基于珠海一号高光谱卫星的巢湖叶绿素a浓度反演

叶绿素a是重要的水质参数，可以衡量水体的富营养化程度。遥感技术可以实时、快速、大范围地获取水体中叶绿素a的浓度与分布，对于水生态环境的评价及治理具有重要意义。内陆水体的光谱特征复杂，宽波段的多光谱遥感难以精确获取水体的光谱信息。国产珠海一号高光谱卫星因其光谱分辨率高，波段多等优势在内陆湖泊的遥感监测中具有广阔的应用前景。基于珠海一号高光谱数据，充分发挥其高光谱分辨率的优势，对巢湖的叶绿素a浓度进行反演，从影像中提取实测点处的遥感反射率曲线，筛选具有显著光谱特征的波段，并以OIF指数衡量不同波段组合获取水体组分信息的能力，以此构建与实测叶绿素a浓度相关性较高的波段组合。结果表明珠海一号OHS-2A星影像的14，16和19波段所构建的三波段模型[R_rs(700 nm)-1-R_rs(670 nm)-1]×R_rs(746 nm)在巢湖的叶绿素a浓度反演中取得了较高的精度，相对误差和均方根误差分别为19.97%和10.85 mg·m-3。由模型反演巢湖2019年5月10日的叶绿素a浓度空间分布图可知，叶绿素a浓度自东向西呈上升趋势，全湖南部和东北部的叶绿素a浓度较低，西巢湖的北部叶绿素a浓度最高。西巢湖的整体叶绿素a浓度是全湖最高的，尤其是其北部水域，水质情况较差，已经出现了一定面积的水华，其主要原因在于该地区紧邻合肥市，人类活动强烈，污水废水排放量大。珠海一号高光谱卫星对于内陆湖泊的水质反演具有一定的优势，但也存在着数据处理困难，波段利用率低，反演模型普适性差等局限，今后仍需借助珠海一号高光谱数据开展更多的湖泊遥感研究，不断提出高光谱遥感影像处理的新方法，提高反演模型的精度与普适性，充分挖掘数据源的潜力，使其更好地服务于水质的遥感监测工作。

Remote Sensing Retrieval of Chlorophyll-a Concentration in Lake Chaohu Based on Zhuhai-1 Hyperspectral Satellite

Chlorophyll-a is a critical water quality parameter which can be used to evaluate the eutrophication degree of lakes. Remote sensing technology has the advantages of real-time, rapidity and wide monitoring range and has been widely used in inland lake water environment monitoring. Obtaining the chlorophyll-a concentration in lakes dynamically in real-time is significant for lake governance. The spectral characteristics of inland lakes are complex. So, it is difficult to accurately obtain the spectral characteristics of water bodies by multi-spectral remote sensing data. The Zhuhai-1 hyperspectral satellite has a broad application prospect in remote sensing monitoring of inland lakes because of its high spectral resolution and sufficient band. In this paper, the hyperspectral data of Zhuhai-1 is selected to retrieve the chlorophyll-a concentration in Chaohu Lake. First, extract the remote sensing reflectance curve at the measured point from the image, filter the bands with significant spectral characteristics according to the curve, and use the OIF index to measure the ability of different band combinations to obtain water body composition information. And finally build the band combination, which is highly correlated with the actual measurement chlorophyll-a concentration. The results show that the three-band model [R_rs(700 nm)-1-R_rs(670 nm)-1]×R_rs(746 nm) constructed by Zhuhai-1 in bands 14, 16 and 19 has achieved high accuracy in retrieving chlorophyll-a concentration in Lake Chaohu, the MRE is 19.97% and the RMSE is 10.85 mg·m-3, which is superior to most previous spaceborne remote sensing data sources. Retrieving the spatial distribution map of chlorophyll-a concentration of Chaohu Lake on May 10, 2019, shows that the chlorophyll-a concentration is increasing from east to west. The concentration of chlorophyll-a in the south and northeast of the lake is low, and the chlorophyll-a concentration in the north of West Chaohu The concentration of a reaches the highest concentration. The overall concentration of chlorophyll-a in West Chao Lake is the highest, especially in its northern waters, where the water quality is poor, and a certain bloom area has appeared. The main reason is that the area is close to Hefei City and is more susceptible to strong solid activities and large discharges of sewage and wastewater. The Zhuhai-1 hyperspectral satellite has certain advantages for the water quality retrieval of inland lakes, but it also has limitations such as difficulty in data processing, low band utilization, and poor universality of inversion models. It is necessary to use the Zhuhai-1 hyperspectral data to carry out more lake remote sensing research, continue to propose new methods of hyperspectral remote sensing image processing, and improve the accuracy and universality of the inversion model, fully tap the potential of the data source.