Numerical simulation of the Adriatic Sea principal tidal constituents

The primary goal of this study was to incorporate data-derived harmonic constants into a complex dynamic model using a form of variational data assimilation, with a view to improve the prediction of 7 dominant tidal constituents in the Adriatic Sea. Firstly, harmonic-constant data for 6 Adriatic stations were fed into a steady-state, 3-D, forward/inverse model to furnish optimal boundary conditions (OBCs). Calculated OBCs were then used to derive individual constituent responses, as well as to synthesise seven-constituent boundary conditions for the time stepping, 3-D model. A separate set of 25 stations provided control harmonic constant data. In validating the model output particular attention has been given to the often-ignored tidal currents. To that end 14 current meter data records were processed into tidal current ellipse parameters and used to examine the comparable model output. Comparison to gauge data has shown that the present solution is better than our own previous one, and shows an improvement over recent solutions by other authors. The model accurately reproduces available data with individual station amplitude differences rarely exceeding 1cm, and with the phase error commonly staying well below 10°. For all tidal constituents individual station differences result in RMSE in the 0.33-0.71-cm range for amplitude, and the 5.6°-19.2° range for phase. Semidiurnal currents appear to be modelled better than the diurnal ones (generally over-predicted). High eccentricity of both data and model-derived ellipses often impaired calculating the proper sense of rotation; inclination of the ellipses proved to be the most robust parameter, successfully predicted for most constituents at all depths

Influence of topography on tide propagation and amplification in semi-enclosed basins

An idealized model for tide propagation and amplification in semi-enclosed rectangular basins is presented, accounting for depth differences by a combination of longitudinal and lateral topographic steps. The basin geometry is formed by several adjacent compartments of identical width, each having either a uniform depth or two depths separated by a transverse topographic step. The problem is forced by an incoming Kelvin wave at the open end, while allowing waves to radiate outward. The solution in each compartment is written as the superposition of (semi)-analytical wave solutions in an infinite channel, individually satisfying the depth-averaged linear shallow water equations on the f plane, including bottom friction. A collocation technique is employed to satisfy continuity of elevation and flux across the longitudinal topographic steps between the compartments. The model results show that the tidal wave in shallow parts displays slower propagation, enhanced dissipation and amplified amplitudes. This reveals a resonance mechanism, occurring when\ud the length of the shallow end is roughly an odd multiple of the quarter Kelvin wavelength. Alternatively, for sufficiently wide basins, also Poincaré waves may become resonant. A transverse step implies different wavelengths of the incoming and reflected Kelvin wave, leading to increased amplitudes in shallow regions and a shift of amphidromic points in the direction of the deeper part. Including the shallow parts near the basin’s closed end (thus capturing the Kelvin resonance mechanism) is essential to reproduce semi-diurnal and diurnal\ud tide observations in the Gulf of California, the Adriatic Sea and the Persian Gulf

Scripta in honorem Igor Fisković: zbornik povodom sedamdesetog rođendana

The International Research Centre for Late Antiquity and the Middle Ages prepared a Festschrift in honour of one of its founders, Igor Fisković on the occassion of his 70th birthday. The Festschrift  includes works addressing the periods that Igor Fisković has dealt with most, thus reflecting the diversity of his interests, ranging from Late Antiquity to contemporary art, with key emphasis on the Late Middle Ages and early modernity. Due to the diversity and the broad period of time the texts are covering, they have been arranged more or less chronologically. The works focus mainly on the Late Middle Ages and the early modern period, Fisković’s forte and the topic of some of his best writings. There are also several texts addressing the baroque period, which was not one of the honouree’s interests, but they were written by some of his closest friends and members of the generation of his former students who have had prestigious careers. (from the Foreword)Zbornik je pripredio Međunarodni istraživački centar za kasnu antiku i srednji vijek povodom sedamdesetog rođendana jednog od svojih osnivača Igora Fiskovića. Zbornik obuhvaća radove koje pokrivaju razdoblja kojima se Igor Fisković ponajviše bavio, reflektirajući raznolikost njegovih interesa, od početne kasne antike i suvremene umjetnosti, do ključnoga naglaska na kasnom srednjem vijeku i početku modernog doba. Zbog te raznolikosti i širokog vremenskog razdoblja koje pokrivaju, radovi su poredani manje-više kronološki. Ističe se brojem radova upravo kasnosrednjovjekovno doba i početci modernoga, forte u kojem je Igor Fisković dao svoje ponajbolje radove. Uz njih je i više priloga koji pokrivaju razdoblje baroka, kojim se slavljenik nije bavio, no koji su iz pera njegovih najbliskijih prijatelja i one generacije njegovih bivših studenata koji su danas ostvarili ugledne karijere. (iz Predgovora

