Error propagation from winds to ocean models was numerically investigated using the Princeton Ocean Model (POM) for the South China Sea with 20-km horizontal resolution and 23 sigma levels conforming to a realistic bottom topography during the lifetime of tropical cyclone Ernie (November 4-18, 1996). Numerical integration was divided into preexperimental and experimental stges. The preexperiment phase generates the initial conditions on November 1 for the sensitivity experiment. During the experimental stage the POM was integrated from November 1 to 30, 1996 under National Centers for Environmental 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 fluctuate 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 indicates 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 perfact forecast model.

Caption:
The sea level in South China Sea simulated by an ocean general circulation model during the passage of Typhoon Ernie, when forced by winds from NSCAT and from operational numerical weather prediction (NWP) products of NCEP are compared in the figure. Scatterometer winds generate more realistic ocean responses (sea surface temperature, ocean current, and sea level changes) than winds from NWP.

Dr. Chu is developing methodology to examine the impact of high resolution coastal winds (see Section on Data System) on Navy's operational Shallow Water Analysis and Forecast System (SWAFS) which was developed from POM.

Reference:
Chu, P.C., S. Lu, W.T. Liu, 1999: Uncertainty of the South China Sea prediction using NSCAT and NCEP winds during tropical storm Ernie 1996, J. Geophys. Res., 104,11,273-11,289.

Chu, P., J.M. Veneziano, C. Fan, M.J. Carron, W.T. Liu, 2000: Response of the South China Sea to tropical cyclone Ernie 1996. J. Geophys. Res., 105, 13,991-14,009.