thanks for Kate's help.
i specified the time series of wind stress at an inlet case study. the model results seemed unreasonable as the velocity and water level change is too small.
i guess i still have trouble in generating the forcing file. i only specified sustr, svstr, and set bhflux,ssflux,shflux as zero. when i set an individual variable, i defined it on a grid (larger than) different from the model grid, then it can run. otherwise, it showed regriding problem, as the forcing grid is the same as model grid.
i don't know what is wrong, and resort to you guys again.
thanks.
Wenping