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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 10
Ann. Geophys., 13, 1107–1116, 1995
https://doi.org/10.1007/s00585-995-1107-7
© European Geosciences Union 1995
Ann. Geophys., 13, 1107–1116, 1995
https://doi.org/10.1007/s00585-995-1107-7
© European Geosciences Union 1995

  31 Oct 1995

31 Oct 1995

Hydroxyl temperature and intensity measurements during noctilucent cloud displays

M. J. Taylor, R. P. Lowe, and D. J. Baker M. J. Taylor et al.

Abstract. Two Fourier transform spectrometers have been used to investigate the properties of the near-infrared hydroxyl (OH) nightglow emission under high-latitude summertime conditions and any association with noctilucent clouds (NLCs). The measurements were made from Poker Flat Research Range, Alaska (65.1°N, 147.5°W), during August 1986. Simultaneous photographic observations of the northern twilight sky were made from Gulkana, Alaska (62.2°N, 145.5°W), approximately 340 km to the south to establish the presence of NLCs over the spectrometer site. Data exhibiting significant short-term variations in the relative intensity (as much as 50–100%) and rotational temperature (typically 5–15 K) were recorded on six occasions when NLCs were observed. Joint measurements were also obtained on several "cloud-free" nights. No obvious relationship was found linking the mean OH intensity or its variation with the occurrence of NLCs. However, a clear tendency was found for the mean OH temperature to be lower on NLC nights than on cloud-free nights. In particular, a significant fraction of the OH(3–1) band spectra recorded by each instrument (16–57%) exhibited temperatures below ~154 K on NLC nights compared with <3% on cloud-free nights. This result is qualitatively consistent with current models for ice particle nucleation and growth, but the mean OH temperature on NLC nights (~156 K) was significantly higher than would be expected for long-term particle growth in this region. These observations raise questions concerning the expected proximity of the high-latitude, summertime OH layer and the NLC growth region.

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