The Study On The Theories And Methods Of Water Exchange Model And Its Applications

Based on the nested ocean numerical model, two classic questions of water exchanges, which are from the shelf sea area and a local sea area of East China Sea (ECS), are discussed in this paper.For satisfying the specific needs of each water exchange question, different ocean circulation models by holding defferent style of mesh structure but similar forced boundary condition are used for each question. Combined with the result of the ocean models and relevant in-situ data, the major factors of influencing water exchanges are firstly analysed.To study these two complementary questions, we construct or apply two appropriate methods for approaching the truth.The complementarity shows like this:One is studying the spatial-temporal distribution regularities of the water exchange zone which is based on the specific strength of water exchange and mixing;Another is calculating and analyzing the water exchange strength between the sea area and its adjacent water,and this sea area is specified.The variability of the Kuroshio in the East China Sea during the period of 1991 to 2008 is studied using a three-dimensional circulation model. The model calculated Kuroshio onshore volume transport in the East China Sea reaches the minimum of 0.48 Sv (1 Sv=106 m3 s-1) in summer and the maximum of 1.69 Sv in winter. Furthermore, the model result indicates that the Kuroshio transport east of Taiwan decreased since 2000. Lateral movements tend to be stronger for both ends of the Kuroshio in the East China Sea compared to the mid segment. The Spectral Mixture Model (SMM) is adapted to determine the exchange zone between the Kuroshio and the shelf water of the East China Sea in this study. There is a significantly negative correlation,-0.78, between the area of the exchange zone and the Kuroshio onshore transport across the 200 meters isobath in the East China Sea. In addition to the annual and semi-annual signals, the intra-seasonal signal likely of the Pacific origin may also induce Kuroshio intrusions and exchange events in the East China Sea.Analysis of tidal current and sea level has made based on the observations during summer in 2006 and winter in 2007, respectively. The result indicates that a two-layer structure of residual current exists in summer, with its upper layer northwestward and lower layer reversed. In addition, some strong residual occurs nearby the pycnocline during astronomical tide; In winter, the entire residual directed to northwestward, with abnormal sea-level fluctuation and associated current. Analysis of tidal ellipse indicates that in summer the semi-diurnal component rotates clockwisely with depth while for diurnal component counterclockwisely. But in winter the vertical structure is almost homogeneous. Moreover, a clockwise rotation exists for the direction of semi-diurnal component from summer to winter,with a angle of 16～18°.County ChangHai is located in North Yellow Sea.It contains five villages and towns. Breed aquatics is the main economy in all of these five villages. Breed aquatics rely heavily on the exchange of nutriment.The nutriment can be denoted by POM(Particulate Organic Matter) and DOM(Dissolved Organic Matter) here.By making use of FVCOM(An Unstructured Grid, Finite-Volume Coastal Ocean Model) and being based on the consecutively observed data from three waterlevel instruments and one ADCP in this sea area, POM and DOM in all these five villages are calculated in twenty conditions.The proportions of different factors in the exchange are given.And the spatial and temporal distribution regularities of water residual time in the ChangHai sea area is estimated.The scientific significances of this study are:Construct the theory frame of the Spectral Mixture Model which is for water exchange studies and water mass analysis; demonstrate two general water exchange models under the basic dynamics; perfect the physical environmental evolution theory system of the East China Sea.