engleski

Lake-land breezes over Kozjak, Plitvice lakes, Croatia

The aim of the study was to investigate if a small, elongated lake (Kozjak, Plitvice Lakes, Croatia ; 2.3 km by 0.1-0.6 km ; maximum depth of 46 m) can produce atmospheric thermal circulation systems, that is, lake-land breezes (LLBs). The lake temperature was measured during summertime over three years (2018-2020) at the depth of 0.2 m at temporal resolution of 1h. Simultaneous standard meteorological variables were obtained from nearby meteorological site. Days with persistent LLBs were identified based on 7 prescribed criteria in which the atmospheric and lake conditions were taken into account. Specifically, these criteria take into account air and lake temperature, wind speed and direction, air pressure and precipitation. The results show that despite of the small lake size, LLBs were established. Thus, 17.7% of the investigated days were associated with persistent LLB events. As these events were accompanied by elevated energy in the normalized wavelet spectra for the wind speed at period of 24 hours, it was concluded that the prescribed criteria well define persistent LLB events. However, it was noted that the observed LLBs were most likely superposed with the thermally induced up- and downslope winds, as Kozjak Lake is confined by nearby mountains. While during the nighttime, land breezes were characterized with a clear clockwise wind rotation, during the daytime, lake breezes were frequently channeled in the along-lake direction due to the surrounding topography. Finally, the results showed a clear relationship between the lake-land temperature difference and the strength of the LLBs.

thermal circulation, temperature gradient, downslope winds

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