FAPAR
Encyclopedia
The Fraction of Absorbed Photosynthetically Active Radiation (FAPAR, sometimes also noted fAPAR or fPAR) is the fraction of the incoming solar radiation in the Photosynthetically Active Radiation
spectral region that is absorbed by a photosynthetic organism
. This biophysical variable is directly related to the primary productivity of photosynthesis and some models use it to estimate the assimilation of carbon dioxide in vegetation.
FAPAR can be derived from space measurements in the solar spectral range and a number of state of the art algorithm
s have been proposed to estimate this important environmental variable. FAPAR can also be used as an indicator of the state and evolution of the vegetation cover; with this function, it advantageously replaces the Normalized Difference Vegetation Index
(NDVI), provided it is itself properly estimated. Currently, there are some remote sensing products of FAPAR, such as AVHRR and MODIS.
FAPAR is one of the 50 Essential Climate Variables recognized by the UN Global Climate Observing System
(GCOS) as necessary to characterize the climate of the Earth. GCOS has issued specific recommendations to monitor this variable systematically, both through a reanalysis of existing databases and in the future with current and forthcoming instruments.
Photosynthetically active radiation
Photosynthetically active radiation, often abbreviated PAR, designates the spectral range of solar radiation from 400 to 700 nanometers that photosynthetic organisms are able to use in the process of photosynthesis. This spectral region corresponds more or less with the range of light visible to...
spectral region that is absorbed by a photosynthetic organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
. This biophysical variable is directly related to the primary productivity of photosynthesis and some models use it to estimate the assimilation of carbon dioxide in vegetation.
FAPAR can be derived from space measurements in the solar spectral range and a number of state of the art algorithm
Algorithm
In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...
s have been proposed to estimate this important environmental variable. FAPAR can also be used as an indicator of the state and evolution of the vegetation cover; with this function, it advantageously replaces the Normalized Difference Vegetation Index
Normalized Difference Vegetation Index
The Normalized Difference Vegetation Index is a simple graphical indicator that can be used to analyze remote sensing measurements, typically but not necessarily from a space platform, and assess whether the target being observed contains live green vegetation or not.-Brief history:The exploration...
(NDVI), provided it is itself properly estimated. Currently, there are some remote sensing products of FAPAR, such as AVHRR and MODIS.
FAPAR is one of the 50 Essential Climate Variables recognized by the UN Global Climate Observing System
Global Climate Observing System
The Global Climate Observing System is an international institution co-sponsored by the World Meteorological Organization , the Intergovernmental Oceanographic Commission of UNESCO, the United Nations Environment Programme , and the International Council for Science...
(GCOS) as necessary to characterize the climate of the Earth. GCOS has issued specific recommendations to monitor this variable systematically, both through a reanalysis of existing databases and in the future with current and forthcoming instruments.