Annual cycle of sea surface temperature along the east Adriatic coast

Abstract

 Time series of sea surface temperature (SST), measured over some 20-year interval at 21 stations along the east Adriatic coast, are analyzed. By means of the Fourier analysis the average annual cycle of temperature is documented and the year-to-year variability of various SST-related parameters is described. It is shown that amplitudes of the first harmonic of the annual cycle are decreasing and its phases increasing in an offshore direction. The amplitudes range from 5.4 to 8.0 °C, the phases vary from 7.2 to 7.5 months (implying maximal time lag of nine days). The variability is mostly controlled by the autumn/winter cooling process. Amplitude of the first harmonic is anomalously low at Senj, whereas the corresponding phase does not depart from the typical coastal values. The finding is due to the exceptionally low summer SSTs that occur in the vicinity of Senj. At the Sv. Ivan station (near Rovinj) the spring/summer heating is significantly faster than the autumn/winter cooling. This can be ascribed to the influence of the Po River waters, which spread over the open Adriatic in spring/summer, but are mostly confined to the western coast in autumn/winter. The year-to-year changes of all parameters considered are found to be much smaller than the multi-year average values, and in some cases prove to be small even if compared with the spatial variations of the long-term averages.