Measurement of vertical phase and group velocities of atmospheric gravity waves by VHF radar |
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| Affiliation: | 1. Asian School of the Environment, Nanyang Technological University, Singapore;2. National Institute of Education, Nanyang Technological University, Singapore;3. Department of Environmental Engineering, Sao Paulo State University, Brazil;1. Institut national de Recherche en Sciences et Technologies pour l''Environnement et l''Agriculture (IRSTEA), UMR TETIS, Montpellier, France;2. Centre d''Etudes Spatiales de la BIOsphere (CESBIO), UMR CNRS 5126, University of Paul Sabatier, Toulouse, France;3. Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy;4. Laboratoire Evolution et Diversite Biologique, UMR CNRS 5174, University of Paul Sabatier, Toulouse, France;5. French Institute of Pondicherry, UMIFRE 21/USR 3330 CNRS-MAEE, Pondicherry, India;6. School of Geography, University of Leeds, University Road, Leeds LS2 9JT, UK;7. Geography, College of Life and Environmental Sciences, University of Exeter, UK;8. Office National d''Etudes et de Recherches Aerospatiales (ONERA), Toulouse, France;9. European Space Research and Technology Centre (ESTEC), Noordwijk, the Netherlands;1. National Atmospheric Research Laboratory, Gadanki, India;2. Department of Physics, S. V. University, Tirupati, India |
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| Abstract: | A systematic method of deriving from MST radar data the group velocity and phase velocity of the atmospheric wave along the radar beam direction is proposed and verified by a series of numerical simulations. We apply the method to two data sets measured by Chung-Li radar under different background wind conditions. It is found that the vertical group velocity and phase velocity are mostly in the opposite direction when the background wind is weak. The energy source of downgoing wave packets was evidently related to the instability in the upper height range (10.5–11.7 km) where strong wind shear existed. When the background wind and wind shear are stronger, the vertical group and phase velocities may propagate in the same direction. We also found from numerical simulation and data analysis that the wave packet of gravity waves following power law spectrum are short-lived. A by-product of the group velocity measurement is that the horizontal wavelength may also be deduced from a vertical radar beam measurement from the dispersion relation if it is valid. |
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