Scripta in honorem Igor Fisković: zbornik povodom sedamdesetog rođendana

The International Research Centre for Late Antiquity and the Middle Ages prepared a Festschrift in honour of one of its founders, Igor Fisković on the occassion of his 70th birthday. The Festschrift  includes works addressing the periods that Igor Fisković has dealt with most, thus reflecting the diversity of his interests, ranging from Late Antiquity to contemporary art, with key emphasis on the Late Middle Ages and early modernity. Due to the diversity and the broad period of time the texts are covering, they have been arranged more or less chronologically. The works focus mainly on the Late Middle Ages and the early modern period, Fisković’s forte and the topic of some of his best writings. There are also several texts addressing the baroque period, which was not one of the honouree’s interests, but they were written by some of his closest friends and members of the generation of his former students who have had prestigious careers. (from the Foreword)Zbornik je pripredio Međunarodni istraživački centar za kasnu antiku i srednji vijek povodom sedamdesetog rođendana jednog od svojih osnivača Igora Fiskovića. Zbornik obuhvaća radove koje pokrivaju razdoblja kojima se Igor Fisković ponajviše bavio, reflektirajući raznolikost njegovih interesa, od početne kasne antike i suvremene umjetnosti, do ključnoga naglaska na kasnom srednjem vijeku i početku modernog doba. Zbog te raznolikosti i širokog vremenskog razdoblja koje pokrivaju, radovi su poredani manje-više kronološki. Ističe se brojem radova upravo kasnosrednjovjekovno doba i početci modernoga, forte u kojem je Igor Fisković dao svoje ponajbolje radove. Uz njih je i više priloga koji pokrivaju razdoblje baroka, kojim se slavljenik nije bavio, no koji su iz pera njegovih najbliskijih prijatelja i one generacije njegovih bivših studenata koji su danas ostvarili ugledne karijere. (iz Predgovora

Wintertime dynamics in the coastal northeastern Adriatic Sea: the NAdEx 2015 experiment

The paper investigates the wintertime dynamics of the coastal northeastern Adriatic Sea and is based on numerical modelling and in situ data collected through field campaigns executed during the winter and spring of 2015. The data were collected with a variety of instruments and platforms (acoustic Doppler current profilers, conductivity–temperature–depth probes, glider, profiling float) and are accompanied by the atmosphere–ocean ALADIN/ROMS modelling system. The research focused on the dense-water formation (DWF), thermal changes, circulation, and water exchange between the coastal and open Adriatic. According to both observations and modelling results, dense waters are formed in the northeastern coastal Adriatic during cold bora outbreaks. However, the dense water formed in this coastal region has lower densities than the dense water formed in the open Adriatic due to lower salinities. Since the coastal area is deeper than the open Adriatic, the observations indicate (i) balanced inward–outward exchange at the deep connecting channels of denser waters coming from the open Adriatic DWF site and less-dense waters coming from the coastal region and (ii) outward flow of less-dense waters dominating in the intermediate and surface layers. The latter phenomenon was confirmed by the model, even if it significantly underestimates the currents and transports in the connecting channels. The median residence time of the coastal area is estimated to be approximately 20 days, indicating that the coastal area may be renewed relatively quickly by the open Adriatic waters. The data that were obtained represent a comprehensive marine dataset that can be used to calibrate atmospheric and oceanic numerical models and point to several interesting phenomena to be investigated in the future

Tidal currents in the northwestern Adriatic: High-frequency radio observations and numerical model predictions

The results of a two-year long deployment of high frequency radars along the Italian coast of the northern Adriatic are analyzed, to characterize the surface tidal currents. M2 and K1 ellipses are aligned with the basin axis and exhibit large eccentricities in the middle of the basin, decreasing toward the Italian coast. Comparisons are made with a 3D finite-element non-linear numerical model of the tides. Complex correlations between modeled and observed tidal currents show a remarkable agreement in the middle of the basin, with magnitudes reaching 0.985 and average phases of -6.4 deg. However the magnitudes drop to 0.5 within 20-30 km from the Italian coast, where the modeled currents amplitudes are underestimated by 2cm/s and the phases lag the observed phases by 60 deg. This shallow region (less than 30-m deep) is characterized by low-salinity water originating at the Po River and laterally sheared coastal flows. The radars may have captured the influence of stratification or mean sheared flows, both absent from the model. The model parameterization of bottom friction may also inadequately represent the effects of real bottom friction on the vertical current shear