Understanding the geographical distribution of
carbon uptake by the terrestrial biosphere is critical for predicting future
trends of atmospheric CO2.
With inverse techniques, atmospheric CO2 measurements can be
used to estimate this uptake. The results from this approach, however, depend
on the accuracy of the transport model(s).
Because of the covariance between the seasonally-varying biosphere
exchange and the strength of vertical mixing (the rectifier effect), using only
the surface CO2 observations for this analysis yields an inferred
carbon flux that is highly sensitive to the details of the boundary-layer
dynamics in the transport model [Gurney
et al., 2004]. One possible way to reduce the sensitivity of these
inversions to poorly-represented boundary-layer dynamics is to use CO2
vertical profiles (and/or column CO2 measurements) in addition to
surface observations. In theory, multi-level aircraft CO2
measurements from several well-positioned sites are capable of improving the
estimate of the true annual mean inter-hemisphere CO2 gradient and
thereby improving the estimate of the partitioning of carbon sinks between the
two hemispheres.
Author: Z. Yang, N. Krakauer, P. Wennberg, J. Randerson (yangzh at gps dot caltech dot edu)
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