Atmospheric Methane at Cape Meares, Oregon, U.S.A.: A High-Resolution Data Base for the Period 1979-1992
M. A. K. Khalil and R. A. Rasmussen
This data base presents continuous automated atmospheric methane (CH4) measurements taken at the atmospheric monitoring facility in Cape Meares, Oregon, by the Oregon Graduate Institute of Science and Technology. The Cape Meares data represent some 119,000 individual atmospheric methane measurements carried out during 1979-1992. Analysis of ambient air (collected 12 to 72 times daily) was carried out by means of an automated sampling and measurement system, using the method of gas chromatography and flame ionization detection. Despite the long course of the record and the large number of individual measurements, these data may all be linked to a single absolute calibration standard.
The data are contained in three files. The largest file (2.14 MB) contains all individual atmospheric methane measurements, collected at Cape Meares over the period January 1979-January 1992. A second file (189 kB) contains daily average concentrations of methane, sampling statistics, and interpolations for days when data were not taken. The last file (10 kB) contains monthly averages (derived from the individual and daily data) and statistics of dispersion, calculated by three different methods: the arithmetic mean (along with 90% confidence limits), the median (along with 5th and 95th percentile values), and a middle value (also with accompanying 90% confidence limits) based on a non-parametric statistical method.