There is cpp options I choose.
#define UV_ADV
#define UV_COR
#define UV_VIS2
#define MIX_S_UV
#define DJ_GRADPS
#define CURVGRID
#define NONLIN_EOS
#define MASKING
#define UV_QDRAG
#define AVERAGES
#define STATIONS

#define SOLVE3D

#define BULK_FLUXES

#define SLP_GRAD
#define LONGWAVE
#define ANA_SRFLUX
#define ANA_CLOUD
#define ANA_RAIN
#define ANA_TAIR
#define ANA_STFLUX
#define ANA_HUMIDITY
#define ANA_SST
#define ANA_BTFLUX
#define ANA_PAIR
#define ANA_WINDS

#define ANA_INITAL
#define ANA_TOBC
#define ANA_M2OBC
#define ANA_M3OBC
#define ANA_FSOBC

#define LMD_MIXING
#ifdef LMD_MIXING
# define LMD_RIMIX
# define LMD_CONVEC
# undef LMD_DDMIX
# define LMD_SKPP
# undef LMD_BKPP
# define LMD_NONLOCAL
#endif
#define SSH_TIDES
#define ADD_FSOBC

#define UV_TIDES
#define ADD_M2OBC

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

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

#define RADIATION_2D

#define EAST_M3RADIATION
#define EAST_M3NUDGING

#define WEST_M3RADIATION
#define WEST_M3NUDGING

#define SOUTH_M3RADIATION
#define SOUTH_M3NUDGING

#define NORTH_M3RADIATION
#define NORTH_M3NUDGING
======================================

Second, I run ROMS putting TIDE(TPXO06) and U10,V10,MSLP in as a forcing.
======================================
There is cpp options I choose.
#define UV_ADV
#define UV_COR
#define UV_VIS2
#define MIX_S_UV
#define DJ_GRADPS
#define CURVGRID
#define NONLIN_EOS
#define MASKING
#define UV_QDRAG
#define AVERAGES
#define STATIONS

#define SOLVE3D

#define BULK_FLUXES

#define SLP_GRAD
#define LONGWAVE
#define ANA_SRFLUX
#define ANA_CLOUD
#define ANA_RAIN
#define ANA_TAIR
#define ANA_STFLUX
#define ANA_HUMIDITY
#define ANA_SST
#define ANA_BTFLUX

#define ANA_INITAL
#define ANA_TOBC
#define ANA_M2OBC
#define ANA_M3OBC
#define ANA_FSOBC

#define LMD_MIXING
#ifdef LMD_MIXING
# define LMD_RIMIX
# define LMD_CONVEC
# undef LMD_DDMIX
# define LMD_SKPP
# undef LMD_BKPP
# define LMD_NONLOCAL
#endif
#define SSH_TIDES
#define ADD_FSOBC

#define UV_TIDES
#define ADD_M2OBC

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

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

#define RADIATION_2D

#define EAST_M3RADIATION
#define EAST_M3NUDGING

#define WEST_M3RADIATION
#define WEST_M3NUDGING

#define SOUTH_M3RADIATION
#define SOUTH_M3NUDGING

#define NORTH_M3RADIATION
#define NORTH_M3NUDGING
======================================

and then I substract the first from the second.
but It happens the score is very big for example it's more than +-5 meter.

what was I wrong. plese let me know.
Thank you.

[drews]

wjlee -

The September 2008 issue of Physics Today had an article by Donald Resio and Joannes Westerink, "Modeling the physics of storm surges", that may be useful. On page 34 they state formula (1):

height of surge eta is proportional to: (tau/gh)W

This formula indicates that wind-driven storm surge is high when the water is shallow (h < 10m) and the shelf width W is long. Does that describe your scenario? Are you modeling strong wind over a long shallow sea?

I assume you are calculating the wind stress with the usual formula:

tau = Cd * rho * W10^2

There is some discussion in the article about the drag coefficient Cd. Large and Pond (1981) say that it increases with wind speed. Resio and Westerink (2008) cite a maximum value of Cd = 0.0025 on page 35. What is your calculated value for tau? Something like 3-5 N/m2?

Since you are calculating the barometric surge, pressure accounts for about 1 meter of surge per 100 mb drop in pressure. That leaves you with about +- 4 meters of surge. That's a large storm surge (13 feet), but certainly possible and historically recorded.

References:
W.G. Large and S. Pond, "Open ocean momentum fluxes
in moderate to strong winds", Journal of Physical Oceanography 11:
pp. 324–336, 1981.

Carl