(1) At 87 and 97 km, the Kelan FPI wind patterns exhibited strong annual variation in the meridional wind and semiannual variation in the zonal wind, as well as diurnal variation, which was dominated by a semidiurnal tidal variation in the meridional and zonal winds during May and September with a diurnal phase difference.
Keeping close pace with the variation of the SAM, the variation in the zonal (eastward) geostrophic flow of the ACC derived from the OBP EOF solution is found to exhibit an obviously enhanced fluctuation in the southern ACC on the order of a few mm/s during the past decade.
This fact makes it possible to assume that the above indicated trend is caused by long-term variations in the zonal component Vny of the horizontal wind in the thermosphere, the latter component contributing into the vertical drift velocity W.
This OBP variation gives rise to a variation in the geostrophic flow field; the result for the same EOF mode shows heightened variations in the zonal velocity that resides primarily in the eastern hemispheric portion of the ACC and coincided geographically with the southernmost boundary of the ACC's main stream.
The high isotropic resolution in this study and the relatively thick cartilage of the lateral femoral condyle specimens allowed us to perform a zonal T2*and T1Gd assessment within articular cartilage in order to recognise variations in the zonal anatomy of articular cartilage in various stages of cartilage degeneration.
A peculiar wind perturbation was recognized on September 1. Figure 20 shows the enlarged plots of wind velocity and temperature on September 1 with the 10-min time resolution, which vividly exhibited large and rapid variations in both the zonal and meridional wind velocity at 2 12 km altitude in the afternoon.
The contribution from other gravitational error sources has been considered, as solid and oceans tides, odd zonal harmonics, and secular variations in the even zonal harmonics.
(2) At 250 km, the FPI wind patterns agreed fairly well with the HWM93 results, where both indicated annual/diurnal variation in the meridional and zonal winds, and weak semidiurnal tidal variation.
The MSAO variation in the deseasonalized-AO zonal wind at 81 km shows almost the same phase relation (approximately 1 month difference) with the SSAO at 10 hPa similar to the finding of Li et al. (2012) based on northern low-latitude observations.
All these perturbations are responsible, with the exception of the secular variations in the even zonal harmonics, of systematic effects smaller than those estimated for the non-gravitational perturbations.
Further, as is known, the background wind condition plays an important role in the upward propagation of these waves and, consequently, variations in the prevalent zonal wind have also been studied into.
