Transcript Koch Bore Presentation

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
IHOP Science Meeting
24-26 March 2003
Data used in Study of this Bore Event
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S-POL reflectivity, (radial velocity), refractivity
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Surface mesoanalysis plots
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Mesonet time series, incl.refractivity calculations
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AERI & CLASS thermodynamic structure evolution
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FM-CW, HARLIE, MAPR, (RAMAN lidar), (GLOW)
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UW King Air flight-level data
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High-resolution MM5 simulations (next talk)
Computation of Refractivity from Surface Data
Refractivity
Vapor Pressure
BORE A
IHOP Science Meeting
24-26 March 2003
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)
BORE B
IHOP Science Meeting
24-26 March 2003
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
SE
UW King Air Data
FL 1850 m AGL
NW
temperature
potential
temperature
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Wave propagation
vertical air velocity
static pressure
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(u,v)

theta-e
mixing ratio
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:
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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

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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.