Title: WAFER: A new method to retrieve sun-induced fluorescence based on spectral wavelet decompositions Show Chinese title

Title: 晶圆：一种基于光谱小波分解的获取太阳诱导荧光的新方法

Abstract: Sun-induced fluorescence (SIF) as a close remote sensing based proxy for photosynthesis is accepted as a useful measure to remotely monitor vegetation health and gross primary productivity. In this work we present the new retrieval method WAFER (WAvelet decomposition FluorEscence Retrieval) based on wavelet decompositions of the measured spectra of reflected radiance as well as a reference radiance not containing fluorescence. By comparing absolute absorption line depths by means of the corresponding wavelet coefficients, a relative reflectance is retrieved independently of the fluorescence, i.e. without introducing a coupling between reflectance and fluorescence. The fluorescence can then be derived as the remaining offset. This method can be applied to arbitrary chosen wavelength windows in the whole spectral range, such that all the spectral data available is exploited, including the separation into several frequency (i.e. width of absorption lines) levels and without the need of extensive training datasets. At the same time, the assumptions about the reflectance shape are minimal and no spectral shape assumptions are imposed on the fluorescence, which not only avoids biases arising from wrong or differing fluorescence models across different spatial scales and retrieval methods but also allows for the exploration of this spectral shape for different measurement setups. WAFER is tested on a synthetic dataset as well as several diurnal datasets acquired with a field spectrometer (FloX) over an agricultural site. We compare the WAFER method to two established retrieval methods, namely the improved Fraunhofer line discrimination (iFLD) method and spectral fitting method (SFM) and find a good agreement with the added possibility of exploring the true spectral shape of the offset signal and free choice of the retrieval window. (abbreviated) Show Chinese abstract

Abstract: 太阳诱导荧光（SIF）作为一种基于遥感的光合作用近似代理，被接受为一种有用的测量方法，用于远程监测植被健康和总初级生产力。 在本工作中，我们提出了新的反演方法WAFER（WAvelet分解荧光反演），该方法基于测量的反射辐射光谱以及不含荧光的参考辐射光谱的小波分解。 通过比较绝对吸收线深度，利用相应的小波系数，可以独立于荧光获得相对反射率，即： 不引入反射率和荧光之间的耦合。 然后可以将荧光作为剩余偏移量进行推导。 该方法可以应用于整个光谱范围内的任意选定波长窗口，从而利用所有可用的光谱数据，包括将吸收线频率（即吸收线宽度）分成多个层次，而无需大量训练数据集。 同时，对反射率形状的假设是有限的，并且不对荧光施加光谱形状假设，这不仅避免了由于不同空间尺度和反演方法之间错误或不同的荧光模型引起的偏差，还允许探索不同测量设置下的此光谱形状。 WAFER在合成数据集以及使用田间光谱仪（FloX）在农业区域获取的几个昼夜数据集上进行了测试。 我们将WAFER方法与两种已建立的反演方法进行比较，即改进的弗劳恩霍夫线歧视（iFLD）方法和光谱拟合方法（SFM），并发现良好的一致性，同时还具有探索偏移信号真实光谱形状以及自由选择反演窗口的可能性。 （缩写）