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

Significant uncertainties in the spectroscopy of collision-induced absorpti on by oxygen have a limited knowledge of the contribution made by molecular oxygen to the shortwave radiation budget of the Earth's atmosphere. As par t of a programme of high-resolution (up to 0.02 cm(-1)) studies of atmosphe ric short-wave transmittance under clear-sky conditions, field measurements in the region of the 1.27 mum (7874 cm(-1)) oxygen absorption are reported here. Measurements of direct solar radiation incident at the ground were m ade using a ground-based Fourier transform spectrometer at the Rutherford A ppleton Laboratory (51.6 degreesN, 1.3 degreesW, altitude 135 m). Model cal culations of the atmospheric transmittance in the region of the broad conti nuum feature underlying the a(1)Delta (g) <-- X(3)Sigma (-)(g) (0,0) band o f oxygen were made using absorption cross sections derived from recent labo ratory measurements. The agreement between the field observations and the m odel calculations validates a simple model developed to describe the atmosp heric oxygen continuum absorption centered at 1.27 mum for atmospheric shor t-wave radiative transfer and remote sensing applications.