Abstract. A South China Sea warm pool with sea surface temperature (SST) higher than 29.5øC, recently reported by Chu and Chang [1995a, b] and Chu et al. [1997], appears in the central South China Sea (west of the Luzon Island) in boreal spring, strengthens until the onset of the summer monsoon (mid-May), and then weakens and disappears at the end of May. The transient features and interannual variabilities of the warm pool have not yet been studied. Here we use a subset of the U.S. Navy's Master Oceanographic Observation Data Set (MOODS) to investigate the surface thermal features. First, we employed an optimal interpolation scheme to build up a 10-day interval synoptic data set for December 1963 to November 1984 on a 0.5øx 1 ø grids (finer resolution in zonal direction) from the MOODS SST data. An ensemble mean SST field (T) was established with a rather weak horizontal gradient (28.5øC near the Palawan Island to 26øC near the southeast China coast). Second, we performed a composite analysis to obtain the averaged SST anomaly field T deviating from the ensemble mean for the winter and spring seasons (December-May). During December-March, T is negative almost everywhere throughout the

Abstract. 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 • 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 stages. The preexperiment phase generates the initial conditions on November i 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 aurface 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 perfect forecast model. 1.

⋅primitive equation model, ⋅warm-core eddy, ⋅ cool-core eddy, ⋅wind effect, ⋅ lateral boundary effect.

The Princeton Ocean Model (POM) has been implemented in the South China Sea for hindcast of circulation and thermohaline structure. A two-step technique is used to initialize POM with temperature, salinity, and velocity for 1 April 1998 and integrate it from 1 April 1998 with synoptic surface forcing for 3 months with and without data assimilation. Hydrographic and current data acquired from the South China Sea Monsoon Experiment (SCSMEX) from April through June 1998 are used to verify, and to assimilate into, POM. The mean SCSMEX data (Apr–Jun 1998) are about 0.58C warmer than the mean climatological data above the 50-m depth, and slightly cooler than the mean climatological data below the 50-m depth, and are fresher than the climatological data at all depths and with the maximum bias (0.2–0.25 ppt) at 75-m depth. POM without data assimilation has the capability to predict the circulation pattern and the temperature field reasonably well, but has no capability to predict the salinity field. The model errors have Gaussian-type distri-bution for temperature hindcast, and non-Gaussian distribution for salinity hindcast with six to eight times more frequencies of occurrence on the negative side than on the positive side. Data assimilation enhances the model capability for ocean hindcast, if even only conductivity–temperature–depth (CTD) data are assimilated. When the model is reinitialized using the assimilated data at the end of a month (30 Apr; 31 May 1998) and the model is run for a month without data assimilation (hindcast capability test), the model errors for both temperature and salinity hindcast are greatly reduced, and they have Gaussian-type distributions for both temperature and salinity hindcast. Hence, POM gains capability in salinity hindcast when CTD data are assimilated. 1.

Abstract. The mean seasonal cycle of surface heat budget is examined using historical temperature data combined with climatological wind stress and surface heat flux in the South China Sea. In most parts of the basin, we see a negative correlation between sea surface temperature (SST) and mixed layer depth (MLD); that is, SST tends to be higher (lower) when MLD is shallower (deeper). Given the characteristics of the MLD distribution, we further partition the South China Sea into four smaller areas: one along the continental slope south of China, one off west Luzon, one in the central part of the basin, and one near the coast of Vietnam. Heat budget assessment in these smaller areas indicates that although surface heat flux is fundamental to the mean seasonal cycle of SST, the effect of ocean dynamics is not negligible. Adding the contribution of ocean dynamics better explains the SST tendency. Ekman advection forced by the northeast monsoon is the primary heating process in winter but becomes less important as the horizontal temperature gradient decreases in the following seasons. Vertical entrainment is effective at cooling when the southwest monsoon prevails, which works against the surface heating and leads to a decrease of SST by up to 5 months earlier than surface

Abstract. A moving tropical cyclone is •n intense localized source of surface wind stress •nd wind stress curl that produces • significant response in the ocean environment, especially in the ocean thermal structure, the upper ocean currents, •nd the se • surface elevation. Such a response has been well identified in the open-ocean region, but not in the coastal ocean region. In this study we use the Princeton Ocean Model with 20 km horizontal resolution •nd 23 sigm • levels conforming to • realistic bottom topography to identify the response of the South Chin • Se • to Tropical Cyclone Ernie 1996. Results show strong similarities in the responses between open ocean •nd coastal regions, including near-surface strong •symmetric response such •s divergent currents with near-inertial oscillations, significant se • surface temperature cooling, bi•se to the right of the storm tr•ck, se• surface depressions in the w•ke of the storm, and subsurface intense upwelling •nd cooling •t the b•se of the mixed l•yer to the right of the storm tr•ck. The unique features of the SCS response to Ernie •re •lso discussed. 1.

⋅Sea surface temperature, ⋅ temporal and spatial variability, ⋅ composite analysis, ⋅ empirical orthogo-nal functions, ⋅ surface air tempera-ture, ⋅wind stress curl.

In this study, the U.S. Navy’s Generalized Digital Environmental Model (GDEM) climatological temperature and salinity data on a 0.58 3 0.58 grid is used to investigate the seasonal variabilities of the Japan/East Sea (JES) thermohaline structure and circulations. The GDEM for the JES was built up on historical (1930–97) 136 509 temperature and 52 572 salinity profiles. A three-dimensional estimate of the absolute geostrophic velocity field was obtained from the GDEM temperature and salinity fields using the P-vector method. The seasonal variabilities of the thermohaline structure and the inverted currents such as the Subpolar Front, the salinity minimum and maximum in the Japan Sea Intermediate Water, and the Tsushima Warm Current and its bifurcation are identified. 1.

This paper investigates the seasonal variabilities of the South China Sea isopycnal-surface circulations and of the Kuroshio intrusion through the Luzon Strait using the U.S. Navy’s climatological temperature and salinity dataset (public domain) with 8 3 8 resolution by the P-vector method. The representative pattern is a persistent basin-scale cyclonic circulation away from the surface, and a seasonally varying circulation with a weak anti-cylonic gyre in the summer and a strong cyclonic gyre in the winter near the surface. This pattern is consistent with a classical view of mean cyclonic circulation in large stratified lakes and semienclosed marginal seas by Emery and Csanady and with a recent numerical simulation using the navy’s Layered Ocean Model by Metzger and Hurlburt. The computed monthly volume transport through the Luzon Strait is negative (inflow) all year round with a minimum value of 213.7 Sv in February (strongest intrusion) and a maximum value of 21.4 Sv in September (weakest intrusion). The annual mean transport is 26.5 Sv (intrusion). 1.

The West Florida Shelf (WFS) is a broad, gently sloping continental margin that is influenced by the Gulf of Mexico Loop Current system located seaward of the