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Atmospheric methane at Cape Meares - Analysis of a high-resolution data base and its environmental implicationsBetween 1979 and 1992 we took some 120,000 measurements of atmospheric methane at Cape Meares on the Oregon coast. The site is representative of methane concentrations in the northern latitudes (from 30 deg N to 90 deg N). The average concentration during the experiment was 1698 parts per billion by volume (ppbv). Methane concentration increased by 190 ppbv (or 11.9 percent) during the 13-year span of the experiment. The rate of increase was about 20 +/- 4 ppbv/yr in the first 2 yr and 10 +/- 2 ppbv/yr in the last 2 yr of the experiment, suggesting a substantial decline in the trend at northern middle and high latitudes. Prominent seasonal cycles were observed. During the year, the concentration stays more or less constant until May and then starts falling, reaching lowest levels in July and August, then rises rapidly to nearly maximum concentrations in October. Interannual variations with small amplitudes of 2-3 ppbv occur with periods of 1.4 and 6.5 yr.
Document ID
19930072129
Document Type
Reprint (Version printed in journal)
Authors
Khalil, M. A. K. (NASA Headquarters Washington, DC United States)
Rasmussen, R. A. (NASA Headquarters Washington, DC United States)
Moraes, F. (Oregon Graduate Inst. of Science and Technology Portland, United States)
Date Acquired
August 16, 2013
Publication Date
August 20, 1993
Publication Information
Publication: Journal of Geophysical Research
Volume: 98
Issue: D8
ISSN: 0148-0227
Subject Category
GEOPHYSICS
Funding Number(s)
CONTRACT_GRANT: NSF ATM-81-09047
CONTRACT_GRANT: NAG1-35
CONTRACT_GRANT: NAG1-160
CONTRACT_GRANT: NAGW-1348
CONTRACT_GRANT: DE-FG06-85ER-60313
Distribution Limits
Public
Copyright
Other