基于Sentinel-3 OLCI影像的秦皇岛海域悬浮物浓度遥感反演

基于2013~2021年期间秦皇岛海域遥感反射率、悬浮物浓度及叶绿素a浓度等实测数据，开展了该海域Sentinel-3 OLCI影像的悬浮物浓度遥感反演模型研究.结果表明，文献中常用的典型经验模型形式均不适用于秦皇岛海域，以490、620及708.75nm为悬浮物反演的敏感波段，以560nm为参比波段，将各敏感波段与参比波段的比值作为自变量，最终建立了适用于秦皇岛海域的Sentinel-3 OLCI四波段悬浮物浓度遥感反演模型（R²=0.69，MAPE=24.79%，RMSE=2.82mg/L）；并采用2021年7月24日Sentinel-3 OLCI影像进行悬浮物浓度遥感反演产品的真实性检验，得到反演值与实测值的平均相对误差为13.24%.将上述四波段模型用于2021年1~12月秦皇岛海域的Sentinel-3 OLCI影像，反演得到月均悬浮物浓度，发现秦皇岛海域悬浮物浓度整体呈现沿岸海域高、离岸海域低，秋冬季高、春夏季低的时空变化特征；且2018~2021年秦皇岛海域悬浮物浓度的年均值逐年递减，水体越来越澄清.

Retrieval of suspended particulate matter concentration from Sentinel-3 OLCI image in the Coastal Waters of Qinhuangdao

Based on the in-situ observed remote sensing reflectance (R_rs), SPM and chlorophyll a concentration in this area from 2013 to 2021, here a regional SPM retrieval model was developed specifically for the Sentinel-3 OLCI image. The results showed that the typical empirical models commonly used in the previous literatures were not applicable to the Qinhuangdao coastal waters, here three wavebands of 490, 620 and 708.75nm are used as the sensitive ones for retrieval of SPM concentration, and the waveband of 560nm was used as the reference one, a four-band retrieval model of SPM concentration (R²=0.69, MAPE=24.79%, RMSE=2.82mg/L) was established. The accuracy of SPM concentration remote sensing product was tested from July 24, 2021, and the mean absolute percentage error (MAPE) between the observed and the retrieval values reached 13.24%. The four-band model was then applied to the Sentinel-3 OLCI images of Qinhuangdao coastal waters from January to December 2021, and the monthly average SPM concentration are obtained and analyzed. It was found that the SPM concentration in this area displays obvious temporal and spatial variation characteristics, generally high in coastal waters and low in offshore waters, high in autumn-winter and low in spring-summer. The annual averaged SPM concentration was decreasing year by year from 2018 to 2021, and the water was becoming clearer and clearer.