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Multi-Platform Observations of a Bore Event on 4 June during IHOP

Multi-Platform Observations of a Bore Event on 4 June during IHOP. Steven E. Koch Frederic Fabry, Bart Geerts, Tammy Weckwerth, James Wilson, Dave Parsons, and Wayne Feltz. Data used in Study of this Bore Event. S-POL reflectivity, (radial velocity), refractivity Surface mesoanalysis plots

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Multi-Platform Observations of a Bore Event on 4 June during IHOP

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  1. Multi-Platform Observations of a Bore Event on 4 June during IHOP Steven E. Koch Frederic Fabry, Bart Geerts, Tammy Weckwerth, James Wilson, Dave Parsons, and Wayne Feltz

  2. Data used in Study of this Bore Event • S-POL reflectivity, (radial velocity), refractivity • Surface mesoanalysis plots • Mesonet time series, incl.refractivity calculations • AERI & CLASS thermodynamic structure evolution • FM-CW, HARLIE, MAPR, (RAMAN lidar), (GLOW) • UW King Air flight-level data • High-resolution MM5 simulations (next talk)

  3. Computation of Refractivity from Surface Data Refractivity Vapor Pressure

  4. BORE A

  5. S-POL: 0430 – 0730 UTC

  6. Surface Analysis at 0500 UTC

  7. FM-CW and HARLIE Displays of Bore A

  8. FM-CW and MAPR Displays of Bore A

  9. Bore A at Verles (0520 Z)

  10. Bore A at Rusty Tank (0530 Z)

  11. Bore A at Playhouse (0552 Z)

  12. Bore A at Lincolns (0635 Z)

  13. BORE B

  14. S-POL: 1000 – 1200 UTC

  15. Surface Analysis at 1000 UTC

  16. UWKA Flight-level data FM-CW Display of Bore B

  17. FM-CW and MAPR Displays of Bore B

  18. SE NW UW King Air Data FL 1850 m AGL • KA penetrated solitary waves at the top of the bore. The waves are ranked in amplitude (as in FM-CW). • 3C cooling and 4 g/kg more moisture found at this level behind the bore (NW) – unlike the drying/warming seen in SPOL near-sfc refractivity. • Vertical motions are in phase quadrature with theta and u/v, as in a typical gravity wave, but strangely out of phase with pressure fluctuations. • Pressure variations are mainly a response of the aircraft to the vertical motion field. Mean 1.2 m/s updraft over 30 sec produces 35 m ascent or 3.5 mb hydrostatic pressure decrease. potential temperature temperature Wave propagation vertical air velocity static pressure (u,v) theta-e mixing ratio

  19. Bore B at Verles (0942 Z)

  20. Bore B at Rusty Tank (1020 Z)

  21. Bore B at Playhouse (1022 Z)

  22. Bore B at Lincolns (1100 Z)

  23. Potential Temperature Relative Humidity AERI and ISS Detection of Bores A & B

  24. Conclusions • Two bores or solitons observed as fine lines in S-POL reflectivity and by FM-CW, MAPR, ISS, Mesonet, UWKA data systems: • Bore A occurred along an outflow boundary that propagated eastward from the Oklahoma Panhandle • Bore B occurred along a cold front enhanced by postfrontal convection in northwestern Kansas • Solitary waves developed to the rear of each leading fine line atop a 700 – 1000 m deep surface stable layer. Depth of stable layer increased by 0.6 km with passage of leading wave in bores A and B. • Solitary wave characteristics: periodicity = 15 – 30 min, horizontal wavelength = 10 – 20 km, phase speed = 11.4 – 12.6 m/s. Waves exhibited amplitude-ordering (leading wave always the largest one).

  25. Conclusions • Pronounced reduction in refractivity due to drying in surface layer occurred when the leading pressure jump was relatively strong. • Cooling & moistening aloft occurring with passage of both bores a likely result of adiabatic lifting (seen in AERI data and UWKA data for Bore B). UWKA pressure data is confusing. • Bore A appears to have been a soliton on a surface inversion layer. Bore B occurred at a higher elevation of 1.2 km as the inversion had lifted by that time, but problems remain with FM-CW data interpretation. It appears to have been a weakening soliton. • Need to understand better why drying (reduction of refractivity) only occurs at certain times. Analysis of MAPR, GLOW, & SPOL wind data, additional mesonet data, and UWKA data will be needed.

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