NRL Researchers Participate in T-REX Project

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Naval Research Laboratory scientists have taken part in a research project studying wind patterns and air turbulence that pose dangers to aircraft along the Sierra Nevada Range. More than 60 scientists from around the world recently gathered in Owens Valley near Bishop, California, to gather data for the project called T-REX (Terrain-induced Rotor Experiment). The project was led by Dr. Vanda Grubisic, an associate research professor from the Desert Research Institute. NRL's principal investigator in the project was Dr. James Doyle, who was also the co-science director of T-REX. Researchers at NRL-Monterey ran real-time forecasts using the NRL-developed Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) model specially configured to operate at very high-resolution to support the T-REX experiment. Real-time COAMPS model forecasts were used to optimize sensor placements and to plan research aircraft flights to obtain the best possible measurements. COAMPS forecasts were well-received by experiment scientists and forecasters.

The T-REX project is intended to help forecasters and pilots better understand treacherous whirlwinds known as rotors, which form on the lee side of high, steep mountains beneath cresting waves of air. These whirlwinds are common in the Sierra because the area has the steepest topography in the continental United States. Rotors are hazardous to aircraft and have contributed to a number of aircraft accidents, but scientists know little about their structure and evolution. There are a number of airports located along the eastern Sierra, including Reno-Tahoe International Airport and Mammoth Airport north of Owens Valley. The name of the experiment, T-REX, refers to the Tyrannosaurus Rex, one of the most ferocious dinosaurs that lived. The rotor winds, like the dinosaur, can be brutal when the winds reach accelerations several times the earth's gravitational acceleration.

The purpose of the T-REX project is to help forecasters predict when and where rotors are most likely to occur and how intense they will be. With a greater understanding about the nature of rotors, researchers hope to improve commercial and military aviation safety in the mountainous terrain all over the globe. It is anticipated that new insight into the characteristics of meteorological phenomena forced by mountains will benefit the Navy and DoD through more accurate numerical forecasts of winds, clouds, visibility, and turbulence, which can adversely impact military operations.

Scientists from the National Center for Atmospheric Research, NRL, and other research institutions from the United Kingdom, Germany, Austria and Croatia worked on the project in Owens Valley through the end of April. Owens Valley is located about 10,000 feet directly below the highest peaks of the adjacent mountains, which makes it ideal for studying a steep vertical range. Owens Valley is one of the most common places on earth for rotors to occur. The Naval Air Station in Lemoore, CA, also participated by providing measurements upstream of the Sierra using radiosondes.

The T-REX research team installed an array of weather stations, balloon launching sites, and laser Doppler sensors to map the three-dimensional structure of the rotor. In addition the team flew instrumented research aircraft at various altitudes to gather data. A University of Wyoming King Air turbo-prop had the dangerous mission of flying in the low-levels through rotors to collect data. The $81.5 million HIAPER -- the nation's newest and most advanced research aircraft -- flew over rotors as they formed above the Sierra. The aircraft, owned by the National Science Foundation, can reach altitudes of 51,000 feet and cruise for 7,000 miles.

The research project is the second phase of an effort to explore the structure and evolution of atmospheric rotors and related phenomena in complex terrain. The initial phase of T-REX, which took place in the Owens Valley in March and April 2004, suggested that rotors are strongly linked to both the structure and evolution of overlying mountain waves and the underlying boundary layer.

The National Science Foundation is providing funding for the T-REX research. NRL's participation in T-REX is supported by 6.1 research funding.

Photo of classic rotor cloud, taken above Owens Valley, CA, where the T-Rex project was conducted.

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The U.S. Naval Research Laboratory provides the advanced scientific capabilities required to bolster our country's position of global naval leadership. The Laboratory, with a total complement of approximately 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 90 years and continues to advance research further than you can imagine. For more information, visit the NRL website or join the conversation on Twitter, Facebook, and YouTube.

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