Precipitable Water Vapor 2014 (ARCA)

The column water vapor or Precipitable Water Vapor (PWV) is measured at Thule Air Base (76.5°N, 68.8°W), Greenland, by means of a ground-based millimeter-wave spectrometer (GBMS) installed at 220 m a.s.l. The GBMS observes rotational lines of atmospheric molecules emitting between 230 and 280 GHz, with a spectral pass band of 600 MHz. The PWV is calculated from direct measurements of atmospheric opacity (tau) at the indicated frequencies by using the linear relation PWV = a+tau*b, where a and b depend only on frequency. Measurements have a temporal resolution of 15 minutes and are carried out continuously when the GBMS is operated.