Study On The Suspended Matter's Distribution From Remote Sensing Retrieval And Its Movement Mechanisms In The Surface Layer Of The East China Seas

As one of the three major components of ocean color, suspended matter has an important influence on the water quality and water environment. The distribution of suspended matter is the integrated reflection of various environment conditions, and it is highly associated with the material sources and dynamic factors such as circulations, wind and waves, as well as the properties of marine sediment and the topography. As the carrier of nutrients and other contaminants, the distribution and transportation of suspended matter will affect the contaminants'distribution and induce their gathering, and further influent the marine ecological environment. Transport of suspended matter can also be taken as a support for the marine sediment dynamics, and it plays a significant role in the marine geodesy and cartography, port planning, protection of marine environment and so on.Because the suspended matter reacts sensitively to the hydrodynamic environment, data with long time series and wide spatial coverage are necessary in order to build a macro-scheme of the distribution and transportation of suspended matter, which can't be achieved by means of the in situ measurement that costs manpower, material and financial resources a lot. With the development of satellite remote sensing, the detection and study of ocean color can be carried out using the water-leaving radiance of different wavebands acquired by ocean color sensors.In this thesis, the formula proposed by Pan et al. in 2001 and the SeaWiFS monthly binned level3 data during 1998 to 2006 supplied by NASA are used to retrieve the concentration of suspended matter in the surface layer of the Bohai Sea, the Yellow Sea and the East China Sea (i.e., East China Seas). The spatial and temporal features of suspended matter in surface layer derived from remote sensing retrieving coincide well with those derived from the in situ measurements and numerical simulations, which indicates that the retrieving method (including the formula and the choose and process of remote sensing data) used in this thesis is effective and feasible. Detailed research is done for the spatial features and seasonal variations of the distribution and transportation of suspended matter in the surface layer of East China Seas using the retrieved results. It's found that the distribution and transportation of suspended matter in the East China Seas present distinct spatial and temporal features. The concentration of suspended matter is high inshore and low offshore, estuaries are often high concentration regions, and perennial high suspended matter concentration regions also exist in the Bohai Bay and the Subei Shoal. Beside, distribution of suspended matter in the Liaodong Bay has the feature of"high in the east and low in the west", especially in winter. The area of high concentration regions is larger in winter half year (November-April) than in summer half year (June-September), and for the same spot the concentration of suspended matter is usually higher in winter than in summer. In the Yellow Sea and the East China Sea the suspended matter spreads farther to the open sea in winter than in summer, and May and October are the transitional period of the extension. Take the 10mg/L contour line as an indicator, the transport of suspended matter can hardly reach 124°00′E in summer or 126°00′E in winter.Factors that can influent the distribution and transportation of suspended matter in the surface layer are composed of topography, marine sediment properties, runoffs, thermocline, wind, waves, circulations and so on. It's found that the resuspension induced by wind waves plays the most important role in the distribution of suspended matter in the shallow sea (generally with depth less than 50m), and the seasonal variation of suspended matter in the shallow sea is highly related with the resuspension, which indicates that the resuspension of marine sediment is the main source for the suspended matter in the surface layer. And circulations play a significant part in the transport of suspended matter from coastal waters to the deep sea, and in the Yellow Sea and East China Sea they control this transport course. River runoffs supply sea water with abundant fresh water and suspended matter, and control the distribution and transportation of suspended matter in summer in the estuary regions. As a barrier to the upward diffusion of suspended matter in ocean bottom, thermocline's appearance and disappearance with seasons have apparent impact on the concentration of suspended matter in the same spot. Marine sediment properties don't play a crucial role in the concentration of suspended matter, and their relationship often turns to be more complicated when taking topography and hydrodynamic factors into consideration. The impact of the Changjiang River catastrophic flood in the summer of 1998 on the distribution and transportation of suspended matter in the Changjiang Estuary and the adjacent sea areas are investigated using monthly and daily remote sensing retrieving results. It's found that in flood period the distribution and transportation of suspended matter in the Changjiang Estuary are mainly controlled by the runoffs. As a result, the extension of suspended matter is farther in the flood season of 1998 than in the same period of other usual years, which can reach almost 125°E in summer of 1998. Besides, the catastrophic flood event also has effects on the distribution and transportation of suspended matter in the following winter in 1998. In winter of 1998/1999, the suspended matter transport southwards much father along the Zhejiang-Fujian coast, and the value of concentration and the area of high concentration regions in the Changjiang Estuary and Hangzhou Bay (30°N-32°N) are larger than those in the same period of other usual years. Furthermore, it can be concluded from the distribution pattern of suspended matter that during 1998 flood period the Changjiang Diluted Water turns to the northeast and points to the Jeju Island.This thesis is the first case to do research with such a large time and area scale on the suspended matter in the surface layer of East China Seas using ocean color remote sensing data. And according to the retrieving result the temporal and spatial features of suspended matter in the study area are derived quantitatively, which indicates the effectivity of this method. Further studies can be continued with higher temporal and spatial resolution in order to obtain more detailed result and get better understandings about the distribution and transportation of suspended matter.