Characterization of gravity waves in the lee of the southern Andes utilizing an autonomous Rayleigh lidar system
| Autor: | Reichert, Robert |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2022 |
| Předmět: |
butterworth filter
southern Andes solar tides FOS: Physical sciences momentum flux potential energy Rio Grande planetary waves hotspot lateral propagation atmospheric gravity waves southern Andes rayleigh lidar middle atmosphere wavelet analysis raytracing Atmospheric gravity waves wavelet transform Physics::Atmospheric and Oceanic Physics |
| DOI: | 10.5282/edoc.30211 |
| Popis: | The largest mountain waves worldwide are excited at the southern Andes where they subsequently propagate vertically and horizontally downwind and transfer their momentum to the mean flow in the middle atmosphere. Many questions regarding excitation, exact propagation, interaction and dissipation of these waves are still unanswered. For this reason, a Rayleigh lidar system was installed on behalf of DLR at Río Grande (53.7◦ S, 67.7◦ W), Argentina, to record vertical temperature profiles, to detect gravity wave signatures. Analysis of the lidar data set, collected in an automated manner between November 2017 and October 2020, is the core of this dissertation. What is new here is not only the measurement at this geographic location, but also the high cadence of the measurements. The measurement coverage of an average of two measurements within three nights allows to define a temperature background, which covers temporal scales from 9 days up to one year and vertical scales from 15 km. In addition, diurnal tides are extracted from nighttime lidar measurements using a new methodology that is also applied to ECMWF reanalysis data for validation. The comparison shows good agreement, although the amplitudes of the diurnal tide in the lidar data are larger in the mesosphere and vary much more than in the reanalysis data. Tidal aliasing likely results in unexpected small/large amplitudes in the annual/semi-annual oscillations. The wave energies studied are the largest ever measured in the stratosphere, reaching a saturation limit at 60 km altitude. Reaching a saturation limit at such low altitudes has not been observed before in that way and suggests that waves are already generated with very large amplitudes and also find good growth conditions during vertical propagation. Also related to saturation is an observed decrease in gravity wave intermittency in the mesosphere. The development of a new spectral tool helps in the determination of wavelengths. Here it becomes clear that about 50 % of the waves have vertical scales greater than 16,5 km. This is an important result considering that previous lidar studies have mostly focused on vertical wavelengths |
| Databáze: | OpenAIRE |
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