Mulligan, F.J. and Horgan, D.F. and Galligan, J.G. and Griffin, E.M.
Mesopause temperatures and integrated band brightnesses calculated from airglow OH emissions recorded at Maynooth (53.2Â°N, 6.4Â°W) during 1993.
Journal of Atmospheric and Terrestrial Physics, 57 (13).
Spectra of the hydroxyl emissions in the wavelength range 1.0-1.6 #m, which originate at
mesopause altitudes, have been obtained, using a Fourier transform spectrometer at Maynooth (53.2Â°N,
6.4Â°W), on all suitable nights during the period January-December 1993. Rotational temperatures and
integrated band brightnesses have been calculated from the spectra of the OH(3, 1) and (4, 2) vibration-
rotation bands. The mean annual temperatures calculated over all measurements were T(3, 1)= 200 + 19
K and T(4, 2)= 206 + 19 K, where the uncertainty represents the standard deviation on the measurements.
Harmonic analysis of the nightly averaged temperature values revealed an amplitude of 27+ 1 K and a
phase of 95 __. 2 days in the annual variation of the (3, 1) band at our latitude. The semiannual component
was found to have an amplitude of 7 _+ 1 K and a phase of - 5 1 ___ 9 days for this band. Results for the (4,
2) band were identical in both amplitude and phase for the annual component, while the semiannual
component gave an amplitude of 8_ 1 K and a phase of - 4 3 + 7 days. These results are compared with
data recorded by the SME satellite, and with the predictions of the MSISE-90 model for a station at 53 Â°
latitude. Temperatures predicted by the MSISE-90 model for Maynooth are consistently below the values
obtained in this study by 15-20 K. Excellent agreement is observed between the absolute value of tempera-
ture, in the case of the SME satellite, and in the amplitude and phase of the annual variation predicted by
MSISE-90. The phase of the semiannual component observed in our data deviates somewhat from the
- 9 9 + 1 days predicted by MSISE-90.
The annual mean brightness of the OH (3, 1) band was found to be 75 + 18 kR, while that of the (4, 2)
band was 106 + 26 kR. Diurnal variations generally showed a steady decrease from dusk to dawn, apart
from a brief period in June and July. Monthly average values of band brightness have been calculated for
each band and are compared with the predictions of a recent photochemical model (Le Texier et al., 1987).
The model shows some elements of agreement with our observations, particularly a pair of maxima near
the equinoxes, but it does not predict the broad winter maximum observed in both bands at this latitude.
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