Proceedings with Extended Abstracts (single PDF file) - Radio ...

Turbulence.The session then moved into studies of the fundamentals of turbulence. Wilson gave a verythorough review of the various modes of diffusion in the atmosphere, examining items likemixing efficiency, kinetic and potential deposition, and modes of diffusion. He alsoconsidered a variety of radar methods for measuring these parameters. Wilson andDalaudier then demonstrated the information that could be deduced by combining radar andin-situ balloon observations of turbulent layers.Klaassen had been invited to give a presentation on the modes of breakdown of gravitywaves, but could not attend. However, Hocking gave a brief review of his work in a latersession, (section II), and we mention it here for completeness. Recent references ofKlaassen’s, which in turn reference his earlier work, are Sonmor and Klaassen, “Toward aunified theory of gravity wave stability”, J. Atmos Sci., p2655, 1997, and Yau, Klaassenand Sonmor, “Principal instabilities of large amplitude inertio-gravity waves”, Physics ofFluids, in press.Several papers discussed the relationship between spectral width and turbulencemeasurements. Van Zandt and colleagues considered new methods for determining thestrength of turbulence by using dual beams with different widths and different azimuthangles, and Nastrom (presented by Van Zandt) discussed use of the Indian MST radar atGadanki to determine strengths. The meaning of “negative” energy dissipation rates wasalso a concern to Van Zandt. In a paper somewhat later in the session, Hocking describedhow current methods for determination of non-turbulent spectral beam-broadening can beimproved using full numerical integrals, and showed how these could be performed veryquickly on a modern computer, therefore possibly reducing some of the complicationswhich Van Zandt had been concerned about when he introduced the dual beam-widthprocedure. In a poster paper, Latteck et al. (I.3.509) compared standard and dual beammethods for determination of turbulence strengths made with an MF radar. Melnikov, Fangand Doviak noted that meteorologists rarely use spectral widths from radar data, andsuggested that it is a resource which should be better employed in the future. Examplesinclude the observation that the spectral width is often quite wide on the leading edge ofsquall lines, an observation which could be better employed in forecasting andidentification.Several papers dealt with measurements of vertical diffusion. Hermawan and Tsudaestimated vertical diffusion coefficients with the MU radar and RASS, and particularlynoted the effect of variations in the Brunt-Vaisala frequency on estimation of energydissipation rates and diffusion coefficients. Fukao et al studied cross-tropopause transportby turbulent processes, and Gavrilov and Fukao, in a poster paper (I.3.504) discusseddownward turbulent transport of ozone from the stratosphere to the troposphere.Hashiguchi et al., in another poster paper, discussed tropopause processes measured withthe EAR radar in Indonesia.Finally, some papers relating to temperature measurements were presented. Kubo et al.discussed temperature and PMSE changes during a strong polar cap absorption event,Holdsworth et al. discussed comparisons between meteor radar temperatures and winds25