Vertical shears of horizontal winds in the lower thermosphere observed
AbstractVertical shears of horizontal winds play an important role in the
dynamics of the middle and upper atmosphere. Prior observations have
indicated that these shears predominantly occur in the lower
thermosphere. MIGHTI observations from the Ionospheric Connection
Explorer indicate that strong wind shears are a common feature of the
lower thermosphere and vary greatly between orbits. This work focuses on
these strong shears, and examines their occurrences, horizontal scales
and underlying organization. No preferred wind shear direction is found.
The shears that persist for a short horizontal extent are slightly
larger in amplitude and more numerous than those that persist across
large horizontal scales. The altitude at which the strongest shears
occur often shows a downward progression with local time, following the
climatological winds. Consistent with prior observations, the strongest
shears are often seen just below the wind maximum, which follows the
downward phase propagation consistent with upward propagating tides.