The observation of coastal waters using satellite remote sensing is of primary importance to gain understanding on the complex processes occurring in those highly dynamical ecosystems. The analysis of ocean color data relies on the interaction between the incident sunlight daytime radiation that propagates within the ocean–atmosphere system and the suspended material (hydrosols and aerosols) present in each medium. The goal of this study is to examine how relevant nighttime radiances as measured by the panchromatic Day–Night Band (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) satellite sensor could be for the detection and monitoring of river plumes in turbid waters. The spatial and temporal variation of the nighttime radiance is studied over areas that are subjected to intense river flooding events, namely, the regions of the delta of Mekong (Vietnam) and the delta of Rhône (France), at seasonal and daily scales and for various magnitudes of the lunar illumination. The VIIRS observations show that the variations of the radiance are closely related to seasonality of the water turbidity; higher radiances are observed during the wet season as a result of the intense rainfalls. The seasonal cycle of the radiance is noticeable near the full moon phase for both areas, thus demonstrating the high sensitivity of VIIRS sensor radiometry for detecting ocean changes at night. It was also noted that the radiance seasonal cycle remains distinguishable for the Rhône area for a lunar illumination that could be far from the full moon condition, namely, for a fraction value $F$ of the full moonlight of 40%. The impact of the adjacency effects induced by the diffuse glow of city lights on the nighttime radiance was examined at seasonal scale. Such an impact could be as high as 40% over water targets, thus suggesting that aquatic areas located sufficiently far from coastal cities should be preferentially used to properly observe water turbidity at night. The analysis of flooding events at a daily time scale revealed that intense river inputs into the ocean could be satisfactorily distinguished, including for low fractions of lunar illumination ( $F \approx 20$ %). The analysis of the influence of ocean dynamics on the spatiotemporal variation of the radiance during river flooding events highlighted that the wind-driven current is the major contributor to the displacement of the suspended matter within the Rhône river plume that could explain the rapid hourly variations of the nighttime radiance. This study demonstrates the high benefit of measuring the nighttime upward radiation over turbid waters using ocean color remote sensing, which topic has not been deeply investigated so far, for the analysis and monitoring of coastal processes, such as the transport of suspended matter.

中文翻译：

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VIIRS 卫星传感器 (NASA/NOAA) 在季节性和每日时间尺度上对沿海水域测量的夜间辐射分析。在洪水事件期间河流流量观测中的应用

使用卫星遥感观测沿海水域对于了解那些高度动态的生态系统中发生的复杂过程至关重要。海洋颜色数据的分析依赖于在海洋-大气系统内传播的入射日光白天辐射与每种介质中存在的悬浮物质（水溶胶和气溶胶）之间的相互作用。本研究的目的是研究可见红外成像辐射计套件 (VIIRS) 卫星传感器的全色昼夜波段 (DNB) 测量的相关夜间辐射如何用于检测和监测浑水中的河流羽流。研究了遭受强烈河流洪水事件的地区夜间辐射的时空变化，即，湄公河三角洲（越南）和罗纳河三角洲（法国）的区域，在季节和日尺度上以及不同程度的月球照明。VIIRS观测表明，辐射度的变化与水浊度的季节性密切相关；由于强降雨，在雨季观察到更高的辐射。在这两个区域的满月相附近，辐射的季节性周期很明显，因此证明了 VIIRS 传感器辐射测量在检测夜间海洋变化方面的高灵敏度。还注意到，对于可能远离满月条件的月球照明，罗纳河地区的辐射季节周期仍然是可区分的，即，对于一个分数值 在季节和日常尺度以及不同程度的月球照明。VIIRS观测表明，辐射度的变化与水浊度的季节性密切相关；由于强降雨，在雨季观察到更高的辐射。在这两个区域的满月相附近，辐射的季节性周期很明显，因此证明了 VIIRS 传感器辐射测量在检测夜间海洋变化方面的高灵敏度。还注意到，对于可能远离满月条件的月球照明，罗纳河地区的辐射季节周期仍然是可区分的，即，对于一个分数值 在季节和日常尺度以及不同程度的月球照明。VIIRS观测表明，辐射度的变化与水浊度的季节性密切相关；由于强降雨，在雨季观察到更高的辐射。在这两个区域的满月相附近，辐射的季节性周期很明显，因此证明了 VIIRS 传感器辐射测量在检测夜间海洋变化方面的高灵敏度。还注意到，对于可能远离满月条件的月球照明，罗纳河地区的辐射季节周期仍然是可区分的，即，对于一个分数值 由于强降雨，在雨季观察到更高的辐射。在这两个区域的满月相附近，辐射的季节性周期很明显，因此证明了 VIIRS 传感器辐射测量在检测夜间海洋变化方面的高灵敏度。还注意到，对于可能远离满月条件的月球照明，罗纳河地区的辐射季节周期仍然是可区分的，即，对于一个分数值 由于强降雨，在雨季观察到更高的辐射。在这两个区域的满月相附近，辐射的季节性周期很明显，因此证明了 VIIRS 传感器辐射测量在检测夜间海洋变化方面的高灵敏度。还注意到，对于可能远离满月条件的月球照明，罗纳河地区的辐射季节周期仍然是可区分的，即，对于一个分数值 $F$满月光的 40%。在季节尺度上研究了由城市灯光的漫射辉光引起的邻接效应对夜间辐射的影响。这样的影响可能高达水体目标的 40%，因此建议应优先使用距离沿海城市足够远的水域来适当地观察夜间水体浊度。对每日时间尺度的洪水事件的分析表明，可以令人满意地区分强烈的河流输入海洋，包括低比例的月球照明。 $F \约 20$%）。对河流洪水事件期间海洋动力学对辐射度时空变化影响的分析强调，风驱动的洋流是罗纳河羽流中悬浮物质位移的主要贡献者，这可以解释罗纳河羽流每小时的快速变化。夜间的光辉。这项研究证明了使用海洋颜色遥感测量混浊水域夜间向上辐射的巨大好处，该主题迄今为止尚未深入研究，用于分析和监测沿海过程，例如悬浮物质的运输。