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Dobricic, Srdjan
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Dobricic, Srdjan
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- PublicationRestrictedImpact of data assimilation of glider observations in the Ionian Sea (Eastern Mediterranean)(2010)
; ; ; ; ;Dobricic, S.; CMCC ;Pinardi, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Testor, P. ;Send, U.; ; ;Glider observations of temperature, salinity and vertically averaged velocity in the Ionian Sea (Eastern Mediterranean Sea), made in the period October 2004–December 2004, were assimilated into an operational forecasting model together with other in situ and satellite observations. The study area has a high spatial and temporal variability of near surface dynamics, characterized by the entrance of the Atlantic Ionian Stream (AIS) into the Northern Ionian Sea. The impact of glider observations on the estimation of the circulation is studied, and it is found that their assimilation locally improves the prediction of temperature, salinity, velocity and surface elevation fields. However, only the assimilation of temperature and salinity together with the vertically averaged velocity improves the forecast of all observed parameters. It is also found that glider observations rapidly impact the analyses even remotely, and the remote impacts on the analyses remain several months after the presence of the glider. The study emphasizes the importance of assimilating as much as possible all available information from gliders, especially in dynamically complex areas.139 22 - PublicationRestrictedOn the assessment of Argo float trajectory assimilation in the Mediterranean Forecasting System(2011)
; ; ; ; ; ;Nilsson, J. A. U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Dobricic, S.; CMCC, Bologna ;Pinardi, N.; Università di Bologna ;Taillandier, V.; Laboratoire d’Oceanographie de Villefranche, France ;Poulain, P.-M.; The National Institute of Oceanography and Applied Geophysics (OGS), Trieste, Italy; ; ; ; The Mediterranean Forecasting System (MFS) has been operational for a decade, and is continuously providing forecasts and analyses for the region. These forecasts comprise local- and basin-scale information of the environmental state of the sea and can be useful for tracking oil spills and supporting search-and-rescue missions. Data assimilation is a widely used method to improve the forecast skill of operational models and, in this study, the three-dimensional variational (OceanVar) scheme has been extended to include Argo float trajectories, with the objective of constraining and ameliorating the numerical output primarily in terms of the intermediate velocity fields at 350 m depth. When adding new datasets, it is furthermore crucial to ensure that the extended OceanVar scheme does not decrease the performance of the assimilation of other observations, e.g., sea-level anomalies, temperature, and salinity. Numerical experiments were undertaken for a 3-year period (2005–2007), and it was concluded that the Argo float trajectory assimilation improves the quality of the forecasted trajectories with ~15%, thus, increasing the realism of the model. Furthermore, the MFS proved to maintain the forecast quality of the sea-surface height and mass fields after the extended assimilation scheme had been introduced. A comparison between the modeled velocity fields and independent surface drifter observations suggested that assimilating trajectories at intermediate depth could yield improved forecasts of the upper ocean currents.247 23 - PublicationOpen AccessMarine climate change and environmental indicators from the Marine Core Service(2009-09-09)
; ; ; ; ; ; ; ; ; ; ; ; ; ;Coppini, Giovanni; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Lyubartsev, Vladyslav; Centro EuroMediterraneo per i Cambiamenti Climatici ;Pinardi, Nadia; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Fratianni, Claudia; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Tonani, Marina; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Adani, Mario; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Oddo, Paolo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Dobricic, Srdjan; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Marullo, Salvatore; ENEA ;Loewe, Peter; BSH ;Santoleri, Rosalia; CNR-ISAC ;Colella, Simone; CNR-ISAC ;Volpe, Gianluca; CNR-ISAC; ; ; ; ; ; ; ; ; ; ; ; ; ENVIROINFOIn the framework of the Mediterranean Operational Oceanography Network (MOON, http://www.moon-oceanforecasting.eu) The Mediterranean Forecasting System (Pinardi et al., 2003) has started the design and development of services that include the routine production of environmental and climate indicators. A process of identifying user requirements has been started in collaboration with European Environment Agency and the indicators definition and implementation aim to take user requirements into account. The indicators are extensively used by EEA (EEA web page on indicators: http://themes.eea.europa.eu/indicators/). INGV has carried out an analysis on the possible improvements of existing indicators in use by EEA and on the development of new indicators based on Marine Core Services (MCS) products. The list of indicators includes: Temperature, Chlorophyll-a (from ocean colour), Ocean Currents and Transport, Salinity, Transparency, Sea Level, Sea Ice and Density. A critical analysis has been carried out to identify the relevance of the above-mentioned indicators for EU policies, their spatial and temporal coverage, their accuracy and their availability (Coppini et al., 2008). INGV in collaboration with CNR-ISAC are directly involved on the development of the indicators in the Mediterranean region and European Seas region the Temperature and Chlorophyll-a (Chl-a) products are the