April 17, 2007 T-REX Data Workshop, NCAR, 17-19 April 2007

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T-REX Research at Mesoscale Dynamics & Modeling Lab at DRI

Vanda GrubišićBrian Billings, Ivana Stiperski, Ming Xiao

Objectives/Research Focus• Insights into the structure of wave-rotor coupling; classification of types of flow

structuresStarting point: UWKA in situ data, stereo photography,DRI surface data, WCR through collaboration with U Wyo team

Initial analyses completed; classification in progress; integrating GAUS (radiosonde) data with UWKA dataGoal: Composite analyses (multiple aircraft, multiple remote sensors, cross-platform: e.g. aircraft-remote sensors) - Seek collaborators

• Case Studies: IOP 6 - Morning - lee-wave rotor; Afternoon/Evening - deep westerly windstorm & jump-type rotor

IOP 3 - Morning - lee-wave rotor (NW); Afternoon - deep westerly windstormIOP 13 - lee-wave rotor

IOP 1, IOP 4, IOP 11 • Process Studies:

o Development of westerly windstorms in Owens Valley o Effects of a downstream boundary condition (mountain range)

• Numerical Modeling: o COAMPS 3D real-data very high-resolution nested simulations (dx=333 m)o COAMPS 2D very high-resolution idealized simulations

April 17, 2007 T-REX Data Workshop, NCAR, 17-19 April 2007

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Dry Wave Rotor Events (Weak Strong)

IOP 2 IOP 1 IOP 13

T-REX Data Workshop, NCAR, 17-19 April 2007

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IOP 6 UWKA & Surface Data

KA 2

KA 3

KA 2

KA 3

KA2

KA3

Need remote sensor data to fill the gap!

KA 1

April 17, 2007 T-REX Data Workshop, NCAR, 17-19 April 2007

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IOP 6

3D COAMPSSIMULATION

=0.01 s-1 whiteW=7.5 ms-1 greenTKE=15 m2s-2 redWind vectors yellow

April 17, 2007 T-REX Data Workshop, NCAR, 17-19 April 2007

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Stage 1: Identification of strong westerlies in DRI network observations

Time of Appearance (LST) Maximum Easterly Penetration Mechanism(km relative to Independence)

T-REXIOP 1 15 -4.5 (16, 5) 2

IOP 3* 08 9 (12, 17) 1 and 2IOP 4 12 9 (14, 6) 2

March 16† 17 6 (18 ,14)IOP 6 09 9 (14, 13) 1 and 2

April 5† 13 9 (14, 15)

IOP 11† 15 6 (18, 15)IOP 13 12 9 (13, 17) 1 and 2

SRPIOP 8 14 9 (14, 30) 1

IOP 12* 15 9 1 and 2IOP 14 13 6 (14, 33) 1

IOP 16* 10 9 (11, 8) 1

* Simultaneous strong westerlies at all 16 stations† Insufficient sounding support

15 km

Penetration of westerly momentum into Owens Valley

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Stage 2: Identification of changes in atmospheric vertical structure upstream and downstream of the Sierra near the time of westerly wind penetration

1. Dynamical Forcing– Changes in wind speed and stability

upwind inducing changes in wavelength, amplitude, gravity wave breaking, etc. downwind

2. Thermal Forcing– Erosion of stable layers downstream

allowing penetration (“lid” removal), upwind-downwind thermal contrast (onset of gravity current)

Stage 3: Understand the basic physics of this process using idealized numerical simulations

• Idealized flow over double bell-shaped mountains based on T-REX wind speed and stability profiles; idealized 2D simulations with COAMPS

• Idealized thermal circulations without larger-scale flow• Combination of both processes

T-REX IOP 6

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Sierra Nevada–White-Inyo ranges - quasi 2D two-mountain barrier

Holmboe and Klieforth (1957)

Numerical study of SRP IOP 8 (Grubišić and Billings 2007)

Sensitivity of wave/rotor structure over Owens Valley to downstream orography

Effects of the Downstream Mountain Range

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Idealized simulations (COAMPS) double bell-shaped mtns idealized profiles 2Dirrotationalfree slip

dx = 400 mdz variable → dzmin = 55 m through

inversion

0

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0 10 20 30 40 50

18 UTC

00 UTC

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N (s-

1) shear (ms-1/km)

below inv 0.012 6.1

inversion 0.037 6.1

above inv 0.010 6.1

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SRP IOP 8 soundings MGAUS (Fresno) 18 UTC Mar 25 & 00 UTC Mar 26 2004

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Normalized drag

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time (h)

drag

double

single

Single mtn: partial trapping, strong leaky mode Double mtn: stronger trapping at low levels, stronger dispersive wave response at upper levels → Presence of the second mtn enhances trapping at low levels; phase locking? FUTURE WORK: examine dependence

on: • height of the second mountain • valley and mountain width• asymmetry of the first mountain

3000 m high mountains, h0N/U0≈2