Red Tide Detection in the East China Seas based on AVHRR and MODIS Data

Abstract

Red tides are important problems in the coastal areas of China. Environmental and economic impacts of red tides have increased in recent years. Thus, considerable efforts have been spent on attempts to detect and monitor red tides. Satellite remote sensing is one of the techniques that have been used to detect and monitor red tide events in China since 1990s. AVHRR and SeaWiFS images have been used to detect and monitor red tides. Algorithms for red tide detection with AVHRR and SeaWiFS images have been developed. These algorithms include the multi-band ratio algorithms, the ocean color-temperature algorithm and the neural network model. In this paper we present an algorithm developed for extracting information about red tide events from AVHRR and MODIS sensors, based on the measurements of the red-tide cruises in the East China Sea during 2002-2005. The algorithm depends on the spectral characteristics and temperature of the red tide waters. The applications of the algorithm to the satellite images are given to the information extraction of the time (start and duration), the location and the spatial extent of the red tide events. The algorithm has been applied to the AVHRR and MODIS data on April 4 2005. The locations and the spatial extents of the red tide events have been figured out. Compared to the in-situ observations, the results retrieved from the AVHRR and MODIS data are in good agree. The algorithm can be used to detect red tide in East China Seas. However, more validations and improvements should be applied.