Naslov
On the turbulence local isotropy during MAP IOP 15 bora event

Autori
Večenaj, Željko ; Belušić, Danijel ; Grisogono, Branko

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Skup
ICAM 2013 - International Conference on Alpine Meteorology

Mjesto i datum
Kranjska Gora, Slovenija, 03.06.2013. - 07.06.2013

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
MAP experiment; Bora wind; Local isotropy

Sažetak
In the lee of the complex terrain of the Dinaric Alps, a well-known strong and gusty downslope airflow, called Bora, extends from the north- eastern quadrant perpendicular to the coastal mountains. Bora may be induced by different synoptic conditions and occurs most frequently during the winter season with duration of several hours to several days. It possesses a wide spectrum of average wind speeds and due to its gustiness the wind-speed maxima may surpass 60 ms −1. The corresponding turbulence is well developed during such vigorous events but, so far, it is addressed inadequately. It is often suitable to use spectral theory and spectral analysis in turbulence research. Such deployment, for example, leads to estimation of the turbulent kinetic energy (TKE) and its dissipation rate, ε. There are several approaches for determination of ε that are based on the spectral analysis and all of them require that in the Fourier spectra of the velocity components the inertial subrange exists ; a part of the wavenumber/frequency domain in which the turbulence is locally isotropic and where the turbulent eddies perform the cascade of TKE from the larger energy containing toward much smaller dissipating eddies. A strong statement of the local isotropy (and therefore, the existence of the inertial subrange) in space is the 4/3 ratio of the lateral to longitudinal spectra Sv(k)/Su(k) and vertical to longitudinal spectra Sw(k)/Su(k). This 4/3 ratio is tested on the MAP IOP 15 bora event which occurred on 07 November 1999 and was documented by the Electra and P-3 aircrafts. According to the results obtained, there are indications that bora turbulence is actually locally anisotropic.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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