Advanced hodograph-based analysis technique to derive gravity-wave parameters from lidar observations

Strelnikova, Irina; Baumgarten, Gerd; Lübken, Franz-Josef

An advanced hodograph-based analysis technique to derive gravity-wave (GW) parameters from observations of temperature and winds is developed and presented as a step-by-step recipe with justification for every step in such an analysis. As the most adequate background removal technique the 2-D FFT is suggested. For an unbiased analysis of fluctuation whose amplitude grows with height exponentially, we propose applying a scaling function of the form inline-formulaexp (z∕(ςH)), where inline-formulaH is scale height, inline-formulaz is altitude, and the constant inline-formulaς can be derived by a linear fit to the fluctuation profile and should be in the range 1–10. The most essential part of the proposed analysis technique consists of fitting cosine waves to simultaneously measured profiles of zonal and meridional winds and temperature and subsequent hodograph analysis of these fitted waves. The linear wave theory applied in this analysis is extended by introducing a wave packet envelope term inline-formula M5inlinescrollmathml exp⁡ ( - ( z - z normal 0 ) normal 2 / normal 2 italic σ normal 2 ) 99pt16ptsvg-formulamathimgce9cdabdd5ff99cc5e5c2905c5c51638 amt-13-479-2020-ie00001.svg99pt16ptamt-13-479-2020-ie00001.png that accounts for limited extent of GWs in the observational data set. The novelty of our approach is that its robustness ultimately allows for automation of the hodograph analysis and resolves many more GWs than can be inferred by the manually applied hodograph technique. This technique allows us to unambiguously identify upward- and downward-propagating GWs and their parameters. This technique is applied to unique lidar measurements of temperature and horizontal winds measured in an altitude range of 30 to 70 km.

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Strelnikova, Irina / Baumgarten, Gerd / Lübken, Franz-Josef: Advanced hodograph-based analysis technique to derive gravity-wave parameters from lidar observations. 2020. Copernicus Publications.

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