Measurement of Low Amounts of Precipitable Water Vapor Using Ground-Based Millimeterwave Radiometry

Extremely dry conditions characterized by amounts of precipitable water vapor (PWV) as low as 1-2 mm commonly occur in high-latitude regions during the winter months. While such dry atmosphere carry only a few percent of the latent heat energy compared to tropical atmospheres, the effects of low vapor amounts on the polar radiation budget--both directly through modulation of longwave radiation and indirectly through the formation of clouds--are considerable. Here, Racette et al demonstrate both theoretically and experimentally the potential of millimeter-wavelength radiometer using the 183-GHz line for measuring low amounts PWV.