Editorial for Special Issue: “Remotely Sensed Albedo”

• Published in: Remote Sensing
• Main Authors: Roujean, Jean-Louis, Liang, Shunlin, He, Tao
• Other Authors: Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS), State Key Laboratory of Remote Sensing Science, School of Geography, Beijing Normal University (BNU), Centre Européen de Réalité Virtuelle (CERV), École Nationale d'Ingénieurs de Brest (ENIB)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: [SDU]Sciences of the Universe [physics]; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; [SDE]Environmental Sciences; Tundra
• Online Access: https://hal.science/hal-02354398; https://hal.science/hal-02354398/document; https://hal.science/hal-02354398/file/remotesensing-11-01941.pdf; https://doi.org/10.3390/rs11161941

International audience Land surface (bare soil, vegetation, and snow) albedo is an essential climate variable that affects the Earth's radiation budget, and therefore, is of vital interest for a broad number of applications: Thematic (urban, cryosphere, land cover, and bare soil), climate (Long Term Data Record), processing technics (gap filling, data merging), and products validation (cal/val). The temporal and spatial patterns of surface albedo variations can be retrieved from satellite observations after a series of processes, including atmospheric correction to surface spectral Bidirectional Reflectance Factor (BRF), and Bidirectional Reflectance Distribution Function (BRDF) modelling. The processing chain for deriving surface albedo introduces cumulative errors that can affect the accuracy of the retrieved satellite albedo products (MISR, MODIS, VEGETATION, and Proba-V). A new method is proposed to estimate Directional Hemispherical Reflectance (DHR) and Bi-Hemispherical Reflectance (BHR) from measured variables (downwelling, upwelling, and diffuse shortwave radiation) at 19 tower sites from the FLUXNET network, Surface Radiation Budget Network (SURFRAD), and Baseline Surface Radiation Network (BSRN) networks. The pixel-to-pixel comparison between DHR/BHR retrieved from coarse-resolution satellite observations and upscaled from tower sites from 2012 to 2016 emphasizes the parameters involved (land cover type, heterogeneity level, and instantaneous vs. time composite retrievals) [1]. Global warming effects pose a significant change in the albedo of the boreal forest areas as revealed by observed trends in AVHRR satellite albedo magnitude before and after the snow/ice melt season between 40 • N and 80 • N from 1982 to 2015. Absolute change is 4.4 albedo percentage units per 34 years. The largest changes in pre-melt-season albedo are concentrated in boreal forest, rather than tundra, and are consistent over large areas. The mean of absolute change of start date of the melt season is 11.2 days per 34 years, ...