MESOPAUSE TEMPERATURES AND INTEGRATED BAND BRIGHTNESSES CALCULATED FROM AIRGLOW OH EMISSIONS RECORDED AT MAYNOOTH (53.2-DEGREES-N, 6.4-DEGREES-W) DURING 1993

Spectra of the hydroxyl emissions in the wavelength range 1.0-1.6 mu m, which originate at mesopause altitudes, have been obtained, using a Fourier transform spectrometer at Maynooth (53.2 degrees N, 6.4 degrees 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 -51 +/- 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 -43 +/- 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 degrees 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 temperature, 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 -99 +/- 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 el 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.