Mesopause temperatures and integrated band brightnesses calculated from airglow OH emissions recorded at Maynooth (53.2°N, 6.4°W) during 1993

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 (53.2°N, 6.4°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 ° 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