An investigation of the near-infrared collision induced absorption bands of oxygen with SCIAMACHY solar occultation data

The present work investigates the Collision Induced Absorption (CIA) bands of oxygen that occur at 1065 and 1270 nm from solar occultation data obtained with the spaceborne spectrometer SCIAMACHY. The effort is motivated by the interest in these two strong CIA bands in atmospheric research and the paucity of data on them under realistic atmospheric conditions. The observing geometry provides long integration paths and in turn easily measurable absorption signals. Our analysis method relies on the accurate separation of the CIA band signature from the rest of the continuum and structured components over selected spectral intervals. We show that the shapes of the two CIA bands seem well described by specific laboratory determinations over a broad range of tropospheric and low-stratospheric conditions. By analyzing a full month of solar occultation data we find that the ratio of peak binary cross sections in air, s 1270 nm=s peak 1065 nm, is 4 and seemingly independent of tangent height from 6 to 18 km. We tentatively estimate the absolute binary cross sections and compare them to existent measurements. A better characterization of the near-infrared CIA bands of oxygen should facilitate their implementation in remote sensing applications in the way it is often done with the CIA bands that occur in the visible. & 2012 Elsevier Ltd. All rights reserved.