HR: 1400h
AN: SA53B-04    [Abstracts]
TI: Solar Diurnal Tides in the MLT Horizontal Winds as Observed by WINDII/UARS and Simulated by CMAM
AU: * Wang, D
EM: dwang@unb.ca
AF: Dept. of Physics, University of New Brunswick, P.O. Box 4400, Fredericton, NB E3B 5A3, Canada
AU: Ward, W
EM: wward@unb.ca
AF: Dept. of Physics, University of New Brunswick, P.O. Box 4400, Fredericton, NB E3B 5A3, Canada
AU: Du, J
EM: p531@unb.ca
AF: Dept. of Physics, University of New Brunswick, P.O. Box 4400, Fredericton, NB E3B 5A3, Canada
AU: Power, A
EM: f9a36@unb.ca
AF: Dept. of Physics, University of New Brunswick, P.O. Box 4400, Fredericton, NB E3B 5A3, Canada
AB: The global experimental observations of the tides were not possible until the advent of satellite measurements at altitudes where the tidal signal is sufficiently large in comparison to other sources of atmospheric variability. This analysis explores the solar diurnal tides in the MLT (mesosphere and lower thermosphere) region of 90-110 km by using the WINDII/UARS horizontal wind measurements taken during November 1991 through May 1997, and compares the observational results with the simulations of the extended Canadian Middle Atmosphere Model (CMAM). Both datasets show great similarities, but some significant differences are also found. In addition to the well-known westward propagating migrating tide with zonal wave number s=1 (W1), our analysis also revealed the most prominent non-migrating diurnal tidal components in the MLT region: the eastward propagating diurnal tide with the wave number s=3 (E3), the standing diurnal oscillation with s=0 (D0), and the westward propagating diurnal tide with s=2 (W2). The W1 mode has the largest annual mean meridional amplitudes of 60 m/s around 20N and 20S and at 90 and 95 km levels, respectively, in the WINDII data, but at 93 and 102 km in the CMAM. The W1 meridional amplitudes show significant semi-annual variation with magnitudes of 15 m/s and northward maxima occurred around early March and late August. The D0 and W2 modes are more or less similar to the W1 mode. They have maximum annual mean meridional amplitudes of 16-20 m/s between 95-100 km at 20N and 20S, and show little annual/semi-annual variations, except for the W2 meridional amplitudes between 90-105 km at 20N, where the annual variation of 10 m/s exists. The strongest E3 mode occurs primarily around the equator at the altitudes between 95-110 km, with maximum annual mean zonal amplitude of 10-22 m/s for both WINDII and CMAM data. The E3 zonal amplitudes are dominated by annual variation, which has the largest magnitude of 12 m/s at altitudes between 95 and 110 km around the equator in the WINDII data, but of 6 m/s at 100 km near 20N and 20S in the CMAM data. The maximum eastward winds are seen around July/August in both hemispheres in the WINDII data, but around December/January in the CMAM. The combination of E3, D0, and W2 with W1 gives rise to significant longitude variations in the diurnal tide between 40S and 40N latitude.
DE: 3332 Mesospheric dynamics
DE: 3360 Remote sensing
DE: 3389 Tides and planetary waves
SC: SPA-Aeronomy [SA]
MN: 2007 Joint Assembly