Measurement Method (Measurement System)

All observation systems in both stations are fully automated, and perform high-precision, unattended, and continuous observations. Each observation system was originally developed by the researchers in charge of the project, and are updated to ensure stable and precise observations by introducing the latest technology.

As an example, an observation system for atmospheric carbon dioxide is shown in the figure. This system employs a non-dispersive infrared (NDIR) analyzer, so one of the key points is how sufficient we can remove water vapor, which has an infrared absorption band similar to that of carbon dioxide. For this purpose, a two-stage dehumidifier (-45°C and -65°C) is installed in front of the analyzer to remove water vapor from the air sample in stages. The -45°C and -65°C dehumidifier has multiple flow paths, which are automatically switched at fixed time intervals to prevent clogging of the flow paths and enable continuous unattended observation. According to the signal drift in NDIR, four standard gases are used for calibration at a fixed cycle. The obtained data are transmitted to Tsukuba through a dedicated line and preliminary values are displayed.