Dayglow emissions of the O2 Herzberg bands and the Rayleigh backscattered spectrum of the earth |
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| Authors: | JE Frederick RB Abrams |
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| Institution: | Laboratory for Planetary Atmospheres, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A.;Computer Sciences Corporation, Silver Spring, MD 20910, U.S.A. |
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| Abstract: | Numerous fluorescent emissions from the Herzberg bands of molecular oxygen lie in the spectral region 242–300 nm. This coincides with the wavelength range used by orbiting spectrometers which observe the Rayleigh backscattered spectrum of the earth for the purpose of monitoring the vertical distribution of stratospheric ozone. Model calculations indicate that Herzberg band emissions in the dayglow could provide significant contamination of the ozone measurements if the quenching rate of O2(A3Σ) is sufficiently small. This is especially true near 255 nm, where the most intense fluorescent emissions relative to the Rayleigh scattered signal are located and where past satellite measurements show a persistent excess radiance above that expected for a pure ozone absorbing and molecular scattering atmosphere. However, very small quenching rates are adequate to reduce the dayglow emission to negligible levels. Available laboratory data have not definitely established the quenching on the rate of O2(A3Σ) as a function of vibrational level, and such information is required before the Herzberg band contributions can be evaluated with confidence. |
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