1. IHOP Science Meeting 24-26 March 2003 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. IHOP Science Meeting 24-26 March 2003 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. IHOP Science Meeting 24-26 March 2003 BORE B

14. S-POL: 1000 – 1200 UTC

15. Surface Analysis at 1000 UTC

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

17. FM-CW and MAPR Displays of Bore B

18. temperature potential temperature vertical air velocitystatic pressure (u,v) theta-e mixing ratio SE NW Wave propagation 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.

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

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.