Atmospheric Infrared Spectrum Atlas


The Atmospheric Infrared Spectrum Atlas provides spectra for a wide range of molecules in Earth's atmosphere. This website includes zenith absorption/optical thickness and limb radiance spectra on fully interactive graphs which can be customised show specific molecules, spectral ranges and satellite bands.

Spectra are calculated using the RFM line-by-line model with HITRAN 2012[1] line data and US Standard Atmosphere absorber profiles.

Zenith absorption, A is the fraction of incident electromagnetic energy which is absorbed by the atmosphere at a given wavelength on a directly vertical path from the Earth's surface to space. It is a dimensionless quantity ranging from A = 0 (full transmission) to A = 1 (full absorption).

Zenith optical thickness, τ can be calculated from the absorption as τ = - ln(1-A). Optical thickness is dimensionless and always ≥ 0, with larger values corresponding to stronger absorption.

Limb radiance at 12 km tangent height is the spectral radiance emerging from the edge of the atmosphere viewed along a line of sight which passes 12 km above the surface, thus excluding any surface emission and the bulk of tropospheric water vapour.

Spectral radiance is the radiant flux (electromagnetic energy emitted per unit time) from a surface per unit solid angle per unit area per unit frequency. The units here are nW/(cm2 sr cm-1).

Other websites

HITRAN, GEISA interactive web-site for creating similar plots, Stanford University, USA, SPECTRA: Spectroscopy of Atmospheric Gases, Institute of Atmospheric Optics, Tomsk, RUSSIA, High-resolution spectral modeling, GATS, Inc., USA


These web-pages were created by Oliver King as part of a physics department undergraduate vacation project, supervised by Anu Dudhia. Graphs created using Highcharts.


  1. Rothman, L.S., Gordon, I.E., Babikov, Y., Barbe, A., Benner, D.C., Bernath, P.F., Birk, M., Bizzocchi, L., Boudon, V., Brown, L.R. and Campargue, A., 2013. The HITRAN2012 molecular spectroscopic database. Journal of Quantitative Spectroscopy and Radiative Transfer, 130, pp.4-50.