HR: 08:00h
AN: SA31A-14    [Abstracts]
TI: Short-Period Mesospheric Gravity Waves and Diurnal Tidal Interactions at a Critical Layer
AU: * Ejiri, M K
EM: mitsumu@cc.usu.edu
AF: Center for Atmospheric and Space Sciences, Utah State University, 4405 Old Main Hill, SER Bldg., Logan, UT 84322-4405, United States
AU: Taylor, M J
EM: mtaylor@cc.usu.edu
AF: Center for Atmospheric and Space Sciences, Utah State University, 4405 Old Main Hill, SER Bldg., Logan, UT 84322-4405, United States
AU: Franke, S J
EM: s-franke@uiuc.edu
AF: Department of Electrical and Computer Engineering, University of Illinois at Urbana- Champaign, 1308 W. Main St., Urbana, IL 61801, United States
AB: The US Maui-MALT program is designed to investigate the properties and dynamics of the low-latitude mesosphere and lower thermosphere region (MLT) in exceptional detail. On June 29, 2003, the University of Illinois Meteor Wind Radar (MWR) at Kihei, Maui (20.8°N, 156.4°W) observed a diurnal tidal wave with an amplitude twice as large as normal at mesospheric height (80--100 km) for 7 hours (1400--2100 UT). At the same time, the Utah State University Mesospheric Temperature Mapper (MTM) measured OH and O₂ band emission intensities and temperatures at nearby Haleakala Crater, Maui (20.8°N, 156.2°W). The MTM observed a short-period gravity wave (GW) event propagating through this region for most of the night from 600 to 1500 UT. The GWs disappeared from the O₂ band data (peak altitude: ~94 km) and the OH band data (~87 km) around 1400 UT and 1430 UT, respectively. Qualitative and quantitative investigations of relationship between the observed GW dissipations and the increasing background wind field show the following. 1. The wave dissipation observed in both emissions was caused by wave absorption at a critical layer (CL) when the background wind speed exceeded the wave phase speed. 2. The wave absorption at the CL appears to accelerate the background wind. 3. The acceleration occurred over a wide altitude range (80--100 km) because the CL was moving down in association with downward progression of the diurnal tidal wave. 4. The change in background wind speed caused by the GW absorption at the CL was comparable with the induced tidal effect.
DE: 0342 Middle atmosphere: energy deposition (3334)
DE: 3332 Mesospheric dynamics
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 3384 Acoustic-gravity waves
DE: 3389 Tides and planetary waves
SC: SPA-Aeronomy [SA]
MN: 2007 Joint Assembly