Detection of Tidal and Planetary Waves in Nighttime Lidar Data: Technique and Application to Winter Mesospheric Temperatures above Logan, Utah

Because of the significant gaps in nighttime-only data, traditional techniques like Fourier analysis are difficult to use to identify oscillations with relatively long periods, such as tides and short-period planetary waves. The Lomb-Scargle periodogram is a method that was developed by astronomers to identify oscillations in nighttime-only and otherwise incomplete data. It is potentially a powerful tool for aeronomers also. The Lomb-Scargle technique is described here along with techniques for the detection of aliasing that arises because of the periodic gaps in the nighttime-only data. These techniques are then applied to Rayleigh lidar (LIght Detecting And Ranging) temperature data acquired from the mid-latitude mesosphere between 40 and 70 km in altitude above Logan, Utah (41.7°N, 111.8°W) in February, 1995. It is shown that these lidar data contain a strong quasi-5-day planetary wave and a diurnal tide, as well as a weaker quasi-2day planetary wave and possibly a semi-diurnal tide. Least-square curve fits are then used to examine the vertical phase and amplitude progression of the diurnal tide and the quasi-5-day wave.