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Investigating mesospheric gravity wave dynamics and temperature variability over the Andes Jonathan Pugmire Mike J. Taylor Center for Atmospheric and Space Sciences Utah State University Rocky Mountain NASA Space Grant Consortium Symposium May 6, 2013
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Overview Andes Lidar Observatory, Cerro Pachon, Chile Instrumentation USU Mesospheric Temperature Mapper Example OH Intensity and temperature data Seasonal Result Seasonal Comparisons Summary
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Andes LIDAR Observatory (ALO) 30.2°S, 70.7°W Cerro Pachon Telescopes Camera installed August 2009 44 months of data to date Data analysis focusing on OH temperatures and waves detection
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Multi-Instrument Measurements of the MLT Region Utah State University Mesospheric Temperature Mapper: Intensity and temperature maps of gravity waves and mesospheric temperature variability in OH and O 2 emissions. University of Illinois All Sky Imager: for gravity wave structure Multi Channel Photometer: Long-period Gravity Waves in different emissions Meteor Wind Radar: background wind measurements in MLT region Na wind-temperature lidar The Aerospace Corporation Aerospace Infrared Camera: small scale waves and wave breaking Maui-MALT (2001-2006): Coordinated investigation of MLT dynamics and climatology over central Pacific Ocean. ALO Program (2009-to date): Same instrument suite employed to investigate mesospheric dynamics over Andes Mountains and effects of orography.
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Mesospheric Temperature Mapper Sensitive bare CCD Imager developed to measure mesospheric temperature variability using airglow emissions. Field of view ~90°, (180 x 180 km at 90 km altitude). Sequential observations (30 sec. exposure) of : - NIR OH (6, 2) Band ~ 87 km - O 2 (0,1) A Band ~ 94 km -Background (~857.5 nm) Cycle time: ~ 3 min per OH/O 2 temperature determination. (Precision ~2K).
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OH Rotational Temperature OH (6,2) Band OH transition parameters from Goldman et al., 1998. Relative band intensity from (S 1c +S 2c ) and T using simplified LTE calculation.
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Example Data
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Example OH Zenith Data
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Example OH Analysis OH Temp Avg = 188.2 ± 0.4 Std.dev. = 7.6 OH Band Int Avg = 38155.5 ± 687.9 Std.dev = 12647.1
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Example of Short-period Wave Measurements OH Temperature and Band intensity in phase
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Example of Large Amplitude OH Temperature Perturbation Phase shift: Temperature leading intensity by ~2hrs Jan12-13, 2010 ΔT ~ 40K (peak to trough)
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MTM Summary OH Temperature
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Average Nightly Temperature: 197.7 K
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AO signature (2.9 K) SAO similar signature (3.8 K) Persistent ~90 day oscillation in T and I (2 K, QAO?) ( similar variability observed at El Leoncito, Argentina, 220 km away) Seasonal Variability at Cerro Pachon
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SABER Comparisons Offset: 6 K
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Mean=197.7 ± 6.4 K Summer SpringAutumn Mean= 197.6 ± 6.7 K Seasonal Comparison of Maui MALT and Cerro Pachon
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Summary Nocturnal variations of temperature are highly variable and at times can exhibit large amplitudes, exceeding 40 K during the course of a night observations probably driven by tidal harmonic oscillations (periods of 8 and 12 hrs). Other nights show evidence for smaller amplitude (several K) gravity waves in both intensity and temperature data with well-defined periods ranging from tens of minute to a few hours. An initial harmonic analysis applied to the 40 months OH intensity and temperature data has been used to study the seasonal variations. The data show clear signature of an annual (AO) and semi-annual oscillation (SAO) signatures with similar amplitude to those observed at Maui. However, the ALO data reveal an unexpected 90 day oscillation that lasted for the first 1.5 years of the measurements and exhibited a significant amplitude. This result is under further investigation. SABER temperature comparisons demonstrate the long-term stability and utility of ongoing MTM observations at ALO. These data are important for studying a broad range of wave phenomena extending from short period gravity waves to seasonal variations.
