Diurnal variation of gravity wave momentum flux and its forcing on the diurnal tide

The diurnal variation of gravity wave (GW) momentum flux is derived from the 5 years of meteor radar wind measurements at Maui, Hawaii. The amplitude and phase relationships between the GW forcing and the diurnal tide are analyzed by calculating their equivalent Rayleigh frictions. The results show that the GW momentum flux is clearly modulated by the diurnal tide. The forcing from the momentum flux convergence has strong effects on both the amplitude and phase of the diurnal tide. They can reach 80 ms ‚àí‚Äâ1 day ‚àí‚Äâ1 for the amplitude and 15 h day ‚àí‚Äâ1 for the phase. The GW forcing tends to increase the diurnal tide amplitude above 90 km but has a small damping effect below 90 km. It tends to increase the phase of the diurnal tide throughout all altitudes. Seasonal variations of the GW forcing exist, which result in differences in their effects on the diurnal tide. The magnitudes of the forcing are in agreement with recent results from satellite observations but are much larger than values used in general circulation models. This work also demonstrates that meteor radar measurements can provide a valuable data set for the study of GW-tide interactions