Satellite study of the influence of coastal upwelling on a red tide in the Zhejiang Coastal Waters

摘要

In this article, EOS MODIS ocean color and sea-surface temperature data were used to study the influence of coastal upwelling on a red tide in the Zhejiang Coastal Waters in the summer of 2007. Several cloud-free and date-continued ocean color and sea-surface temperature images during the red tide event were selected and processed in this study. According to the field observations of the red tide, pixels with chlorophyll concentration higher than a certain value were considered as the red tide waters in the ocean color images. And the coastal upwelling in the Zhejiang Coastal Waters was measured by applying a temperature threshold approach from the sea-surface temperature images. Then, the temporal and spatial distributions of the red tide and the coastal upwelling were contrastively analyzed. Results show that there exists a high degree of correlation in spatial distribution between the coastal upwelling and the red tide. The coastal upwelling affects the spatial cover of the red tide according to their spatial correlation and the upwelling plays a crucial role in the development of the red tide in term of water temperature. The upwelling in the Zhejiang Coastal Waters is an important dynamic factor for the formation of red tides there.