April 17, 2007T-REX Data Workshop, NCAR, April T-REX Research at Mesoscale Dynamics & Modeling Lab at DRI Vanda Grubišić Brian Billings, Ivana Stiperski, Ming Xiao

Objectives/Research Focus Insights into the structure of wave-rotor coupling; classification of types of flow structures Starting 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 data Goal: 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 windstorm IOP 13 - lee-wave rotor IOP 1, IOP 4, IOP 11 Process Studies: oDevelopment of westerly windstorms in Owens Valley oEffects of a downstream boundary condition (mountain range) Numerical Modeling: oCOAMPS 3D real-data very high-resolution nested simulations (dx=333 m) oCOAMPS 2D very high-resolution idealized simulations

April 17, 2007T-REX Data Workshop, NCAR, April Dry Wave Rotor Events (Weak  Strong) IOP 2 IOP 1IOP 13

T-REX Data Workshop, NCAR, April 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, 2007T-REX Data Workshop, NCAR, April IOP 6 3D COAMPS SIMULATION  =0.01 s -1 white W=7.5 ms -1 green TKE=15 m 2 s -2 red Wind vectors yellow

April 17, 2007T-REX Data Workshop, NCAR, April Stage 1: Identification of strong westerlies in DRI network observations 15 km Penetration of westerly momentum into Owens Valley

7 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

9 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

10 Idealized simulations (COAMPS)  double bell-shaped mtns  idealized profiles  2D  irrotational  free slip  dx = 400 m  dz variable → dz min = 55 m through inversion N (s -1 )shear (ms -1 /km) below inv inversion above inv SRP IOP 8 soundings MGAUS (Fresno) 18 UTC Mar 25 & 00 UTC Mar

11 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, h 0 N/U 0 ≈2