ABSTRACT

This collaborative research project is as part of the international T-REX (Terrain- Induced Rotor Experiment), which is designed to improve understanding of gravity-wave induced rotors and lee waves in the Owens Valley east of the Sierra Nevada range. The research supported under this award will contribute to the achievement of the overall T REX by focusing on the diurnal structure and evolution of the boundary layer in the Owens Valley and its relation to mountain wave and rotor formation.

The objectives of the this research are to investigate: 1) interactions between the mountain boundary layer in the deep Owens Valley and the formation of lee waves and rotors, 2) the interaction of wave/rotor flows and valley wind systems including diurnal thermally driven flows, channeled flows, and turbulent erosion of valley cold pools, and (3) the climatology of windstorm events in the Owens Valley and its relationship to synoptic weather events. These objectives will be met through observations, analysis, and modeling. The data analyses will involve both case study and climatological analyses in the Owens Valley and will benefit from insights gained by the investigators in their previous investigations of other valleys and basins. A mesoscale meteorological model will be used to interpret the observations, verify hypotheses, and provide further insight into physical mechanisms.

The data required to meet these objectives will be collected as part of the T-REX field experiment to be conducted in March-April 2006. The Principal Investigators will assist in the planning and execution of the field experiment and make necessary measurements using a sodar/RASS, an energy budget station, and a network of 50 temperature data loggers as part of a integrated T-REX measurement network. The Principal Investigators will use the T-REX data along with longer-term routinely collected data from the Owens Valley, NCEP 3-hourly regional reanalysis data from 1979 through 2003, and data from the Sierra Rotor and Sierra Wave Projects.

The T-REX field experiment, with its large component of continuously operating in situ and remote sensing equipment, will provide concurrent measurements of both the Owens Valley boundary layer and the lee wave/rotor conditions aloft. The different degrees of coupling that occur within the two-month experimental period will allow, for the first time, a comprehensive study of the effects of upper level disturbances on the valley boundary layer, and the effects of boundary layer evolution on lee wave/rotor characteristics. Previous studies of valley boundary layers have focused almost exclusively on undisturbed conditions. The experiments also will allow the first comprehensive evaluation of channeled flows in deep valleys and turbulent erosion at the top of valley cold air pools. Additionally, wind climatology analyses will focus on determining the synoptic conditions that lead to high wind events in the valley and on gaining an improved understanding of the bi-modal seasonal distribution of the high wind events, which are significant different from high wind events in the Central Rocky Mountains.

Intellectual Merit: The proposed research will advance knowledge and understanding of the physical processes that affect temperature and wind field evolution in a deep valley on both wave and nonwave days. This increase in knowledge is expected to lead to improvement in the ability of models to adequately capture waves/rotors and their interaction with boundary layer dynamics. This will lead to improvements in weather forecasts for the western U.S. and throughout the world. The work explores innovative approaches and concepts and uses a combination of analyses of prior data, climatological analyses, comparison with data from other climate settings, collection of new data and numerical modeling to gain understanding.

Broader Impacts: Broader societal impacts are promoted through the proposed integration of the research into university teaching, through the support of undergraduate and graduate students and through the promotion of investigator/student diversity. Project results will be widely disseminated through peer reviewed scientific publications and presentations, and the results have potential benefits to society through improved understanding of complex terrain boundary layer evolution with potential applications for air pollution dispersion, weather forecasting and climate.

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