Observations of the Mesospheric and Lower Thermospheric Mean Winds at 30°N With MF radars

Winds data of Wuhan (30.5°N, 114.4°W) MF radar available during 2001-01-01-03-18, 2002-02-05-03-18, and 2002-10-18-12-31, Yamagawa (31.2°N, 130.6°W) MF radar of Japan available during 1997-01-01-10-17 were used to analyze features of the mesospheric and lower ther-mospheric mean winds within 60-98km altitude ranges at near 30°N. It is shown that there are obviously seasonal variations in mean zonal winds and mean meridional winds. Westerly winds prevail in winter mean zonal winds, and decrease versus increasing heights, and even reverse near the top sometimes. During summer, Easterly winds prevail in the mesosphere but westerly winds prevail in the lower thermosphere. The summer zonal wind reversed height is about 80km. The spring and autumn are the transition time between summer structures and winter structures. An easterly winds tongue shows in spring. In the mesopause regions near 80km the mean meridional winds blow northwards during winter time, but southwards during summer time. Mean winds also show inter-annual variability. The above climate features of mean winds agree very well with the HWM93 model.