Momentum budget of the migrating diurnal tide

The migrating diurnal tide in the mesosphere and lower

thermosphere is examined in SABER temperature and

geopotential, and concurrent TIDI horizontal winds.

Amplitudes generally maximize near the March equinox, and

minimize in August. Considerable year-to-year variations

are noted between 2004 and 2007, with the weakest amplitudes

seen in 2005. Simultaneous retrievals of diurnal winds,

temperature, and geopotential allow the diurnal vertical

wind to be inferred using the adiabatic and the

kinematic methods. We also compute the momentum

budget of the diurnal zonal wind. Advection of zonal

momentum by the diurnal meridional wind is a

key nonclassical effect. A net zonal momentum

residual is present during all seasons, with an average

amplitude near 60 m/s/day.