The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) experiment is one of four experiments that will fly on the Thermosphere, Ionosphere, Mesosphere, Energetics, and Dynamics (TIMED) mission to be launched in May, 2000. The primary science goal of SABER is to achieve major advances in understanding the structure, energetics, chemistry, and dynamics, in the atmospheric region extending from 60 km to 1 80 km altitude. This will be accomplished using the space flight proven experiment approach of spectral broadband limb emission radiometry. SABER will scan the horizon in 10 selected bands ranging from 1.27 im to 17 tm wavelength. The observed vertical horizon emission profiles will be processed on the ground to provide vertical profiles with 2 km altitude resolution, of temperature, 03, H20, and CO2 volume emission rates due to O2(1i), OH(u=3,4,5), OH(i=7,8,9), and NO; key atmospheric cooling rates, solar heating rates, chemical heating rates, airglow losses; geostrophic winds, atomic oxygen and atomic hydrogen. Measurements will be made both night and day over the latitude range from the southern to northern polar regions. The SABER instrument uses an on-axis Cassegrain design with a clam shell reimager. Preliminary test and calibration results show excellent radiometric performance.

[1] The seasonal and interannual variability of migrating (Sun-synchronous) and nonmigrating solar atmospheric tides at altitudes between 100 and 116 km are investigated using temperature measurements made with the SABER instrument on the TIMED spacecraft during [2002][2003][2004][2005][2006]. Quasi-biennial variations of order ±10-15% in migrating diurnal and semidiurnal tidal amplitudes are found, presumably due to modulation by the quasi-biennial oscillation (QBO) as the tides propagate from their troposphere and stratospheric sources to the lower thermosphere. A number of nonmigrating tidal components are found that have the potential to produce significant longitudinal variability of the total tidal fields. The most prominent of these, i.e., those that appear at amplitudes of order 5-10 K in a 5-year mean climatology, include the zonally symmetric (s = 0) diurnal tide (D0); the eastward propagating diurnal and semidiurnal tides with zonal wave numbers s = À2 (DE2 and SE2) and s = À3 (DE3 and SE3); and the following westward propagating waves: diurnal s = 2 (DW2); semidiurnal s = 1 (SW1), s = 3 (SW3), and s = 4 (SW4); and terdiurnal s = 5 (TW5). These waves can be plausibly accounted for by nonlinear interaction between migrating tidal components and stationary planetary waves with s = 1 or s = 2 or by longitudinal variations of tropospheric thermal forcing. Additional waves that occur during some years or undergo phase cancellation within construction of a 5-year climatology include DW5, SE1, SE4, SW6, TE1, TW1, and TW7. It is anticipated that the winds that accompany all of these waves in the 100-170 km region will impose longitudinal variability in the electric fields produced through the ionospheric dynamo mechanism, thereby modulating vertical motion of the equatorial ionosphere and the concomitant plasma densities. In addition to the wave-4 modulation of the equatorial ionosphere that has recently been discovered and replicated in modeling studies, the waves revealed here will generate wave-1 (SW1, SW3, D0, DW2), wave-2 (SW4, TW1), wave-3 (DE2, SE1), wave-4 (DE3, SE2, DW5, SW6, TE1, TW7), wave-5 (SE3), and wave-6 (SE4) components of this ionospheric variability, depending on year and time of year. However, the absolute and relative efficiencies with which these waves produce electric fields remains to be determined.

[1] Global satellite observations of temperature and geopotential height (GPH) from the Microwave Limb Sounder (MLS) on the EOS Aura spacecraft are discussed. The precision, resolution, and accuracy of the data produced by the MLS version 2.2 processing algorithms are quantified, and recommendations for data screening are made. Temperature precision is 1 K or better from 316 hPa to 3.16 hPa, degrading to $3 K at 0.001 hPa. The vertical resolution is 3 km at 31.6 hPa, degrading to 6 km at 316 hPa and to $13 km at 0.001 hPa. Comparisons with analyses (Goddard Earth Observing System version 5.0.1 (GEOS-5), European Centre for Medium-range Weather Forecasts (ECMWF), Met Office (MetO)) and other observations (CHAllenging Minisatellite Payload (CHAMP), Atmospheric Infrared Sounder/Advanced Microwave Sounder Unit (AIRS/AMSU), Sounding of the Atmosphere using Broadband Radiometry (SABER), Halogen Occultation Experiment (HALOE), Atmospheric Chemistry Experiment (ACE), radiosondes) indicate that MLS temperature has persistent, pressure-dependent biases which are between À2.5 K and +1 K between 316 hPa and 10 hPa. The 100-hPa MLS v2.2 GPH surface has a bias of $150 m relative to the GEOS-5 values. These biases are compared to modeled systematic uncertainties. GPH biases relative to correlative measurements generally increase with height owing to an overall cold bias in MLS temperature relative to correlative temperature measurements in the upper stratosphere and mesosphere.

