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Evolution of suspended sediment patterns in the East China and Yellow Seas
안유환,Palanisamy Shanmugam,Sonia Gallegos 한국해양과학기술원 2004 Ocean science journal Vol.39 No.1
The evolution of intricate and striking patterns of suspended sediments (SS), which are created by certain physical dynamics in the East China and Yellow Seas, has been investigated using satellite ocean color imageries and vertical profiles of particle attenuation and backscattering coefficients. The structure of these patterns can reveal a great deal about the process underlying their formation. Sea surface temperature (SST) analyzed from the Advanced Very High Resolution Radiometer (AVHRR) thermal infrared data were used to elucidate the physical factors responsible for the evolution of suspended sediment patterns in the East China Sea. The concomitant patterns of suspended sediments were tracked from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color data. The detailed examination about these patterns gave birth to the definition of the evolution of suspended sediments (SS) into four stages: (1) Youth or Infant stage, (2) Younger stage, (3) Mature stage, and (4) Old stage. We describe about the three directional forces of the tidal currents, ocean warm currents and estuarine circulations that lead to occurrence of various stages of the evolution of suspended sediments that increase turbidity at high levels through out the water column of the inner and outer shelf areas during September to April. The occurrence of these four stages could be repeatedly observed. In contrast, vertical profiles of the particle attenuation (cp) and backscattering (bbp) coefficients displayed obvious patterns of the propagation of suspended sediment plume from the southwestern coastal sea that leads to eventual collision with the massive sediment plume originating from the Yangtze banks of the East China Sea.
해색 원격탐사를 위한 원격반사도 및 수출광 모델의 개발
안유환 ( Yu Hwan Ahn ) 大韓遠隔探査學會 2000 大韓遠隔探査學會誌 Vol.16 No.3
가시광 영역에서 해수의 원격반사(Rrs)도 및 수출광(water leaving radiance: Lw) 스펙트럼 크기를 해수의 광 특성(흡광도; a, 역산란; b(b))에 영향을 가장 크게 미치는 3개 물질 즉, 클로로필, 무기성 부유입자, 용해유기물의 량으로 모델링 하였다. 모델은 간략하게 Rrs=0.046 b(b)/(a+b(b))로 주어졌으며, 모델의 대상 해역은 광특성이 전혀 다른 적조 발생해역, 밝은 해수, 탁수해역으로 나누어 연구하였다. 모델로 얻어진 원격반사도는 현장 관측치와 스펙트럼의 모양, 값의 분포 및 기존의 해색 클로로필 알고리즘 등으로 비교하여 모델의 타당성을 검증하였다. 결과는 아주 다양한 광 특성을 같은 해양이라 하여도 본 연구의 모델은 거의 완벽하게 해색 스펙트럼, 원격반사도 혹은 water leaving radiance(Lw)를 재현할 수 있는 것으로 나타났다. 본 모델은 앞으로 OSMI와 갚은 해색위성 알고리즘 개발, CASE-Ⅱ water 알고리즘, neural network 알고리즘 개발에 크게 기여할 것으로 사료되며 그 외에도 해색 대가보정 모델 개발에서 대기 신호의 정밀 보정에 활용될 수 있을 것으로 기대된다. Ocean remote sensing reflectance of just above water level was modeled using inherent optical properties of seawater contents, total absorption (a) and backscattering(bb) coefficients(Rrs=0.046 b(b)(a+b(b)). This modeling was based on the specific absorption and backscattering coefficients of 5 optically active seawater components; phytoplankton pigments, non-chlorophyllous suspended particles, dissolved organic matters, heterotrophic microorganisms, and the other unknown particle components. Simulated remote sensing reflectance(Rrs) and water leaving radiance(Lw) spectra were well agreed with in-situ measurements obtained using a bi-directional field remote spectrometer in coastal waters and open ocean. Rrs values in SeaWiFS bands from the model were analyzed to develop 2-band ratio ocean color chlorophyll algorithms employing statistical approaches. The model algorithms were examined and compared with those observed insitu. Also, chlorophyll algorithm based on remote reflectance developed in this study fell in those obtained by a SeaBAM working group. The remote reflectance model will be very helpful to understand the variation of water leaving radiances caused by the various components in the seawater, and to develop new ocean color algorithm for CASE-Ⅱ water using neural network method or other analytical method, and in the model of fine atmospheric signal correction.