Quality Assessment of PROBA-V Surface Albedo V1 for the Continuity of the Copernicus Climate Change Service

Sánchez-Zapero, Jorge; Camacho, Fernando; Martínez-Sánchez, Enrique; Lacaze, Roselyne; Carrer, Dominique; Pinault, Florian; Benhadj, Iskander; Muñoz‐Sabater, Joaquín

doi:10.3390/rs12162596

Cited by 8 publications

(17 citation statements)

References 53 publications

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“…Our results agree with the previous hypothesis, and indeed, the lower temporal resolution of C3S and GLASS may be one of the reasons of the superior performance of MCD43C3 over snow. The overestimation of snow-free albedo against stations, and also compared to MCD43C3, was also reported by Lellouch et al [51] and Sánchez-Zapero et al [52], particularly at regions covered by forests [38]. Our results suggests that this positive bias might exist in all types of land cover, since none of the stations used were surrounded by forests.…”

Section: Discussionsupporting

confidence: 88%

“…C3S-v2 albedo improves during the snow-free season, reaching an accuracy level similar to that of MCD43C3, despite showing a small positive bias. C3S underestimation over snow was also observed by Song et al [19], Lellouch et al [51], Sánchez-Zapero et al [52] and Song et al [20], who suggested that the low temporal resolution and large compositing window hinder C3S capacity to detect snow events. Our results agree with the previous hypothesis, and indeed, the lower temporal resolution of C3S and GLASS may be one of the reasons of the superior performance of MCD43C3 over snow.…”

Section: Discussionmentioning

confidence: 56%

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Comparison of Long-Term Albedo Products against Spatially Representative Stations over Snow

et al. 2022

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Multiple satellite products are available to monitor the spatiotemporal dynamics of surface albedo. They are extensively assessed over snow-free surfaces but less over snow. However, snow albedo is critical for climate monitoring applications, so a better understating of the accuracy of these products over snow is needed. This work analyzes long-term (+20 years) products (MCD43C3 v6/v6.1, GLASS-AVHRR, C3S v1/v2) by comparing them against the 11 most spatially representative stations from FLUXNET and BSRN during the snow-free and snow-covered season. Our goal is to understand how the performance of these products is affected by different snow cover conditions to use this information in an upcoming product inter-comparison that extends the analysis spatially and temporally. MCD43C3 has the smallest bias during the snow season (−0.017), and more importantly, the most stable bias with different snow cover conditions. Both v6 and v6.1 have similar performance, with v6.1 just increasing slightly the coverage at high latitudes. On the contrary, the quality of both GLASS-AVHRR and C3S-v1/v2 albedo decreases over snow. Particularly, the bias of both products varies strongly with the snow cover conditions, underestimating albedo over snow and overestimating snow-free albedo. GLASS bias strongly increases during the melting season, which is most likely due to an artificially extended snow season. C3S-v2 has the largest negative bias overall over snow during both the AVHRR (−0.141) and SPOT/VGT (−0.134) period. In addition, despite the improvements from v1 to v2, C3S-v2 still is not consistent enough during the transition from AVHRR to SPOT/VGT.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 56%

Comparison of Long-Term Albedo Products against Spatially Representative Stations over Snow

et al. 2022

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“…The Spectral Response Function (SRF) of MODIS, SPOT-VGT, and PROBA-V indicates the difference of band location, band width, and response percentage of input signal over similar spectral channels [59]. Compared with SPOT and PROBA -V, the MODIS sensor has narrower band width, especially at NIR and SWIR bands [60], which may enhance the difference at NIR albedo band over the vegetation region during leaf-on season as presented in the results section, and can also propagate into other broadband albedo values. The SRF shape of MODIS and SPOT is close to "Gaussian distribution", while that of PROBA -V shows an asymmetric shape with higher response percentage at the lower or upper range of each spectral regime [14,59], while the SPOT/VGT and PROBA-V channels provide very similar spectral characteristics in the Blue, Red and NIR bands, but the PROBA-V spectral response in SWIR band is narrower than that of SPOT/VGT [14], which may be one of the reasons inducing the albedo difference of CGLS at NIR and SW bands from June 2014 (Figure 4(A1,A2,B1,B2,C1,C2,D1,D2)).…”

Section: Discussionmentioning

confidence: 99%

Cross-Comparison of Global Surface Albedo Operational Products-MODIS, GLASS, and CGLS

