Attenuation and emission of the atmosphere at 3.3 mm

Four empirical relationships are presented between the 3.3-mm attenuation determined from observations of the sun and 1) radiosonde measurements of the total amount of precipitable water in the atmosphere, 2) surface measurements of absolute humidity, 3) IR spectral hygrometer observations of the sun, and 4) observations of differential atmospheric emission at 3.3 mm. Fluctuations in atmospheric emission at 3.3 mm during good weather do not put any limit on the sensitivity of a dual-beam observing system using a receiver whose rms noise fluctuations in an output bandwidth of 0.25 Hz are
\approx0.5\deg
K.