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Data collected by the Institute of Atmospheric Physics of CNR (Italy) during the 1991 Italian Antarctic expedition are used for the development of Earth-air-sea interaction studies. In this paper wind and temperature data obtained by a digitized ultrasonic anemometer-thermometer describe the temporal, statistical and spectral turbulence behaviour in the surface atmospheric boundary layer at different wind conditions and in morphologically different sites. The vertical momentum and thermal fluxes, evaluated through the direct method, are found to be strictly dependent on the local stability condition recorded during the measurements. The examination of the velocities and temperature probability density functions confirms the Lumley and Panofsky hypothesis on the influence of both velocity components on temperature fluctuations. A multichannel spectral analysis confirms the obtained results for the low-frequency range. [ABSTRACT FROM AUTHOR]

In a recent note by Shepherd it is claimed that the main conclusions discussed in a paper by Petroni et al. about certain instability mechanisms for steady equivalent barotropic flows are incorrect and, although no criticism is made regarding the analytical treatment, two counterexamples are presented to support this thesis. In addition to this it is asserted that the envisaged necessity for energy and enstrophy to be transferred in both spatial directions in a normal-mode instability is «extremely well known». Here we demonstrate that Shepherd's conclusions are without foundation and confirm the validity and originality of Petroni et al. results by showing that: a) the first counterexample describes a situation that is in fact provided for by Petroni et al.'s analysis; b) the second counterexample is not dynamically realizable and, even if it were, the related conclusions would not apply to flows defined in doubly periodic or bounded domains such as those considered by Petroni et al.; c) the mechanism cited above is not known at all in the specific context dealt with by Petroni et al. We emphasize this by pointing out that for steady equivalent barotropic flows the range of parameters for which such an instability mechanism is allowed complements exactly the range for which the steady states are stable according to Benzi et al. [ABSTRACT FROM AUTHOR]

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Copyright of Il Nuovo Cimento: C is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Il Nuovo Cimento: C is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Il Nuovo Cimento: C is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Il Nuovo Cimento: B is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)