Naslov
Characteristics of the bora related turbulence

Autori
Večenaj, Željko

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, doktorska disertacija

Fakultet
Prirodoslovno-matematički fakultet

Mjesto
Zagreb

Datum
24.02

Godina
2012

Stranica
83

Mentor
Grisogono, Branko

Neposredni voditelj
Belušić, Danijel

Ključne riječi
bora wind ; turbulence averaging scale ; turbulent kinetic energy ; dissipation rate ; WRF-ARW numerical model

Sažetak
Bora is a downslope windstorm that blows at the eastern Adriatic coast from the northeastern quadrant in the lee of the Dinaric Alps. Due to possible severity, it represents a significant threat to traffic, infrastructure, tourism agriculture and human lives. Therefore, it is important to understand the bora dynamics on the synoptic as well as on meso- and micro(turbulent)- scale. While the bora dynamics on the synoptic scale has been largely investigated, only a few papers in the literature can be found on its turbulence. The goal of this dissertation is to estimate temporal and spatial distribution of bora turbulence characteristics, e.g., turbulent kinetic energy (TKE) and for the first time, its dissipation rate, ε. To that end, four case studies of bora events using three different data sets are analyzed: a winter bora case that occurred in November 1999 and was recorded offshore above the Adriatic Sea by the National Center for Atmospheric Research (NCAR) Electra aircraft, two winter bora cases that occurred in February 2005 and January 2005 and were recorded by the single point ground based measurements in Senj and Vratnik Pass, and summer bora case that occurred in July 2010 and was recorded on the three levels tower on Pometeno brdo. Much of this work is dedicated to determination of the turbulence averaging scale which is needed for definition of turbulent fluctuations. It seems that there is no unique averaging scale for deriving the bora turbulence. Two different methods are used for estimation of ε: inertial dissipation method and the third-order structure function. It is shown that the variability of ε is captured well with both methods, but also that the third-order structure function underestimates ε obtained by the inertial dissipation method. At the end, the relationship between ε and TKE is investigated, according to which success of the WRF-ARW numerical model to reproduce turbulence may become questionable.

Izvorni jezik
Engleski

Znanstvena područja
Geofizika

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