摘要
The massive Ulva （U.）prolifera bloom in the Yellow Sea was first observed and reported in summer of 2008. After that, the green tide event occurred every year and influenced coastal areas of Jiangsu and Shandong provinces of China. Satellite remote sensing plays an important role in monitoring the floating macroalgae. In this paper, U. prolifera patches are detected from quasi- synchronous satellite images with different spatial resolu- tion, i.e., Aqua MODIS （Moderate Resolution Imaging Spectroradiometer）, HJ-1A/B （China Small Satellite Con- stellation for Environment and Disaster Monitoring and Forecasting）, CCD （Charge-Coupled Device）, Landsat 8 OLI （Operational Land Imager）, and ENVISAT （Environ- mental Satellite） ASAR （Advanced Synthetic Aperture Radar） images. Two comparative experiments are per- formed to explore the U. prolifera monitoring abilities by different data using detection methods such as NDVI （Normalized Difference Vegetation Index） with different thresholds. Results demonstrate that spatial resolution is an important factor affecting the extracted area of the floating macroalgae. Due to the complexity of Case II sea water characteristics in the Yellow Sea, a fixed threshold NDVI method is not suitable for U. prolifera monitoring. A method with adaptive ability in time and space, e.g., the threshold selection method proposed by Otsu （1979）, is needed here to obtain accurate information on the floating macroalgae.
The massive Ulva （U.）prolifera bloom in the Yellow Sea was first observed and reported in summer of 2008. After that, the green tide event occurred every year and influenced coastal areas of Jiangsu and Shandong provinces of China. Satellite remote sensing plays an important role in monitoring the floating macroalgae. In this paper, U. prolifera patches are detected from quasi- synchronous satellite images with different spatial resolu- tion, i.e., Aqua MODIS （Moderate Resolution Imaging Spectroradiometer）, HJ-1A/B （China Small Satellite Con- stellation for Environment and Disaster Monitoring and Forecasting）, CCD （Charge-Coupled Device）, Landsat 8 OLI （Operational Land Imager）, and ENVISAT （Environ- mental Satellite） ASAR （Advanced Synthetic Aperture Radar） images. Two comparative experiments are per- formed to explore the U. prolifera monitoring abilities by different data using detection methods such as NDVI （Normalized Difference Vegetation Index） with different thresholds. Results demonstrate that spatial resolution is an important factor affecting the extracted area of the floating macroalgae. Due to the complexity of Case II sea water characteristics in the Yellow Sea, a fixed threshold NDVI method is not suitable for U. prolifera monitoring. A method with adaptive ability in time and space, e.g., the threshold selection method proposed by Otsu （1979）, is needed here to obtain accurate information on the floating macroalgae.
