The influence of digitisation and timing errors on the estimation of tidal components at Split (Adriatic Sea)

International audienceThe paper comprises the calculations of amplitudes and phases of tidal harmonic constituents, performed on hourly sea level data recorded at the Split tide gauge in the period 1957-2001. Interannual changes in all constituents have been detected, stronger in phases than in amplitudes. For example, the estimated change in M2 amplitude and phase is 22% (1.31 cm) and 24.9° between the 1962?1978 and 1957?1961 periods, respectively. Some of the differences are generated artificially throughout the measurements (clock errors, positioning and stretching of a chart) and within the digitising procedure, rather than by natural processes and changes (e.g. changes in mean sea level). This is the reason why the M2 and K1 amplitudes were recomputed with 3?4 mm larger values using newer software, thereby decreasing their standard deviation by 60?70% in the 1986?1995 period. Artificial errors may be reduced by the upgrading of digitising software; however, most of the errors still remain in the series. These errors may have repercussions when trying to explain some unusual findings: the energy of de-tided sea level series at the M2 tidal period (12.4 h) has been assumed previously to be a result of nonlinear coupling, but it may be caused, at least partly, by timing errors in the time series

Forced and free response of the Adriatic Sea level

The aim of this paper is to improve the knowledge of the variations of the sea level in the Adriatic Sea in the domains of forced and free oscillations. For this purpose, one-year long-time series of data collected at nine tide gauge stations placed on the eastern shoreline have been collected and processed by spectral analysis. The harmonic constituents have been calculated too. Semidiurnal and diurnal tides have got larger variations of amplitude on the islands than on the coast. The response of the sea level in the domain of synoptic and planetary formations is quite synchronous in the whole Adriatic for periods longer than 3.5 days, with a gap around 9.5 days. These formations excite the sea level first in the North Adriatic, and then, secondly in the Middle and South Adriatic. The seiches occurred at already known periods of 22-23, 10.8 and 7.5-8 hours, and at a new one of about 4 hours. 4 hour seiche occurs in the region inside the Middle Adriatic islands, and it is predominantly influenced by the Sirocco wind forcing

EDDY PROCESSES OF THE WESTERN ADRIATIC CURRENT NEAR CAPE GARGANO

Abstract Eddy processes of the Western Adriatic Current near Cape Gargano are highly modulated by the wind, growing during calm periods following strong wind events. Both single anticyclones and trains of multiple eddies with a regular spacing are observed. Suppression of a single anticyclone in the lee of the Cape was observed by profiling SEPTR moorings to occur when the horizontal gradient of the thermocline depth was increased by the wind. Eddies also form cyclonic filaments extending offshore. Such a filament was observed through the new technique of seismic oceanography to have downslope tilting isotherms and a long, thin, offshore extension in the bottom boundary layer. Recent measurements from two international collaborative research programs reveal new details of eddy activity and instability of the Western Adriatic Current (WAC) as it rounds Cape Gargano in the central Adriatic Sea. The "Dynamics of the Adriatic in Real-Time" (DART) program was focused on understanding the predictability of this system with observation and modelling from October 2005 through September 2006. These included, among other things, measurements from long-term current moorings, profiling SEPTR moorings, tow-yo CTD profiles, remote sensing, and high-resolution modelling using the U.S. Navy Coastal Ocean Model. Remote sensing and modelling, supported by in situ observations, revealed two distinct cases of WAC eddy activity Although Adriatic wind regimes and Cape topography provide the background setting for eddy formation, frontal instabilities and mixing processes determine many details of eddy structure and evolution. Acknowledgments: We thank the Italian CNR for providing R/V Urania ship time and CNR-ISMAR for coordinating the AdriaSeismic09 cruise

Coastal high-frequency radars in the Mediterranean - Part 1: Status of operations and a framework for future development

Due to the semi-enclosed nature of the Mediterranean Sea, natural disasters and anthropogenic activities impose stronger pressures on its coastal ecosystems than in any other sea of the world. With the aim of responding adequately to science priorities and societal challenges, littoral waters must be effectively monitored with high-frequency radar (HFR) systems. This land-based remote sensing technology can provide, in near-real time, fine-resolution maps of the surface circulation over broad coastal areas, along with reliable directional wave and wind information. The main goal of this work is to showcase the current status of the Mediterranean HFR network and the future roadmap for orchestrated actions. Ongoing collaborative efforts and recent progress of this regional alliance are not only described but also connected with other European initiatives and global frameworks, highlighting the advantages of this cost-effective instrument for the multi-parameter monitoring of the sea state. Coordinated endeavors between HFR operators from different multi-disciplinary institutions are mandatory to reach a mature stage at both national and regional levels, striving to do the following: (i) harmonize deployment and maintenance practices; (ii) standardize data, metadata, and quality control procedures; (iii) centralize data management, visualization, and access platforms; and (iv) develop practical applications of societal benefit that can be used for strategic planning and informed decision-making in the Mediterranean marine environment. Such fit-for-purpose applications can serve for search and rescue operations, safe vessel navigation, tracking of marine pollutants, the monitoring of extreme events, the investigation of transport processes, and the connectivity between offshore waters and coastal ecosystems. Finally, future prospects within the Mediterranean framework are discussed along with a wealth of socioeconomic, technical, and scientific challenges to be faced during the implementation of this integrated HFR regional network

