SA31A-01 INVITED 

Greenhouse Cooling in the Mesosphere and Lower Thermosphere (MLT)

* Akmaev, R A (Rashid.Akmaev@noaa.gov), CIRES, Univ. of Colorado, 216 UCB, Boulder, CO 80309, Emmert, J T

Marcos, F A) Hill, S M

The classical work by Roble and Dickinson (1989) predicted the upper atmosphere to be extremely sensitive to greenhouse forcing resulting primarily in its substantial cooling. Relevant mechanisms, including in-situ radiative forcings, feedbacks, and their uncertainties will be discussed from the modeling perspective. The MLT region is also expected to respond to changes in underlying atmospheric layers, including the stratosphere, in a complex manner presenting certain challenges for interpretation of observations, trend detection and attribution. Atmospheric density has proven to be a robust indicator of global change in the upper atmosphere. Comparisons with current data analyses will be presented and emerging perspectives for long-term monitoring in the MLT briefly discussed.

SA31A-02 INVITED 

Investigation of solar cycle effect and temperature trends in the mid-latitude mesopause region

* She, C (joeshe@lamar.colostate.edu), Colorado State University, 200 West Lake Street, Fort Collins, CO 80523, United States Krueger, D A (krueger@lamar.colostate.edu), Colorado State University, 200 West Lake Street, Fort Collins, CO 80523, United States Talaat, E (elsayed.talaat@jhuapl.edu), JHU/APL, 11100 Johns Hopkins Road, Laurel, MD 20723, United States Yee, S (Sam.Yee@jhuapl.edu), JHU/APL, 11100 Johns Hopkins Road, Laurel, MD 20723, United States

It has long been surmised that due to its large anticipated temperature change in response to external perturbations, solar cycle and/or anthropogenic effect, the mesopause region (80 – 105 km) of the earth's atmosphere is a region of choice for the evaluation of long-term climatic change. Using passive instrumentations, such as OH imagers and in-situ observation by rockets, mesopause region temperatures have been measured intermittently in various locations for more than 3 decades, deducing solar cycle effect and temperature trends. More recently, theoretical prediction and assessment of these effects have been made by a number of general circulation models. Generally, while there is arguably agreement in the solar cycle effect, the observed temperature trends based on simple assumptions is much larger than the predicted values. In this paper, we will examine the effect of wave perturbations on deduced responses and discuss the potential impact of model variability due to various schemes of gravity wave parametrization used. We will present the results of both effects in a mid-latitude location using mesopause temperatures deduced from 16 years nocturnal and 4 years of full-diurnal-cycle sodium lidar observations over Fort Collins, CO (40.6N, 105W), as well as 6 years of TIMED/SABER temperature observations. Comparison of these results with previous observations and model predictions, will likely reveal the need for improvements in methods of data analysis, and for continued and enhanced global observations, and thus will indirectly encourage further model studies, seeking a closure between observations and predictions.

SA31A-03 

The Variabilities of the Mesosphere and Lower Thermosphere as observed by TIMED

* Yee, J (sam.yee@jhuapl.edu), Johns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States Talaat, E (elsayed.talaat@jhuapl.edu), Johns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States Zhu, X (xun.zhu@jhuapl.edu), Johns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States Russell, J (james.russell@hamptonu.edu), Center for Atmospheric Sciences, Hampton University, 23 Tyler Street, Hampton, VA 23668, United States Mlynczak, M (m.g.mlynczak@larc.nasa.gov), NASA Langley, Mail Stop 401B Langley Research Center National Aeronautics and Space Admin., Hampton, VA 23681-0001, United States Skinner, W (Wskinner@umich.edu), Space Physics Research Laboratory, 2455 Hayward Street, Ann Arbor, MD 48109, United States Paxton, L (larry.paxton@jhuapl.edu), Johns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States

The Mesosphere and Lower Thermosphere (MLT) is a region of the Earth atmosphere that is very sensitive to external influences from the sun above and lower atmosphere below it. Its chemical, momentum and thermal balance, thus basic states (i.e. pressure, density, and temperature, and winds) can change in different time scales due to naturally-occurring and/or human-induced changes to the composition and energy contained within this region. The NASA Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) mission, since its successful launch in December 2001, has provided for the first time a comprehensive view of the basic structure and its variabilities of the MLT system during the descreasing phase of this current solar cycle. This paper gives a 5-year climatological view of the MLT system as observed by the TIMED spacecraft and reports the characteristics and magnitudes of its temporal and spatial variabilities. Examples of the observed climatology and variabilities will be used to examine and assess our basic understanding of coupled radiative/chemical/dynamical processes that occur in the system.

