The Analysis Of The Structure Of T-S And The Current Characteristics In Baohai Sea During Winter And Summer

The Bohai Sea is one of the shelf seas in China. Changes of the global climate and local environment recently make great effect to the physical field of the Bohai Sea. For example, the average salinity of the Bohai Sea have risen almost 2, and the structure of the salinity field have changed a lot, which induce the adjustment of the circulation structure. In order to know the temperature and salinity distribution and the density current structure induced comprehensively, the CTD temperature and salinity data in 2006 summer and 2007 winter is used in this paper, which is derived through the summer and winter cruises of the Bohai Sea area (908-01-ST01) and the north Yellow Sea area (908-01-ST02) of the Chinese 908 Project. The distribution characters of temperature and salinity of the Bohai Sea in summer and winter are analyzed. The Analysis indicates that: In summer the three bays are high in temperature, and temperature of central area of the Bohai Sea is low. Above the 10 meters, three high-salinity areas and three low-salinity areas distributes alternately. It is high in salinity in the Bohai Bay, the central area of the Liaodong Bay and the Bohai Strait, and it is low in the mouth of Liaodong Bay, the Laizhou Bay and the central area of the Bohai Sea.Bellow the 10 meters, the high salinity areas of the Bohai Sea show the distribution of'人'shape . There is a high salinity and low temperature water mass near 120.2°E 38.8°N bellow the 10 meter. Compared with the former survey data, it can be found that the temperature has risen a little in the Liaodong Bay, but have not changed a lot in the three bays as a whole. The temperature in the central area of the Bohai Sea have declined, which is more obvious in the bottom. In the past, the salinity in the August of 2000 raise to a large extent compared to that in the August of 1958, but now the salinity has declined compared to that in the August of 2000. Affected by the mixture of strong wind in winter, the temperature and salinity are both uniform from surface to bottom. The temperature is low in the nearshore area, and is high in the central part. It is low in temperature in the bayhead of the three bays, and the water is frozen in the north of the Liaodong Bay and the south of Bohai Bay, where the temperature is about 0℃. The salinity is low in the Liaodong Bay and Laizhou Bay, and is high in the Baihai Bay, the central area of the Bohai Sea and the Bohai Strait. The salinity in the bayhead of the Laizhou Bay is lowest, and that in the north of the Bohai Bay is highest in the whole Bohai Sea. A few typical sections are selected in the paper, and the temperature and salinity structure of the sections are analyzed. It is found that mixture plays an important role in the formation of the spring layer, and directly affects the formation of the spring layer of the sections. There are thermoclines and haloclines in the Liaodong Bay and Bohai Bay, but the temperature and salinity present the vertical distribution in the Laizhou Bay and central area of the Bohai Sea.In order to research the circulation structure induced by the temperature and salinity distribution, the ECOMSED numerical model is used. Driven by the M2 Constituent, a diagnostic model of the Bohai Sea is built. It is found that in summer the density current is larger than the tidal residual current in the Bohai Sea. In the surface, there is an anticyclone circulation near 120.2°E 38.9°N. The anticyclone circulation induces a downwelling, makes the surface high temperature and low salinity water decline and forms the high temperature and low salinity water mass in the temperature and salinity distribution figures. The structure exists from surface to bottom, and is the dynamic mechanism maintaining the high temperature and low salinity water in the central area of the Bohai Sea.A wide current moves towards southeast near 118.6°E 38.7°N in the north of the Bohai Bay, then moves towards north through the mouth of the Laizhou Bay, and passes through the Bohai Sea Strait, enters into the north Yellow Sea along the coast of the Shandong Peninsula. Another current moves towars northeast near 119.5°E 39.5°N. The two currents above are just the dynamic mechanism of"人"shape high salinity area in the temperature and salinity distribution figures. The currents in the three bays are weak compared to that in the central area of the Bohai Sea. In the Bohai Strait current entersinto the Bohai Sea in the north, and leaves it in the south, which is similar to the tidal residual current. In the middle layer, the current structure is similar to that in the surface, but the velocity is smaller in the value, and in the bottom the velocity is even smaller.