WIND DIRECTION FREQUENCY ANALYSIS FOR THE JUGO WIND IN THE ADRIATIC

The strong wind blowing from the south-eastern quadrant over the Adriatic Sea region is known as jugo, in the eastern coastal area customarily also called scirocco. The jugo wind type has been separated from the five-year hourly wind data (1976-1980) for three stations (Pula, Split and Dubrovnik), by introducing a criterion with conditions a wind vector should satisfy during a jugo event. The stations are situated on the northern, middle and southern part of the eastern (Croatian) Adriatic coast. All jugo events consisting of hourly mean wind velocities ≥ 0.3 ms-1, and subsets of jugo events, referred to as stronger jugo, consisting of hourly mean wind velocities ≥ 3 ms-1, were analysed. The results show that wind from the SE quadrant (6 wind directions), independent of any wind type criterion, accounts for 33% to 40% of all the five-year wind data (16 wind directions) with percentages growing from the north toward the south, along the Croatian part of the Adriatic coast. All jugo events contribute from 19% to 27%, going from the north toward the south. Stronger jugo contributes only 6% to 20% going in the same direction along the coast. Increased seasonal frequencies of jugo events were obtained in spring for Pula, and in both winter and spring for Split and Dubrovnik. The mathematical approximation of the jugo wind roses by means of mixture distribution resulted in two components in each of the seasonal wind roses. The shape and contribution of these components change from season to season and from station to station. Two components for the jugo wind roses approximation calls to mind the known, but yet unproved empirical statement about the existence of a cyclonic and an anticyclonic jugo wind type