SA31A-04 INVITED 

Aeronomy of Ice in the Mesosphere Mission Overview and Collaborative Studies Using the AIM and TIMED Data Sets

* Rusell, J M (james.russell@hamptonu.edu), Hampton University, Center for Atmospheric Sciences 23 Tyler Street, Hampton, VA 232668, United States Bailey, S M (baileys@vt.edu), Virginia Tech, Bradley Department of Electrical and Computer Engineering, Blacksburg, VA 24061, United States Rusch, D (david.rusch@lasp.colorado.edu), University of Colorado, Laboratory for Atmospheric and Space Physics 1234 Innovation Drive, Boulder, CO 80303, United States Gordley, L L (l.l.gordley@gats-inc.com), GATS, Inc., 11864 Canon Blvd Suite 101, Newport News, VA 23606, United States Hervig, M E (m.e.hervig@gats-inc.com), GATS, Inc., 11864 Canon Blvd Suite 101, Newport News, VA 23606, United States Merkel, A (Aimee.Merkel@lasp.colorado.edu), University of Colorado, Laboratory for Atmospheric and Space Physics 1234 Innovation Drive, Boulder, CO 80303, United States

The Aeronomy of Ice in the Mesosphere (AIM) mission was launched from Vandenberg Air Force Base in California on April 25, 2007 becoming the first satellite mission dedicated to the study of noctilucent clouds that occur at approximately 83km altitude. A Pegasus XL rocket launched the satellite into a near perfect 600 km sun synchronous circular orbit. AIM carries three instruments - a nadir imager, a solar occultation instrument and an in-situ cosmic dust detector - that were specifically selected because of their ability to provide key measurements needed to address the six AIM science objectives. The Thermosphere Ionosphere Mesosphere Energetics and Dynamics mission was launched from Vandenberg Air Force Base on December 7, 2001 and is dedicated to the study of the structure, chemistry, energetics and dynamics of the atmospheric region between 60 km and 180 km altitude. TIMED carries four instruments including an infrared limb sounder to characteristic the temperature, chemistry, energetics and dynamics of the region; a global ultraviolet imager; a solar flux monitor and an instrument to measure winds. Together AIM and TIMED form an important component of the Heliophysics Great Observatory. This paper will provide an overview of the AIM mission and will discuss collaborative studies using the combined AIM/TIMED data sets in a synergistic way to advance our knowledge of this region where the sun first interacts with Earth's atmosphere.

SA31A-05 

Long-term Meteor Radar Observations of Atmospheric Winds and Tides in the Polar Mesosphere and Lower Thermosphere above Svalbard and Tromso

* Aso, T (t-aso@nipr.ac.jp), National Institute of Polar Research, Kaga 1-9-10, Itabashi, Tokyo, 173-8515, Japan Tsutsumi, M (tutumi@uap.nipr.ac.jp), National Institute of Polar Research, Kaga 1-9-10, Itabashi, Tokyo, 173-8515, Japan Hall, C (Chris.Hall@tgo.uit.no), Tromso Geophysical Observatory, University of Tromso, Tromso, N-9037, Norway

We have been running meteor radars in Svalbard and Tromso for 7 and 4 years, respectively, to observe wind and waves, especially tides, in the polar upper mesosphere and lower thermosphere. The results hence suggest the climatology and variability of tides in the polar region where wave disturbance comes from below forced by insolation absorption, modified by the intervening middle atmosphere and also from above in relation to solar disturbances. Furthermore behavior at polar latitudes is characteristic of Hough and velocity expansion functions. Collaborative circumpolar and bipolar comparison with MF radars depicts global nature of waves and also localized comparison with EISCAT, SOUSY MST and MF radars helps to clarify intercomparison of wind measurement while near-by meteor radars tells us about local disturbances due to smaller-scale gravity-waves. Non-migrating tide as semidiurnal zonal wavenumber 1 and diurnal zonally symmetric mode which might be attributed to interaction of migrating tide with planetary waves is relevant in view of its dominance at higher latitudes. Neutral temperature is also derivable from decay rate of echo returns and long term temperature variation and temperature tide are the other issues of interest.

