Variations of the mean winds and diurnal tides in the mesosphere and lower thermosphere observed by WINDII from 1992 to 1996 - art. no. L14111

摘要

Wind measurements of the satellite-based Wind Imaging Interferometer (WINDII) for Februaries of 1992-1996 are used to investigate the variations of the dynamics in the mesosphere and lower thermosphere (90-120 km) between 40 degrees S and 40 degrees N and any possible connection with the solar cycle. The period of 1992-1996 is in the descending phase of solar cycle 22, in that the solar F10.7 flux (2800 MHz) decreases from about 300 to 70 in units of 10(-22) Wm(-2) Hz(-1). The salient features are as follows. (1) Mean zonal winds in the tropical region and upward propagating diurnal tides in the subtropical regions are stronger in 1992, 1993 and 1995 than in 1994 and 1996. (2) The mean eastward winds below 100 km at mid-latitudes in February 1992 are larger in the winter hemisphere and smaller in the summer hemisphere compared to those in the other four years. (3) There is significant enhancement of the upward propagating diurnal tide above 100 km in February 1992, particularly in the winter hemisphere; and the diurnal amplitude in 1996 is the smallest among the five Februaries. (4) The upward propagating diurnal tide has a higher altitude range in 1992 than in 1996 by 2-4 km. (5) The in situ thermospheric diurnal tide at mid-latitudes above 100 km in the summer hemisphere has amplitudes at 50 ms(-1) in February 1992 compared to that in February 1996 at 8 ms(-1).