A numerical simulation is performed using the Princeton Ocean Model (POM) to investigate the behavior of the Changjiang Diluted Water (CDW), and to evaluate the freshwater budget in the Yellow and East China Seas. In addition, the major process controlling the behavior of the CDW is discussed. The simulated CDW distributions are fairly consistent with the observed distributions, showing a remarkable seasonal variation. The CDW extends to the northeast toward the Tsushima/Korea Straits during summer, while it hugs the Chinese coast to the southwest within a narrow band in winter. Tracer experiment is carried out to track the freshwater originating only from the Changjiang, and to evaluate the freshwater budget in the Yellow and East China Seas. The result shows that about 68 percent of the Changjiang discharge is transported through the Tsushima/Korea Straits, and that about 27 percent is transported through the Taiwan Strait in autumn and winter. To investigate the main process controlling the behavior of the CDW mentioned above, another experiment is carried out without wind‐forcing. It is found that the eastward extension of the CDW is strongly constrained by the “Taiwan‐Tsushima Warm Current System” over the shelf regime. The wind is, however, responsible for the northeastward extension of the CDW in summer. In addition, the southwestward extension at the Taiwan Strait during winter is done by strong northeasterly monsoon. The experiment without wind‐forcing shows that freshwater transport through the Tsushima/Korea Straits increases to 90 percent of the total Changjiang discharge.

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The two-way Lagrangian particle-tracking model (PTM) is proposed for specifying sources of objects drifting with random-walk processes on the sea surface. First, to determine object source candidates, modeled particles are released from the point (hereafter, ''receptor'') where an observer finds the objects using a backward-in-time PTM with modeled ocean currents of which directions are reversed in sign. Second, the modeled particles are released from these source candidates in a forward-in-time PTM using ocean currents originally computed in hydrographic models. Third, the source candidates are considered to be reliable at a 5% significance level if the observed receptor is located inside the ellipse whose center is the mean position of the modeled particles at the time when the observer found the objects and whose axis length is twice the standard deviation computed using all modeled particle positions. The two-way PTM experiments are carried out in a realistic hydrographic model over the East China Sea shelf for the period from June through August 2004. Statistically significant sources are well specified close to the true source because 58%-90% of source candidates are rejected in the experiments.