A preliminary comparison of observations with MF radars in Wuhan and Yamagawa at 30-31∘N

The simultaneous observation of the mesosphere and lower thermosphere winds with MF radars in Wuhan (30∘N,114∘E), China, and in Yamagawa (31∘N,131∘E), Japan, available from February 28 to March 13, 2001 are preliminary compared. Their hourly mean winds show similar magnitudes and oscillations. Phases of Yamagawa winds lead those of Wuhan. Statistics on the 14-day data shows that the profiles of mean zonal winds and their standard deviations agree with each other, but the mean meridional winds in Wuhan are slightly larger than those in Yamagawa. Mean winds from HWM93 for the same time show agreement with the radar measurements below 90 km but difference above 90 km, especially for the meridional winds. Profiles of the means and standard deviations of their diurnal tides' amplitudes agree well, but mean phases of diurnal tides in Wuhan are about 2-3 h larger than those in Yamagawa below 95 km. Semidiurnal tides have similar amplitudes and phases, especially in meridional component. In both sites, semidiurnal meridional tides activities are rather stable with very small standard deviations at all levels. GSMW00's calculations in March show good agreement with radar measurements for the diurnal tidal waves but large differences for the semidiurnal tidal waves from radars. The rms zonal winds due to atmospheric gravity waves show slight differences below 90 km between those two sites. The longitudinal variations of atmospheric gravity waves forcing may contribute to the differences of the mean winds and tides between Wuhan and Yamagawa, as well as their small differences of their geographic locations.