Atmospheric Chemistry and Physics
www.atmos-chem-phys.net
1680-7316
1680-7324
7
14
2007
10.5194/acp-7-3737-2007
http://www.atmos-chem-phys.net/7/3737/2007/
http://www.atmos-chem-phys.net/7/3737/2007/acp-7-3737-2007.html
http://www.atmos-chem-phys.net/7/3737/2007/acp-7-3737-2007.pdf
3737
3747
2007-07-17
On using radon-222 and CO<sub>2</sub> to calculate regional-scale CO<sub>2</sub> fluxes
A. I. Hirsch
adam.hirsch@noaa.gov
Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA
NOAA/ESRL Global Monitoring Division, Boulder, Colorado, USA
Because of its ubiquitous release on land and well-characterized atmospheric
loss, radon-222 has been very useful for deducing fluxes of greenhouse gases
such as CO<sub>2</sub>, CH<sub>4</sub>, and N<sub>2</sub>O. It is shown here that the
radon-tracer method, used in previous studies to calculate regional-scale
greenhouse gas fluxes, returns a weighted-average flux (the flux field <i>F</i>
weighted by the sensitivity of the measurements to that flux field, <i>f</i>) rather
than an evenly-weighted spatial average flux. A synthetic data study using a
Lagrangian particle dispersion model and modeled CO<sub>2</sub> fluxes suggests
that the discrepancy between the sensitivity-weighted average flux and
evenly-weighted spatial average flux can be significant in the case of
CO<sub>2</sub>, due to covariance between <i>F</i> and <i>f</i> for biospheric CO<sub>2</sub> fluxes
during the growing season and also for anthropogenic CO<sub>2</sub> fluxes in
general. A technique is presented to correct the radon-tracer derived fluxes
to yield an estimate of evenly-weighted spatial average CO<sub>2</sub> fluxes. A
new method is also introduced for correcting the CO<sub>2</sub> flux estimates for
the effects of radon-222 radioactive decay in the radon-tracer method.
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