engleski

Analysis of a strong mid-Adriatic bora event: the role of complex orography

While extreme bora winds in the northern Adriatic were since long in the focus of the relevant research, strong bora winds in the hinterland of Dalmatian coast are much less studied, yet frequent phenomenon in the region. The predictability of these events is considerably lower than for its northern counterpart due to the flow complexity induced by the chain of secondary orographic mountain sub-ranges and deep valleys. A late winter case of a strong bora event in the mid-Adriatic was analyzed with the use of measurements and numerical experiments carried out with the WRF model. The analysis utilized three ultrasonic anemometers at 10 m, 22 m and 40 m levels and two additional classic cup and vane anemometers at 30 m and 60 m levels. The event was simulated with a number of numerical sensitivity experiments with modified orography. The results assessing the observed and modeled properties of the selected bora event are presented. It is shown that the orographic complexity considerably modulates the bora flow. The observed and modeled turbulent properties, such as momentum fluxes and turbulent kinetic energy enabled the evaluation of the model performance as well as the assessment of the validity of similarity theory in the surface layer during the event. Certain differences in the bora subtle structure there and over the northern areas, the latter pertaining to more known bora cases, are pointed out.

Bora wind; Complex orograpghy; WRF model; Ultrasonic anemometers

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