Extended Abstract (388K)P3.1
Observations of the horizontal structure of the Boundary Layer with the Turbulent Eddy Profiler
Paco Lopez Dekker, University of Massachusetts, Amherst, MA; and S. J. Frasier
During Summer and Fall 2001, the University of Massachusetts' Turbulent Eddy Profiler (TEP) and S-band FMCW radar were deployed at Amherst, Massachusetts observing the convective boundary layer. The TEP is a UHF volume-imaging radar designed to image local refractive index fluctuations and their radial velocity structure within a 30 degree cone centered about zenith. At an altitude of 500 m AGL, the system has 30 m spatial resolution. Mean winds are calculated by combining the Doppler moments for all beams, providing a context in which to interpret the volumetric data. The S-band FMCW radar is designed to complement TEP measurements providing 2.5 m height-resolution profiles of the BL. Its beamwidth approximately matches that of a focused TEP-beam.
Time-height cross sections from both TEP and the FMCW radar are compared to spatial images obtained from slices through the TEP volume in the streamwise, cross-stream, and horizontal planes. Vertical streamwise slices display horizontal structures qualitatively similar to those observed in the time-series. Radar reflectivity, which is associated primarily with the refractive index structure parameter, shows variations of 10-20 dB at 100 m horizontal scales. Cross-stream slices show similar morphology, suggesting a degree of isotropy at the scales observable by TEP.
Animations of volumetric slices provide a unique view of the translation of scattering features. However, these sequences also suggest significant evolution of these structures as they are advected. Interpretation is complicated in some cases, when horizontal mean-winds vary in both magnitude and direction with height making it impossible to uniquely define a streamwise direction. Some apparent evolution of structures observed in streamwise slices may be the result of the instantaneous wind having a cross-stream component, advecting structures through the plane of the vertical slice.
Supplementary URL: http://abyss.ecs.umass.edu/tep/
Poster Session 3, Fundamental Studies
Tuesday, 16 July 2002, 2:00 PM-2:00 PM
Next paper