Measurement of submillimeter zenith atmospheric opacity at 492 GHz

Presented are measurements of the zenith opacity (τ0) of the earthʹs atmosphere at 492 GHz made with the Portable Submillimeter Telescope (POST) at the observing station (elevation 3200 meters) located in the Qinghai-Tibet Plateau and belonging to Purple Mountain Observatory. The measurement spanned about 870 hours in the two winter seasons of 1999–2000 and 2000–2001, and resulted in 25842 sets of ro values. The measured values of ro are mainly distributed between 1.5 and 3.0, and about 3 percent of the total observing time had τ0 ≤ 1.0. A preliminary comparison is made with data obtained at other available submillimeter observing sites in the world.