The atmospheric absorption in the 10µm-window is characterised mainly by CO₂ and ozone. The principal effect of an increase in the water vapour column above the site is an overall reduction of transmission, and consequent increase in the sky background, as shown by the curves for 1.0 and 3.0mm of H₂O in the following figure:

The far greater atmospheric absorption in the 20µm window is dominated by water vapour, as shown by the curves for 1.0 and 3.0mm of H₂O in the following figure:

The raw data files used to produce these figures are available: 1.0mm, 1.6mm, 3.0mm, 5.0mm (all at airmass=1.5). Any use of these data should reference Lord (1992) and acknowledge Gemini Observatory. The models are in ASCII two-column format: (a) wavelength with a sampling of 0.0005µm and a resolution of 0.001µm (1nm) and (b) transmission