The T-REX experimentRalph Burton1, Stephen Mobbs1, Barbara Brooks1

Harold Klieforth2, Martin Hill1

1 IAS 2 Desert Research Institute, Reno NV

1. Motivation.

2. Rotors: brief overview.

3. T-REX.

From

“Hazardous Mountain Windsand their Visual Indicators”Federal Aviation Authority,

U.S.Dept. of Transportation, 1988

• Accidents not limited to one operating altitude, or time of year, or specific type of aircraft

• In many cases, other aircraft operating in thevicinity of the accident encountered only weakturbulence severe wind events can be highly

localised, violent, andshort-lived

From “Hazardous Mountain

Windsand their

Visual Indicators”,

1988

Accident rate less than 3 per 100,000Accident rate greater than 3 per 100,000

Accident rate 40% higher in the 11 mountainstates

DEM of the U.S. showing regionsof elevated terrain

http://adds.aviationweather.gov

From

From http://adds.aviationweather.gov

For aviation weather reports,see

http://adds.aviationweather.gov

Extensive mountain

obscuration

Owens (dry) lake

• Probably the largest single source of PM10 dust in the United States

• Dust plumes tracked to 3000m AGL, 100 km north of the lake

• Affects visibility and vegetation in many neighbouring wilderness areas

• Dust storms regularly cause suspension of operations at China Lake Naval Weapons Center

See geochange.er.usgs.gov/sw/impacts/geology/owens

From Reheis (1997)

Looking South from 9800m/32000ft

W

I

Sierra wave Project (1950s)

Sierra WaveProject (1950s)

Flight of Feb. 16th 1952

From Holmboeand Klieforth 1957

A: Type 1 rotor

B: Type 2 rotor

From Kuettner (1959)

Maximum rates of climb

Cessna 172: 720 ft/min

Ibis aerospace 270: 1791 ft/min

Boeing Chinook: 1840 ft/min

Sierra WaveProject (1950s)

Flight of Feb. 16th 1952

From Holmboeand Klieforth 1957

W=-31ft/s

w=+41ft/s

Maximum rates of climb

Cessna 172: 720 ft/min

Ibis aerospace 270: 1791 ft/min

Boeing Chinook: 1840 ft/min

Rotor: -1860ft/min

Net downward

Net downward

Net downward

“Type 1”rotor

“Type 2”rotor

“Inversion effects onmountain lee waves”

Vosper, QJR 2003

Inversion height

Wind constant with height

Regime diagram

H = hill heightzi = inversion height;

Fi = U/(g’zi)1/2

g’ = g/0

U = background wind

BLASIUS;idealised ridge

H/Zi > 0.3

Consider u=10 ms-1

surf temp = 200C,Zi = 3600m,

then we have

U2 ~ 45

gives ~ 2K

Climatologyof wave events

Based upon satellite imagery,1km resolution,15 minute intervals(visible channel)

From Grubišić,T-REX proposal

Oct 29th 2000

From Doyle and Durran (2004)

GOES -Vis

Regime diagram

“Inversion effects onmountain lee waves”

Vosper, QJR 2003

29/10/2000

Doyle and Durran (2004)

• Fully 3-d simulation using 5 nested grids, finest resolution x=333m

• Fully compressible, nonhydrostatic

• Mixing length scheme

• Terrain-following coordinates

Coupled Ocean-Atmospheric MesoscalePrediction System (COAMPS)

Doyle and Durran (2004)

Doyle and Durran (2004)

The biggest field campaign ever mounted to studyrotors/gravity waves

T-REX

ARL White Sands Missile RangeScripps Institute of Oceanography

Colorado Research AssociatesCooperative Research in Environmental

ScienceDesert Research Institute

DLRLawrence Livermore National Laboratory

UK Met OfficeNASANCAR

Naval Research LaboratoryNOAA

Arizona State UniversityColorado State University

Harvard UniversityUniversity of Houston

University of InnsbruckUniversity of LeedsUniversity of New

HampshireNorth Carolina State

UniversityStanford UniversityUniversity of Utah

Yale University

Location of field campaign

Masts currently installed in the Owens Valley (DRI)

See www.wrcc.dri.edu/trex

Roll cloud observed over the Owens Valley, April 2004Photo by James Pinto

From Grubišić and Cohn (2004)

Roll cloud over Owens Valley March 24 2004

From Grubišić and Cohn (2004)

From Grubišić and Kuettner (2004)

T-REX Phase I

NationalForest Service

Bureau of Land

Management

Dept. ofWater

Resources

Sierra

Inyo

Valley

Location of proposed Leeds masts

Lower Sierra station site

Valley station site

Inyo station site

Sonic anemometer

GPS aerial

Solar panel

Logger box

Batteries

Temperature sensors

T-REX IOP: March – April 2006

• At least 28 10m towers• Wind profilers• Lidars• Radiosondes• NCAR Gulfstream• Univ. of Wyoming King Air• FAAM BAe146• 50 temperature loggers• 3 x 30m flux towers• Univ. Innsbruck mobile met system• …

T-REX Phase II

Map: V. Grubišić in collaboration with the UCAR Joint Office of Scientific Support

T-REX Phase II

Typical flight plans

Schematic: V. Grubišić and J. Doyle

Rotors – some key scientific questions

Climatology:

- frequency,preferred location

Dynamics

-to establish the conditions required for the formation of rotors

Modelling

- Ability of current models to predict the occurrence of rotor events

- Model validation

Summary

• Preparations in place for the most comprehensive field campaign to study rotors/lee waves ever made, using AWS, lidars, aircraft, flux towers, …

• Permissions granted for installation of a further 12 10m towers: deployment early 2005

• Phase I completed; some case studies already being undertaken in the US

Rotors pose a severe aviation hazard and have been citedas being responsible for several major accidents.Still poorly understood.