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Abstract Meteoroids of sub‐milligram sizes burn up high in the Earth's atmosphere and cause streaks of plasma trails detectable by meteor radars. The altitude at which these trails, or meteors, form depends on a number of factors including atmospheric density and the astronomical source populations from which these meteoroids originate. A previous study has shown that the altitude of these meteors is affected by long‐term linear trends and the 11‐year solar cycle related to changes in our atmosphere. In this work, we examine how shorter diurnal and seasonal variations in the altitude distribution of meteors are dependent on the geographical location at which the measurements are performed. We use meteoroid altitude data from 18 independent meteor radar stations at a broad range of latitudes and investigate whether there are local time (LT) and seasonal variations in the altitude of the peak meteor height, defined as the majority detection altitude of all meteors within a certain period, which differ from those expected purely from the variation in the visibility of their astronomical source. We find a consistent LT and seasonal response for the Northern Hemisphere locations regardless of latitude. However, the Southern Hemisphere locations exhibit much greater LT and seasonal variation. In particular, we find a complex response in the four stations located within the Southern Andes region, which indicates that the strong dynamical atmospheric activity, such as the gravity waves prevalent here, disrupts, and masks the seasonality and dependence on the astronomical sources. 

Abstract The variations of the horizontal phase velocity of an internal gravity wave, generated by wave “blocking” or “reflection” due to an inhomogeneous wind field, have been predicted theoretically and numerically investigated but had yet to be captured experimentally. In this paper, through a collaborative observation campaign using a sodium (Na) Temperature/Wind lidar and a collocated Advanced Mesospheric Temperature Mapper (AMTM) at Utah State University (USU), we report the first potential evidence of such a unique gravity wave process. The study shows that a small‐scale wave, captured by the AMTM, with initial observed horizontal phase velocity of 37 ± 5 m/s toward the northwest direction, experienced a large and increasing headwind as it was propagating in the AMTM field of view. This resulted in significant deceleration along its initial traveling direction, and it became quasi‐stationary before it was “reflected” to the opposite direction at later time. The USU Na lidar measured the horizontal wind and temperature during the event, when the wave was found traveling within a temperature inversion layer and experiencing an increasing headwind relative to the wave. The wind agrees well with the expected value for wave blocking suggested by the wave tracing theory, implying the existence of a large horizontal wind gradient that night near the OH layer altitudes. The study indicates the critical role of horizontal winds and their horizontal gradients in determining propagation in vertical and horizontal directions.