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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Modeling lidar waveforms with time-dependent stochastic radiative transfer theory for remote estimations of forest structure - art. no. 4484
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Modeling lidar waveforms with time-dependent stochastic radiative transfer theory for remote estimations of forest structure - art. no. 4484

机译：利用随时间变化的随机辐射传递理论为激光雷达波形建模以进行森林结构的远程估计-艺术没有。 4484

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Large footprint waveform-recording laser altimeters (lidars) have demonstrated a potential for accurate remote sensing of forest biomass and structure, important for regional and global climate studies. Currently, radiative transfer analyses of lidar data are based on the simplifying assumption that only single scattering contributes to the return signal, which may lead to errors in the modeling of the lower portions of recorded waveforms in the near-infrared spectrum. In this study we apply time-dependent stochastic radiative transfer (RT) theory to model the propagation of lidar pulses through forest canopies. A time-dependent stochastic RT equation is formulated and solved numerically. Such an approach describes multiple scattering events, allows for realistic representation of forest structure including foliage clumping and gaps, simulates off-nadir and multiangular observations, and has the potential to provide better approximations of return waveforms. The model was tested with field data from two conifer forest stands (southern old jack pine and southern old black spruce) in central Canada and two closed canopy deciduous forest stands (with overstory dominated by tulip poplar) in eastern Maryland. Model-simulated signals were compared with waveforms recorded by the Scanning Lidar Imager of Canopies by Echo Recovery (SLICER) over these regions. Model simulations show good agreement with SLICER signals having a slow decay of the waveform. The analysis of the effects of multiple scattering shows that multiply scattered photons magnify the amplitude of the reflected signal, especially that originating from the lower portions of the canopy. [References: 33]
机译：大型波形记录激光高度计（激光雷达）已显示出对森林生物量和结构进行精确遥感的潜力，这对区域和全球气候研究至关重要。当前，激光雷达数据的辐射传递分析是基于简化的假设，即只有单个散射会影响返回信号，这可能会导致在近红外光谱中记录的波形下部建模时出现错误。在这项研究中，我们应用时间相关的随机辐射转移（RT）理论来模拟激光雷达脉冲通过林冠层的传播。建立了与时间相关的随机RT方程，并进行了数值求解。这种方法描述了多个散射事件，可以真实地表示包括叶子丛生和空隙的森林结构，模拟离最低点和多角度的观测，并有可能提供更好的返回波形近似值。使用来自加拿大中部的两个针叶林林分（南部的老杰克松和南部的老黑云杉）和马里兰州东部的两个封闭林冠落叶林林分（以郁金香杨树为主）的实地数据对模型进行了测试。在这些区域上，将模型仿真的信号与通过回声恢复（SLICER）通过机盖的扫描激光雷达成像仪记录的波形进行比较。模型仿真显示与波形缓慢衰减的SLICER信号具有良好的一致性。对多重散射的影响的分析表明，多重散射的光子会放大反射信号的幅度，尤其是源自冠层下部的信号。 [参考：33]

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