scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Thermospheric response to gravity wave coupling from the lower atmosphere
Vadas Sharon
NorthWest Research Assoc., CoRA div.
In this talk, we discuss the response on the thermosphere to gravity waves from the lower
atmosphere. In particular, we examine the spectrum of gravity waves excited by deep
convective overshoot near the tropopause and by wave breaking near the mesopause. We
examine which portion of these wave spectra can survive dissipative filtering and propagate
into the thermosphere. We then calculate the horizontal body forces which result when these
waves dissipate in the thermosphere. We examine their altitudinal, spatial, and temporal
characteristics. We then determine the "mean" wind and secondary gravity wave responses
which occur from these forcings using models and simulation. We then review the literature
which shows evidence of these responses. This includes PFISR, CHAMP satellite, EISCAT,
and TIDBBIT sounder published data.
We also review recent global model simulations showing the effects of parameterized gravity
wave dissipation on the thermosphere. Finally, we calculate the thermospheric response to 6
hours of deep convection in Brazil using a global model. We find that these forces create a
``mean'' eastward wind perturbation at z=150 km as large as 200-340 m/s. We find that these
forces also excite large-scale secondary GWs for at least 3 hours with horizontal wavelengths
of 4000 km and horizontal phase speeds of 600 m/s. We also show the scale and speeds of
the medium scale secondary gravity waves that are excited by thermospheric body forces
using our new compressible solutions.