The T-REX experiment Ralph Burton 1, Stephen Mobbs 1, Barbara Brooks 1 Harold Klieforth 2, Martin Hill 1 1 IAS 2 Desert Research Institute, Reno NV

1. Motivation. 2. Rotors: brief overview. 3. T-REX.

From “Hazardous Mountain Winds and 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 the vicinity of the accident encountered only weak turbulence severe wind events can be highly localised, violent, and short-lived

From “Hazardous Mountain Winds and their Visual Indicators”, 1988 Accident rate less than 3 per 100,000 Accident rate greater than 3 per 100,000 Accident rate 40% higher in the 11 mountain states

DEM of the U.S. showing regions of elevated terrain

From

From

For aviation weather reports, see 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 Wave Project (1950s) Flight of Feb. 16 th 1952 From Holmboe and 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 Wave Project (1950s) Flight of Feb. 16 th 1952 From Holmboe and 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 on mountain lee waves” Vosper, QJR 2003 Inversion height Wind constant with height

Regime diagram H = hill height z i = inversion height; F i = U/(g’z i ) 1/2 g’ = g  /  0 U = background wind BLASIUS; idealised ridge

H/Z i > 0.3 Consider u=10 ms -1 surf temp = 20 0 C, Z i = 3600m, then we have U 2 ~ 45  gives  ~ 2K

Climatology of wave events Based upon satellite imagery, 1km resolution, 15 minute intervals (visible channel) From Grubišić, T-REX proposal

Oct 29 th 2000 From Doyle and Durran (2004) GOES -Vis

Regime diagram “Inversion effects on mountain lee waves” Vosper, QJR /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 Mesoscale Prediction System (COAMPS)

Doyle and Durran (2004)

The biggest field campaign ever mounted to study rotors/gravity waves T-REX ARL White Sands Missile Range Scripps Institute of Oceanography Colorado Research Associates Cooperative Research in Environmental Science Desert Research Institute DLR Lawrence Livermore National Laboratory UK Met Office NASA NCAR Naval Research Laboratory NOAA Arizona State University Colorado State University Harvard University University of Houston University of Innsbruck University of Leeds University of New Hampshire North Carolina State University Stanford University University of Utah Yale University

Location of field campaign

Masts currently installed in the Owens Valley (DRI) See

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

From Grubišić and Cohn (2004) Roll cloud over Owens Valley March

From Grubišić and Cohn (2004) From Grubišić and Kuettner (2004) T-REX Phase I

National Forest Service Bureau of Land Management Dept. of Water 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 BAe 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 cited as being responsible for several major accidents. Still poorly understood.