基于3D真实植被场景的全波段辐射传输模型研究

本文基于3D真实场景CLAMP模型模拟的植被冠层，对冠层在可见一近红外波段和热红外波段的辐射传输进行了综合建模。针对CLAMP模型生成场景的通用和近似特征，在可见一近红外波段，对植被和土壤的单次散射贡献利用光子逆向追踪算法进行了精确计算，多次散射的贡献则采用四流近似理论来计算，以提高运算效率。模型结果与SAILH模型结果进行了比较，具有较好的一致性，并且体现出了优于一维辐射传输模型的模拟结果。在热红外波段，采用几何光学原理，冠层方向亮度温度由可视光照叶片、遮荫叶片、光照土壤和遮荫土壤的比例与对应组分亮温乘积之和得到，模拟结果体现了合理的变化趋势。对冠层主要结构参数LAI和ALA的敏感性进行了比较分析，不同波段模型模拟的方向性辐射结果，很好地反映了结构参数对冠层辐射特性的影响。

Modeling of 3D Canopy's Radiation Transfer in the VNIR and TIR Domains

In this paper,a synthetic strategy has been employed to model 3D canopy's radiation transfer in the whole optical spectral domains.3D plant architecture model(the Clumped Architecture Model of Plants: CLAMP) is used to generate the realistic vegetation scene.In the visible and NIR region,the canopy BRDF was decomposed into three parts: single scattering contribution from leaves,single scattering contribution from the soil,and multiple scattering part of the canopy.The single scattering contributions come from illuminated leaves and soil components which are computed by the reverse ray-tracing procedure with their corresponding reflectance.The multiple scattering contribution is approximated by the four-stream theory.As a result,the modeling of VNIR region is more efficient and fairl accurately describes the anisotropically scattering features of vegetation.Simulation results show good consistency with SAILH's,and more details can be simulated than the one dimensional rediative transfer models.In the TIR region,the directional brightness temperature of canopy is calculated as the linear combination of four(component's)(illuminated leaves,illuminated ground,shadowed leaves,and shadowed ground) brightness temperature multiplied by its fractional cover computed by the reverse ray-tracing procedure.Initial modeling results show typical features of(vegetation's) anisotropic scattering and directional temperature distributions,for example,hot spot,bowl shape and reach a good agreement with theoretical results in those three domains.This strategy shows potential of exploring the impact of canopy structure on the radiometric response measured by remote sensors.