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.

(JES) are major east Asian marginal seas (EAMS). The complex topography includes the broad shallows of the Sunda Shelf in the south/southwest of SCSi the continental shelf of the Asian landmass in the north, extending from the Gulf of Tonkin to the YES; a deep, elliptical shaped SCS and JES basins, and numerous reef islands and underwater plateaus scattered throughout (Fig. 1a). The shelf that extends from the Gulf of Tonkin to the YES is consistently near 70 m deep, and averages 150 km in width. The EAMS is subjected to a seasonal monsoon system. From April to Au-gust, the weaker southwesterly summer monsoon winds result in a wind stress of just over 0.1 N/m2. From November to March, the stronger northeasterly winter monsoon winds corresponds to a maximum wind stress of nearly 0.3 N /m2. Re-cent observational studies show that the EAMS is energetic and has multi-eddy structure. For example, the SCS synoptic eddy structure was identified in May 1995 using the airborne expendable bathythermograph (AXBT) data (Chu et al., 1998a), the eddy spatiotemporal scales in the YES were identified using the Navy's Master Oceanographic Observational Data Set (MOODS) during 1929-1991 (Chu et al., 1997a,b), and the seasonal JES multi-eddy structure from a

(JES) are major east Asian marginal seas (EAMS). The complex topography includes the broad shallows of the Sunda Shelf in the south/southwest of SCSi the continental shelf of the Asian landmass in the north, extending from the Gulf of Tonkin to the YES; a deep, elliptical shaped SCS and JES basins, and numerous reef islands and underwater plateaus scattered throughout (Fig. 1a). The shelf that extends from the Gulf of Tonkin to the YES is consistently near 70 m deep, and averages 150 km in width. The EAMS is subjected to a seasonal monsoon system. From April to Au-gust, the weaker southwesterly summer monsoon winds result in a wind stress of just over 0.1 N/m2. From November to March, the stronger northeasterly winter monsoon winds corresponds to a maximum wind stress of nearly 0.3 N /m2. Re-cent observational studies show that the EAMS is energetic and has multi-eddy structure. For example, the SCS synoptic eddy structure was identified in May 1995 using the airborne expendable bathythermograph (AXBT) data (Chu et al., 1998a), the eddy spatiotemporal scales in the YES were identified using the Navy's Master Oceanographic Observational Data Set (MOODS) during 1929-1991 (Chu et al., 1997a,b), and the seasonal JES multi-eddy structure from a

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

(JES) are major east Asian marginal seas (EAMS). The complex topography includes the broad shallows of the Sunda Shelf in the south/southwest of SCSi the continental shelf of the Asian landmass in the north, extending from the Gulf of Tonkin to the YES; a deep, elliptical shaped SCS and JES basins, and numerous reef islands and underwater plateaus scattered throughout (Fig. 1a). The shelf that extends from the Gulf of Tonkin to the YES is consistently near 70 m deep, and averages 150 km in width. The EAMS is subjected to a seasonal monsoon system. From April to Au-gust, the weaker southwesterly summer monsoon winds result in a wind stress of just over 0.1 N/m2. From November to March, the stronger northeasterly winter monsoon winds corresponds to a maximum wind stress of nearly 0.3 N /m2. Re-cent observational studies show that the EAMS is energetic and has multi-eddy structure. For example, the SCS synoptic eddy structure was identified in May 1995 using the airborne expendable bathythermograph (AXBT) data (Chu et al., 1998a), the eddy spatiotemporal scales in the YES were identified using the Navy's Master Oceanographic Observational Data Set (MOODS) during 1929-1991 (Chu et al., 1997a,b), and the seasonal JES multi-eddy structure from a

nG eo C om m un ic a te

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East Asian marginal seas prediction using a coastal atmosphere-ocean coupled system (CAOCS)

China Sea (YES), and Japan/East Sea (JES) are