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Oxidized nitrogen and ozone interaction with forests. II: Multi‐layer process‐oriented modelling results and a sensitivity study for Douglas fir
Author(s) -
Duyzer J. H.,
Dorsey J. R.,
Gallagher M. W.,
Pilegaard K.,
Walton S.
Publication year - 2004
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1256/qj.03.125
Subject(s) - canopy , atmospheric sciences , environmental science , flux (metallurgy) , ozone , tree canopy , nitrogen , meteorology , ecology , chemistry , geography , geology , organic chemistry , biology
An existing process‐oriented multi‐layer canopy model is applied to data from an intensive NO x and O 3 surface exchange experiment, and a sensitivity study is conducted. The canopy was a mature 22.5 m Douglas fir stand. Comparison of measured data and model results shows that the model represents the concentration and fluxes of ozone well above the canopy, with adequate accuracy for concentration and fluxes below the canopy. A similar pattern is demonstrated for NO 2 concentration above and below a forest canopy, with the fluxes being calculated correctly to within at least an order of magnitude below the canopy, and more accurately above. The model can reproduce the processes leading to the observed NO 2 emission from forest stands. The sensitivity study demonstrates the complex interdependence of oxidized nitrogen flux controlling variables within the canopy, with NO 2 emission favoured by high NO soil emission and canopy resistance and by low global radiation, leaf area index and ambient NO 2 concentrations. Realistic alterations of these variables can cause reversal of the NO 2 flux, leading to an ‘ecosystem compensation point’ between 17 and 35 ppbv at night, and 5 to 10 ppbv during the day for the forest canopy investigated. This highlights our improved understanding of the controls on NO 2 flux, explaining and quantifying some previously reported reversals in NO 2 flux above forest canopies. The effect of soil NO emission on ozone flux is investigated. During the day, reaction with NO may account for only 10% of observed ozone deposition, however, at night, this figure can rise to around 50%. The effect of volatile organic compounds on forest ozone deposition was found not to be large. Copyright © 2004 Royal Meteorological Society.