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Chapman Conferences ABSTRACTS listed by name of presenter Alexander, M. Joan (between one day and one week apart). The stratopause temperature and height vary between observation nights on Mountain Wave Momentum Fluxes in the Southern scales of several kilometres and tens of Kelvin as a result of Hemisphere from Satellite Measurements planetary wave activity. The stratopause is also affected by Alexander, M. Joan1; Grimsdell, Alison1; Teitelbaum, Hector2 gravity-wave activity during the night, with the regular passage of inertia-gravity waves changing the stratopause 1. Colorado Research Associates Division, NWRA, Boulder, altitude by up to ~10km over the course of 18 hours. Gravity CO, USA wave dissipation above 40 km occurs during winter, while 2. LMD, Paris, France significant dissipation is only noted below the stratopause Accurate representation of stratospheric winds in the during autumn. Temporally filtered data with ground based Southern Hemisphere in climate models depends on the periods of 2 – 6 hours are examined in addition to the non- parameterization of gravity wave drag. Parameterization of filtered data, with similar seasonal cycles and short-term orographic wave drag is widely considered to be insufficient variability noted. We compare the seasonality of gravity-wave in these models, and additional drag from non-orographic energy with other high latitude sites and suggest that the waves is very important. Previous work has shown the main contribution to wave energy above Davis is from non- stratospheric circulation affects both the seasonal orographic sources. development of the ozone hole, and predicted changes in 21st century Southern Hemisphere climate. Recent Alexander, Simon observational evidence suggests that small islands in the The effect of orographic waves on Antarctic Polar Southern Ocean may be important sources of orographic Stratospheric Cloud (PSC) occurrence and wave drag that is currently missing in existing parameterizations. Latitudinal and downstream propagation composition of Andean mountain waves has also been demonstrated in Alexander, Simon1; Klekociuk, Andrew1; Pitts, Michael2; recent model studies. We provide observational estimates of McDonald, Adrian3; Arevalo-Torres, Andolsa3 momentum flux carried by Southern Hemisphere mountain 1. Australian Antarctic Division, Kingston, TAS, Australia waves as derived from Atmospheric Infrared Sounder (AIRS) 2. NASA Langley Research Center, Hampton, VA, USA observations from the Aqua satellite. The fluxes from these 3. University of Canterbury, Christchurch, New Zealand sources will be shown to cover a much broader range of longitudes and latitudes than current orographic The first seasonal analysis of the relationship between parameterizations predict. The analysis reveals errors in the mesoscale orographic gravity-wave activity and polar existing parameterizations due to missing island sources and stratospheric cloud (PSC) composition occurrence around due to the assumption that the orographic drag only affects the whole of Antarctica is presented, for austral winter 2007. the column of air directly above the topography. Our results Gravity-wave variances are derived from temperature provide some quantitative guidance for future improvements measurements made with the Constellation Observing in orographic gravity wave drag parameterizations. System for Meteorology, Ionosphere and Climate (COSMIC) Global Positioning System Radio Occultation (GPS-RO) Alexander, Simon satellites. Data from the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) instrument onboard the Wintertime gravity-wave activity in the Antarctic Cloud-Aerosol Lidar and Infrared Pathfinder Satellite upper stratosphere and lower mesosphere revealed Observations (CALIPSO) satellite are used to determine the by the Davis (69°S, 78°E) lidar PSC composition class distribution and spatial volume. The Alexander, Simon1; Klekociuk, Andrew1; Murphy, Damian1 results show intermittent large wave activity above the Antarctic Peninsula which is co-incident with large volumes 1. Australian Antarctic Division, Kingston, TAS, Australia of water ice PSCs. These ice PSC volumes advect Gravity-wave activity throughout the Antarctic upper downstream, where increases in nitric acid trihydrate (NAT) stratosphere and lower mesosphere (USLM) is investigated PSC volumes occur, supporting the mountain wave seeding using temperature data collected with a Rayleigh lidar at hypothesis throughout winter. We calculate the approximate Davis, Antarctica (69°S, 78°E) during the 2007 and 2008 amount of PSCs attributable to these orographic gravity winters. We present the first results of gravity-wave activity waves. While we show that planetary waves are the major in the Antarctic lower mesosphere