All Physics Faculty Publications

Title

Hydroxyl Temperature and Intensity Measurements During Noctilucent Cloud Displays

Document Type

Article

Journal/Book Title/Conference

Annales Geophysicae

Volume

13

Issue

10

Publisher

European Geosciences Union

Publication Date

1995

First Page

1107

Last Page

1116

DOI

10.1007/s00585-995-1107-7

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.

Comments

Published by European Geosciences Union in Annales Geophysicae: http://www.ann-geophys.net/13/1107/1995/angeo-13-1107-1995.html

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http://www.ann-geophys.net/13/1107/1995/angeo-13-1107-1995.html