Seasonal and interannual variability of the northern Adriatic surface fluxes

Coastal meteorological data and sea surface temperature collected over a 27 -year interval (1966-1992) have been used to evaluate seasonal cycle and in terannual variability of surface heat, water and buoyancy fluxes at three l ocations in the northern Adriatic (Trieste, Rovinj and Mall Losinj). Annual averages of downward heat and water fluxes and upward buoyancy flux ranged between - 7 W m(-2) and 3 W m(-2), 0.3 mm day(-1) and 0.8 mm day(-1), and - 0.4 x 10(-8) m(2) s(-3) and 0.2 x 10(-8) m(2) s(-3), respectively. Season al cycle of buoyancy flux depended almost entirely on surface heat exchange . Considerable spatial variations of fluxes, controlled by evaporation and to a less extent by sensible heat flux, have been observed at seasonal time scale. The finding was supported by an error analysis, which included esti mation of random error (due to uncertainties in basic observations and in m ethod of computation), estimation of the error due to averaging and correct ion for the use of coastal data while computing open-sea fluxes. Short time series (8 November 1992-21 February 1993) of hourly measurements at two ne arby locations (Rovinj and Pula) have been used to show that spatial variab ility in air-sea forcing was even more pronounced at hourly and daily time scales. In order to discuss long-term variations of surface fluxes, monthly values computed for the 1966-1992 interval were considered. By relating th e extreme values of surface fluxes to global meteorological conditions the reliability of our computation was confirmed. In addition, an attempt has b een made to relate the interannual variability of the northern Adriatic sur face fluxes to the winter dense-water formation processes and to the change s in temperature, salinity and density of water found in the bottom layer o f central Adriatic between 1966 and 1980. (C) 1999 Elsevier Science B.V. Al l rights reserved.