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Ann. Geophys., 24, 3241-3256, 2006
www.ann-geophys.net/24/3241/2006/
© European Geosciences Union 2006
A numerical study on the impact of nonlinear interactions on the amplitude of the migrating semidiurnal tide
C. M. Huang1,2, S. D. Zhang1,2, and F. Yi1,2
1School of Electronic Information, Wuhan University, Wuhan, HUBEI 430079, People's Republic of China
2Laboratory of Geospace Environment and Geodesy, Wuhan University, Wuhan, HUBEI 430079, People's Republic of China
Abstract. To quantitatively study the effects of nonlinear interactions on tide
structure, a nonlinear numerical tidal model is developed, and the
reliability and convergence of the adopted algorithm and coding are checked
by numerical experiments. Under the same conditions as those employed by the
GSWM-00 (Global Scale Wave Model 2000), our model provides the nonlinear
quasi-steady solution of the migrating semidiurnal tide, which differs from
the GSWM-00 result (the linear steady solution) in the MLT region,
especially above 100 km. Additionally, their amplitude difference displays a
remarkable month-to-month variation, and its significant magnitudes occur
during the month with strong semidiurnal tide. A quantitative analysis
suggests that the main cause for the amplitude difference is that the
initial migrating 12-h tide will interact with the mean flow as well as the
nonlinearity-excited 6-h tide, and subsequently yield a new 12-h tidal
part. Furthermore, our simulations also show that the mean flow/tidal
interaction will significantly alter the background wind and temperature
fields. The large magnitudes of the tidal amplitude difference and the
background alteration indicate that the nonlinear processes involved in
tidal propagations should be comprehensively considered in the description
of global atmospheric dynamics in the MLT region. The comparisons among our
simulations, the GSWMs and some observations of tides suggest that the
nonlinearity-induced tidal structure variation could be a possible mechanism
to account for some discrepancies between the GSWMs and the observations.
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