Physicobiological oceanographic remote sensing of the East China Sea: Satellite and in situ observations

Abstract

The satellite remote sensing on the NOAA Advanced Very High Resolution Radiometer (AVHRR, 1981 to 1986) and the Nimbus7 coastal zone color scanner (CZCS) (1978 to 1986) data sets were used to study the physicobiological characteristics of the East China Sea. The oceanographic dynamics of the East China Sea are greatly influenced by a counterclockwise circulation system that consists of the Kuroshio ‐ Tsushima Current ‐ Yellow Sea Warm Current on the eastern side of the Sea, and the Coastal Current on the western side. The former, coming from tropical open ocean with high temperature and salinity, brings oligotrophic water with very low chlorophyll concentrations; the latter has a low salinity but high nutrient and chlorophyll concentrations. Our analysis demonstrated that variation of the physicobiological features shifted systematically from each subarea to the next, as exemplified by the temperature increase and the pigment decrease from northwest to southeast. This was matched by spatial and seasonal distributions of dissolved oxygen in the East China Sea. We also found that the CZCS pigment images clearly indicated the positions of the biological productivity front in the Changjiang Estuary, which was just beyond the boundary of the turbid zone along the coastal areas of the East China Sea. They also showed the seasonal variation of the direction of the Changjiang River discharge tongue. The ocean color and infrared images complemented each other, and they were very useful in the interpretation of the spatial and monthly variations of the circulation patterns in the East China Sea.