Spectra over complex terrain
Spectra have been measured over land downwind of a water surface, over hilltops and escarpments, and over rolling farmland. The following hypotheses can be used to explain the differences between these spectra. (1) For wavelengths short compared to the fetch over the new terrain, spectral densities are in equilibrium with the new terrain. (2) For wavelengths long compared to this fetch, spectral densities remain unchanged if the ground is horizontal. If the flow is over a steep hill, the low-frequency structure is modified by distortion of the mean flow, with the longitudinal component losing energy relative to the lateral and vertical components. Because vertical-velocity spectra contain relatively less low-frequency energy than horizontal-velocity spectra, energetic vertical-velocity fluctuations tend to be in equilibrium with local terrain.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Pennsylvania State Univ., University Park (USA). Dept. of Meteorology; Research and Data Systems, Lanham, MD (USA); National Oceanic and Atmospheric Administration, Boulder, CO (USA)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 6282995
- Report Number(s):
- LA-UR-81-2380; CONF-810742-1; ON: DE81028734
- Resource Relation:
- Conference: 4. U.S. national conference on wind engineering research, Seattle, WA, USA, 26 Jul 1981
- Country of Publication:
- United States
- Language:
- English
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