An Extended 3-D Radiosity–Graphics Combined Model for Studying Thermal-Emission Directionality of Crop Canopy

Liu, Qinhuo; Huang, Huaguo; Qin, Wei; Fu, Kaihua; Li, Xiaowen

doi:10.1109/tgrs.2007.902272

Cited by 51 publications

(31 citation statements)

References 43 publications

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“…kB −1 > 0), except for bare soils for which negative values of kB −1 have been found (see Verhoef et al, 1997). Small negative values have also been found for tall, dense canopies (Liu et al, 2007a;Jia, 2004). Values for closed canopies are usually around 2, but kB −1 increases for sparse canopies (up to 15 for very sparse canopies), Values of kB −1 > 8 are therefore deemed too large for the maize crop with LAI = 3.7 m 2 m −2 .…”

Section: Roughness Heightsmentioning

confidence: 90%

“…This low value is attributed to the height of the canopy. In high, dense vegetation the incoming radiation only affects the leaf temperature in the upper part of the canopy; in the lower region the radiation is absorbed too much to play a significant role in the temperatures of the leaves (Liu et al, 2007a;Jia, 2004). However, these leaves or twigs still play a role as part of the sink for momentum.…”

Section: Roughness Heightsmentioning

confidence: 99%

“…The evaporative fraction is calculated by SEBS at the time of overpass and considered constant during the rest of the day. However, several researchers have reported a diurnal dependence of the evaporative fraction (Li et al, 2008;Farah et al, 2004;Lu and Zhuang, 2010). Combining SCOPE and SEBS allows us to investigate not only the diurnal pattern of EF, but also the uncertainties of EF at overpass time and the daily average of EF.…”

Section: Evaporative Fractionmentioning

confidence: 99%

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Quantifying the uncertainty in estimates of surface–atmosphere fluxes through joint evaluation of the SEBS and SCOPE models

Timmermans

Tol

et al. 2013

Hydrol. Earth Syst. Sci.

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Abstract. Accurate estimation of global evapotranspiration is considered to be of great importance due to its key role in the terrestrial and atmospheric water budget. Global estimation of evapotranspiration on the basis of observational data can only be achieved by using remote sensing. Several algorithms have been developed that are capable of estimating the daily evapotranspiration from remote sensing data. Evaluation of remote sensing algorithms in general is problematic because of differences in spatial and temporal resolutions between remote sensing observations and field measurements. This problem can be solved in part by using soilvegetation-atmosphere transfer (SVAT) models, because on the one hand these models provide evapotranspiration estimations also under cloudy conditions and on the other hand can scale between different temporal resolutions.In this paper, the Soil Canopy Observation, Photochemistry and Energy fluxes (SCOPE) model is used for the evaluation of the Surface Energy Balance System (SEBS) model. The calibrated SCOPE model was employed to simulate remote sensing observations and to act as a validation tool. The advantages of the SCOPE model in this validation are (a) the temporal continuity of the data, and (b) the possibility of comparing different components of the energy balance. The SCOPE model was run using data from a whole growth season of a maize crop.It is shown that the original SEBS algorithm produces large uncertainties in the turbulent flux estimations caused by parameterizations of the ground heat flux and sensible heat flux. In the original SEBS formulation the fractional vegetation cover is used to calculate the ground heat flux. As this variable saturates very fast for increasing leaf area index (LAI), the ground heat flux is underestimated. It is shown that a parameterization based on LAI reduces the estimation error over the season from RMSE = 25 W m −2 to RMSE = 18 W m −2 . In the original SEBS formulation the roughness height for heat is only valid for short vegetation. An improved parameterization was implemented in the SEBS algorithm for tall vegetation. This improved the correlation between the latent heat flux predicted by the SEBS and the SCOPE algorithm from −0.05 to 0.69, and led to a decrease in difference from 123 to 94 W m −2 for the latent heat flux, with SEBS latent heat being consistently lower than the SCOPE reference. Lastly the diurnal stability of the evaporative fraction was investigated.

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Section: Roughness Heightsmentioning

confidence: 90%

Section: Roughness Heightsmentioning

confidence: 99%

Section: Evaporative Fractionmentioning

confidence: 99%

See 1 more Smart Citation

Quantifying the uncertainty in estimates of surface–atmosphere fluxes through joint evaluation of the SEBS and SCOPE models

Timmermans

Tol

et al. 2013

Hydrol. Earth Syst. Sci.

