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引用本文:

DOI:

10.11834/jrs.20210414

收稿日期:

2020-09-18

修改日期:

2021-01-23

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近20年(2002~2020)渤黄海真光层深度的时空变化遥感分析
摘要:

真光层深度(Euphotic zone depth, Zeu)是指光合有效辐照度衰减为水体表面处1%时所对应的深度。它是描述水质特性的重要参数,对浮游植物光合作用,全球碳循环以及海洋环境变化的研究具有重要意义。本文基于多年在渤黄海现场实测数据,建立了针对MODIS(Moderate resolution imaging spectroradiometer)传感器的Zeu遥感估算模型,该模型表现出良好的估算精度。在此基础上,利用2002~2020年MODIS长时序卫星遥感数据,研究揭示了渤黄海Zeu的时空变化规律,结果显示:渤黄海Zeu具有近岸低、外海高的特点,并且明显表现出夏深冬浅的季节变化特征;长江口北舌状低值区夏季时往东北方向伸展,而在秋初时转向东南;在2002~2020年间,渤海、北黄海以及苏北浅滩的Zeu单调变化,而南黄海、济州岛南及长江口北的Zeu呈现波动式的变化趋势。此外,本文结合多源卫星遥感数据资料分析了Zeu时空变化的驱动因素,结果显示:在渤海、南黄海、北黄海及苏北浅滩,Zeu的时空变异受多种驱动因素的综合影响,其中海表面温度和光合有效辐射对Zeu的变化呈正向驱动,而风速和总悬浮颗粒物浓度呈负向驱动;此外,长江径流量对长江口北Zeu的变化也起着负向驱动作用(相关系数R = -0.55)。

Remote sensing of spatial and temporal variations of euphotic zone depth in the Bohai Sea and Yellow Sea during recent 20 years (2002~2020)
Abstract:

Euphotic zone depth (Zeu) reflects the depth where photosynthetic available radiation is 1% of its surface value. Euphotic zone is in the upper water column, in which marine phytoplankton can effectively photo-synthesize, which plays an important role in air–sea interaction through transfer of either gases or heat, espe-cially with regards to greenhouse gases such as carbon dioxide. Thus, Euphotic zone has an important im-pact on the study of marine primary productivity, phytoplankton biomass and global carbon cycle. On the other hand, the spatial and temporal variations of Zeu is closely related to the variability of water color ele-ments, so Zeu is considered as an indicator of water clarity, which even has a certain indicative significance for ecosystems. Thus, marine researchers have attached importance to the monitoring of Zeu. In this study, based on in situ data collected from several cruises in the Bohai Sea and Yellow Sea, a remote sensing model was proposed to estimate Zeu from moderate resolution imaging spectroradiometer (MODIS) satellite data. The designed model uses the logarithm of slope of the remote sensing reflectance (Rrs) between 443 and 667 nm as an input. In situ data validations indicated that the algorithm shows good per-formances, with the R2 (Coefficient of determination) values of 0.86, RMSE (Root-mean-square error) val-ues of 4.14 and MAPE (Mean absolute percentage error) values of 17.2%. Compared with current common models, the model based on Rrs performs well. Then, long term MODIS satellite data (2002~2020) was further used to investigate the spatial and temporal distribution of Zeu in the Bohai Sea and Yellow Sea. The results indicate that, 1) in general, Zeu is low in coastal regions but high in offshore waters. Meanwhile, clear temporal variability in Zeu was observed, showing that for the most regions, Zeu is generally high in summer but low in winter. 2) It is worth noting that the tongue-shaped structure with low value in the North of Yangtze River Estuary extends to the northeast in summer and turns to the southeast in early autumn. 3) From 2002 to 2020, in the Bohai Sea, Northern Yel-low Sea and Subei Shoal, Zeu varied monotonously. In the Bohai Sea and Subei Shoal, Zeu showed a down-ward trend, while it displayed an upward trend in the Northern Yellow Sea. Meanwhile, Zeu indicated a fluc-tuating trend in the Southern Yellow Sea, South of Jeju Island and North of Yangtze River Estuary. In addition, the potential driving factors responsible for these spatiotemporal variations were examined based on multi-source satellite data. The results indicate that, in the Bohai Sea, Southern Yellow Sea, North-ern Yellow Sea and Subei Shoal, the spatial and temporal variations of Zeu are influenced by a variety of driving factors. In general, Zeu is positively driven by the sea surface temperature and photosynthetic active radiation but negatively driven by wind speed and total suspended matter concentration. Specifically, it is worth noting that total suspended matter concentration has a significant effect on the variations of Zeu. Meanwhile, Zeu in the North of Yangtze River Estuary is strongly related with amount of runoff (Correlation coefficient R = -0.55).

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