Modeling the Northern Adriatic Double-Gyre Response to Intense Bora Wind: A Revist

摘要

A combination of recent intensive observations and simulations with two numerical models is used to revisit the issue of the northern Adriatic response to strong bora episodes. New observed and simulated data reinforce the view that an episode of a strong bora wind provokes a double-gyre (cyclonic, Trieste, and anticyclonic, Rovinj) response north of the Po Delta-Pula line. During an intense bora episode, both measured and modeled statistics picture a downwind, highly polarized, and almost depth-independent flow within the Trieste gyre NW arm. Its NE arm maintains a sharp polarization and strong depth dependence while exhibiting lower speeds, with models in good accord with observations. The current statistics for Rovinj gyre provide lower maximum and average speed values and less polarized but still rather depth-independent flow, while exhibiting clockwise rotation. The north arm of the Senj gyre (positioned south of the Po Delta-Pula line) enjoys more lateral freedom, and exhibits less rectilinear flow. Our review reinforces the notion that modeling studies based on ECMWF wind forcing fail to properly take into account the orographic control of the Dinaric Alps, and to produce correct bora-induced gyral pattern. The OAMPSR model successfully simulated the onset, duration, and decay of the wind peaks, but exhibited a tendency to over predict the strength of the bora wind. Our simulations have identified the shallow NW coastal strip as an important source of colder water observed in a sequence of remotely sensed SST fields derived from AVHRR data.