Research on the chlorophyll-a distribution in Bohai Sea based on the MODIS data

Chlorophyll-a (Chla) concentration data is one of the key parameters for the evaluation of water eutrophication and primary productivity. Compared with traditional monitoring methods, it has the advantages of quasi-real-time, largescale and long-term by using remote sensing data to retrieve Chla concentration data. Analyzing the temporal and spatial distribution of Chla concentration and its long time series changes will help relevant institutions to comprehensively evaluate and control the water environment. However, there is no consensus on the long-term change mechanism of Chla concentration in coastal waters. In this study, the Modis data from 2003 to 2009 was used to retrieve the Chla concentration data in the Bohai Sea and its temporal and spatial distribution characteristics were analyzed. In addition, the potential relationship between wind speed and Chla concentration was analyzed using Quick Scatterometer wind field data over the same time period. The results showed that there were different seasonality characteristics in different dynamic regions. The concentration of Chla was the lowest in summer in the Bohai Sea, and it showed an obvious interannual variation trend in summer and autumn in Laizhou Bay and Bohai Bay. The comparison results of wind speed and Chla showed that the seasonal changes of wind speed and Chla were consistent to some extent. It should be considered that the wind field of sea surface was one of the influencing factors of Chla change mechanism in the shallow sea ecological environment system.