Terdiurnal oscillations in OH Meinel rotational temperatures for fall conditions at northern mid-latitude sites

High-precision (similar to 0.5 K) measurements of OH Meinel (M) (6,2) rotat ional temperatures above the Bear Lake Observatory, UT (42 degrees N, 112 d egrees W) during October 1996 have revealed an interesting and unexpected m ean nocturnal pattern. Ten quality nights (>100 h) of data have been used t o form a mean night for autumnal, near-equinoctial conditions. The mean tem perature and RMS variability associated with this mean night were 203 +/- 5 K and 2.4 K, respectively, and compare very favorably with expectations ba sed on Na-lidar measurements of mean tidal temperature perturbations over U rbana, IL (40 degrees N, 88 degrees W) during the fall 1996. Furthermore, t his comparison shows that the 8-h tide was the dominant source of the mean nocturnal temperature variability in the OH M region during this period. Ad ditional data, obtained at Fort Collins, CO (41 degrees N, 105 degrees W) i n November 1997, illustrate the occurrence of an g-h component of OH temper ature variability about two months after the equinox and show that daily am plitudes as high as congruent to 15 K are possible.