engleski

Separation of the turbulence from the mean bora flows at the NE Adriatic coast

Bora is a downslope windstorm that blows at the Eastern Adriatic coast from the northeastern quadrant, most often during winter seasons. It possesses a wide spectrum of average wind speeds, and due to its gustiness the speed maxima may surpass 60 m/s. During a bora event, the turbulence is strongly developed in the lee of the mountains. So far the bora wind has been intensively studied in terms of its spatio- temporal statistics as well as macro- and meso- scale dynamics, but its turbulence characteristics still remain relatively unexplored. In order to investigate turbulence, a suitable time/space averaging scale has to be deployed in order to define turbulent perturbations which are then used for calculation of turbulence statistical moments. This study addresses the turbulence averaging scale determined by applying several different approaches on the four cases of bora events using three different data sets. These four events are: winter bora case that occurred in November 1999 and was recorded offshore above the Adriatic Sea by the National Center for Atmospheric Research Electra aircraft, two winter bora cases that occurred in February 2005 and January 2006 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-level tower on Pometeno brdo in the hinterland of the city of Split. According to the results obtained from those four typical bora episodes, it appears that there is no unique averaging scale for determination of the bora turbulence statistics.

Bora; Turbulence; Averaging scale

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