Collision-induced absorption of solar radiation in the atmosphere by molecular oxygen at 1.27 μm: Field observations and model calculations


  • K. M. Smith,

  • D. A. Newnham,

  • R. G. Williams


Significant uncertainties in the spectroscopy of collision-induced absorption by oxygen have a limited knowledge of the contribution made by molecular oxygen to the short-wave radiation budget of the Earth's atmosphere. As part of a programme of high-resolution (up to 0.02 cm−1) studies of atmospheric short-wave transmittance under clear-sky conditions, field measurements in the region of the 1.27 μm (7874 cm−1) oxygen absorption are reported here. Measurements of direct solar radiation incident at the ground were made using a ground-based Fourier transform spectrometer at the Rutherford Appleton Laboratory (51.6°N, 1.3°W, altitude 135 m). Model calculations of the atmospheric transmittance in the region of the broad continuum feature underlying the a1Δg ← X3 (0,0) band of oxygen were made using absorption cross sections derived from recent laboratory measurements. The agreement between the field observations and the model calculations validates a simple model developed to describe the atmospheric oxygen continuum absorption centered at 1.27 μm for atmospheric short-wave radiative transfer and remote sensing applications.