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Analysis of a Gravity Wave Traversing Oklahoma on April 26, 2011

Analysis of a Gravity Wave Traversing Oklahoma on April 26, 2011. Timothy A. Bonin and Phillip B. Chilson Atmospheric Radar Research Center and School of Meteorology, University of Oklahoma, Norman, OK, USA. Gravity Waves – The Basics.

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Analysis of a Gravity Wave Traversing Oklahoma on April 26, 2011

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  1. Analysis of a Gravity Wave Traversing Oklahoma on April 26, 2011 • Timothy A. Bonin and Phillip B. Chilson • Atmospheric Radar Research Center and School of Meteorology, University of Oklahoma, Norman, OK, USA

  2. Gravity Waves – The Basics • Gravity waves have a direct influence on the wind field near the surface (e.g. Brunk 1949; Ferguson, 1967) • Often, clouds and precipitation form in regions of rising motion (pressure rise) (Uccellini, 1975) and reduction of precipitation in pressure falls (Bosart and Cussen, 1973) • Can result in more intense convective activity/lightning (Bosart and Sanders, 1986) • Triggering mechanisms: Geostrophic adjustment, shearing instability (Uccellini and Koch, 1987), orography, and convection (from Bosart and Sanders, 1986)

  3. Short Overview of the SMARTSonde • Small Multifunction Research and Teaching Sonde • Capable of measuring T, RH, p, mean wind, and trace gas concentrations (ozone) • Use of open source autopilot software for preconfigured flight patterns

  4. Flight Plan – Constant ThrottleHelical Ascent • Used for wind best wind estimation, PBL thermodynamic profiles

  5. Motivation - Final Flight Path on April 26 SMARTSonde seemingly pushed downward midway through ascent. Why?

  6. RUC Sounding from 19Z Over Central Oklahoma Thick inversion with large N2 Conditionally unstable layer aloft Near-critical level aloft High vertical wind shear (Low Ri)

  7. NWC Mesonet Meteogram

  8. Meteograms from SW -> NE

  9. Track of Gravity Wave x – No distinguishable pressure oscillation 0.7 – Magnitude of pressure oscillation Line – Time (LT) of pressure rise

  10. Speed of the gravity wave

  11. Winds from sodar (at NWC) Between a trough and crest in the wave, would expect u and v to increase and rising motion ( Thanks to Charlotte Wainwright at OU for the sodar data)

  12. Vertical Velocities from SMARTSonde

  13. Vertical Velocities from SMARTSonde

  14. Summary • Gravity wave was observed traversing Oklahoma from SW -> NE • Could be observed from satellite imagery, surface pressure field, and winds throughout the PBL • Wave speed close to theoretical value, but slightly larger • Wind shift largely follows what would be expected with gravity wave except 10 minute window where trends reverse, accompanied with sinking motion • Multiple wave interactions? • Wave tilt with height? • Gravity wave may have induced convection for a severe storm later

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