[1] The quality of the retrieved temperature-versus-pressure (or T(p)) profiles is described for the middle atmosphere for the publicly available Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) Version 1.07 (V1.07) data set. The primary sources of systematic error for the SABER results below about 70 km are (1) errors in the measured radiances, (2) biases in the forward model, and (3) uncertainties in the corrections for ozone and in the determination of the reference pressure for the retrieved profiles. Comparisons with other correlative data sets indicate that SABER T(p) is too high by 1-3 K in the lower stratosphere but then too low by 1 K near the stratopause and by 2 K in the middle mesosphere. There is little difference between the local thermodynamic equilibrium (LTE) algorithm results below about 70 km from V1.07 and V1.06, but there are substantial improvements/differences for the non-LTE results of V1.07 for the upper mesosphere and lower thermosphere (UMLT) region. In particular, the V1.07 algorithm uses monthly, diurnally averaged CO 2 profiles versus latitude from the Whole Atmosphere Community Climate Model. This change has improved the consistency of the character of the tides in its kinetic temperature (T k ). The T k profiles agree with UMLT values obtained from ground-based measurements of column-averaged OH and O 2 emissions and of the Na lidar returns, at least within their mutual uncertainties. SABER T k values obtained near the mesopause with its daytime algorithm also agree well with the falling sphere climatology at high northern latitudes in summer. It is concluded that the SABER data set can be the basis for improved, diurnal-to-interannual-scale temperatures for the middle atmosphere and especially for its UMLT region.Citation: Remsberg, E. E., et al. (2008), Assessment of the quality of the Version 1.07 temperature-versus-pressure profiles of the middle atmosphere from TIMED/SABER,

[1] Microwave Limb Sounder and Sounding of the Atmosphere with Broadband Emission Radiometry data provide the first opportunity to characterize the four-dimensional stratopause evolution throughout the life-cycle of a major stratospheric sudden warming (SSW). The polar stratopause, usually higher than that at midlatitudes, dropped by $30 km and warmed during development of a major ''wave 1'' SSW in January 2006, with accompanying mesospheric cooling. When the polar vortex broke down, the stratopause cooled and became ill-defined, with a nearly isothermal stratosphere. After the polar vortex started to recover in the upper stratosphere/lower mesosphere (USLM), a cool stratopause reformed above 75 km, then dropped and warmed; both the mesosphere above and the stratosphere below cooled at this time. The polar stratopause remained separated from that at midlatitudes across the core of the polar night jet. In the early stages of the SSW, the strongly tilted (westward with increasing altitude) polar vortex extended into the mesosphere, and enclosed a secondary temperature maximum extending westward and slightly equatorward from the highest altitude part of the polar stratopause over the cool stratopause near the vortex edge. The temperature evolution in the USLM resulted in strongly enhanced radiative cooling in the mesosphere during the recovery from the SSW, but significantly reduced radiative cooling in the upper stratosphere. Assimilated meteorological analyses from the European Centre for Medium-Range weather Forecasts (ECMWF) and Goddard Earth Observing System Version 5.0.1 (GEOS-5), which are not constrained by data at polar stratopause altitudes and have model tops near 80 km, could not capture the secondary temperature maximum or the high stratopause after the SSW; they also misrepresent polar temperature structure during and after the stratopause breakdown, leading to large biases in their radiative heating rates. ECMWF analyses represent the stratospheric temperature structure more accurately, suggesting a better representation of vertical motion; GEOS-5 analyses more faithfully describe stratopause level wind and wave amplitudes. The high-quality satellite temperature data used here provide the first daily, global, multiannual data sets suitable for assessing and, eventually, improving representation of the USLM in models and assimilation systems.