Uncertainty of South China Sea prediction using NSCAT and National Centersfor Environmental Prediction winds during tropical storm Ernie, 1996

Error propagation from winds to ocean models was numerically investigated u sing the Princeton Ocean Model (POM) for the South China Sea with 20-km hor izontal, resolution and 23 sigma levels conforming to a realistic bottom to pography during the lifetime of tropical cyclone Ernie (November 4-18, 1996 ). Numerical integration was divided into preexperimental and experimental stages. The preexperiment phase generates the initial conditions on Novembe r 1 for the sensitivity experiment. During the experimental stage the POM w as integrated from November 1 to 30, 1996 under National Centers for Enviro nmental Prediction (NCEP) reanalyzed surface fluxes along with two surface wind data sets, namely, the daily averaged interpolated NASA scatterometer winds and the NCEP winds. The relative root-mean-square differences fluctua te from 0.5 to 1.0 for winds, 0.25 to 0.7 for surface elevations, 0.47 to 1 .02 for surface currents, and 0 to 0.23 for surface temperatures. This indi cates that the model has less uncertainty overall than the wind fields used to drive it, which in turn suggests that the ocean modeling community may progress without waiting for the atmospheric modelers to build the perfect forecast model.