| Ocean chlorophyll concentration can function as an important factor to measure the marine phytoplankton biomass and primary productivity,and it has been frequently applied to the analysis of Offshore ecological environment features and the ocean resource environmental impact assessment. In recent years, with the rapid development of the marine satellite remote sensing technology, the satellite remote sensing data has occupied an important role in the marine ecosystem research and monitoring of dynamic applications, with the virtue of its large-scale, long, high frequency, and low cost. However, due to various factors like weather and the climate, satellite remote sensing data of chlorophyll is experiencing an issue of irregular Lack in a large scale, and to some extent hindered the application of the data. So, it is an urgent need for the current application research to adopt a scientific method to reconstruct the satellite remote sensing data of chlorophyll. To achieve this, the paper developed a method which can be applied to the reconstruction of the satellite remote sensing data of chlorophyll, and completed the reconstruction of the data in the years between 1998 and 2014. And based on this, it analyzed the characteristics of the time-space changes of chlorophyll in Offshore China and the relationship between the features and the environment factor. Here are the results:(1) Based on the classical DINEOF reconstruction method, this paper applied the EMO method to efficiently detect the characteristics of the noise and eliminate the outlier of the original data, introduced the reconstruction method which was based on the idea of data-assimilation, forming a DINEOF-EMD method which can further optimize the reconstruction results. The experiment shows the DINEOF-EMD method developed by this paper can successfully describe the characteristics of temporal and spatial variation of chlorophyll in Offshore China. This method does not need priori parameters and is very fast in calculation. Compared with the classical DINEOF method, this DINEOF-EMD method has increased the reconstruction precision by 5-10%.(2) The characteristic of temporal and spatial variation of the chlorophyll in East China Sea and the relationship between it and the environmental factors(1)The climatic feature of the chlorophyll concentration: distributed in strip from the shore the the high seas and decreased starting from the shore to the high seas. The the chlorophyll concentration in the northern sea area of the exit of the Yangtze River is higher, with the maximum of 5mg/m3.(2)The result of linear fitting shows that in the years between 1998 and 2014, the chlorophyll concentration has increased 0.1360 mg/m3, and the increasing rate is 0.0085 mg/m3?a-1; and the increment in shore of Lianyungang, Laizhou Bay, northern Bohai Bay and the northern Yellow River is more than 2mg/m3, while the chlorophyll concentration in exit of the Yangtze River has decreased a lot.(3)The chlorophyll concentration reaches the yearly maximum of 2.974 mg/m3 in Spring and the minimum of 2.560mg/m3 in July.(4)There is never any simple or consistent relationship between chlorophyll and main marine environmental factors such as SST and SSS. And the relationship varies greatly as the season changes and the waters differ. The waters where the chlorophyll is related to SST are the exit of the Yangtze River(Spring and autumn) and Jizhou Island( Summer and autumn), while in other waters there is a negative correlation. The waters where the chlorophyll is related to SSS are the central part and the northeastern part of the Yellow Sea(Summer and autumn) while in other waters there is a negative correlation. In addition,in summer,the relationship between chlorophyll and SST and SSS varies by waters.(3) The characteristic of temporal and spatial variation of the chlorophyll in South China Sea and the relationship between it and the environmental factors(1)The climatic feature of the chlorophyll concentration: it is high in shore area nearby area of islands and reefs in central part of the sea basin and it is low in offshore area.(2) During 1998 and 2014, the overall average chlorophyll concentration in whole sea area decreased a little, by 0.005 mg/m3 and the decrease rate is 0.0009 mg/m3?a-1;The nearby waters in the eastern side of Qiongzhou Strait decreased greatly--most waters decreased while the waters northern shore increased.(3)The maximum variation is in January which is about 0.647mg/m3 and while the minimum is in April, which is 0.461mg/m3. In addition, there will be a second peak in July or August, which is about 0.54 mg/m3.(4) There is a negative relationship between chlorophyll and SST and the relation between it and SSS greatly varies by waters and seasons, which is different from the situation in eastern China Sea. Also, in summer, chlorophyll is negatively related to SSS in most waters and there is no consistent relation in other seasons. |
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