The article mentions that water vapor (humidity, fog, clouds, etc.) is the most significant source of attenuation at these frequencies/wavelengths. This is also

The article mentions that water vapor (humidity, fog, clouds, etc.) is the most significant source of attenuation at these frequencies/wavelengths. This is also the most important source of attenuation for radio astronomy observations as well, along with atomic oxygen and ozone. This is why millimeter-wave observatories have to be located in high altitude (> 10,000 feet) and dry locations, like the practical moonscape of the Atacama Plateau in Chile where the Atacama Large Millimeter Array (ALMA) [1] is. ALMA is a truly amazing instrument that's transforming modern astronomy, and they operate between 4 mm to 0.350 mm (70 to 890 GHz). If you want to see the effect of water vapor on these sorts of astronomical observations, take a look at a nearby telescopes transmission calculator [2], where it shows the percent of light that's transmitted from space to the ground as a function of frequency. The "PWV" means precipitable water vapor, and is the height of a column of water from precipitating all of the water in a 1 centimeter square extended from the ground all the way up. The Atacama is a super dry site, and 1 millimeter of PWV is routine there, but try putting in 100-1000 GHz with 0.5, 2, and 5 millimeters PWV that are typical of other observatories! [1] http://www.almaobservatory.org/ http://www.almaobservatory.org/ [2] http://www.apex-telescope.org/sites/chajnantor/atmosphere/transpwv/ http://www.apex-telescope.org/sites/chajnantor/atmosphere/tr...