Analytical Development Company (ADC) Ltd., model ADC 7000. The nondispersive IR absorption spectrometer produces a voltage proportional to the absolute amount of water vapour which is converted to % water vapour mixing ratio. H2O vapour is a strong absorber of IR radiation, and the instrument measures water vapour in the range 0-1 %, LOD 5 ppm. The measurements takes place every few seconds and returns the 1 minute average. The output consists of the Julian day (for the relevant year), and water vapour as a % mixing ratio.
For ACSOE campaign, measurements from this instrument are recorded in files with naming convention of ccyymmdd.wv2 where cc is the platform (e.g. mh is Mace Head), yy is the two digit year, mm is the two digit month and dd is the two digit day.