scholarly journals Simulating Imaging Spectroscopy in Tropical Forest with 3D Radiative Transfer Modeling

2021 ◽  
Author(s):  
Dav M. Ebengo ◽  
Florian de Boissieu ◽  
Gregoire Vincent ◽  
Christiane Weber ◽  
Jean-Baptiste Féret
Keyword(s):  
Radiative Transfer ◽  
Tropical Forest ◽  
Imaging Spectroscopy ◽  
Data Availability ◽  
Species Discrimination ◽  
Transfer Model ◽  
Canopy Reflectance ◽  
Individual Tree ◽  
Airborne Imaging ◽  
Radiative Transfer Modeling

Optical remote sensing can contribute to biodiversity monitoring and species composition mapping in tropical forests. Inferring ecological information from canopy reflectance is complex and data availability suitable to such a task is limiting, which makes simulation tools particularly important in this context. We explored the capability of the 3D radiative transfer model DART to simulate top of canopy reflectance acquired with airborne imaging spectroscopy in complex tropical forest, and to reproduce spectral dissimilarity within and among species, as well as species discrimination based on spectral information. We focused on two factors contributing to these canopy reflectance properties: the horizontal variability in leaf optical properties (LOP) and the fraction of non-photosynthetic vegetation (NPVf). The variability in LOP was induced by changes in leaf pigment content, and defined for each pixel based on a hybrid approach combining radiative transfer modeling and spectral indices. The influence of LOP variability on simulated reflectance was tested by considering variability at species, individual tree crown and pixel level. We incorporated NPVf into simulations following two approaches, either considering NPVf as a part of wood area density in each voxel or using leaf brown pigments. We validated the different scenarios by comparing simulated scenes with experimental airborne imaging spectroscopy using statistical metrics, spectral dissimilarity (within crowns, within species, and among species dissimilarity) and supervised classification for species discrimination. The simulation of NPVf based on leaf brown pigments resulted in the closest match between measured and simulated canopy reflectance. The definition of LOP at pixel level resulted in conservation of the spectral dissimilarity and expected performances for species discrimination. Our simulation framework could contribute to better understand performances for species discrimination and relationship between spectral variations and taxonomic and functional dimensions of biodiversity.

scholarly journals Simulating Imaging Spectroscopy in Tropical Forest with 3D Radiative Transfer Modeling

2021 ◽  
Vol 13 (11) ◽  
pp. 2120
Author(s):  
Dav M. Ebengo ◽  
Florian de Boissieu ◽  
Grégoire Vincent ◽  
Christiane Weber ◽  
Jean-Baptiste Féret
Keyword(s):  
Remote Sensing ◽  
Radiative Transfer ◽  
Tropical Forest ◽  
Physical Modeling ◽  
Imaging Spectroscopy ◽  
Species Discrimination ◽  
Canopy Reflectance ◽  
Modeling Tools ◽  
Airborne Imaging ◽  
Radiative Transfer Modeling

Optical remote sensing can contribute to biodiversity monitoring and species composition mapping in tropical forests. Inferring ecological information from canopy reflectance is complex and data availability suitable to such a task is limiting, which makes simulation tools particularly important in this context. We explored the capability of the 3D radiative transfer model DART (Discrete Anisotropic Radiative Transfer) to simulate top of canopy reflectance acquired with airborne imaging spectroscopy in a complex tropical forest, and to reproduce spectral dissimilarity within and among species, as well as species discrimination based on spectral information. We focused on two factors contributing to these canopy reflectance properties: the horizontal variability in leaf optical properties (LOP) and the fraction of non-photosynthetic vegetation (NPVf). The variability in LOP was induced by changes in leaf pigment content, and defined for each pixel based on a hybrid approach combining radiative transfer modeling and spectral indices. The influence of LOP variability on simulated reflectance was tested by considering variability at species, individual tree crown and pixel level. We incorporated NPVf into simulations following two approaches, either considering NPVf as a part of wood area density in each voxel or using leaf brown pigments. We validated the different scenarios by comparing simulated scenes with experimental airborne imaging spectroscopy using statistical metrics, spectral dissimilarity (within crowns, within species, and among species dissimilarity) and supervised classification for species discrimination. The simulation of NPVf based on leaf brown pigments resulted in the closest match between measured and simulated canopy reflectance. The definition of LOP at pixel level resulted in conservation of the spectral dissimilarity and expected performances for species discrimination. Therefore, we recommend future research on forest biodiversity using physical modeling of remote-sensing data to account for LOP variability within crowns and species. Our simulation framework could contribute to better understanding of performances of species discrimination and the relationship between spectral variations and taxonomic and functional dimensions of biodiversity. This work contributes to the improved integration of physical modeling tools for applications, focusing on remotely sensed monitoring of biodiversity in complex ecosystems, for current sensors, and for the preparation of future multispectral and hyperspectral satellite missions.

