Bidirectional Polarized Reflectance Factors of Vegetation Covers: Influence on the BRF Models Results

Sun, Zhongqiu; Wu, Di; Lv, Yuguang; Zhao, Yunsheng

doi:10.1109/tgrs.2017.2712137

Cited by 11 publications

(5 citation statements)

References 69 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Moreover, field measurements of vertical profiles of mean flux density are also necessary for a better understanding of the influence of leaf specular reflection, as well as for further validations and applications of the improved SRTM. It should be noted that many empirical and theoretical analyses show that leaf specular reflection is partly polarized, whereas the leaf diffuse scattering is not [38][39][40][41]. Polarization measurement can, thus, be useful for a full understanding of leaf specular reflection and its influences in the remote sensing community [42,43].…”

Section: Discussionmentioning

confidence: 99%

Influence of Leaf Specular Reflection on Canopy Radiative Regime Using an Improved Version of the Stochastic Radiative Transfer Model

et al. 2018

View full text Add to dashboard Cite

Interpreting remotely-sensed data requires realistic, but simple, models of radiative transfer that occurs within a vegetation canopy. In this paper, an improved version of the stochastic radiative transfer model (SRTM) is proposed by assuming that all photons that have not been specularly reflected enter the leaf interior. The contribution of leaf specular reflection is considered by modifying leaf scattering phase function using Fresnel reflectance. The canopy bidirectional reflectance factor (BRF) estimated from this model is evaluated through comparisons with field-measured maize BRF. The result shows that accounting for leaf specular reflection can provide better performance than that when leaf specular reflection is neglected over a wide range of view zenith angles. The improved version of the SRTM is further adopted to investigate the influence of leaf specular reflection on the canopy radiative regime, with emphases on vertical profiles of mean radiation flux density, canopy absorptance, BRF, and normalized difference vegetation index (NDVI). It is demonstrated that accounting for leaf specular reflection can increase leaf albedo, which consequently increases canopy mean upward/downward mean radiation flux density and canopy nadir BRF and decreases canopy absorptance and canopy nadir NDVI when leaf angles are spherically distributed. The influence is greater for downward/upward radiation flux densities and canopy nadir BRF than that for canopy absorptance and NDVI. The results provide knowledge of leaf specular reflection and canopy radiative regime, and are helpful for forward reflectance simulations and backward inversions. Moreover, polarization measurements are suggested for studies of leaf specular reflection, as leaf specular reflection is closely related to the canopy polarization.

show abstract

Section: Discussionmentioning

confidence: 99%

Influence of Leaf Specular Reflection on Canopy Radiative Regime Using an Improved Version of the Stochastic Radiative Transfer Model

et al. 2018

View full text Add to dashboard Cite

show abstract

“…Spectral reflection has an average relative uncertainty of 1%, which is effective in the wavelength range of 400–2300 nm. NENULGS has been used to measure the optical properties of leaves and vegetation covers (Sun, Peng, Wu, & Lv, ; Sun, Wu, Lv, & Zhao, ; Sun, Wu, Lv, & Zhao, ; Sun, Wu, & Zhao, ).…”

Section: Methodsmentioning

confidence: 99%

“…NENULGS has been used to measure the optical properties of leaves and vegetation covers (Sun, Peng, Wu, & Lv, 2018;Sun, Wu, Lv, & Zhao, 2017a;Sun, Wu, Lv, & Zhao, 2017b;Sun, Wu, & Zhao, 2018).…”

Section: Multiangle Spectral Reflection Measurementsmentioning

confidence: 99%

Estimation of the leaf chlorophyll content using multiangular spectral reflectance factor