SA31A-06 

Intra-Annual Variability of the Mesosphere Wind Field as Observed by TIDI

* Skinner, W (wskinner@umich.edu), Department of Atmospheric, Oceanic and Space Sciences University of Michigan, 2455 Hayward, Ann Arbor, Mi 48109-2143, United States Niciejewski, R J (niciejew@umich.edu), Department of Atmospheric, Oceanic and Space Sciences University of Michigan, 2455 Hayward, Ann Arbor, Mi 48109-2143, United States Cooper, M (mlcooper@umich.edu), Department of Atmospheric, Oceanic and Space Sciences University of Michigan, 2455 Hayward, Ann Arbor, Mi 48109-2143, United States Marshall, A (armarsh@umich.edu), Department of Atmospheric, Oceanic and Space Sciences University of Michigan, 2455 Hayward, Ann Arbor, Mi 48109-2143, United States

Since early 2002, the TIMED Doppler Interferometer (TIDI) on Thermosphere-Ionosphere-Mesosphere- Energetics-Dynamics (TIMED) spacecraft has provided unprecedented spatial and temporal coverage of the Mesosphere and Lower Thermosphere/Ionosphere (MLTI) dynamics. Combined with wind data obtained from the High Resolution Doppler Imager (HRDI) and the Wind Imaging Interferometer (WINDII) on the Upper Atmosphere Research Satellite (UARS), space based wind measurements are continuous since late 1991. This covers the time from just past the peak of solar cycle 22 to the minimum of solar cycle 23 and includes approximately 7 QBO cycles. This paper will examine the wind field over this time, emphasizing the intra-annual variability.

SA31A-07 

Inter-annual and long-term variations observed in the ITM system

* Talaat, E R (elsayed.talaat@jhuapl.edu), The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States Yee, J (sam.yee@jhuapl.edu), The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States Ruohoniemi, J M (michael.ruohoniemi@jhuapl.edu), The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States Zhu, X (xun.zhu@jhuapl.edu), The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States DeMajistre, R (Robert.DeMajistre@jhuapl.edu), The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States Russell, J (james.russell@hamptonu.edu), Hampton University, 23 Tyler Street, Hampton, VA 23668, United States Mlynczak, M (m.g.mlynczak@larc.nasa.gov), Hampton University, 23 Tyler Street, Hampton, VA 23668, United States Mlynczak, M (m.g.mlynczak@larc.nasa.gov), NASA Langley Research Center, Mail Stop 420 Atmospheric Sciences Research, Hampton, VA 23681, United States Paxton, L (larry.paxton@jhuapl.edu), The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States Christensen, A (Andrew.B.Christensen@aero.org), The Aerospace Corporation, PO Box 92957, Los Angeles, CA 90009, United States

The Ionosphere-Thermosphere-Mesosphere (ITM) region is highly variable and has a complex system of drivers including variable solar radiation, geomagnetic activity, and forcing from the lower atmosphere. Waves that originate in the troposphere grow in amplitude as they travel upwards into decreasing density at higher altitudes where they become the most prominent dynamical features of the ITM. Planetary and gravity waves modify the zonal mean temperature and winds through dissipation and momentum deposition. The effects of these waves on the ITM are expected to depend on the level of solar activity. For all types of waves, how high they penetrate into the thermosphere depends on the temperature, wind, and viscosity profiles. Current observations have shown signatures of both gravity waves and planetary waves in upper atmospheric measurements of winds, temperature, and ion density. The momentum deposition from upward propagating waves is thought to generate the quasi-biennial oscillation (QBO) and semiannual oscillation (SAO) in the zonal circulation of the stratosphere and mesosphere. These zonal wind oscillations, in turn, modulate the waves as they propagate upwards, including the migrating and nonmigrating tides. Understanding the behavior of the tides is not only crucial to characterizing mesopause variability but also transport in the region. Momentum deposition by the diurnal tide at low latitudes in the lower thermosphere produces indirect circulations that will transport neutral and ionized constituents both vertically and horizontally to higher latitudes. Six years of measurements by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite and longer time series from the Super Dual Auroral Radar Network (SuperDARN) HF radars are analyzed to examine the seasonal and inter-annual variations of the diurnal, semidiurnal and terdiurnal tides in the mesosphere and lower thermosphere. We present estimates of both the migrating and nonmigrating of these tides from the lower stratosphere to the lower thermosphere and discuss evidence of nonlinear interaction between the tides and other wave modes. We also examine the inter-relationship the tides may have with lower and middle atmosphere variability (e.g., QBO, SAO, and stratospheric warmings) and tidal impacts on the zonal mean structure of the upper atmosphere and ionosphere using additional data from TIMED/GUVI and TOPEX/Jason data.

Author(s) (2007), Title, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract #####-##.