Atmospheric Methane Mixing Ratios - The NOAA/CMDL Global Cooperative Air Sampling Network, 1983-1993
E. J. Dlugokencky, P. M. Lang, K. A. Masarie, and L. P. Steele
This data base presents atmospheric methane (CH4) mixing ratios from flask air samples collected over the period 1983-1993 by the National Oceanic and Atmospheric Administration, Climate Monitoring and Diagnostics Laboratory's (NOAA/CMDL's) global cooperative air sampling network. Air samples were collected approximately once per week at 44 fixed sites (37 of which were still active at the end of 1993). Samples were also collected at 5 degree latitude intervals along shipboard cruise tracks in the Pacific Ocean between North America and New Zealand (or Australia) and at 3 degree latitude intervals along cruise tracks in the South China Sea between Singapore and Hong Kong. The shipboard measurements were made approximately every 3 weeks per latitude zone by each of two ships in the Pacific Ocean and approximately once every week per latitude zone in the South China Sea. All samples were analyzed for CH4 at the NOAA/CMDL laboratory in Boulder, Colorado, by gas chromatography with flame ionization detection, and each aliquot was referenced to the NOAA/CMDL methane standard scale.
In addition to providing the complete set of atmospheric CH4 measurements from flask air samples collected at the NOAA/CMDL network sites, this data base also includes files which list monthly mean mixing ratios derived from the individual flask air measurements. These monthly summary data are available for 35 of the fixed sites and 21 of the shipboard sampling sites.
The data for the complete set of individual measurements are contained in 85 files, ranging in size from 2.7 kB to 187 kB and totaling 2.7 MB. Two additional files contain the monthly summary data.
One of these files (30.2 kB) contains all monthly mean methane values for NOAA/CMDL fixed monitoring sites. The second file (14.3 kB) contains all monthly mean methane values for NOAA/CMDL shipboard sites. An additional file (151.0 kB) contains a PostScript image showing the locations of all fixed sampling sites in the NOAA/CMDL cooperative air sampling network; also shown are the approximate sampling locations from ocean vessels participating in the shipboard sampling program. The data and accompanying descriptive material are available in electronic form only; hard copy documentation is not available.