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Future Work Ongoing seasonal measurements will be used to build a clearer understanding of the temperature variability and its intra-annual variability. For the first two years of operation at ALO the MTM also measured O 2 temperatures. Phase differences between the O 2 and OH temperature waves will be measured to investigate gravity wave growth/dissipation over the Andes Mountains for comparison with Maui-MALT wave data over an oceanic site. These results will be used to study regional differences in gravity wave forcing in the MLT region. Detailed comparison of MTM temperature data with Na lidar temperature measurements as well as ongoing OH spectrometer measurements at El Leoncito, Argentina. Investigation of long-and short period gravity waves using MTM and collaborative Na lidar and meteor radar winds to investigate intrinsic wave characteristics, propagation and momentum fluxes. Advanced MTM data from South Pole.
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References Eckerman, S.D. and P. Preusse (1999), Global Measurements of Stratospheric Mountain Waves from Space, Science, 286, 5444, 1534-1537. Fritts, D.C., and M.J. Alexander (2003), Gravity wave dynamics and effects in the middle atmosphere. Review of Geophysics, 41, 1/1003. Goldman, A., et al. (1998). Updated line parameters for the OH X 2 π– X 2 π (v’’,v’) transitions. J. Quant. Spectrosc. Radiat. Transfer, 59, 453-469. Meriwether, J.W., (1984). Ground based measurements of mesospheric temperatures by optical means. MAP Handbook 13, 1-18. Pendleton Jr., W.R., Taylor, M.J., Gardner, L.C., (2000). Terdiurnal oscillations on OH Meinel rotational temperatures for fall conditions at northern mid-latitude sites. GRL 27 (12), 1799-1802. 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, J. Geophys. Res., 113, D17101 Smith, S.,Baumgardner, J.,Mendillo (2009), M., Evidence of mesospheric gravity-waves generated by orographic forcing in the troposphere, Geophys. Res. Lett., Vol. 36 Taori, A. and M.J. Taylor (2006), Characteristics of wave induced oscillations in mesospheric O 2 emission intensity and temperature, Geophys. Res. Lett., 33. Zhao, Y., M. J. Taylor, and X. Chu (2005), Comparison of simultaneous Na lidar and mesospheric nightglow temperature measurements and the effects of tides on the emission layer heights, J. Geophys. Res., 110, D09S07 Zhao, Y., Taylor, M.J., Liu, H.-L., Roble, R.G., (2007). Seasonal oscillations in mesospheric temperatures at low-latitudes. JASTP 69, 2367-2378
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Thanks! Questions?
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AMTM Optical Design (2010) Circular120º field of view: ~ 180 km diameter at 90 km 22 lens elements, throughput A = 1.0 cm 2.sr Length ~2 m, Weight ~ 100 kg
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ANtarctic Gravity Wave Imaging Network (ANGWIN) All-sky IR Imager Halley Davis McMurdo Collaborating institutes from: USA, Japan, UK, Australia, Brazil, and Argentina Goal: To measure and understand large scale gravity wave climatology and effects over the Antarctic Continent
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Seasonal Comparison with El Leoncito OH (6,2) Band at ~87 km.
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Mountain Waves Summer months: GW from deep convection arising from thunderstorms over the continent to the east. Winter this convective activity is expected to be replaced by strong orographic forcing due to intense prevailing zonal winds blowing eastward from the Pacific Ocean and suddenly encountering the towering Andes mountain range (6000m). This creates large amplitude mountain waves that have been measured well into the stratosphere and occasionally into the mesosphere Smith et al., 2009 OH all-sky Images showing unusual wave structures associated with the penetration of mountain waves into the mesosphere during the night of July 4, 2008. The wave pattern originated just westward of El Leoncito, Argentina.
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