SA33B-01 13:40h
Solar Cycle and Seasonal Variations in the Energy Balance of the Middle and Upper Atmosphere
The Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIMEGCM) encapsulates our current understanding of the MLTI and provides insight into the processes responsible for changes in the MLTI structure. We use the global 3-D model to determine the energy balance of the middle and upper atmosphere for different portions of the solar cycle and for different seasons. The simulations indicate significant changes in the relative importance of various terms in the energy balance for the different conditions. The TIMED mission seeks to resolve the basic atmospheric structure and energy balance of the Mesosphere Lower Thermosphere between 60 and 180 kilometers. The satellite was launched near solar maximum, and the extended mission is occurring in the declining phase. The model simulations for solar maximum compare favorably with TIMED observations, and provide a framework for the interpretation of the data. Our results indicate that significant new information could be obtained by operating the satellite through solar minimum conditions, and that these data would be important for understanding outstanding MLTI science questions.
SA33B-02 INVITED 13:55h
Hemispheric Differences and Evolution of the Cold Summer Mesopause Observed by the SABER Experiment on the TIMED Satellite
The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) experiment was launched on December 7, 2001 into a 74.1 degree inclined, 625 km orbit onboard the TIMED satellite. 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 to 180 km altitude. SABER has been operating almost continuously since activation using the space flight proven experiment approach of spectral broadband limb emission radiometry applied in 10 selected infrared spectral bands ranging from 1.27 micrometers to 17 micrometers wavelength. Observed limb emission profiles are being processed on the ground to provide vertical profiles with 2 km altitude resolution of key constituents, energetics parameters and temperature. Measurements are made both night and day over the latitude range from 52 degrees to 83 degrees with alternating hemisphere coverage every 60 days. During the time SABER has been operating, there have been two major solar storms in April 2002 and October 2003. The temporal and geographic coverage provided by SABER has provided path finding observations on the atmospheric effects of these events. In addition, the battery of measurements made by SABER has yielded new information on atmospheric energetics effects including radiative cooling due to the 15 micrometer band of CO2 and the persistence of heating due to exothermic chemical reactions. SABER observations have also provided new information on the mesopause latitudinal structure and evolution and have revealed the presence of a two-day wave in the mesopause region that previously was known only through modeling. Further, the data have shed light on the global distribution of the effects of nitric oxide vertical descent into the upper stratosphere and on the variability of atomic oxygen. This paper summarizes the major scientific results from SABER up to now using illustrative examples.
SA33B-03 14:15h
Observations of ozone and odd-oxygen in the mesosphere by the SABER instrument on the TIMED satellite
The Sounding of the Atmosphere using Broadband Emission Radiometery (SABER) instrument operating on the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite provides, among other parameters, measurements of ozone and atomic oxygen in the mesosphere. Specifically, daytime ozone is derived from measurements of the molecular oxygen airglow at 1.27 um. Ozone is also derived day and night from measurements of ozone emission at 9.6 um. Both of these emissions are in non-LTE and the non-LTE retrieval algorithms will be reviewed. Comparisons we will present of the daytime ozone retrieved from both techniques provide an important internal consistency check of the ozone measurements. SABER ozone measurements can also be used to derive atomic oxygen in the mesosphere using various photochemical relationships between ozone and atomic oxygen in the daytime. At night, the SABER hydroxyl emission measurements provide a measure of atomic oxygen. The combination of these measurements yields the global distribution of odd-oxygen in the mesosphere.
SA33B-04 INVITED 14:30h
TIMED Doppler Interferometer Observations of Mesosphere and Lower Thermosphere Tides
Using neutral winds measured by the TIMED Doppler Interferometer (TIDI), we examine the global distribution and seasonal variation of migrating and non-migrating tides. These results are compared with ground-based measurements, the Global Scale Wave Model (GSWM02), and the NCAR Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM). The comparisons show general consistency between the observational and modeling results. The TIDI data exhibit a nearly symmetric amplitude distribution of the migrating diurnal tide across the equator, which compares favorably with the GSWM02. TIDI neutral wind measurements have similar diurnal variations to those observed by ground-based meteor radars in Hawaii and at other locations. TIDI observations combined with ground-based measurements and global models will provide a truly global view of tides and planetary waves in the mesosphere and lower thermosphere, and reveal the salient features of MLT dynamics.