et al. 2021

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Surface albedo, as an important parameter for land surface geo-biophysical and geo-biochemical processes, has been widely used in the research communities involved in surface energy balance, weather forecasting, atmospheric circulation, and land surface process models. In recent years, operational products using satellite-based surface albedo have, from time to time, been rapidly developed, contributing significantly to the estimation of energy balance at regional or global scales. The increasing number of research topics on dynamic monitoring at a decades-long scale requires a combination of albedo products generated from various sensors or programs, while the quantitative assessment of agreement or divergence among different surface albedo products still needs further understanding. In this paper, we investigated the consistency of three classical operational surface albedo products that have been frequently used by researchers globally via the official issued datasets-MODIS, GLASS (Global LAnd Surface Satellite), and CGLS (Copernicus Global Land Service). The cross-comparison was performed on all the identical dates available during 2000–2017 to represent four season-phases. We investigated the pixel-based validity of each product, consistency of global annual mean, spatial distribution and different temporal dynamics among the discussed products in white-sky (WSA) and black-sky (BSA) albedo at visible (VIS), near-infrared (NIR), and shortwave (SW) regimes. Further, varying features along with the change of seasons was also examined. In addition, the variation in accuracy of shortwave albedo magnitude was explored using ground measurements collected by the Baseline Surface Radiation Network (BSRN) and the Surface Radiation Budget Network (SUFRAD). Results show that: (1) All three products can provide valid long-term albedo for dominant land surface, while GLASS can provide additional estimation over sea surfaces, with the highest percentage of valid land surface pixels, at up to 93% in 24 October. The invalid pixels mainly existed in the 50°N–60°N latitude belt in December for GLASS, Central Africa in April and August for MODIS, and northern high latitudes for CGLS. (2) The global mean albedo of CGLS at the investigated bands has significantly higher values than those of MODIS and GLASS, with a relative difference of ~20% among the three products. The global mean albedo of MODIS and GLASS show a generally increasing trend from April to December, with an abrupt rise at NIR and SW of CGLS in June of 2014. Compared with SW and VIS bands, the linear temporal trend of the NIR global albedo mean in three products continues to increase, but the slope of CGLS is 10–100 times greater than that of the other two products. (3) The differences in albedo, which are higher in April, October, and December than in August, exhibit a small variation over the main global land surface regions, except for Central Eurasia, North Africa, and middle North America. The magnitude of global absolute difference among the three products usually varies within 0.02–0.06, but with the largest value occasionally exceeding 0.1. The relative difference is mainly within 10–20%, and can deviate more than 40% away from the baseline. In addition, CGLS has a greater opportunity to achieve the largest difference compared with MODIS and GLASS. (4) The comparison with ground measurements indicates that MODIS generally performs better than GLASS and CGLS at the sites discussed. This study demonstrates that apparent differences exist among the three investigated albedo products due to the ingested source data, algorithm, atmosphere correction etc., and also points at caution regarding data fusion when multiple albedo products were organized to serve the following applications.

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“…Currently, surface albedo can be generated using the Bidirectional Reflectance Distribution Function (BRDF) with a kernel-driven model [18][19][20][21]. The short-period and multi-angle reflectance data required can be obtained from the MODerate Resolution Imaging Spectroradiometer (MODIS) [20], Polarization and Directionality of the Earth Reflectance (POLDER) [22], Visible Infrared Imaging Radiometer Suite (VIIRS) [23], Airborne Visible-InfraRed Imaging Spectrometer (AVIRIS) [24], VEGETATION (VGT) [25], PROBA-VEGETATION (PROBA-V) [25,26], or Spinning Enhanced Visible and Infrared Imagers (SEVIRI) [27]. However, these albedo products are too coarse to describe the detailed features of the surface, which hinders downstream calculations of surface processes such as land transformations [28], forest structure [29], fire extent and burn severity [30], and snow cover extent and melt [30][31][32].…”

Section: Introductionmentioning

confidence: 99%

An Algorithm for the Retrieval of High Temporal-Spatial Resolution Shortwave Albedo from Landsat-8 Surface Reflectance and MODIS BRDF

et al. 2021

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Variations in surface physicochemical properties and spatial structures can prominently transform surface albedo which conversely influence surface energy balances and global climate, making it crucial to continuously monitor and quantify surface dynamics at fine scales. Here, we made two improvements to propose an algorithm for the simultaneous retrieval of 30-m Landsat albedo, based on the coupling of Landsat-8 and MODIS BRDF. First, two kinds of prior knowledge were added to disaggregate BRDF, including the Anisotropic Flat Index (AFX) and the Albedo-to-Nadir reflectance ratio (AN ratio), from MODIS scales into Landsat scales. Second, a simplified data fusion method was used to simulate albedo for the same, subsequent, or antecedent dates. Finally, we validated the reliability and correlations of the algorithm at six sites of the Surface Radiation (SURFRAD) budget network and intercompared the results with another algorithm called the ‘concurrent approach’. The results showed that the proposed algorithm had favorable usability and robustness, with a root mean square error (RMSE) of 0.015 (8%) and a mean bias of −0.005; while the concurrent approach had a RMSE of 0.026 (14%) and a mean bias of −0.018. The results emphasized that the proposed algorithm has captured subtle changes in albedo over a 16-day period.

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Quality Assessment of PROBA-V Surface Albedo V1 for the Continuity of the Copernicus Climate Change Service

Cited by 8 publications

References 53 publications

Comparison of Long-Term Albedo Products against Spatially Representative Stations over Snow

Comparison of Long-Term Albedo Products against Spatially Representative Stations over Snow

Cross-Comparison of Global Surface Albedo Operational Products-MODIS, GLASS, and CGLS

An Algorithm for the Retrieval of High Temporal-Spatial Resolution Shortwave Albedo from Landsat-8 Surface Reflectance and MODIS BRDF

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