Guo et al. (2025) Bidirectional Reflectance Sensitivity to Hemispherical Samplings: Implications for Snow Surface BRDF and Albedo Retrieval

Identification

• Journal: Remote Sensing
• Year: 2025
• Date: 2025-10-31
• Authors: Jing Guo, Ziti Jiao, Anxin Ding, Zhilong Li, Chenxia Wang, Fangwen Yang, Ge Gao, Zheyou Tan, Sizhe Chen, X. Dong
• DOI: 10.3390/rs17213614

Research Groups

• State Key Laboratory of Remote Sensing and Digital Earth, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China
• Institute of Remote Sensing Science and Engineering, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China
• School of Resources and environment engineering, Hefei University of Technology, Hefei 230009, China

Short Summary

This study systematically analyzes the sensitivity of snow surface Bidirectional Reflectance Distribution Function (BRDF) and albedo retrieval to different multi-angular sampling configurations. It proposes an Angular Information Index (AII) to quantify angular information content, demonstrating that sampling configuration significantly impacts BRDF and albedo accuracy, especially at longer wavelengths.

Objective

• To systematically analyze how different illuminating–viewing configurations (view zenith angle, relative azimuth angle, and solar zenith angle) influence snow surface BRDF and albedo retrieval results within a kernel-driven BRDF model framework.
• To propose an Angular Information Index (AII) by incorporating a weighting mechanism and information effectiveness to quantify the angular information content for various sampling distribution schemes.

Study Configuration

• Spatial Scale: Elson Lagoon (71°18′N, 156°24′W) in Barrow, Alaska, USA; Eastern Antarctic Plateau (75°06′N, 123°18′E).
• Temporal Scale: 7 April 2008 (CAR data from ARCTAS campaign); Austral summers of 2003–2004 and 2004–2005 (Dome-C data).

Methodology and Data

• Models used: RossThick-LiSparseReciprocal-Snow (RTLSRS) BRDF model, a semi-empirical kernel-driven model extended with a snow scattering kernel.
• Data sources:
  • Airborne Cloud Absorption Radiometer (CAR) multi-angular data (Level 1D product, 8 spectral bands from 339 nm to 2196 nm, view zenith angle (VZA) from -90° to 90° with 0.5° interval, relative azimuth angle (RAA) from 0° to 360° with 1° interval).
  • Tower-based Dome-C multi-angular data (FieldSpec Pro JR spectroradiometer, 350–2400 nm, VZA sampled at 15° intervals from ±7.5° to ±67.5°, RAA sampled at 15° intervals, solar zenith angle (SZA) from 51.57° to 86.56°).

Main Results

• The proposed Angular Information Index (AII) serves as a robust indicator for BRDF retrieval efficiency, with the RTLSRS model providing stable inversion when the AII value exceeds a threshold of -2.
• Different illuminating–observing sampling distribution schemes influence BRDF and albedo more significantly for longer wavelengths; relative differences in Black-Sky Albedo (BSA) and White-Sky Albedo (WSA) can reach up to 30% for longer wavelengths (e.g., 2196 nm), while mostly remaining within 5% for short bands.
• Observations with smaller VZA ranges can reconstruct BRDF shapes that amplify the anisotropic effect of snow, and forward scattering tends to be more pronounced at larger SZAs.
• The variations in BRDF shape reconstructed from off-principal plane (PP) observations depend on both wavelength and SZAs.
• WSA and BSA retrieved from observations under different actual illumination zenith angles (SZAi) show significant divergences. As SZAi increases from 51.57° to 86.56°, WSA decreases (relative differences of 4.14% to 29.24% across wavelengths), and BSA estimations exhibit an overall downward trend, more pronounced at longer wavelengths.

Contributions

• Proposed a novel Angular Information Index (AII) that quantifies the angular information content of multi-angular sampling schemes by incorporating a weighting mechanism (prioritizing principal plane observations) and information effectiveness (reducing redundancy via cosine similarity).
• Systematically investigated the impact of various angular sampling configurations (VZA, RAA, SZA) on snow surface BRDF and albedo retrieval accuracy using a kernel-driven model, specifically for snow-covered surfaces.
• Provided practical guidance for the design of future multi-angle sensors (e.g., emphasizing principal-plane coverage and azimuthal balance) and for evaluating the quality of multi-angular data before operational application.

Funding

• Major program of the National Natural Science Foundation of China (No. 42090013)
• General Program of the National Nature Science Foundation of China (No. 42471352)
• Open Fund of State Key Laboratory of Remote Sensing Science (Grant No. OFSLRSS202412)
• National Natural Science Foundation of China (No. 42301363, No. 42501422)
• Xiamen Natural Science Foundation Project (Grant 3502Z202473059)
• Beijing Natural Science Foundation (No. QY25415)

Citation

@article{Guo2025Bidirectional,
  author = {Guo, Jing and Jiao, Ziti and Ding, Anxin and Li, Zhilong and Wang, Chenxia and Yang, Fangwen and Gao, Ge and Tan, Zheyou and Chen, Sizhe and Dong, X.},
  title = {Bidirectional Reflectance Sensitivity to Hemispherical Samplings: Implications for Snow Surface BRDF and Albedo Retrieval},
  journal = {Remote Sensing},
  year = {2025},
  doi = {10.3390/rs17213614},
  url = {https://doi.org/10.3390/rs17213614}
}