HR: 1400h
AN: SA53B-07    [Abstracts]
TI: The Terdiurnal Tide Simulated by the Extended Canadian Middle Atmospheric Model (CMAM)
AU: * Du, J
EM: p531w@unb.ca
AF: Physics Department, University of New Brunswick, P.O.Box 4400, Fredericton, NB, E3B 5A3, Canada
AU: Ward, W E
EM: wward@unb.ca
AF: Physics Department, University of New Brunswick, P.O.Box 4400, Fredericton, NB, E3B 5A3, Canada
AB: The diurnal (24-hour) tide, which is dominated in the subtropics, and the semidiurnal (12-hour) tide, which is larger at high latitudes, have been extensively studied from the observations and models. However, our understanding of the terdiurnal (8-hour) tide remains limited, partly because of it being the third harmonic in the wind decomposition. Horizontal winds simulated from the extended Canadian Middle Atmosphere Model (CMAM) are analyzed to delineate diurnal, semidiurnal and terdiurnal tidal structures and stationary planetary waves. Each frequency component is then subjected to Fast Fourier Transform (FFT) to perform the zonal wavenumber decomposition for s = -5 to s = 5. In this paper, the seasonal-latitudinal and height structures of these 11 terdiurnal tide components are now revealed. The migrating terdiurnal component is dominated over other components at middle latitudes with significant amplitudes (wind speed over 15 m/s) in the lower thermosphere (90 -110 km). The amplitudes vary strongly with season below 95 km and are maximum during winter; however above 95 km, the seasonal variation is not as obvious. Other components tend to peak at Polar Regions with amplitudes between 2 - 6 m/s. There is uncertainty about the origin of the terdiurnal tides. Solar heating, convective heating and latent heat release in the model at March and June for terdiurnal tidal components are utilized to aid in interpreting their behaviors and ascertaining their origins.
DE: 3389 Tides and planetary waves
DE: 4255 Numerical modeling (0545, 0560)
SC: SPA-Aeronomy [SA]
MN: 2007 Joint Assembly