most suitable for an indicator development test phase. In particular the OO Chl-a product, deduced from satellite data, is able to contribute to the further development of the EEA Chl-a indicator on eutrohpication that is based on in-situ measurements (CSI023). For this indicator a development phase has been undertaken in 2008 and 2009 within the European Topic Center for Water (ETC-W) for EEA. The temperature indicators, developed with the support of MyOcean and Operational Oceanography community, consist of long time series (1870-Today) of SST anomaly able to describe ocean temperature increase due to climate change in the European Seas and on SST trends map of the last 25 years for the European Seas. These last two indicators have been included in the last 2008 EEA report on Impacts of Climate change in the European Seas (http://www.eea.europa.eu/publications/eea_report_2008_4). Moreover MFS re-analysis have been produced for the Mediterranean Sea and it consists of daily output of MFS-OPA hydrodinamic model (1/16 of degree horizontal resolution) that assimilates all available in situ and satellite observation for 1985 to 2007. This reanalysis product is used to detect temperature anomalies over the last 20 years in the coastal zone that could be related with environmental stresses. In addition to that we have also identified a Density indicator that appears relevant for the ecosystem health assessment in the coastal waters.560 373 - PublicationRestrictedImpact of Multialtimeter Sea Level Assimilation in the Mediterranean Forecasting Model(2010)
; ; ; ; ;Pujol, M.-I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Dobricic, S.; CMCC ;Pinardi, N. ;Adani, M.; ; ;In this article the impact of multisatellite altimeter observations assimilation in a high-resolution Mediterranean model are analyzed. Four different altimeter missions [Jason-1, Envisat, Ocean Topography Experiment (TOPEX)/Poseidon interleaved and Geosat Follow-On] are used over a 7-month period (from September 2004 to March 2005) to study the impact of the assimilation of one to four satellites on the analyses quality. The study highlights three important results. First, it shows the positive impact of the altimeter data on the analyses. The corrected fields capture missing structures of the circulation, and eddies are modified in shape, position, and intensity with respect to the model simulation. Second, the study demonstrates the improvement in the analyses induced by each satellite. The impact of the addition of a second satellite is almost equivalent to the improvement given by the introduction of the first satellite: the second satellite’s data bring a 12% reduction of the root-mean-square of the differences between the analyses and observations for the sea level anomaly (SLA). The third and fourth satellites also improve the rms, with a more than 3% reduction for each of them. Finally, it is shown that Envisat and Geosat Follow-On additions to Jason-1 impact the analyses more than the addition of TOPEX/Poseidon, suggesting that the across-track spatial resolution is still one of the important aspects of a multimission satellite observing system. This result could support the concept of multimission altimetric monitoring done by complementary horizontal resolution satellite orbits.124 23 - PublicationRestrictedAssimilating Along-Track Altimetric Observations through Local Hydrostatic Adjustment in a Global Ocean Variational Assimilation System(2011-03)
; ; ; ; ;Storto, A.; Centro Euro-Mediterraneo per i Cambiamenti Climatici, Bologna, Italy ;Dobricic, S.; Centro Euro-Mediterraneo per i Cambiamenti Climatici, Bologna, Italy ;Masina, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Di Pietro, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; ; ; A global ocean three-dimensional variational data assimilation system was developed with the aim of assimilating along-track sea level anomaly observations, along with in situ observations from bathythermographs and conventional sea stations. All the available altimetric data within the period October 1992–January 2006 were used in this study. The sea level corrections were covariated with vertical profiles of temperature and salinity according to the bivariate definition of the background-error vertical covariances. Sea level anomaly observational error variance was carefully defined as a sum of instrumental, representativeness, observation operator, and mean dynamic topography error variances. The mean dynamic topography was computed from the model long-term mean sea surface height and adjusted through an optimal interpolation scheme to account for observation minus first-guess biases. Results show that the assimilation of sea level anomaly observations improves the model sea surface height skill scores as well as the subsurface temperature and salinity fields. Furthermore, the estimate of the tropical and subtropical surface circulation is clearly improved after assimilating altimetric data. Nonnegligible impacts of the mean dynamic topography used have also been found: compared to a gravimeter-based mean dynamic topography the use of the mean dynamic topography discussed in this paper improves both the consistency with sea level anomaly observations and the verification skill scores of temperature and salinity in the tropical regions. Furthermore, the use of a mean dynamic topography computed from the model long-term sea surface height mean without observation adjustments results in worsened verification skill scores and highlights the benefits of the current approach for deriving the mean dynamic topography.336 397 - PublicationOpen AccessAn improved calculation of Coriolis terms on the C grid(2006)
