OH(6–2) spectra and rotational temperature measurements at Davis, Antarctica

Abstract

The OH(6±2) band was monitored during 1990 at Davis, Antarctica 68X6 S, 78.0 E using a Czerny-Turner scanning spectrometer. Spectra obtained with a 0.15-nm bandwidth and wavelength steps of 0.005 nm have been recorded in an attempt to isolate auroral features. This has enabled detailed study of weak features in the region k837X5À 855X5 nm. These weak features can contribute to the apparent intensity of Pbranch lines and to the background. Their presence is allowed for in our calculation of rotational temperature, but the P 1 3 line is excluded because of signi®cant contamination. An average temperature of 221 AE 2 K is obtained from a selected data set of 104 spectra. The midwinter average temperature, for the months of May, June and July, is 224 AE 2 K, which is consistent with the 1986 CIRA model values for midwinter at this height and latitude, but this result is dependent on the choice of transition probabilities. Preliminary assessments of seasonal and diurnal variations in rotational temperature and intensity are presented.

The influence of large-scale oscillations on long-term trend assessment in hydroxyl temperatures over Davis, Antarctica

“…Greet et al, 1998;Burns et al, 2001;2002a) and some 1994 data is also available. Both of these years however, are subject to a low-resolution sampling regime and increased calibration uncertainty which makes comparison with later years for trend analysis di cult.…”

“…A resolution of ∼0:16 nm was achieved with 250 m slits and the ÿeld-of-view was ∼5:3 • in the zenith. Further instrument details may be found in Williams (1996), Greet et al (1998), French et al (2000) and Burns et al (2002a).…”

“…P1(3) is blended with the unthermalised OH(5-1) P1(12) emission and is not used for the rotational temperature determination (see Greet et al, 1998). A wavelength step of 0:01 nm and dwell time of 1 s give an integration time of 100 s per nm, equivalent to the integration time used in 1995 and 1996.…”

“…The method applied to determine rotational temperatures is detailed in Greet et al (1998) and Burns et al (2002a). Transition probabilities used in this work are those presented in Langho et al (1986).…”

Planetary waves and intraseasonal oscillations at Davis, Antarctica, from undersampled time series

“…Auroral, cloud and moonlight contaminations are handled and investigated as described by Burns et al [2002]. Discussion of the effect of clouds on the observations is provided by Burns et al [2002] and Greet et al [1998]. Typically the temperature error associated with spectral response uncertainty is less than 0.5 K [Burns et al, 2002].…”