Transcript 13 th Mtn Met, 13.6 15 August, 2008

Airborne Radar Observations of
Breaking Waves/Rotors in the Lee of
the Medicine Bow Mountains in
SE Wyoming, USA
Jeffrey R. French1, Samuel Haimov1, Larry
Oolman1, Vanda Grubisic2, and Dave Leon1
1University
of Wyoming
2Desert Research Institute
This work supported by NASA Grant NCC5-578
(Geerts, Leon, Snider PI) and NSF ATM-0742110
13th Mtn Met, 13.6
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Objective(s):
• Utilize data from the WCR and UWKA to investigate the
internal structure of rotors
scales (temporal and spatial), amplitude, turbulence and
sub-rotor features
• Use the data to better understand rotor typology, including
numerical modeling studies to augment and aid the
interpretation of the observations.
Motivation:
• Inability to penetrate some rotors with aircraft due to
severe turbulence?
• Use of WCR during TREX campaign to “see” into rotor
clouds
• Data mining for observations obtained in SE Wyoming
13th Mtn Met, 13.6
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USE of NASA06 dataNASA06 CampaignFollowing the TREX campaign
(Mar/Apr
06) we found
Investigate
orographic
that:
precipitation formation over
1. Under certain conditions
WCR
can be very
Med.the
Bow
Mountains
in SE
useful in investigating
the internal structure of
Wyoming
rotors
measures
from UWKA
2. Closer examination In
of situ
the earlier
campaigns
and suitable
WCR
(NASA06) indicated data
of rotor/wave
investigation to augment data collected in
TREX
Wintertime data, collected in regions with significant
snow cover, in the presence of strong surface winds
provides environment rich with scatterers (small
ice)!!!
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Case of 26 January:
Rapidly evolving Wave/Rotor system
Two passes over 30 minutes
Capture beginning of event
Strong vertical motion at UWKA flight level (>12 m s-1)
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Case of 5 February:
Relatively stationary lee wave
4 passes over 1 hour
Multiple waves, weaker vertical motion (4 m s-1)
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t = 0 min
t = 14 min
t = 48 min
t = 59 min
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Pass 1
t = 0 min
Vertical Velocity
from WCR
and
UWKA
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Pass 1
t = 0 min
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Pass 3
t = 48 min
Vertical Velocity
from WCR
and
UWKA
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Pass 3
t = 48 min
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Summary:
• two cases observed from which vertical x-sections of the
two-dimensional velocity field were retrieved; one case
evolved/changed rapidly, the other was rather stationary
over the 1-hour observation period.
• Observations at level of UWKA indicated moderate
turbulence on Jan26, single wave-type feature, less
turbulent on Feb05, with trapped lee waves evident.
• Internal structure of the rotors/waves near the surface
indicated very shallow (Jan26) strong downslope flow, with
region of strong turbulence along the shear layer from the
point of BL separation over the wave crest and
downstream…sub-rotor scale features of hundreds of m in
size evident on Jan 26.
13th Mtn Met, 13.6
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13th Mtn Met, 13.6
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