Coastal high-frequency radars in the Mediterranean - Part 2: Applications in support of science priorities and societal needs

The Mediterranean Sea is a prominent climate-change hot spot, with many socioeconomically vital coastal areas being the most vulnerable targets for maritime safety, diverse met-ocean hazards and marine pollution. Providing an unprecedented spatial and temporal resolution at wide coastal areas, high-frequency radars (HFRs) have been steadily gaining recognition as an effective land-based remote sensing technology for continuous monitoring of the surface circulation, increasingly waves and occasionally winds. HFR measurements have boosted the thorough scientific knowledge of coastal processes, also fostering a broad range of applications, which has promoted their integration in coastal ocean observing systems worldwide, with more than half of the European sites located in the Mediterranean coastal areas. In this work, we present a review of existing HFR data multidisciplinary science-based applications in the Mediterranean Sea, primarily focused on meeting end-user and science-driven requirements, addressing regional challenges in three main topics: (i) maritime safety, (ii) extreme hazards and (iii) environmental transport process. Additionally, the HFR observing and monitoring regional capabilities in the Mediterranean coastal areas required to underpin the underlying science and the further development of applications are also analyzed. The outcome of this assessment has allowed us to provide a set of recommendations for future improvement prospects to maximize the contribution to extending science-based HFR products into societally relevant downstream services to support blue growth in the Mediterranean coastal areas, helping to meet the UN's Decade of Ocean Science for Sustainable Development and the EU's Green Deal goals

Challenges for Sustained Observing and Forecasting Systems in the Mediterranean Sea

The Mediterranean community represented in this paper is the result of more than 30 years of EU and nationally funded coordination, which has led to key contributions in science concepts and operational initiatives. Together with the establishment of operational services, the community has coordinated with universities, research centers, research infrastructures and private companies to implement advanced multi-platform and integrated observing and forecasting systems that facilitate the advancement of operational services, scientific achievements and mission-oriented innovation. Thus, the community can respond to societal challenges and stakeholders needs, developing a variety of fit-for-purpose services such as the Copernicus Marine Service. The combination of state-of-the-art observations and forecasting provides new opportunities for downstream services in response to the needs of the heavily populated Mediterranean coastal areas and to climate change. The challenge over the next decade is to sustain ocean observations within the research community, to monitor the variability at small scales, e.g., the mesoscale/submesoscale, to resolve the sub-basin/seasonal and inter-annual variability in the circulation, and thus establish the decadal variability, understand and correct the model-associated biases and to enhance model-data integration and ensemble forecasting for uncertainty estimation. Better knowledge and understanding of the level of Mediterranean variability will enable a subsequent evaluation of the impacts and mitigation of the effect of human activities and climate change on the biodiversity and the ecosystem, which will support environmental assessments and decisions. Further challenges include extending the science-based added-value products into societal relevant downstream services and engaging with communities to build initiatives that will contribute to the 2030 Agenda and more specifically to SDG14 and the UN's Decade of Ocean Science for sustainable development, by this contributing to bridge the science-policy gap. The Mediterranean observing and forecasting capacity was built on the basis of community best practices in monitoring and modeling, and can serve as a basis for the development of an integrated global ocean observing system

Challenges for Sustained Observing and Forecasting Systems in the Mediterranean Sea

The Mediterranean community represented in this paper is the result of more than 30 years of EU and nationally funded coordination, which has led to key contributions in science concepts and operational initiatives. Together with the establishment of operational services, the community has coordinated with universities, research centers, research infrastructures and private companies to implement advanced multi-platform and integrated observing and forecasting systems that facilitate the advancement of operational services, scientific achievements and mission-oriented innovation. Thus, the community can respond to societal challenges and stakeholders needs, developing a variety of fit-for-purpose services such as the Copernicus Marine Service. The combination of state-of-the-art observations and forecasting provides new opportunities for downstream services in response to the needs of the heavily populated Mediterranean coastal areas and to climate change. The challenge over the next decade is to sustain ocean observations within the research community, to monitor the variability at small scales, e.g., the mesoscale/submesoscale, to resolve the sub-basin/seasonal and inter-annual variability in the circulation, and thus establish the decadal variability, understand and correct the model-associated biases and to enhance model-data integration and ensemble forecasting for uncertainty estimation. Better knowledge and understanding of the level of Mediterranean variability will enable a subsequent evaluation of the impacts and mitigation of the effect of human activities and climate change on the biodiversity and the ecosystem, which will support environmental assessments and decisions. Further challenges include extending the science-based added-value products into societal relevant downstream services and engaging with communities to build initiatives that will contribute to the 2030 Agenda and more specifically to SDG14 and the UN's Decade of Ocean Science for sustainable development, by this contributing to bridge the science-policy gap. The Mediterranean observing and forecasting capacity was built on the basis of community best practices in monitoring and modeling, and can serve as a basis for the development of an integrated global ocean observing system