SA33B-05 INVITED 14:50h
New Perspectives on Atmospheric Tides and Planetary Waves From the TIMED Mission
Measurements from the TIMED satellite afford a new perspective on tides and planetary waves in the mesosphere-lower thermosphere-ionosphere (MLTI) region (ca. 60-180 km). Migrating diurnal, semidiurnal and terdiurnal tides are now measured in the region where the transition occurs from dominance of upward-propagating waves to in-situ generation by EUV heating. The 73-deg inclination of TIMED enables investigations of stationary and planetary wave vertical and latitudinal coupling, and provides insights into semidiurnal and terdiurnal oscillations that tend to dominate at high latitudes. The high inclination of TIMED has also enabled joint space-based and ground-based investigations, since many of the instrument arrays are most prevalent at middle and high latitudes, including Antarctica. Due to the exponential growth of upward-propagating tides, the high altitudes reached by TIMED instruments make possible identification of a wider spectrum of waves, leading to new interpretations in terms of wave-wave interactions and convective forcing. In addition, TIMED's near-continuous sampling permits the evolution of planetary waves to be delineated, affording the opportunity to identify source regions, regions of amplification, and ducting through the background wind field. All of these new perspectives greatly improve our ability to formulate and test theories, and to exercise a range of numerical models. In this paper, examples of TIMED analyses and investigations exemplifying these capabilities will be presented.
SA33B-06 15:10h
Observations of Tides and Planetary Waves from the stratosphere to the thermosphere
We present initial observations of migrating tides, nonmigrating tides, and planetary waves from the lower stratosphere to the thermosphere. The migrating tide is extracted from the temperature inferred by the TIMED/SABER instrument in the stratosphere, mesosphere and lower thermosphere and TIMED/GUVI instrument in the thermosphere. The zonal mean temperatures are subtracted from each day of data and the perturbation fields are fitted to extract the nonmigrating tides and planetary waves. The daytime longitudinal variations of the thermospheric O/N$_2$ ratio are also examined.
SA33B-07 15:25h
Seasonal diurnal tidal variation in the mesopause region over Ft. Collins, CO (40.6N, 105W).
Abstract: Based on a first yearlong lidar observation (May 2002 - April 2003) over full diurnal cycles, harmonic analysis, binned bi-monthly, was performed to extract diurnal perturbations of temperature, zonal and meridional winds in the mesopause region over Fort Collins, CO (40.6N, 105W). The results were compared to predictions of the 2000 and 2002 versions of Global Scale Wave Model (GSWM00 and GSWM02) as well as of the 2002 version of Thermosphere, Ionosphere, Mesosphere and Electrodynamics general circulation model (TIME-GCM). The observed diurnal phases are in good agreement with GSWM predictions, except the Nov-Dec period temperature, which shows roughly constant diurnal phase with the altitude. The agreement with TIME-GCM 2002 version predictions, however, is not as good, especially in temperature. As far as the tidal amplitudes comparison, GSWM00 diurnal amplitudes predictions are reasonably close to lidar observations, while GSWM02 diurnal amplitudes calculations, on the other hand, seems to overestimate the observations. In this paper, we focus on diurnal-period perturbations in winter temperature and on the seasonal variation in zonal wind. We discuss winter anomaly using newer data in 2003 and older data in 1998, both collected in winter months. We also compare observed seasonal variation in zonal wind tidal perturbations with those of radar observation from nearby Platteville, CO and with GSWM00 prediction. To the extent feasible, collaborative study with TIMED/SABER and TIMED/TIDI observations will be evaluated.