Fifteen open-sea time-series observations of tidal velocities and tidal bottom pressures for more than six months duration provide a new database for North Adriatic tides. The observations show nearly reversing tidal currents at most locations and increasing tidal-current strength near Istria. Tidal elevation amplitudes and phases respectively increase northwestward and counterclockwise, strongly for semidiurnal tides and weakly for diurnal tides. The data are used for optimal determination of boundary conditions for a linear strong-constraint variational data assimilation model and the resulting average rms difference errors for tidal elevations and currents are below 1 cm and 0.5 cm s-1, respectively. The Q factors from the model are 14.0 for M2 and 22.4 for K1, but comparisons between frictional dissipation estimated from the model and from the data suggest that model dissipation values could be too high by a factor of two and Q factors too small. Model potential energy is 1.5 times kinetic energy for M2 and 6.1 times kinetic energy for K1. Observational and modeling results suggest that energy fluxes from Kvarner Bay are significant in the North Adriatic tidal energy balance. M2 energy fluxes support the concept of an incident and reflected Kelvin wave in the North Adriatic with some modification. K1 energy fluxes show a northeastward cross-basin flux near the 50 m isobath where the bathymetric slope is particularly steep, with Kelvin-wave-like structures north of the ridge and departures from Kelvin-wave structure south of the ridge.
Keywords: tidal velocity, tidal elevation, tidal dissipation, Kelvin wave, Topographic Rossby wave, energy flux.
In-situ measurements indicate the existence of reversed near-surface airflow over the north-eastern Adriatic during the bora wind. Here we examine its structure and evolution by means of a numerical simulation. The studied phenomenon developed during typical summer frontal bora that is associated with a cold air advection from the north-east. It is characterized by a sudden increase in wind speed and a brief duration. Within a sheltered area near the town of Malinska on the island of Krk, onshore flow occurred as the bottom branch of the lee rotor-like circulation that was associated with the hydraulic jump. While the closed circulation somewhat resembles the hypothesized hydraulic-jump rotor, there are significant differences, particularly in the strength of the turbulence associated with the rotor formation.
Keywords:wake, hydraulic jump, lee rotor.
Two simulations of the response of Adriatic Sea to severe wind performed by an atmosphere-ocean coupled model and the comparisons with observed data and modelled fields published in literature are presented.
The model RAMS-DieCAST was applied to simulate the variations of sea currents and temperature profiles, from surface to bottom, induced by two episodes of intense wind over the Adriatic sea: a Bora wind event that occurred in January 1995 and a Sirocco wind event in November 2002.
The results of the simulations are compared with observed data at the sea surface. In the Bora episode, the computed surface temperatures are compared with satellite SSTs and in situ observed temperatures; in the Sirocco event the simulated surface currents and temperatures are compared with experimental data collected by surface drifters released in different regions of the Adriatic Sea during the same Sirocco event.
In both episodes the simulated temperature trends agree with the observed values and during the Sirocco episode the current fields are in quite good agreement with the drifter data.
The modelled sea temperature and velocity fields show also a good concordance with other simulation results in literature.
Keywords: Adriatic Sea, Bora, Sirocco, Ocean-Atmosphere Interaction, Ocean-Atmosphere coupled model, surface currents, surface temperature, temperature profiles.
The goal of this research was to simulate and analyze the response of the Western Adriatic Current (WAC) to an abnormal event that occurred in the Adriatic Sea in mid-summer of 2003. At this time, a combination of extremely low discharge from the Po River and from other northwestern rivers caused by the prolonged dry season and the dominant Sirocco wind produced an ‘unusual’ upwelling and caused the WAC to reverse along the northern and central Italian coasts. The simulations employed a high-resolution, low dissipative version of the DieCAST circulation model that was initialized with monthly averaged temperature and salinity data and spun up with a use of climatological wind data. Numerical experiments were performed with the use of COAMPS wind stress and heat flux data. The model runs performed under Sirocco wind forcing in combination with low river discharge (a quarter of the climatic mean) revealed that such these conditions do trigger upwelling and the reversal of the WAC along the Italian coast. The upwelling relaxation caused by changes in the wind direction was also studied. Qualitative simulation results were in agreement with the observations by Poulain et al. (2004).
Keywords: Adriatic Sea, unusual upwelling event, Western Adriatic Current, Sirocco, Mistral, DieCAST.
