engleski

On the interplay between sea-land breezes and Etesian winds over the Adriatic

We investigate the interaction of the synoptically forced southeastward Etesian winds with small-scale, thermally induced sea-land breezes (SLB) during two multiday summertime periods over the Adriatic. Synoptic conditions favorable for the simultaneous establishment of these two airflows are characterized by weak large-scale forcing and fair weather conditions over the area of interest. We analyze both measured and modeled surface air temperature and wind data. Measuring sites were selected so as to cover the northern, eastern and western Adriatic coast, as well as one offshore and one open-sea location. Modeled fields were obtained from the operational hydrostatic mesoscale meteorological model ALADIN at a horizontal resolution of 8 km. In addition, modeled wind fields were dynamically adapted to a resolution of 2 km. We show that the model at the current operational horizontal resolution of 8 km reproduces reasonably well the surface airflow over the Adriatic. Further, the finer horizontal resolution results in similar wind fields, except for occasional, somewhat stronger winds (up to about 2– 3 m s− 1) that were found downstream of several topographically complex regions along the eastern coast. The air temperature, however, is not well reproduced for the open-sea site (Palagruža, P) or the coastal site (Brindisi, Br), compared to the other coastal sites, due to its specific location, which is more exposed to the effects of large water bodies. The results also reveal salient differences in airflow above the eastern and western Adriatic, caused by the different topographic setups of the two coasts. Specifically, in summer above the eastern and western Adriatic, sea-land breezes and the Etesians dominate, respectively. Along the eastern coast, the sea-land breezes are enhanced by additional topographic forcing and channeling effects, while along the western coast they are weaker and mainly found only above the land. Further, results suggest several noticeable, region-specific airflow features that seem to be typical for summertime fair weather conditions over the Adriatic. During the daytime, these are: 1) a pronounced divergence above the northern Adriatic ; 2) very strong winds west of Montenegrin and the Albanian coast ; and 3) enhanced winds above the central portion of the eastern coastal area. At night, 4) topographically-induced jets along the eastern coast are typical, while the entire day is characterized by 5) elevated wind speeds adjacent to the Gargano Peninsula. Both the differences between the eastern and western Adriatic and the occurrence of the above region-specific features can be attributed to the topographic setup and consequent slope flows and airflow channeling.

ALADIN; Coastal; Offshore; Open-sea; Summertime; Topography

Coastal Processes: Challenges for Monitoring and Prediction Edited by Michel Rixen, Jeffrey W. Book and Mirko Orlic