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Research article - Peer-reviewed, 2021

Retrieval and validation of forest background reflectivity from daily Moderate Resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF) data across European forests

Pisek, Jan; Erb, Angela; Korhonen, Lauri; Biermann, Tobias; Carrara, Arnaud; Cremonese, Edoardo; Cuntz, Matthias; Fares, Silvano; Gerosa, Giacomo; Gruenwald, Thomas; Hase, Niklas; Heliasz, Michal; Ibrom, Andreas; Knohl, Alexander; Kobler, Johannes; Kruijt, Bart; Lange, Holger; Leppänen, Leena; Limousin, Jean-Marc; Lopez Serrano, Francisco Ramo;
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Information about forest background reflectance is needed for accurate biophysical parameter retrieval from forest canopies (overstory) with remote sensing. Separating under- and overstory signals would enable more accurate modeling of forest carbon and energy fluxes. We retrieved values of the normalized difference vegetation index (NDVI) of the forest understory with the multi-angular Moderate Resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF)/albedo data (gridded 500 m daily Collection 6 product), using a method originally developed for boreal forests. The forest floor background reflectance estimates from the MODIS data were compared with in situ understory reflectance measurements carried out at an extensive set of forest ecosystem experimental sites across Europe. The reflectance estimates from MODIS data were, hence, tested across diverse forest conditions and phenological phases during the growing season to examine their applicability for ecosystems other than boreal forests. Here we report that the method can deliver good retrievals, especially over different forest types with open canopies (low foliage cover). The performance of the method was found to be limited over forests with closed canopies (high foliage cover), where the signal from understory becomes too attenuated. The spatial heterogeneity of individual field sites and the limitations and documented quality of the MODIS BRDF product are shown to be important for the correct assessment and validation of the retrievals obtained with remote sensing

Published in

2021, volume: 18, number: 2, pages: 621-635

Authors' information

Pisek, Jan
University of Tartu
Erb, Angela
University of Massachusetts
Korhonen, Lauri
University of Eastern Finland
Biermann, Tobias
Lund University
Carrara, Arnaud
Cremonese, Edoardo
Environmental Protection Agency of the Aosta Valley
Cuntz, Matthias
Universite de Lorraine
Fares, Silvano
University of Lorraine
Gerosa, Giacomo
Catholic University of the Sacred Heart
Gruenwald, Thomas
Technische Universitat Dresden
Hase, Niklas
Helmholtz Centre for Environmental Research (UFZ)
Heliasz, Michal
Lund University
Ibrom, Andreas
Technical University of Denmark
Knohl, Alexander
University of Gottingen
Kobler, Johannes
Environm Agcy Austria
Kruijt, Bart
Wageningen University and Research
Lange, Holger
Norwegian Inst Bioecon Res
Leppänen, Leena
Finnish Meteorological Institute
Limousin, Jean-Marc
Univ Montpellier
Lopez Serrano, Francisco Ramo
University of Castilla-La Mancha
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UKÄ Subject classification

Geosciences, Multidisciplinary

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