The growth rate and distribution of atmospheric methane
- NOAA, Boulder, CO (United States)
Methane was measured in air samples collected approximately weekly from a globally distributed network of sites from 1983 to 1992. Sites range in latitude from 90 deg S to 82 deg N. All samples were analyzed by gas chromatography, with flame ionization detection at the National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostics Laboratory in Boulder, Colorado, and the measurements were referenced against a single calibration scale. The estimated precision of the measurements is +/- 0.2%. Samples which had clear sampling or analytical errors, or which appeared to be contaminated by local CH4 sources, were identified and excluded from the data analysis. The data reveal a strong north-south gradient in methane with an annual mean difference of about 140 ppb between the northernmost and southernmost sampling sites. Methane time series the high southern latitude sites have a relatively simple seasonal cycle with a minimum during late summer-early fall, almost certainly dominated by the seasonality in its photochemical destruction. Typical seasonal cycle amplitudes there are about 30 ppb. Seasonal cycles at sites in the northern hemisphere are complex when compared to sites in the southern hemisphere due to the interaction among CH4 sources and sinks, and atmospheric transport. Seasonal cycle amplitudes in the high north are about twice those observed in the high southern hemisphere. Annual mean methane mixing ratios were approximately 1% lower at 3397 m than at sea level on the island of Hawaii. Trends were determined at each site in the network and globally.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 57377
- Journal Information:
- Journal of Geophysical Research, Vol. 99, Issue D8; Other Information: PBD: Aug 1994
- Country of Publication:
- United States
- Language:
- English
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