Observed atmospheric collision-induced absorption in near-infrared oxygen bands

A recent high-resolution measurement of surface solar radiance taken under cloud-free conditions by the Absolute Solar Transmittance Interferometer shows clear indication of continuum absorption associated with the three strongest O-2 a(1) Delta(g) <-- X-3 Sigma(g)(-) transitions. The differences between these measurements and a calculation by the line-by-line radiative transfer model (LBLRTM) were used to determine the properties of these collision-induced bands and, for two of the bands, led to parameterizations of the spectral behavior of the absorption coefficients. The results indicate that these continuum bands absorb 0.84 W/m(2) at the 71.5 degrees solar zenith angle associated with the observation. For the observed 3000-9965 cm(-1) spectrum, with the exception of the spectral range in which this collision-induced absorption occurs, there is good agreement between the measured and calculated radiance values, with no evidence for discrete absorption by unknown gases.