TY  - JOUR
AU  - Pisek, Jan
AU  - Erb, Angela
AU  - Korhonen, Lauri
AU  - Biermann, Tobias
AU  - Carrara, Arnaud
AU  - Cremonese, Edoardo
AU  - Cuntz, Matthias
AU  - Fares, Silvano
AU  - Gerosa, Giacomo
AU  - Grünwald, Thomas
AU  - Hase, Niklas
AU  - Heliasz, Michal
AU  - Ibrom, Andreas
AU  - Knohl, Alexander
AU  - Kobler, Johannes
AU  - Kruijt, Bart
AU  - Lange, Holger
AU  - Leppänen, Leena
AU  - Limousin, Jean-Marc
AU  - Serrano, Francisco Ramon Lopez
AU  - Loustau, Denis
AU  - Lukeš, Petr
AU  - Lundin, Lars
AU  - Marzuoli, Riccardo
AU  - Mölder, Meelis
AU  - Montagnani, Leonardo
AU  - Neirynck, Johan
AU  - Peichl, Matthias
AU  - Rebmann, Corinna
AU  - Rubio, Eva
AU  - Santos-Reis, Margarida
AU  - Schaaf, Crystal
AU  - Schmidt, Marius
AU  - Simioni, Guillaume
AU  - Soudani, Kamel
AU  - Vincke, Caroline
TI  - Retrieval and validation of forest background reflectivity from daily Moderate Resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF) data across European forests
JO  - Biogeosciences
VL  - 18
IS  - 2
SN  - 1726-4189
CY  - Katlenburg-Lindau [u.a.]
PB  - Copernicus
M1  - FZJ-2021-03851
SP  - 621 - 635
PY  - 2021
AB  - 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.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000613959500003
DO  - DOI:10.5194/bg-18-621-2021
UR  - https://juser.fz-juelich.de/record/901828
ER  -