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

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 a 1 Δ g ← X 3 ∑ g¯ (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.