[1] Since February 2002, the SABER (sounding of the atmosphere using broadband emission radiometry) satellite instrument has measured temperatures throughout the entire middle atmosphere. Employing the same techniques as previously used for CRISTA (cryogenic infrared spectrometers and telescopes for the atmosphere), we deduce from SABER V1.06 data 5 years of gravity wave (GW) temperature variances from altitudes of 20 to 100 km. A typical annual cycle is presented by calculating averages for the individual calendar months. Findings are consistent with previous results from various satellite missions. Based on zonal mean, SABER data for July and zonal mean GW momentum flux from CRISTA, a homogeneous and isotropic launch distribution for the GROGRAT (gravity wave regional or global ray tracer) is tuned. The launch distribution contains different phase speed mesoscale waves, some of very high-phase speed and extremely low amplitudes, as well as waves with horizontal wavelengths of several thousand kilometers. Global maps for different seasons and altitudes, as well as time series of zonal mean GW squared amplitudes based on this launch distribution, match the observations well. Based on this realistic observation-tuned model run, we calculate quantities that cannot be measured directly and are speculated to be major sources of uncertainty in current GW parameterization schemes. Two examples presented in this paper are the average cross-latitude propagation of GWs and the relative acceleration contributions provided by saturation and dissipation, on the one hand, and the horizontal refraction of GWs by horizontal gradients of the mean flow, on the other hand.

[1] Recent observations and model simulations demonstrate unequivocally that non-Sunsynchronous (nonmigrating) tides due to deep tropical convection produce large longitudinal and local time variations in bulk ionosphere-thermosphere-mesosphere properties. We thus stand at an exciting research frontier: understanding how persistent, large-scale tropospheric weather systems affect the geospace environment. Science challenge questions include: (1) How much of the tropospheric influence is due to tidal propagation directly into the upper thermosphere? (2) How large is the interannual and the solar cycle variability of the tides and what causes them? These questions are addressed using solar maximum to solar minimum tidal wind and temperature analyses from the Thermosphere Ionosphere Mesosphere Electrodynamics and Dynamics (TIMED) satellite in the mesosphere/lower thermosphere (MLT), and from the Challenging Minisatellite Payload (CHAMP) satellite at $400 km. A physics-based empirical fit model is used to connect the TIMED with the CHAMP tides, i.e., to close the ''thermospheric gap'' of current spaceborne observations. Temperature, density, and horizontal and vertical wind results are presented for the important diurnal, eastward, wave number 3 (DE3) tide and may be summarized as follows. (1) Upper thermospheric DE3 tidal winds and temperatures are fully attributable to troposphere forcing. (2) A quasi-2-year 15-20% amplitude modulation in the MLT is presumably caused by the QBO. No perceivable solar cycle dependence is found in the MLT region. DE3 amplitudes in the upper thermosphere can increase by a factor of 3 in the zonal wind, by $60% in temperature and by a factor of 5 in density, caused by reduced dissipation above 120 km during solar minimum.

[1] A major challenge in delineating and understanding the "space weather" of the ionosphere-thermosphere system is the lack of global tidal observations in the 120-400 km "thermospheric gap" between satellite remote-sensing and in-situ tidal diagnostics. This paper aims to close this gap by presenting an observation-based Climatological Tidal Model of the Thermosphere (CTMT) of self-consistent upward propagating migrating and nonmigrating diurnal and semidiurnal tides from 80-400 km and pole-to-pole for moderate (F10.7 = 110 sfu) solar flux conditions. CTMT includes the 6 (8) most important diurnal (semidiurnal) tidal components for temperature, density, and zonal, meridional and vertical winds and is based on Hough Mode Extension fits to 2002-2008 mean TIMED satellite tidal diagnostics in the mesosphere/lower thermosphere (MLT). Validation with independent 2002-2008 CHAMP tidal diagnostics (F10.7 = 105 sfu) around 400 km proves that the approach captures nonmigrating tides well, indicating that these waves propagate directly upward without significant tidal forcing occurring in the thermosphere. Notable exceptions are the DW2 and D0 components that are most likely generated in-situ by nonlinear interaction forcing in the upper thermosphere. CTMT is suitable for driving upper atmosphere models that require self-consistent tidal fields in the MLT region as a lower boundary condition. It does not include migrating tides due to in-situ EUV absorption in the upper thermosphere but allows us to quantitatively assess thermospheric variability due to tides from the lower atmosphere. This is done by discussing longitude/latitude maps of reconstructed diurnal and semidiurnal tidal variations as function of altitude and local time.

[1] TIMED Doppler Interferometer (TIDI) measurements of zonal and meridional winds in the mesosphere/lower thermosphere are analyzed for diurnal nonmigrating tides (June 2002 to June 2005. Climatologies of monthly mean amplitudes and phases for seven tidal components are presented at altitudes between 85 and 105 km and latitudes between 45°S and 45°N (westward propagating wave numbers 2, 3, and 4; the standing diurnal tide; and eastward propagating wave numbers 1, 2, and 3). The observed seasonal variations agree well with 1991-1994 UARS results at 95 km. Comparisons between the TIDI results and global scale wave model (GSWM) and thermosphere-ionospheremesosphere-electrodynamics general circulation model (TIME-GCM) tidal predictions indicate that the large eastward propagating wave number 3 amplitude is driven by tropical tropospheric latent heat release alone. In contrast, latent heating and planetary wave/ migrating tidal interactions are equally important to westward 2 and standing diurnal tidal forcing. There is good quantitative agreement between TIDI and the model predictions during equinox, but the latter tend to underestimate the westward 2 and standing diurnal tide during solstice. Neither model reproduces the observed seasonal variations of the eastward propagating components.

[1] Numerous observations and model studies made during the past 5 years have unequivocally revealed that the ionosphere and thermosphere owe a considerable amount of their longitudinal, local time, seasonal latitudinal and day-to-day variability to waves originating in the lower part of the atmosphere. The most prominent pattern is the four-peaked ("wave 4") longitudinal structure frequently observed by (quasi-) Sun-synchronous satellites in a variety of ionospheric and thermospheric parameters. The "wave 4" has often been attributed to the diurnal, eastward, wave number 3 (DE3), nonmigrating tide alone. A more detailed analysis of TIMED observations, supported by physics-based empirical modeling and data from the CHAMP satellite, now indicates that this interpretation needs to be revised. Secondary wave generation due the nonlinear interaction between the migrating diurnal tide and the DE3 leads to a large stationary planetary wave 4 (SPW4) and a large semidiurnal, eastward wave number 2 (SE2) tide in the equatorial zonal wind at E-region heights. Combined amplitudes can equal those of the DE3. SE2 penetrates into the upper thermosphere with transequatorial wind speeds in excess of 10 m/s. This paper discusses the resulting implications for electric field generation in the E-region and tidal-ionosphere coupling in the F-region and provides observational constraints for future modeling efforts.Citation: Oberheide, J., J. M. Forbes, X. Zhang, and S. L. Bruinsma (2011), Wave-driven variability in the ionospherethermosphere-mesosphere system from TIMED observations: What contributes to the "wave 4"?,