Sun

et al. 2019

Plant Cell & Environment

Self Cite

View full text Add to dashboard Cite

Chlorophyll is one of the primary pigments of plant leaves, and changes in its content can be used to characterize the physiological status of plants. Spectral indices have been devised and validated for estimating leaf chlorophyll content (LCC). However, most of the existing spectral indices do not consider the influence of angular reflection on the accuracy of the LCC estimation. In this study, the spectral reflectance factors of leaves from three plant species were measured from several observations in the principal plane. The relationship between the existing spectral indices and the LCC from different directions suggests that the directional reflection of a leaf surface impacts the accuracy of its LCC estimation. Subsequently, the ratio of reflectance differences, that is, the modified Datt index, was tested to reduce the directional reflection effect when predicting LCC. Our results indicated that the modified Datt index not only estimated LCC with high accuracy for all observation directions and plant species but also consistently predicted the LCC of each species in individual observation directions. Our method opens the possibility for optical detection of LCC using multiangular spectral reflection, which is convenient for plant science studies focused on the variation in LCC.

show abstract

“…Assuming the Landsat pixel number of land cover type C is n, then the relationship between all Landsat and MODIS pixel reflectance of land cover type C can be described as (3), and the relationship between Landsat and MODIS average reflectance of land cover type C can be described as (4…”

Section: Sensor-bias Adjustmentmentioning

confidence: 99%

“…The surface reflectance, which characterizes the ability of the land surface to reflect solar and sky radiation pertaining to vegetation cover, soil moisture and surface roughness [1][2][3], is a valuable indicator for recognizing ground objects [4,5] and retrieving biophysical variables, e.g., vegetation indices (VIs) [6,7], leaf area index (LAI) [8,9] and biomass [10,11]. The requirement for reflectance data with both high spatial and temporal resolution is increasingly important to simulate the surface energy budget [12][13][14] and monitor ecosystem and hydrologic dynamics [15][16][17][18] at regional and global scales.…”

Section: Introductionmentioning

confidence: 99%

A Robust Method for Generating High-Spatiotemporal-Resolution Surface Reflectance by Fusing MODIS and Landsat Data

et al. 2020

View full text Add to dashboard Cite

The methods for accurately fusing medium- and high-spatial-resolution satellite reflectance are vital for monitoring vegetation biomass, agricultural irrigation, ecological processes and climate change. However, the currently existing fusion methods cannot accurately capture the temporal variation in reflectance for heterogeneous landscapes. In this study, we proposed a new method, the spatial and temporal reflectance fusion method based on the unmixing theory and a fuzzy C-clustering model (FCMSTRFM), to generate Landsat-like time-series surface reflectance. Unlike other data fusion models, the FCMSTRFM improved the similarity of pixels grouped together by combining land cover maps and time-series data cluster algorithms to define endmembers. The proposed method was tested over a 2000 km2 study area in Heilongjiang Provence, China, in 2017 and 2018 using ten images. The results show that the accuracy of the FCMSTRFM is better than that of the popular enhanced spatial and temporal adaptive reflectance fusion model (ESTARFM) (correlation coefficient (R): 0.8413 vs. 0.7589; root mean square error (RMSE): 0.0267 vs. 0.0401) and the spatial-temporal data fusion approach (STDFA) (R: 0.8413 vs. 0.7666; RMSE: 0.0267 vs. 0.0307). Importantly, the FCMSTRFM was able to maintain the details of temporal variations in complicated landscapes. The proposed method provides an alternative method to monitor the dynamics of land surface variables over complicated heterogeneous regions.

show abstract

Bidirectional Polarized Reflectance Factors of Vegetation Covers: Influence on the BRF Models Results

Cited by 11 publications

References 69 publications

Influence of Leaf Specular Reflection on Canopy Radiative Regime Using an Improved Version of the Stochastic Radiative Transfer Model

Influence of Leaf Specular Reflection on Canopy Radiative Regime Using an Improved Version of the Stochastic Radiative Transfer Model

Estimation of the leaf chlorophyll content using multiangular spectral reflectance factor

A Robust Method for Generating High-Spatiotemporal-Resolution Surface Reflectance by Fusing MODIS and Landsat Data

Contact Info

Product

Resources

About