Speculation on the origin of sub-baseline excursions of CH4 at Cape Grim
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Date
2016-01-01
Journal Title
Journal ISSN
Volume Title
Publisher
NOAA Earth System Research Laboratory
Abstract
The Advanced Global Atmospheric Gases Experiment (AGAGE) program has historically measured in situ
methane (CH4
) at Cape Grim via gas chromatography with flame ionization detection (GC-FID) in 40 minutely
grab samples. By adding continuous, high precision in situ measurements of CH4
(Picarro cavity ring-down
spectroscopy [CRDS]) at both Cape Grim, Tasmania, and Casey, Antarctica, a new feature has become apparent
in the Cape Grim CH4
record. During the austral summer (December to February), the Cape Grim CH4
record
periodically drops below baseline. For example, in Figure 1, a number of sustained episodes of depressed CH4
concentration can be seen below the baseline selected data shown in red. Notably, these episodes are also seen
in the GC-FID record.
In this presentation, we examine these sub-baseline excursions of CH4
. In conjunction with meteorology and a
variety of other chemical species measured at Cape Grim, including radon, ozone, hydrogen and ethane, we speculate on a number of possible mechanisms that might be responsible for these dips in CH4 mixing ratio.
Description
Keywords
Origin, Hydrogen, Ethane, Radon, Allocations, Ozone
Citation
Loh, Z. M., Krummel, P. B., Gregory, R. L., Steele, L. P., Stavert, A. R., Schoot, M. V. V. D., Spencer, D. A., Mitrevski, B., Thornton, D. P., Galbally, I. E., Ward, J. Z., Somerville, N. T., Chambers, S. D., & Williams, AG. (2016). Speculation on the origin of sub-baseline excursions of CH4 at Cape Grim. Paper presented at the 44th NOAA Global Monitoring Annual Conference, Boulder Colorado. Retrieved from http://www.esrl.noaa.gov/gmd/annualconference/agenda.php