Assessment of MODIS BRDF/Albedo Model Parameters (MCD43A1 Collection 6) for Directional Reflectance Retrieval

Abstract

Measurements of solar radiation reflected from Earth's surface are the basis for calculating albedo, vegetation indices, and other terrestrial attributes. However, the "bi-directional" geometry of illumination and viewing (i.e., the Bi-directional Reflectance Distribution Function (BRDF)) impacts reflectance and all variables derived or estimated based on these data. The recently released MODIS BRDF/Albedo Model Parameters (MCD43A1 Collection 6) dataset enables retrieval of directional reflectance at arbitrary solar and viewing angles, potentially increasing precision and comparability of data collected under different illumination and observation geometries. We quantified the ability of MCD43A1 Collection 6 for retrieving directional reflectance and compared the daily Collection 6 retrievals to those of MCD43A1 Collection 5, which are retrieved on an eight-day basis. Correcting MODIS-based estimates of surface reflectance from the illumination and viewing geometry of the Terra satellite (MOD09GA) to that of the MODIS Aqua (MYD09GA) overpass, as well as MCD43A4 Collection 6 and Landsat-5 TM images show that the BRDF correction of MCD43A1 Collection 6 results in greater consistency among datasets, with higher R 2 (0.63-0.955), regression slopes closer to unity (0.718-0.955), lower root mean squared difference (RMSD) (0.422-3.142), and lower mean absolute error (MAE) (0.282-1.735) compared to the Collection 5 data. Smaller levels of noise (observed as high-frequency variability within the time series) in MCD43A1 Collection 6 in comparison to Collection 5 corroborates the improvement of BRDF parameters time series. These results corroborates that the daily MCD43A1 Collection 6 product represents the anisotropy of surface features and results in more precise directional reflectance derivation at any solar and viewing geometry than did the previous Collection 5.

Winter snow and spring temperature have differential effects on vegetation phenology and productivity across Arctic plant communities

“…Vegetation phenology and productivity metrics were calculated from the Normalized Difference Vegetation Index (NDVI; Rouse et al, 1973; Tucker, 1979). Daily NDVI values from 2001 to 2017 were derived from the MODIS nadir BRDF‐Adjusted Reflectance (NBAR) data product (MCD43A4 Collection 6) at 500 m spatial resolution (Che et al, 2017). Although the MCD43A4 input is smoothed with a 16‐day kernel to minimize anisotropic and other high‐frequency noise, residual effects of cloud contamination, atmospheric variability, and model error can disturb time‐series analysis of NDVI data (Atkinson et al, 2012; Che et al, 2017).…”

“…Daily NDVI values from 2001 to 2017 were derived from the MODIS nadir BRDF‐Adjusted Reflectance (NBAR) data product (MCD43A4 Collection 6) at 500 m spatial resolution (Che et al, 2017). Although the MCD43A4 input is smoothed with a 16‐day kernel to minimize anisotropic and other high‐frequency noise, residual effects of cloud contamination, atmospheric variability, and model error can disturb time‐series analysis of NDVI data (Atkinson et al, 2012; Che et al, 2017). Therefore, a Savitsky–Golay filter (Savitzky & Golay, 1964) was applied to the NDVI time series to further remove noise.…”

Relationship between Spatiotemporal Variations of Climate, Snow Cover and Plant Phenology over the Alps—An Earth Observation-Based Analysis

“…The effect of the relief on the NDVI metric was thus assumed negligible. In order to reduce Bidirectional Reflectance Distribution Function (BRDF) effects due to different overpass times, only the Terra acquisitions were used [89]. Further BRDF corrections were not conducted in order not to exclude observation for which the BRDF modeling would fail.…”

Analysis of Accuracy of Modis BRDF Product (Mcd43 C6) Based on Misr Land Surface BRF Product – A Case Study of the Central Part of Northeast Asia

“…This provides the possibility of testing extrapolating accuracy of MCD43A1 BRDF model in these crucial observation geometries. In contrast, results of analysis based on Aqua/MODIS and Landsat data (Che et al, 2017) can only represent the performance of MCD43A1 C6 BRDF model in the directions of cross orbit or cross principal plane. From this perspective, results of this paper complement a larger part of the whole picture of testing MCD43A1 C6 BRDF model in hemisphere space of observation.…”

“…Independent validation of MCD43A1 C6 is just beginning. The performance of MCD43A1 C6 was evaluated using Landsat data and MODIS surface reflectances from both Terra and Aqua satellite (Che et al, 2017). Though their conclusions are convincing, their results cannot represent the performance of MCD43A1 C6 model in the directions along the sub-satellite track, particularly within principal plane and its vicinity.…”