Abstract
Methode are described to evaluate accuracy of monitored data of atmospheric methane st 15 air monitoring stations in the Okayama prefecture. Methane concentrations in 15: 00-16: 00 hour of day are lowest with the lowest deviations and similar to the background levels at the all stations. The monthly averaged concentrations of atmospheric methane in 15: 00-16: 00 hour may be used as standards to estimate systematic errors over long term at the monitoring stations.
Deviation of methane concentrations from the average in this period may be regarded as a systematic error in the monitoring system.
Difference between hourly atmospheric methane and ones at 15: 00-16: 00 houre could be used to observe local characterization of methane emission sources without influence of the wide spread trends of atmospheric methane concentration.
