High-frequency observation of floating algae from AHI on Himawari-8
High-frequency observation of floating algae from AHI on Himawari-8
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Himawari-8 上 AHI 对漂浮藻类的高频观测
DOI：
10.1016/j.rse.2019.03.038
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发表时间：
2019-06-15
影响因子：
13.5
通讯作者：
Li, Yonghong
中科院分区：
文献类型：
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作者：
Chen, Xinrong;Shang, Shaoling;Li, Yonghong
Himawari-8 (H8) 是一颗由 JAXA（日本宇宙航空研究开发机构）发射的地球静止气象卫星，目前由 JMA（日本气象厅）运营。它以 10 分钟的时间分辨率进行测量，以获得完整的磁盘视图。尽管被设计为气象卫星，H8 上的先进向日葵成像仪 (AHI) 具有三个可见光波段（460、510 和 640 nm）、一个近红外波段（860 nm）和两个短波红外波段（1610 和 2257 nm）来观测地球系统。在这项研究中，为海洋颜色卫星（Hu，2009）开发的浮藻指数（FAI）首次适用于处理 AHI 数据，并应用于中国太湖水域。在总共 18 张近无云图像中，AHI FAI 得出的藻类面积与中分辨率成像光谱仪 (MODIS) FAI 得出的藻类面积之间的相关系数 (r) 为 0.92，藻类覆盖率的平均百分比差异接近 5%。由于 GOCI 也是一颗对地静止卫星，因此收集了更多并发图像 (n = 80)，以对 AHI 和对地静止海洋彩色成像仪 (GOCI) 进行比较，导致相关系数为 0.91，观测到的藻类覆盖度百分比偏差接近 8%。这些结果表明 H8/AHI 可以在超高时间分辨率（10 分钟）下获得对漂浮藻类的可靠观测。特别是，这种超高频测量表明，太湖部分地区（例如梅梁湾）的浮藻事件（大多数> 60％）比GOCI观测到的浮藻事件（通常< 40％）更频繁。这些结果表明，超高频测量不仅对于有效的环境监测很重要，而且对于科学理解藻类动力学也很重要。
Himawari-8 (H8) is a geostationary meteorological satellite launched by JAXA (Japan Aerospace Exploration Agency) and is now operated by JMA (Japan Meteorological Agency). It takes measurements at a temporal resolution of 10 min for full disk view. Although designed as a meteorological satellite, the Advanced Himawari Imager (AHI) onboard H8 has three visible (460, 510 and 640 nm), one near infrared (860 nm) and two shortwave infrared bands (1610 and 2257 nm) to observe the Earth system. In this study, the Floating Algae Index (FAI) developed for ocean color satellites (Hu, 2009) is adapted to process AHI data for the first time and applied for waters of Lake Taihu, China. For a total of 18 near-cloud-free images, a correlation coefficient (r) of 0.92 was obtained between the algae area derived from AHI FAI and that from the Moderate Resolution Imaging Spectroradiometer (MODIS) FAI, and the mean percentage difference is similar to 5% in algae coverage. More concurrent images (n = 80) were collected for a comparison between AHI and Geostationary Ocean Color Imager (GOCI), as GOCI is also a geostationary satellite, resulting in a correlation coefficient of 0.91 and percentage deviation of similar to 8% in observed algae coverage. These results indicate that H8/AHI can obtain reliable observations of floating algae at ultrahigh temporal resolutions (10 min). Especially, such ultrahigh-frequency measurements show that part of Lake Taihu (e.g., Meiliang Bay) experienced more frequent events of floating algae (mostly > 60%) than that observed by GOCI (generally < 40%). These results indicate that ultrahigh-frequency measurements are important not only for efficient environmental monitoring but also for the scientific understanding of algae dynamics.