9. Russo, A., A. Coluccelli, I. Iermano, F. Falcieri, M. Ravaioli, G. Bortoluzzi, P. Focaccia, G. Stanghellini, C.R. Ferrari, J. Chiggiato and M. Deserti (2009): An operational system for forecasting hypoxic events in the northern Adriatic Sea.
The northern Adriatic Sea (NA), the northernmost region of the Mediterranean Sea, is affected by strong anthropogenic pressure (e.g., tourism, fisheries, maritime traffic, discharge from agriculture and industry), superimposed to a large river runoff. The consequent pressure exerted on the NA ecosystem either triggers or worsens massive mucilage insurgence, harmful algal blooms, eutrophication and even anoxic/hypoxic events. This work focuses on the anoxic/hypoxic events. During the summer-autumn period, the NA is often exposed to these events, which can be categorised as either coastal (relatively frequent south of the Po River delta during the summer) and offshore (rare, affecting wider areas). In order to improve our knowledge about these processes and to meet the needs of local governments and decision makers, an operational system for monitoring and forecasting anoxic and hypoxic events has been set up in the framework of the EU LIFE "EMMA" project. The system is composed of a meteo-oceanographic buoy; a numerical prediction system based on the Regional Ocean Modelling System (ROMS), including a Fasham-type module for biogeochemical fluxes; and periodic oceanographic surveys. Every day since June 2007, the system provides 3-hourly forecasts of marine currents, thermohaline and biogeochemical fields for the incoming three days. The system has demonstrated its ability to produce accurate temperature forecasts and relatively good salinity and dissolved oxygen forecasts. The Root Mean Square Error of the dissolved oxygen forecast was largely due to the mean bias. The system is currently being improved to include a better representation of benthic layer biogeochemical processes and several adjustments of the model. While developing model improvements, dissolved oxygen forecasts were improved with the removal of the 10-day mean bias.
Keywords: anoxia, hypoxia, operational model, biogeochemical fluxes, Adriatic Sea, ROMS, marine forecast
10. Campanelli, A., A. Bulatović, M. Cabrini, F. Grilli, Z. Kljajić, R. Mosetti, E. Paschini, P. Penna and M. Marini: Spatial distribution of physical, chemical and biological oceanographic properties, phytoplankton, nutrients and Coloured Dissolved Organic Matter (CDOM) in the Boka Kotorska Bay (Adriatic Sea).
The temporal variations of temperature, salinity, fluorescence, dissolved oxygen concentration, Coloured Dissolved Organic Matter (CDOM) and of chemical (nutrients, chlorophyll a) and biological (phytoplankton composition) parameters in the Boka Kotorska Bay were observed during two periods. CDOM regulates the penetration of UV light into the sea and therefore plays an important role in many hydrological and biogeochemical processes in the sea surface layer including primary productivity.
In the framework ADRICOSM-STAR it was possible to investigate the Boka Kotorska Bay during May and June 2008 in order to increase an understanding of optical and chemical characteristics and their evolution during these periods. In both periods station KO (located furthest from the open sea) presented different physical, chemical and biological characteristics with respect to the other stations inside the Boka Kotorska Bay.
A positive correlation was found between CDOM and chlorophyll a (R = 0.7, P < 0.001, n = 15) and this implies that in this area, similarly to the open sea, the primary source of CDOM should be the biological production from phytoplankton. This is probably due to the fact that the rivers entering the Boka Kotorska Bay are not severely impacted by man.
Keywords: CDOM, nutrients, hydrological data, phytoplankton, Adriatic Sea.
This paper aims to quantify the productivity of research concerning the Adriatic Sea, with a focus on oceanography and meteorology. Productivity and impact were measured by analysing articles and citations from the Thomson Reuters Web of Science database, spanning the period 1994–2008. The most productive country was Italy but the highest number of citations was achieved by articles from Germany (all Adriatic publications) and Spain ("Oceanography" and "Meteorology and atmospheric sciences", only). By contrast, the second-most productive country, Croatia, had the lowest citation rate. Collaborations between Adriatic researchers were driven not only by the geographical position of a country (e.g., Italy vs. Croatia), but also by investment rates in Adriatic research (e.g., Italy vs. USA and Croatia vs. USA). Such collaborations substantially improved the impact of the research, especially from transitional countries such as Croatia.
Keywords: bibliometrics, Adriatic, oceanography, meteorology.