; ;Dobricic, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, ItaliaThe central differencing grid with fully staggered velocity components (C grid) is widely used in primitive equations oceanographic models despite potential problems in simulating baroclinic inertiagravity and Rossby waves that can arise due to the averaging of velocity components in the Coriolis terms. This note proposes a new averaging of the velocity components in order to calculate the Coriolis terms on the C grid. The averaging weights are calculated from the minimum of a suitably defined cost function which optimally minimizes the error in the inertial part of frequencies of inertia-gravity waves and maintains the second order accuracy of the computations. The theoretical analysis of wave frequency diagrams shows that the new scheme results in more accurate frequencies of long inertia-gravity and Rossby waves, especially when the Rossby radius of deformation is not resolved well by the grid resolution.114 244 - PublicationRestrictedMyOcean Scientific Validation Report (ScVR) for WP9 – Med-MFC(2011-04-01)
; ; ; ; ; ; ; ; ; ; ; ;Nilsson, Jenny; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Vladyslav, Lyubartsev; CMCC, Italy ;Grandi, Alessandro; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Teruzzi, Anna; OGS, Trieste ;Bolzon, Giorgio; OGS, Trieste ;Drudi, Massimiliano; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Tonani, Marina; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Oddo, Paolo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Adani, Mario; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Dobricic, Srdjan; CMCC, Italy ;Fratianni, Claudia; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; ; ; ; ; ; ; ; ; ; 114 25 - PublicationRestrictedDaily oceanographic analyses by the Mediterranean basin scale assimilation system(2007)
; ; ; ; ; ; ; ;Dobricic, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Pinardi, N.; 2Centro Interdipartimentale di Ricerche per le Scienze Ambientali, Ravenna, Italy ;Adani, M.; 2Centro Interdipartimentale di Ricerche per le Scienze Ambientali, Ravenna, Italy ;Tonani, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Fratianni, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Bonazzi, A.; 2Centro Interdipartimentale di Ricerche per le Scienze Ambientali, Ravenna, Italy ;Fernandez, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; ; ; ; ; ; This study presents the upgrade of the Optimal Interpolation scheme used in the basin scale assimilation scheme of the Mediterranean Forecasting System. The modifications include a daily analysis cycle, the assimilation of ARGO float profiles, the implementation of the geostrophic balance in the background error covariance matrix and the initialisation of the analyses. A series of numerical experiments showed that each modification had a positive impact on the accuracy of the analyses: The daily cycle improved the representation of the processes with the temporal variability shorter than a week, the assimilation of ARGO floats profiles significantly improved the salinity analyses quality, the geostrophically balanced background error covariances improved the accuracy of the surface elevation analyses, and the initialisation removed the barotropic adjustment in the forecast first time steps starting from the analysis.310 25 - PublicationRestrictedAn oceanographic three-dimensional variational data assimilation scheme(2008)
; ; ;Dobricic, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Pinardi, N.; Corso di Scienze Ambientali, University of Bologna, Ravenna, Italy; This study describes the development and evaluation of an oceanographic three-dimensional variational (3D-VAR) data assimilation scheme based on a novel specification of the background error covariances. The new 3D-VAR scheme allows for regional variability of the background error covariance matrix, complex coastal boundary conditions and variable bottom topography. The error covariance matrix is formed by the successive application of linear operators that can consider vertical EOFs, horizontal covariance functions that consider coastlines, sea level corrections that vary from shallow to deep regions and divergence dumping of velocity corrections near the coasts. The scheme is applied to the Mediterranean Sea and the quality of analysis is assessed by comparing background estimates with observations in the period October 2005–October 2006.118 33 - PublicationOpen AccessIonian Sea circulation as clarified by assimilation of glider observations(2008)
; ; ; ; ;Dobricic, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Pinardi, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Testor, P. ;Send, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; ; ;Glider observations of temperature and salinity in the Ionian Sea (Eastern Mediterranean Sea), made in the period October 2004-December 2004, were assimilated into an operational forecasting model together with other in-situ and satellite observations. The impact of glider data on the estimation of the circulation is studied and it is found that the assimilation of glider data significantly improve the vertical structure of temperature and salinity fields and remove biases. The accurate representation of the dynamical structures due to the assimilation of glider data allowed a detailed analysis of the dynamics of the Atlantic Ionian Stream (AIS). During autumn and in the Sicily Strait, the AIS is strengthened by the positive but weak wind stress curl near the southern Sicilian coast and by the temperature gradient between the warm surface mixed layer and the cold upwelled waters near Sicily. In winter the change of position of the wind stress curl zero line and the cooling of the surface mixed layer forces the AIS to shift southward in the Ionian Sea. The AIS is shown for the first time to pinch off an eddy in the Ionian Sea.126 470
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