Retrieving structural and chemical properties of individual tree crowns in a highly diverse tropical forest with 3D radiative transfer modeling and imaging spectroscopy

2018 ◽  
Vol 211 ◽  
pp. 276-291 ◽  
Author(s):  
Matheus Pinheiro Ferreira ◽  
Jean-Baptiste Féret ◽  
Eloi Grau ◽  
Jean-Philippe Gastellu-Etchegorry ◽  
Cibele Hummel do Amaral ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Tropical Forest ◽  
Imaging Spectroscopy ◽  
Chemical Properties ◽  
Individual Tree ◽  
Tree Crowns ◽  
Radiative Transfer Modeling ◽  
And Chemical Properties

scholarly journals A Refined Four-Stream Radiative Transfer Model for Row-Planted Crops

2020 ◽  
Vol 12 (8) ◽  
pp. 1290 ◽  
Author(s):  
Xu Ma ◽  
Tiejun Wang ◽  
Lei Lu
Keyword(s):  
Radiative Transfer ◽  
Computer Simulations ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Growth Stages ◽  
Canopy Reflectance ◽  
Transfer Equations ◽  
Radiative Transfer Equations ◽  
Different Growth Stages

In modeling the canopy reflectance of row-planted crops, neglecting horizontal radiative transfer may lead to an inaccurate representation of vegetation energy balance and further cause uncertainty in the simulation of canopy reflectance at larger viewing zenith angles. To reduce this systematic deviation, here we refined the four-stream radiative transfer equations by considering horizontal radiation through the lateral “walls”, considered the radiative transfer between rows, then proposed a modified four-stream (MFS) radiative transfer model using single and multiple scattering. We validated the MFS model using both computer simulations and in situ measurements, and found that the MFS model can be used to simulate crop canopy reflectance at different growth stages with an accuracy comparable to the computer simulations (RMSE < 0.002 in the red band, RMSE < 0.019 in NIR band). Moreover, the MFS model can be successfully used to simulate the reflectance of continuous (RMSE = 0.012) and row crop canopies (RMSE < 0.023), and therefore addressed the large viewing zenith angle problems in the previous row model based on four-stream radiative transfer equations. Our results demonstrate that horizontal radiation is an important factor that needs to be considered in modeling the canopy reflectance of row-planted crops. Hence, the refined four-stream radiative transfer model is applicable to the real world.

scholarly journals Radiative Transfer Modeling of Phytoplankton Fluorescence Quenching Processes

2018 ◽  
Vol 10 (8) ◽  
pp. 1309 ◽  
Author(s):  
Peng-Wang Zhai ◽  
Emmanuel Boss ◽  
Bryan Franz ◽  
P. Werdell ◽  
Yongxiang Hu
Keyword(s):  
Quantum Yield ◽  
Radiative Transfer ◽  
Sensitivity Study ◽  
Radiative Transfer Model ◽  
Photochemical Quenching ◽  
Transfer Model ◽  
Fluorescence Signal ◽  
New Space ◽  
Non Photochemical Quenching ◽  
Radiative Transfer Modeling

We report the first radiative transfer model that is able to simulate phytoplankton fluorescence with both photochemical and non-photochemical quenching included. The fluorescence source term in the inelastic radiative transfer equation is proportional to both the quantum yield and scalar irradiance at excitation wavelengths. The photochemical and nonphotochemical quenching processes change the quantum yield based on the photosynthetic active radiation. A sensitivity study was performed to demonstrate the dependence of the fluorescence signal on chlorophyll a concentration, aerosol optical depths and solar zenith angles. This work enables us to better model the phytoplankton fluorescence, which can be used in the design of new space-based sensors that can provide sufficient sensitivity to detect the phytoplankton fluorescence signal. It could also lead to more accurate remote sensing algorithms for the study of phytoplankton physiology.

scholarly journals Estimation of Needleleaf Canopy and Trunk Temperatures and Longwave Contribution to Melting Snow

2017 ◽  
Vol 18 (2) ◽  
pp. 555-572 ◽  
Author(s):  
K. N. Musselman ◽  
J. W. Pomeroy
Keyword(s):  
Energy Balance ◽  
Radiative Transfer ◽  
Thermal Inertia ◽  
Longwave Radiation ◽  
Ambient Air ◽  
Balance Model ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Individual Tree ◽  
Energy Balance Approach

AbstractA measurement and modeling campaign evaluated variations in tree temperatures with solar exposure at the edge of a forest clearing and how the resulting longwave radiation contributed to spatial patterns of snowmelt energy surrounding an individual tree. Compared to measurements, both a one-dimensional (1D) energy-balance model and a two-dimensional (2D) radial trunk heat transfer model that simulated trunk surface temperatures and thermal inertia performed well (RMSE and biases better than 1.7° and ±0.4°C). The 2D model that resolved a thin bark layer better simulated daytime temperature spikes. Measurements and models agreed that trunk surfaces returned to ambient air temperature values near sunset. Canopy needle temperatures modeled with a 1D energy-balance approach were within the range of measurements. The radiative transfer model simulated substantial tree-contributed snow surface longwave irradiance to a distance of approximately one-half the tree height, with higher values on the sun-exposed sides of the tree. Trunks had very localized and substantially lower longwave energy influence on snowmelt compared to that of the canopy. The temperature and radiative transfer models provide the spatially detailed information needed to develop scaling relationships for estimating net radiation for snowmelt in sparse and discontinuous forest canopies.

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