IHOP Science Meeting24-26 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
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)
Computation of Refractivity from Surface Data
17.676.112 exp
100 243.5
o
o
T CRHe
T C
52
PRESSURE MOISTTERM TERM
77.6 3.73 10O O
P hPa e hPaN
T K T K
Refractivity
Vapor Pressure
IHOP Science Meeting24-26 March 2003
BORE A
S-POL: 0430 – 0730 UTC
Surface Analysis at 0500 UTC
FM-CW and HARLIE Displays of Bore A
FM-CW and MAPR Displays of Bore A
Bore A at Verles (0520 Z)
Bore A at Rusty Tank (0530 Z)
Bore A at Playhouse (0552 Z)
Bore A at Lincolns (0635 Z)
IHOP Science Meeting24-26 March 2003
BORE B
S-POL: 1000 – 1200 UTC
Surface Analysis at 1000 UTC
FM-CW Display of Bore B
UWKA Flight-level data
FM-CW and MAPR Displays of Bore B
temperature
potential temperature
vertical air velocity static pressure
(u,v)
theta-e
mixing ratio
SE NW
Wave propagation
UW King Air DataFL 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.
Bore B at Verles (0942 Z)
Bore B at Rusty Tank (1020 Z)
Bore B at Playhouse (1022 Z)
Bore B at Lincolns (1100 Z)
AERI and ISS Detection of Bores A & B
Potential Temperature
Relative Humidity
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).
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.