Precise CO2 concentration
measurements at marine stations and tall towers are crucial for quantifying
global trends in atmospheric CO2 concentrations.
We propose that measurements in the continental planetary boundary layer—the
poor cousin of the clean background stations—can be used to understand trends
in, and controls, of atmospheric CO2 concentrations
at local and regional scales as well as global scales. The key is choosing
appropriate time scales of integration for the data. In the US Southern Great
Plains, we are measuring precise CO2 concentrations
continuously at 2–60 m and weekly at 300 and 3300 m above ground level (agl). CO2 flux is measured in individual crop fields and pastures (4 m
towers) and at 60 m. The precise CO2 concentrations
show strong continental influence in both diurnal and seasonal cycles. In
continental regions, atmospheric CO2 profiles are
strongly influenced by atmospheric dynamics as well as ecosystem and
anthropogenic fluxes. Relating site level measurements or atmospheric profiles
to regional CO2 budgets requires methods to represent or evaluate these
influences. We observe inter-annual differences in the
climatology of diurnal cycles (seasonal average diurnal cycles). Using the several years’ data for
boundary layer concentrations, the annual trend in CO2
growth nearly matches the value estimated by National Oceanic and
Atmospheric Administration (NOAA) Climate Monitoring Diagnostic
Laboratory for our latitude band.
Author: M.S. Torn, M.L. Fischer, S.C. Biraud, W.J. Riley, et al (scbiraud at lbl dot gov)
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