Atmospheric transmission coefficients for hydroxyl rotational lines used in rotational temperature determinations

Abstract

In an effort to retrieve accurate rotational temperatures from hydroxyl (OH) nightglow spectra, a computer model of atmospheric absorption has been combined with a Doppler model of the Λ-doubled OH rotational lines in order to derive transmission coefficients for the individual lines. Atmospheric transmission coefficients have been tabulated for the first three to four major P, Q and R-branch rotational lines of the OH Meinel (4,2), (3,1), (7,4), (6,2) and (8,3) bands. These coefficients have been calculated for OH Doppler temperatures over the typical mesospheric range from 150 to 250 K and for mid- and high-latitude, winter and summer conditions. Finally, the resulting atmospheric transmission coefficients have been applied to a low-noise, near-infrared data set obtained during the high-latitude summer under quiet geophysical conditions. It is shown that these coefficients correct the selective absorption of individual rotational lines in different OH vibrational bands, and thus, resolve the differences in the rotational temperatures inferred from the different vibrational levels of the uncorrected spectra.