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Nov 1976

Volume 60, Issue S1, pp. S1-S125

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back to top Session O. Physical Acoustics III: Atmospheric Acoustics II
Invited Papers
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Interpretation of sodar measurements: relevant properties of the atmosphere's planetary boundary layer (A)

D. W. Thomson

J. Acoust. Soc. Am. Volume 60, Issue S1, pp. S30-S31 (1976); (2 pages)

Online Publication Date: 11 Aug 2005

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Assuming a Kolmogorov spectrum of turbulence, the acoustic scattering cross section may be written as a function of incident wavelength, scattering angle, and the magnitude of the root‐mean‐square turbulent temperature and velocity fluctuations. In the “surface” layer SL (max ≃ 3–30 m height) of the atmosphere the statistical properties of turbulent velocity, temperature, humidity, and pressure fluctuations above many surface types are well understood for a wide variety of meteorological conditions. Hence, it is possible using sodar to derive unique, quantitative measurements of SL atmospheric turbulence. Detailed information about planetary boundary layer PBL (max ≃ 300 m–2 km height) turbulence is not required in order to make continuous sodar measurements of vertical profiles of turbulence related atmospheric structure and winds (from signal Doppler shifts). Sodar is, thus, now routinely used, e.g., for air pollution related, micrometeorological research, and wind‐shear detection measurements. Our perception of many complicated PBL structural features and processes has been greatly expanded by the now familiar vertical‐time section sodar records of various “layers” and thermal convection. However, except for “unstable” conditions of free convection, SL turbulence models are not generally applicable for the quantitative interpretation of PBL sodar data. In order to realize the full indirect sounding potential of sodar during “stable” atmospheric conditions, it is necessary to determine the relationship(s) between observed “macroscale” features such as multiple layers (with and without waves), intermittant “patches” of turbulence and “bursts” of vertical momentum or heat transport and the space‐time dependent properties of the turbulence in such situations. This paper first reviews the application of contemporary SL and PBL models to the interpretation of sodar measurements. Functional relationships between sodar observed and model implicit parameters are summarized. Finally, the application of sodar for development and verification of selected atmospheric models is discussed. [Research supported by EPA Grant R800397.]
Contributed Papers
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Applications of digital color display techniques for sodar (A)

D. W. Thomson and J. P. Sheib

J. Acoust. Soc. Am. Volume 60, Issue S1, pp. S32-S32 (1976); (1 page)

Online Publication Date: 11 Aug 2005

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The monostatic—bistatic Doppler Sodar at Penn State University has been equipped with a digital color display unit for presenting signal amplitude and Doppler information. Effective system performance for measurements of planetary boundary layer structure and dynamics has been markedly improved. The color technique greatly enhances effective grey‐scale resolution in vertical‐time section displays of received signal amplitude. Color presentation of signal Doppler information facilitates analysis of wave phenomena and thermal convection in the planetary boundary layer. The system is in use for a variety of field measurements. In some, a research aircraft is radio directed into the region of meteorological interest. Other experiments involve the development of user‐oriented color display techniques for ready interpretation of air pollution related parameters. [Research supported by EPA Grant R800397.]
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