engleski

Wind-induced vertical shearing : ALPEX/MEDALPEX data and modelling exercise

The wind-induced vertical shearing in the Northern Adriatic, duc to vorticity in the wind field, has been studied using hydrodynamical numerical model and empirical data collected during ALPEX/MEDALPEX. The influence of heterogeneous wind fields on the currents in the Northern Adriatic during winter has been modelled using climatological wind data for a ten-year period (1956-1965) and six stations along the Yugoslavian coast, as well as two-month time series of hourly wind magnitudes and directions for a coastal station in the area (Pula Airport). lt is shown, through several gradually refined numerical experiments, thai the heterogeneity in the wind field is a major factor ìn determining the wind-induced vertical shear. Model to data comparison shows that wind vorticity can produce current vectors of a magnitude, direction and relative position comparable to the ones obtained by measurements. The wínd-vorticiry interpretation presented here is an alternative to the one put forward in a previous paper in which improved prediction was sought by changing the magnitude of the depth­ ìndependent eddy viscosity coefficient. The ALPEX/MEDALPEX wind and current data have been analysed in both the time and frequency domains. Both analyses support the notion that dominant response of the Northern Adriatic to the wind is of the forced type. However, the analyses also indicate the presence of free oscillations and appear to provide, for the first time, evidence for the existence of basin-wide topographic waves in the Adriatic Sea.

numerical model; wind-curl effect; ALPEX; MEDAPLEX; Northern Adriatic; vertical shearing

nije evidentirano