Departments of Mechanical & Aerospace Engineering and Earth System Science

Our research is on atmospheric turbulence in the boundary layer over the earth's surface. The air motion in the boundary layer is typically in a state of turbulent motion. Turbulence enhances the transfer of heat, matter, and momentum between the surface and the overlying atmosphere. However, turbulence is random and remains one of major unsolved problems in physics and engineering. Progress is made by the synergistic combination of experiments, theory, and computer models. Our emphasis in on field experiments focused on geophysical turbulence. Results of the experiments increase our understanding of turbulence and provide parameterizations for models. Boundary-layer experiments are performed from aircraft, towers over land, and the stable ocean platform R/P FLIP. Instruments for the measurement of the three-dimensional velocity vector, temperature, water vapor, and carbon dioxide with appropriate spatial resolution and frequency response are developed or purchased. Data are recorded with modern digital data aquisition systems and analyzed with specialized statisical and spectral software. A typical experiment may produce 10-20 GB of data. Most of our experiments are part of larger projects. The following is a partial list:

CODE :: Coastal Dynamics Experiment, 1981-1982. This NSF experiment was the study of wind-driven coastal upwelling off of northern California. The NCAR Queenair aircraft mapped the vertical and horizontal structure between Bodega Bay and Pt. Arena. A major result was the study of the low-level jet (up to 32 ms^{-1}), which was shown to result from the thermal wind above the marine-layer inversion and turbulent stress divergence below (Zemba and Friehe, 1982). The horizontal aircraft maps at 30 m altitude revealed the existence of two forms of hydraulic control of the marine layer: an expansion fan around Pt. Arena and a hydraulic jump at Stewart's Point (Winant, et al., 1985).

FASINEX :: Frontal Air-Sea Interaction Experiment. This ONR experiment was the study of air-sea interaction around the sea-surface temperature front in the Sargasso Sea. A Naval Research Laboratory RP3A aircraft was instrumented for turbulence and meteorological measurements and flew in conjunction with the NCAR Electra. The two-aircraft formation showed the significant effects of the temperature front on the air-sea fluxes (Friehe, et al., 1991).

Land Surface-Layer Turbulence, NSF :: Measurements of the wind, temperature and humidity profiles were measured over an open field in Wyoming during fall to maximize the probability of neutral conditions. The controversial von Karman constant in the flux-profile relation was found to decrease slightly with Revnolds number. A data set was obtained as a sudden snow storm dramtically lowered the roughness of the surface, and the von Karman constant decreased significantly (Oncley, et al., 1995).

SMILE :: Shelf Mixed Layer Experiment. This NSF experiment was a continuation of coastal circulation off of Northern California during winter with the NCAR Kingair aircraft. Surface flux measurements under up-coast and downcoast winds showed upwelling-favorable stresses exist in both situations due to the opposite cross-coast variation of the stresses.

 

[More Information]

 

:: Address and Contact Info. ::
University of California, Irvine Irvine, CA 92697-3975 USA
Carl A. Friehe
cfriehe@uci.edu
(949) 824-6159
Djamal Khelif
jamal@wave.eng.uci.edu
(949) 824-7437
Fax: (949)824-2249/8585

 

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Department of Mechanical and Aerospace Engineering University of California at Irvine Irvine, CA, 92697-3975

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