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Sodar measurements during severe bora


Ivančan-Picek, Branka; Stiperski, Ivana; Bajić, Alica; Grubišić, Vanda; Xiao, Ming
Sodar measurements during severe bora // First International Conference on Remote Sensing Techniques in Disaster Management and Emergency Response in the Mediterranean Region - Abstract Book / Oluić, Marinko ; Gušić, Ivan (ur.).
Zagreb: EARSeL, HAZU, University of Zadar, GEOSAT Ltd., 2008. str. 95-95 (predavanje, međunarodna recenzija, sažetak, znanstveni)


Naslov
Sodar measurements during severe bora

Autori
Ivančan-Picek, Branka ; Stiperski, Ivana ; Bajić, Alica ; Grubišić, Vanda ; Xiao, Ming

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

Izvornik
First International Conference on Remote Sensing Techniques in Disaster Management and Emergency Response in the Mediterranean Region - Abstract Book / Oluić, Marinko ; Gušić, Ivan - Zagreb : EARSeL, HAZU, University of Zadar, GEOSAT Ltd., 2008, 95-95

Skup
First International Conference on Remote Sensing Techniques in Disaster Management and Emergency Response in the Mediterranean Region

Mjesto i datum
Zadar, Hrvatska, 22-24.09.2008

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Bora flow; sodar; flow separation; mesoscale variability

Sažetak
In this study, we investigate small-scale characteristics and spatial variability of severe Bora flow in the wider Zadar area. Zadar is situated on the eastern coast of the Adriatic Sea in the region of northern Dalmatia. Due to the vicinity of the southern end of Velebit – the 145 km long coastal mountain range that forms part of the Dinaric Alps – the area less than 20 km inland from Zadar is known for high frequency of severe Bora. In contrast, in the city of Zadar, Bora is considerably less frequent and weaker compared to its surroundings. Knowledge of the space-time variability of Bora flow and its strong shear and turbulence in the wider Zadar area is very important for traffic safety, in particular of the air traffic at the nearby Zadar-Zemunik airport. During the winter-spring 2004/5 season, a new Scientec MFAS sodar system was deployed at the Zadar airport. The Zadar sodar provides continuous vertical soundings in the range from 40 to 700 m MSL at the temporal resolution of 10 minutes and the vertical resolution of 20 m. The availability of these continuous high-resolution wind profiles allows us to examine mesoscale variability at very short temporal scales. Due to the limitations of the sodar system and its vertical reach, we focus here on the analysis of data obtained between 50 and 500 m MSL. The sodar data reveal a significant variability in the wind speed and direction during the severe Bora events. The maximum Bora speeds were observed in the layer between 300 and 700 m. The sodar also provides continuous measurement of vertical motions. The temporal variability of the vertical wind velocities evidences the existence of wave flow and turbulent mixing in the layers above 200 m by the alternation of patches of upward and downward motions. The observations are compared with results of very high-resolution numerical simulation carried out with the NRL COAMPS model. Initial simulation results indicate that the Bora flow never fully penetrated to the surface near the coast in the Zadar area. The simulation results also suggest that the primary mountain wave could be responsible for low-level flow separation over the steep terrain, leading to weak surface winds over Zadar, downstream of Velebit.

Izvorni jezik
Engleski

Znanstvena područja
Geologija



POVEZANOST RADA


Projekt / tema
004-1193086-3036 - Oluje i prirodne katastrofe u Hrvatskoj (Branka Ivančan-Picek, )

Ustanove
Državni hidrometeorološki zavod