植被日光诱导叶绿素荧光辐射传输模拟研究

Sun-induced chlorophyll fluorescence (SIF) of vegetation can be used as a direct probe of the functional status of photosynthetic machinery because of its close relationship with photosynthesis, thus enabling large-area monitoring of photosynthetic activity and offering a non-destructive method for the evaluation of plant physiological conditions. Technical advancement of hyper-spectral remote sensors promotes the research of SIF retrieval methods. However, there is still lacking of radiative transfer (RT) model that can accurately describe the excitation of fluorescence and its radiation transfer for three dimensional vegetation canopy. Without this kind of mechanism models, it is hard to quantitatively interpret the SIF signals and hinders the wide application of remote sensing of SIF. The goal of this project is to develop a RT model of three-dimensional canopy based on Monte Carlo ray-tracing technique, in which the atmospheric RT will also be included to study the influence of the atmosphere on the excitation and radiation transfer of SIF. Then the impact of the main parameters of canopy three dimensional structure, optical properties of canopy elements and atmosphere on the excitation and RT of SIF will be studied. We will evaluate and validate the precision of our SIF RT model by carrying out systematic measurements for agricultural crops, such as wheat, corn, and soybean, on several key growing stages. Based on the coupled vegetation and atmosphere SIF RT model, we will analyse and compare different retrieval methods of SIF, so as to provide helpful suggestions and guide for the study of SIF retrieval for various sensors’ altitude, the choose and design of spectral specifications of sensors.

日光诱导叶绿素荧光与植被的光合作用有着密切的联系，能够灵敏地反映植被生长状况，对荧光特性的探测可以了解植物的生长、病害及受胁迫等生理状况。高光谱遥感技术推动了植被荧光提取算法的发展，但尚缺乏能够精确模拟三维植被冠层荧光激发和辐射传输的机理模型，难以对荧光信号进行定量解释，无法满足荧光遥感应用的需求。本项目的目标是基于蒙特卡罗正向光子追踪算法，耦合植被冠层和大气，建立考虑大气影响的三维植被冠层日光诱导叶绿素荧光的辐射传输模型，研究植被三维结构、组分光学特性和大气参数对植被荧光激发和辐射传输的影响。通过对典型农作物冠层（如小麦、玉米和大豆等）主要生长期的观测试验，来系统验证正向建模精度。利用植被-大气耦合模型进行植被日光诱导叶绿素荧光提取方法的分析、比较，为从不同观测平台传感器提取荧光算法研究，以及传感器光谱性能指标的选择和设计提供参考和指导。

日光诱导叶绿素荧光与植被的光合作用有着密切的联系，能够灵敏地反映植被生长状况，对荧光特性的探测可以了解植物的生长、病害及受胁迫等生理状况。本项目基于蒙特卡罗正向光子追踪算法，耦合植被冠层和大气，建立考虑大气影响的三维植被冠层日光诱导叶绿素荧光的辐射传输模型，研究植被三维结构、组分光学特性和大气参数对植被荧光激发和辐射传输的影响。通过与其它成熟的地气耦合辐射传输模型相互比较验证，和遥感观测试验，系统验证了正向建模的精度。该模型同时具有模拟大气透过率、大气层顶总辐亮度、程辐射、双向直射辐射等遥感常用辐射量和地气耦合结果的能力。拓展后的模型基于蒙特卡洛原理和正向光线追踪，整个传输过程基于真实物理过程，结果精度高，应用场景广泛。利用植被-大气耦合模型进行植被日光诱导叶绿素荧光提取方法的分析、比较，为从不同观测平台传感器提取荧光算法研究，以及传感器光谱性能指标的选择和设计提供参考和指导。