Characterization of the semi-annual-oscillation in mesospheric temperatures at low-latitudes

Novel measurements of the seasonal variability in mesospheric temperature at low-latitudes have been obtained from Maui, Hawaii (20.8 degrees N, 156.2 degrees W) during a 25-month period from October 2001 to January 2004. Independent observations of the OH (6,2) Meinel band (peak height similar to 87 km) and the O-2 (0-1) atmospheric band emission (similar to 94 km) were made using the CEDAR Mesospheric Temperature Mapper. The data revealed a coherent oscillation in emission intensity and rotational temperature with a well-defined periodicity of 181 +/- 7 days. The amplitude of this oscillation was determined to be similar to 5-6 K in temperature and similar to 8-9% in intensity for both the OH and O-2 data sets. In addition, a strong asymmetry in the shape of the oscillation was also observed with the spring maximum significantly larger than the fall peak. These data provide new evidence in support of a semi-annual-oscillation in mesospheric temperature (and airglow emission intensities) and help quantify its seasonal characteristics. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.