Chlorophyll-a (chl-a) concentration is an indicator of algal biomass. The Sentinel 2 platform offers greatly improved spatial resolution over other satellite platforms designed for water based chl-a retrievals and includes a “red-edge” band at 704 nm not present on the Landsat 8 operational land imager. This study provides validation of an improved version of a well known semi-analytical chl-a retrieval algorithm. The algorithm is provided with several free image processing utilities and the improved approach can be implemented with minimal technology skills. The improved performance is the result of replacing a fixed chl-a specific absorption coefficient (a*) with a variable model. This method was applied to three Sentinel 2 images taken over the Lake Erie western basin correlating with an in-situ dataset of 24 samples where chl-a ranged from 1.89 mg m⁻³ to 70.20 mg m⁻³. The variable a* model produced chl-a retrievals with normalised root mean squared error of prediction (NRMSEP) = 7.5%, bias = -0.47 mg m⁻³, coefficient of determination (R²) = 0.91 and Nash-Sutcliffe efficiency (NSE) = 0.90). This represented a 23% reduction in NRMSEP, an 85% reduction in bias and an increase in NSE of 7% over the default algorithm using a fixed a* value. Creation of chl-a retrieval algorithms that consider the variability in a* should result in algorithms that perform better against a wide range of chl-a concentrations and are less likely to require local recalibration. Obtaining accurate chl-a retrievals from a satellite platform with the spatial resolution of Sentinel 2 will allow satellite monitoring of many more inland waters than previously possible.

叶绿素-a（chl-a）浓度是藻类生物量的指标。与为水基chl-a检索而设计的其他卫星平台相比，Sentinel 2平台提供了大大提高的空间分辨率，并且包括Landsat 8可操作陆地成像仪上不存在的704 nm“红边”波段。这项研究提供了对众所周知的半分析式chl-a检索算法的改进版本的验证。该算法提供了几个免费的图像处理实用程序，并且可以用最少的技术技能来实现改进的方法。性能的提高是替换固定的chl-a比吸收系数（a*）带有可变模型。该方法应用于在伊利湖西部盆地上拍摄的三张Sentinel 2图像，并与24个样品的原位数据集相关，其中chl-a的范围从1.89 mg m ^-3到70.20 mg m ^-3。变量a *模型产生的chl-a检索结果具有标准化的均方根预测误差（NRMSEP）= 7.5％，偏差= -0.47 mg m ^-3，确定系数（R ²）= 0.91和Nash-Sutcliffe效率（NSE） ）= 0.90）。与使用固定a *值的默认算法相比，这意味着NRMSEP降低了23％，偏差降低了85％，NSE增加了7％。那考虑的变异叶绿素a检索算法创建一个*应该使算法在宽范围的chl-a浓度下表现更好，并且不太可能需要本地重新校准。从具有Sentinel 2空间分辨率的卫星平台获得准确的chl-a检索结果，将使卫星监视内陆水域的能力超过以前的水平。