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show abstract

“…To simulate the combined effects of heterogeneous terrain and complex vegetation composition on MODIS or MISR BRDF products, RT models are expected to contend with a domain (or scene) size greater than 0.5 km. Although many 3D models may simulate such a large scene, there are very few that are specifically optimized to cope RAPID is a radiosity-based model using computer graphics methods to compute RT within and above 3D vegetated scenes from visible/near infrared (VNIR, 0.47-2.5 µm) [16] to thermal infrared (TIR, 8-14 µm) [32], and microwave (MV, 2.5-30 cm) parts [33] of the electromagnetic spectrum [16,33].…”

Section: Introductionmentioning

confidence: 99%

“…The traditional radiosity methods [32] use planar surfaces to create the 3D scene and solve the RT in VNIR and TIR as follows:…”

Section: Introductionmentioning

confidence: 99%

Accelerated RAPID Model Using Heterogeneous Porous Objects

Huang

2018

Remote Sensing

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Abstract:To enhance the capability of three-dimensional (3D) radiative transfer models at the kilometer scale (km-scale), the radiosity applicable to porous individual objects (RAPID) model has been upgraded to RAPID3. The major innovation is that the homogeneous porous object concept (HOMOBJ) used for a tree crown scale is extended to a heterogeneous porous object (HETOBJ) for a forest plot scale. Correspondingly, the radiosity-graphics-combined method has been extended from HOMOBJ to HETOBJ, including the random dynamic projection algorithm, the updated modules of view factors, the single scattering estimation, the multiple scattering solutions, and the bidirectional reflectance factor (BRF) calculations. Five cases of the third radiation transfer model intercomparison (RAMI-3) have been used to verify RAPID3 by the RAMI-3 online checker. Seven scenes with different degrees of topography (valleys and hills) at 500 m size have also been simulated. Using a personal computer (CPU 2.5 GHz, memory 4 GB), the computation time of BRF at 500 m is only approximately 13 min per scene. The mean root mean square error is 0.015. RAPID3 simulated the enhanced contrast of BRF between backward and forward directions due to topography. RAPID3 has been integrated into the free RAPID platform, which should be very useful for the remote sensing community. In addition, the HETOBJ concept may also be useful for the speedup of ray tracing models.

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The fourth radiation transfer model intercomparison (RAMI‐IV): Proficiency testing of canopy reflectance models with ISO‐13528

et al. 2013

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[1] The radiation transfer model intercomparison (RAMI) activity aims at assessing the reliability of physics-based radiative transfer (RT) models under controlled experimental conditions. RAMI focuses on computer simulation models that mimic the interactions of radiation with plant canopies. These models are increasingly used in the development of satellite retrieval algorithms for terrestrial essential climate variables (ECVs). Rather than applying ad hoc performance metrics, RAMI-IV makes use of existing ISO standards to enhance the rigor of its protocols evaluating the quality of RT models. ISO-13528 was developed "to determine the performance of individual laboratories for specific tests or measurements." More specifically, it aims to guarantee that measurement results fall within specified tolerance criteria from a known reference. Of particular interest to RAMI is that ISO-13528 provides guidelines for comparisons where the true value of the target quantity is unknown. In those cases, "truth" must be replaced by a reliable "conventional reference value" to enable absolute performance tests. This contribution will show, for the first time, how the ISO-13528 standard developed by the chemical and physical measurement communities can be applied to proficiency testing of computer simulation models.Step by step, the pre-screening of data, the identification of reference solutions, and the choice of proficiency statistics will be discussed and illustrated with simulation results from the RAMI-IV "abstract canopy" scenarios. Detailed performance statistics of the participating RT models will be provided and the role of the accuracy of the reference solutions as well as the choice of the tolerance criteria will be highlighted.

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An Extended 3-D Radiosity–Graphics Combined Model for Studying Thermal-Emission Directionality of Crop Canopy

Cited by 51 publications

References 43 publications

Quantifying the uncertainty in estimates of surface–atmosphere fluxes through joint evaluation of the SEBS and SCOPE models

Quantifying the uncertainty in estimates of surface–atmosphere fluxes through joint evaluation of the SEBS and SCOPE models

Accelerated RAPID Model Using Heterogeneous Porous Objects

The fourth radiation transfer model intercomparison (RAMI‐IV): Proficiency testing of canopy reflectance models with ISO‐13528

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