James D' Doyle1 and Ronald Smith2

1
Three-Dimensional Characteristics of Mountain
Waves A Perspective from T-REX
?
Preliminary
James D. Doyle1 and Ronald Smith2 A. Cooper3, V.
Grubisic4, J. Jensen3, Q. Jiang5, J. Kuettner3,
L. Pan3 1Naval Research Laboratory, Monterey,
CA 2Yale University, New Haven, CT 3NCAR/UCAR,
Boulder, CO 4DRI, Reno, NV 5UCAR, Monterey, CA

• Outline
• Overview of T-REX and Hiaper
• Observational Analysis of Hiaper Data
• Linear and Nonlinear Modeling Results

2
Terrain-Induced Rotor Experiment

• Objective Explore rotor and mountain wave
  dynamics interaction with BL
• Sierra Nevada Range and Owens Valley
• International effort NCAR, DRI, NRL, DLR, NOAA,
  Leeds, Met Office, Univ. (Yale, Stan., Utah, Cal,
  Wash, Houston)
• March-April 2004 and 2006 (29 IOPs)
• Observational Assets 3 aircraft, lidars,
  radars, profilers, gt130 obs. systems

3
NCAR/NSF HIAPER

• Gust probe system Cameras
• Static pressure (for D-value) GPS Dropwindsondes
• Fast temperature Differential GPS
• Fast tracers (H2O, O3, CO, Cond. Nuclei) -
  position altitude
• Slow water, aerosols

4
HIAPER Observing Strategy

• Long racetracks to deduce 3-D aspects of the wave
  field and compute circulations. Upstream and
  downstream regions to be compared.
• Multiple racetrack stacks spanning 4 km in
  altitude (30 to 43kft) to observe how the waves
  change as they propagate upwards into the
  stratosphere.
• Immediately repeated racetracks to check
  steadiness of fast changing fields
• Deep soundings for chemistry and dynamics
• Mission timing based on mountain wave activity
  forecasts (COAMPS, WRF, ECMWF). Cross-mountain
  wind at 700 mb gt 15m/s. Track selection based on
  direction

5
Sierra Nevada Terrain
?
Independence
6
Large-Scale Conditions during T-REX 700-hPa Winds
and RH
7
Summary of HIAPER Research Flights
8
HIAPER IOP4 (RF04) 13.1 km
Shorter Wavelengths
Steady
Transience
9
HIAPER IOP6 (RF05)
10
HIAPER IOP6 (RF05) 13.1 km
Transience
Steady
11
HIAPER IOP6 (RF05) Southern Leg (13.1 km and 11.9
km)
13.1 km (black) 11.9 km (red)
Speed (m s-1)
q (K)
Largest Amplitude at Higher Levels
w (m s-1)
Ter (m)
30 m between legs
12
HIAPER IOP6 (RF05) Southern Leg (13.7 km)
Turbulent vertical velocity signature consistent
with wave breaking
u 40 m s-1
Speed (m s-1)
q 30 K
q (K)
w (m s-1)
O3 (ppm)
11 m s-1
Ter (m)
13
HIAPER IOP13 (RF10) 11.9 km and 13.1 km
North
South
Short Waves
Ter (m)
14
HIAPER Flight Legs Maximum Vertical Velocity
(13.1 km)
15
HIAPER Flight Legs Maximum Vertical Velocity
(11.3 km)
16
HIAPER Flight Legs Dominant Horizontal Wavelength
(13.1 km)
y 0.2509x 11.677
17
HIAPER and COAMPS Comparisons w (m s-1) at 13.1
km (18-24 h) Real-Time Nonhydrostatic Forecasts
(2 km)
North
South
IOP4
Shorter Wavelengths
No Short Waves
IOP6
Weak Short Waves
IOP13
Terrain
Terrain
COAMPS ___ HIAPER ___
18
Real-Time COAMPS ux (m s-1) and q (K) at 24 h
57
0
-17

• Strong cross barrier flow in low-levels with
  strong forward shear aloft.
• Suggestion of reversed low-level flow in valley.
• Backward shear above the jet leads to steepening
  aloft (gt15 km).
• Wave breaking near GV levels present in IOP6
  forecast.

19
Real-Time COAMPS w (m s-1) and q (K) at 24 h
IOP4
IOP6

• Relatively long wavelength waves (20-30 km)
  generated in troposphere
• Shorter wavelengths dominant in stratosphere

20
Linear Theory h and w (m s-1)

• Linear calculations based on a generalized
  nonhydrostatic semi-analytic model with 1.5 km
  horizontal resolution and 10 layers.
• Initialized using upstream mobile radiosonde
  (MGAUS)

IOP13
IOP4
IOP6
14
0
-14

• Larger amplitude vertically propagating wave
  (IOP6 and IOP13) with trapped waves downstream or
  just trapped waves (IOP4)
• Evanescent waves leak into the stratosphere
  yielding (amplifying and sometimes propagating)
  short waves downstream of main wave crest.

21
Summary

• Observations of three dimensionality legs 50 km
  apart over 2D terrain
• - North and south flight segments are broadly
  similar
• - Secondary differences are present (synoptic
  component, terrain, )
• Stratospheric waves
• -Steady large-amplitude, longer-wavelength
  primary wave (hydrostatic?)
• - displaced well downstream of peaks (nonlinear
  effect?)
• -Nonsteady small-amplitude, short-wavelength
  secondary waves
• - present both upstream and downstream of primary
  wave
• - nonlinear effects, dispersion, or trapped waves
  from below???
• Nonlinear numerical modeling (Dx2 km)
• -Reasonable agreement with GV in stratosphere
• -Longer wavelengths in troposphere and shortwaves
  in stratosphere
• Linear theory
• -Trapped waves in troposphere leak vertically
  propagate in stratosphere

22
A Few Questions

• What is the source for the short waves in the
  stratosphere?
• Is the observed three dimensionality important?
  Source?
• Why wasnt wave breaking observed more often?
  (often predicted)
• - Low level breaking (seemed to be common)?
• - Broke at higher altitudes (models seemed to
  indicate this)?
• - Other small-scale turbulence processes
  limiting amplitude?
• What are the mixing properties associated with
  the breaking event?
• How important are nonlinear effects?
• What is the predictability of mountain waves in
  stratosphere?
• Are there longer wavelength IGW present in
  stratosphere?
• - Opportunity to combine satellite and aircraft
  analysis
• - Critical level near 20 km