Vertical propagation characteristics of internal gravity waves around the mesopause observed by the Arecibo UHF radar |
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| Institution: | 1. Department of Physics, Shikshanmaharshi Dr. Bapuji Salunkhe College, Miraj, MS 416410, India;2. Department of Physics, Kisan Veer Mahavidyalaya, Wai, MS 412803, India;3. Centre for Climate Change Research, Indian Institute of Tropical Meteorology, Pune 411008, India;4. Department of Physics, Bharati Vidyapeeth (Deeemed to be University), Yashwantrao Mohite College of Arts, Science and Commerce, Pune, MS 411038, India;5. School of Physics, Shri Mata Vaishno Devi University, Kakryal, Katra, Jammu & Kashmir 182320, India;6. MF Radar, Indian Institute of Geomagnetism, Shivaji University Campus, Vidyanagar, Kolhapur, MS 416004, India;7. Department of Physics, Sir Parashurambhau College, Pune 411030, India;8. Department of Physics, Smt Kasturbai Walchand College, Sangli, MS 416416, India;1. Equatorial Geophysical Research Laboratory, Indian Institute of Geomagnetism, Tirunelveli, Tamil Nadu, 627011, India;2. Manonmaniam Sundaranar University, Abhishekapatti, Tirunelveli, Tamil Nadu, 627012, India;3. National Atmospheric Research Laboratory, Gadanki, 517112, PakalaMandal, Tirupati District, Andhra Pradesh, India;4. Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pashan, Pune, 411 008, Maharashtra, India |
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| Abstract: | A high resolution wind observation of the mesosphere and lower thermosphere (73–95 km) was conducted with the aid of the high power UHF Doppler radar at Arecibo (18.4°N, 66.8°W). Zonal wind velocities were continuously observed during day-time hours on 1–15 August 1980. We discuss here the observed wind fluctuations with periods of 1–4 h in the light of internal gravity waves. The phase propagation associated with these fluctuations is, on average, shown to be downward, indicating an upward energy flux. A space-time spectral analysis shows that waves with vertical wavelengths shorter than 10 km disappear around the mesopause (about 85km), while those with longer vertical wavelengths exist throughout the observational height. This result is explained in terms of wave absorption at a critical layer where the mean zonal wind has a westerly shear with height. This feature is consistent with the behavior expected for internal gravity waves around the summer mesopause in order to explain general circulation models. |
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