Remote Sensing Research And Application Of Salinity And Suspended Partilce Size Of The Bohai Sea

The Bohai Sea is a semi-enclosed inland sea of China, where water exchange ability is poor. Accordingly, the temporal and spatial patterns of salinity and suspended sediments of Bohai Sea are heavily influenced by river discharge and human activities. By utilizing in situ and remote sensing data, two aspects of research work are carried out in this dissertation, which are remote sensing retrieval of salinity and of suspended particle size research.(1) Remote sensing retrieval of salinity: The remote sensing retrieval algorithm of salinity is developed and tested based on in situ measured remote sensing reflectance and salinity data. The algorithm is adaptable to in situ measured reflectance with the root mean square error of 0.833ppt (R2=0.64,e=1.9%). However, this algorithm is inadaptable to MERIS data because there are many noises in the reflectance of this data. Therefore the salinity retrieval algorithm is developed and improved based on the reflectance derived by MERIS and in situ salinity data, which is adaptable to MERIS data with the RMSE of 1.311ppt (e=3.3%).(2) Remote sensing retrieval of suspended particle size: The relationship between the inherent optical properties (cp(676) or bp(676)) and the salinity is established for MERIS,HJ-1 CCD and HY-1B data. The retrieval error of salinity from two IOPs is similar. The retrieval error of median particle size is in the range from 29.1% to 32.7% in Bohai Bay and from 11.8% to 13.4% in Laizhou Bay. Then the relationship between remote sensing reflectance and salinity is developed for the three remotely sensed data. The retrieval error is in the range from 20.8% to 21.4% in Bohai Bay and from 8.3% to 17.2% in Laizhou Bay. The second algorithm is more adaptable to MERIS data retrieval than the first one. The percentage average error between the retrieved salinity and their in situ values is 21.8% (N=14).(3) The MERIS derived salinity map shows that the salinity is low in the Laizhou Bay and nearshore of the Bohai Bay and Liaodong Bay but high in the middle of the Bohai Sea and Bohai Strait. Then the temporal and spatial changes of salinity and its constraint factors are analyzed by using time-series MERIS and MODIS data. During 2004~2009, the salinity in the most parts of the Bohai Sea was increasing. The Yellow River discharge has significant effect on the salinity of the near eatuary districts which are the Yellow River estuary, Laizhou Bay and the south part of the Bohai Bay. The variance of salinity is large in these districts. However, the salinity changed slightly in the middle of the Bohai Sea and Liaodong Bay where the salinity changes were weakly influenced by Yellow River discharge.The MERIS derived particle size map shows that the size of suspended paritcle is low in the Laizhou Bay, Bohai Bay and Liaodong Bay but high in the middle of the Bohai Sea and Bohai Strait. Then the time-series MERIS and MODIS data are used to analyze the temporal and spatial pattern of salinity and its constraint factors. The wind speed has a great effect on the particle size distribution. Because of the resuspensions of small particles, the sizes of suspended particles in the sea surface water are small during strong winds. There is a prominent seasonal cycle in the size of suspended particles because of the seasonal cycle of organisms. The size of suspended particle is large in summer but small in winter.