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Parameterization of PAR vertical profile within horizontally uniform forest canopies for use in environmental modeling
Author(s) -
Lalic Branislava,
Firanj Ana,
Mihailovic Dragutin T.,
Podrascanin Zorica
Publication year - 2013
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/jgrd.50626
Subject(s) - canopy , atmospheric sciences , environmental science , photosynthetically active radiation , amazonian , tree canopy , earth's energy budget , microclimate , radiation , geography , physics , ecology , amazon rainforest , optics , photosynthesis , botany , archaeology , biology
The radiation transfer within the forest canopy plays crucial role in energy balance and turbulent transfer processes. Objective of this study is to suggest a new relation for vertical profile of photosynthetically active radiation (PAR) in case of horizontally uniform forest canopy. It is based on (i) the Lambert‐Beer law relationship and (ii) new parameterization of leaf area density ( LAD ) profile. We have supposed that absorption coefficient μ varies with height and depends on LAD distribution. To check validity of the relation proposed, we have compared calculated values with the observations using data sets assimilated during Anglo‐Brazilian Amazonian Climate Observation Study experiment at two observational sites located in Reserva Jaru and Reserva Ducke (Brazil) with different types of forest. Among all available measurements, 615 profiles observed between 08 and 18 local mean time for 72 days at 2 locations were selected. For comparison study, two more profiles based on constant‐ and variable‐ LAD approximation were introduced. Obtained results indicate that suggested relation: (i) well reproduces PAR profile within the forest in comparison with observations and (ii) shows better agreement with observations in comparison with two other profiles used in this study.