obtained using lidar determinant of PSC presence at temperatures close to the measurements. Potential energy per unit mass shows a NAT formation threshold, we also demonstrate the seasonal cycle throughout the USLM with the winter peak important role of mesoscale, intermittent orographic resulting from gravity wave Doppler shifting by the strong gravity-wave activity in accounting for the composition and background winds. Significant variability in gravity-wave distribution of PSCs around Antarctica. activity occurs on short time scales between observations 15 Alexander, Simon where extremely cold temperatures exist because of gravity waves. Simulations of PMCs using WACCM/CARMA, a Global observations of stratospheric gravity waves three-dimensional chemistry climate model based upon the made with COSMIC GPS-RO and comparisons Whole-Atmosphere Community Climate Model (WACCM) with an atmospheric general circulation model with sectional microphysics from the Community Aerosol Alexander, Simon1; Tsuda, Toshitaka2; Kawatani, Yoshio3; and Radiation Model for Atmospheres (CARMA) compare Takahashi, Masaaki4; Sato, Kaoru5; Klekociuk, Andrew1 well with observations from the Solar Occultation for Ice Experiment (SOFIE); however, despite using a relatively low 1. Australian Antarctic Division, Kingston, TAS, Australia nucleation barrier the model underestimates the ice particle 2. Research Center for Sustainable Humanosphere, Kyoto number density. In this study, we add subgrid scale University, Uji, Japan temperature variability from unresolved gravity waves to the 3. Frontier Research Center for Global Change, Japan model and examine its impact on nucleation rates and PMC Agency for Marine-Earth Science and Technology, number density. Yokohama, Japan 4. Atmosphere and Ocean Research Institute, University of Baumgarten, Gerd Tokyo, Kashiwa, Japan 5. Department of Earth and Planetary Science, University of Gravity Wave Observations in the Strato- and Tokyo, Tokyo, Japan Mesosphere by Lidar at 54°N and 69°N The launch of the six Constellation Observing System Baumgarten, Gerd1; Fiedler, Jens1; Gerding, Michael1; for Meteorology, Ionosphere and Climate (COSMIC) Hildebrand, Jens1; Höffner, Josef1; Lübken, Franz-Josef1 satellites in 2006 and resultant ~2000 daily profiles of 1. Optical Soundings, Leibniz-Institute of Atmospheric temperature below 40km altitude have provided a rich Physics, Kuehlungsborn, Germany dataset for the analysis of mesoscale gravity waves. We will discuss some of the highlights of our research over the last We present characteristics of gravity waves observed by few years, including comparisons between observed and Rayleigh- and resonance- lidars at Kühlungsborn (54°N, modelled gravity-wave activity. Gravity wave and equatorial 15°E) and ALOMAR (69°N, 16°E). A dataset of hourly wave-mean flow interaction is clearly apparent in the resolved temperature measurements covering the years since COSMIC results. Tropical stratospheric gravity waves 1997 was analyzed. Gravity waves are usually directly visible observed with COSMIC are seen above regions of active in the residual temperature fluctuations with a downward convection. Kelvin waves and mixed Rossby-gravity waves phase progession. The combination of lidar systems allows with zonal wavenumbers < 9 are observed intermittently to study waves with periods of several hours and vertical throughout the equatorial upper troposphere and lower wavelengths from 5 to about 50 km. We have derived the stratosphere. A T106L60 atmospheric general circulation potential energy density (GWPED) and found that it model is used to examine the same part of the gravity-wave increases with altitude throughout the strato- and spectrum seen by COSMIC, with good agreement in wave mesosphere, but slower than expected for freely propagating activity noted between observations and model. Large gravity waves. The GWPED seasonal variation depends on gravity-wave activity occurs around and above the winter altitude and latitude. The Rayleigh-lidar at ALOMAR was sub-tropical jet, which decreases with altitude but increases recently upgraded for measuring wind speed by direct poleward and upward as these waves are focussed into the detection of the Doppler shift between about 30 and 80 km polar night jets. Gravity waves seen by COSMIC in the polar with two hours time resolution. We present a climatological regions capture the very large but intermittent nature of study on mean GW characteristics as derived from orographic waves forced by surface topography. The temperature fluctuations and case studies of simultaneous descending nature of the austral springtime enhanced observation of both components of the horizontal wind and gravity-wave activity will also be discussed, along with temperature.
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