Remote Sensing Of The Zhejiang Coastal Upwelling And Its Relationship With Red Tides

Red tide is one of the several marine disaters, and the Zhejiang Coastal Waters (ZCW) is the worst and major area of red tide disaster in China. There exist significant upwelling phenomena in the ZCW. Red tides and physical processes are closely related. This paper systematically carried out four research efforts about remote sensing technique of upwelling, temporal and spatial characteristics of the Zhejiang Coastal Upwelling (ZCU), statistical analysis of red tides occurred in the ZCW, and relationships between ZCU and red tides occurred in the ZCW.This study has collected a large number of EOS MODIS visible and thermal infrared data from 2007 to 2009 year, and the image features of ZCU are extracted from above remote sensing data sets. Based on the upwelling features in sea surface themperature images, a dynamic temperature threshold model is proposed and established to measure the ZCU, and then attributes of the ZCU are calculated. A semi-automatic method is achieved to obtain the ZCU information for the operational EOS MODIS satellite remote sensing data.With the established upwelling measure model, remote sensing information of the ZCU are extracted and then statistically analyzed with EOS MODIS data durring 2007~2009. Temporal characteristics of the ZCU are obtained, and development periods of the ZCU are proposed. Spatial distribution and variation of the ZCU are discussed. The variation discipline of spatial distribution of ZCUis set up, and position relationships between the ZCU and the submarine steep slope along the Zhejiang coast are also established. The development processes of the ZCU and its factors are investigated.By collecting red tide events’data from 2000 to 2009, the red tides in the ZCW are statistically analyzed. Temporal characteristics of red tides in the ZCW are obtained and two temporal types of red tide are classified. Based on the spatial distribution of red tide, location of the red tide-prone regions is pointed out and its position relationship with the submarine steep slope along the Zhejiang coast is cleared out. The annual characteristics of spatial distribution of red tides in the ZCW are also found.By applying multi-scale temporal-spactial analysis method, the relationship between ZCU and red tides in the ZCW are carried out and established. There exists a high degree of correlation in space, time and intensity distribution between ZCU and red tides occurred in the ZCW. The effects of the ZCU on red tides about time, scale and postion in the ZCW are analyzed. The roles of ZCU in the development processes of red tide in the ZCW are also discussed.