| Abstract: | The waters in the shallow part of the Yellow Sea and East China Sea are affected greatly by climatic and geographical conditions and fail to possess homogeneity and conservativeness like oceanic waters. They have apparent difference in modified degrees, so we may regard a certain range of mixed water as a relatively independent one. In fact, the study of water masses in the shallow sea means a modified analysis of waters. The idea of modified water masses is introduced, i. e., a water body which holds the similar physical and chemical characters, occupies a certain space, and varies seasonally and regularly. On the T-S diagram, it displays as a certain amount of points aggregated together, the centre of which changes regularly and may have a process of combination and separation.According to the clustering method, there are eight modified water masses in this area. They may also be divided into three salinity types. On the T-S diagram, the points concerning temperature and salinity of different modified waser masses are distributed around a curve, from which the characteristics of gradual modification may be embodied. The increase of temperature and the decrease of salinity in warm season and the reversal of them in cold season are regarded as the characteristics of modification of the sea water in all the Huanghai Sea and East China Sea.The modification of water masses is created by the combinative action of thermodynamic and dynamic factors. Through the analysis of modified water masses, we believe that the thermodynamic factors play a major part in the modification of water masses in this area. The correlations between the tonguelike distribution of boundary of modified water masses and the current direction are very apparent, which can be used as a collateral evidence for analyzing circulation. Finally, the relationships between the modified water masses and the central fishing grounds at bottom layer are illustrated. |
