In:
Biogeosciences, Copernicus GmbH, Vol. 15, No. 17 ( 2018-09-06), p. 5395-5413
Abstract:
Abstract. We develop and evaluate a method to estimate O3
deposition and stomatal O3 uptake across networks of eddy
covariance flux tower sites where O3 concentrations and
O3 fluxes have not been measured. The method combines standard
micrometeorological flux measurements, which constrain O3
deposition velocity and stomatal conductance, with a gridded dataset of
observed surface O3 concentrations. Measurement errors are
propagated through all calculations to quantify O3 flux
uncertainties. We evaluate the method at three sites with O3 flux
measurements: Harvard Forest, Blodgett Forest, and Hyytiälä Forest.
The method reproduces 83 % or more of the variability in daily stomatal
uptake at these sites with modest mean bias (21 % or less). At least
95 % of daily average values agree with measurements within a factor of 2
and, according to the error analysis, the residual differences from measured
O3 fluxes are consistent with the uncertainty in the
underlying measurements. The product, called synthetic O3 flux or SynFlux, includes 43
FLUXNET sites in the United States and 60 sites in Europe, totaling 926 site
years of data. This dataset, which is now public, dramatically expands the
number and types of sites where O3 fluxes can be used for ecosystem
impact studies and evaluation of air quality and climate models. Across these
sites, the mean stomatal conductance and O3 deposition velocity is
0.03–1.0 cm s−1. The stomatal O3 flux during the growing
season (typically April–September) is 0.5–11.0 nmol
O3 m−2 s−1 with a mean of 4.5 nmol
O3 m−2 s−1 and the largest fluxes generally occur where
stomatal conductance is high, rather than where O3 concentrations
are high. The conductance differences across sites can be explained by
atmospheric humidity, soil moisture, vegetation type, irrigation, and land
management. These stomatal fluxes suggest that ambient O3 degrades
biomass production and CO2 sequestration by 20 %–24 % at
crop sites, 6 %–29 % at deciduous broadleaf forests, and
4 %–20 % at evergreen needleleaf forests in the United States and
Europe.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-15-5395-2018
DOI:
10.5194/bg-15-5395-2018-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2018
detail.hit.zdb_id:
2158181-2
