Amplitude, phase, and period variations of the quasi 2-day wave in the mesosphere and lower thermosphere over London, Canada (43°N, 81°W), during 1993 and 1994

Abstract

Because there is as yet no conclusive evidence pointing to the source of the quasi 2-day wave, further observations are required in order to resolve questions about the generating mechanism as well as to better understand the role of the wave in the middle atmosphere. In this paper we investigate the period, amplitude, phase, and vertical wavelength for the quasi 2-day wave in the mesosphere and lower thermosphere, using the University of Western Ontario 2 MHz radar near London, Canada, and in addition, we look at possible coupling with atmospheric tides. The results of the present study bring out certain new aspects of the quasi 2-day wave at midlatitude in the northern hemisphere that have not been previously reported. In particular, we show that the period of the quasi 2-day wave determined from our study is smaller (46-47 hours) than the 51- to 52-h period generally suggested by other northern hemisphere results, and our periods also showed variability as a function of time. We also draw attention to the annual variability and especially highlight the occurrence of the wave in nonsummer months. For example, a brief occurrence in April is not uncommon. Our study also contributes additional midlatitude geographical data that should aid in developing a better picture of the quasi 2-day wave.