Preface "Operational oceanography in the Mediterranean Sea: the second stage of development"

The papers of this special issue overview some of the scientific results of the second phase of development of the Mediterranean Forecasting System (MFS) realised during the EU project "Mediterranean ocean Forecasting System: Toward Environmental Predictions-MFSTEP" that started 1 March 2003 and ended in June 2006. The MFS oceanographic service that is now operational in the Mediterranean Sea was developed, implemented and quality assessed during MFSTEP. MFS is composed of: a) a near real time observing system with satellite and in situ elements; b) a numerical ocean forecasting system at basin scale, assimilating all data available in real time, and a set of limited area forecasting models in different sub-regional and shelf areas; c) biochemical models for algal biomass forecasting; d) a product dissemination system. Moreover, the products of MFS are used to develop downstream services, such as oil spill drift and dispersion, sediment transport in the coastal areas and fish stock assessment that demonstrate the value of the operational service for end-users. MFSTEP contained several phases of development and realised a demonstration exercise, the so-called Targeted Operational Period-TOP that started in September 2004 and ended in March 2005. During TOP all possible observing platforms were active, the numerical models were capable to assimilate the observations and the all models were running in forecast mode, from the basin scale to the shelf areas. The deployed observing and modelling components of MFS are now part of a sustained operational oceanographic service for the Mediterranean Sea, so-called Mediterranean Operational Oceanography Network (MOON, http: //www.moon-oceanforecasting.eu)

A generalized model of pelagic biogeochemistry for the global ocean ecosystem. Part I: theory

The set of equations for global ocean biogeochemistry deterministic models have been for-mulated in a comprehensive and unified form in order to use them in numerical simulations of the marine ecosystem for climate change studies (PELAGOS, PELAgic biogeochemistry for Global Ocean Simulations). The fundamental approach stems from the representation of marine trophic interactions and major biogeochemical cycles introduced in the European Regional Seas Ecosystem Model (ERSEM). Our theoretical formulation revisits and generalizes the stoichiometric approach of ERSEM by defining the state variables as Chemical Functional Families (CFF). CFFs are further subdivided into living, non-living and inorganic components. Living CFFs are the basis for the definition of Living Functional Groups, the biomass-based functional prototype of the real organisms. Both CFFs and LFGs are theoretical constructs which allow us to relate measurable properties of marine biogeochemistry to the state variables used in deterministic models. This approach is sufficiently generic that may be used to describe other existing biomass-based ecosystem model

Mediterranean ocean Forecasting System: Toward Environmental Predictions-MFSTEP Executive Summary

Objectives: The Project aims at the further development of an operational forecasting system for the Mediterranean Sea based upon three main components: a) a Real Time-RT Observing system; b) a numerical forecasting system at the basin scale and for the sub-regional/shelf areas; c) the forecast products dissemination/exploitation system. The Observing system component consists of: • a SOOP-VOS system with RT data dissemination and test of new sensors that collect multidisciplinary data; • a moored buoy network (M3A) designed to serve the RT validation of the basin scale models and the calibration of the ecosystem models; • a satellite RT data analysis system using several satellites for sea surface elevation, sea surface temperature and sea surface winds; • a high space-time resolution network of autonomous subsurface profiling floats (Array for Real-Time Geostrophic Oceanography-ARGO); • a basin scale glider autonomous vehicle experiment; The sampling strategy is continuously assessed by the Observing System Simulation Experiment (OSSE) activities and a RT data management and delayed mode archiving system has been organized

On the corrections of ERA-40 surface flux products consistent with the Mediterranean heat and water budgets and the connection between basin surface total heat flux and NAO

This is a study of heat fluxes and heat budget of the Mediterranean Sea using the European Centre for Medium-Range Weather Forecasts (ECMWF) 45 year reanalysis data set ERA-40. The simple use of the ERA-40 surface flux components fails to close the budget and, in particular, the shortwave radiation flux is found to be underestimated with respect to observed data by about 10%. The heat flux terms are recomputed and corrected in order to close the heat and freshwater budgets of the Mediterranean basin over the period 1958 to 2001, thus producing a corrected ERA-40 surface flux data set. Various satellite and in situ observational data are used to construct spatially varying corrections to the ERA-40 products needed to compute the air-sea fluxes. The corrected interannual and climatological net surface heat and freshwater fluxes are and , respectively, which are regarded as satisfactorily closing the Mediterranean heat and water budgets. It is also argued that there is an important contribution from large heat losses associated with a few severe winters over the Mediterranean Sea. This is shown to be related to wind regime anomalies, which strongly affect the latent heat of evaporation that is the main responsible for the interannual modulation of the total heat flux. Furthermore, the surface total heat flux anomaly time series is compared with the North Atlantic Oscillation (NAO) index, and the result is a positive correlation with ocean warming for positive NAO index and cooling associated to negative index periods

Use of real-time observations in an operational ocean data assimilation system: the Mediterranean case

Real-time observations are essential for operational forecasting that in turn can be used to predict changes of the state of the ocean and its associated biochemical fi elds. In addition, real-time observations are useful to detect changes in the past with the shortest delay, to standardize practices in data collection and to exchange data between remote regions of the ocean and seas. Th e drawback is that real-time observations could be less accurate than their delayed mode counterparts due to the time constraints for data dissemination. In situ real-time data are usually decimated to be transmitted in real time (loss of accuracy and resolution), whereas satellite data are corrected with approximate algorithms and less ancillary data. Delayed mode quality control analysis increases the value of the observational data set, fl agging outliers and producing climatological estimates of the state of the system. Th us real-time data, together with a modelling system and the climatological estimates, give the appropriate information for scientifi c studies and applications. Th e principles of operational science started to develop in the 1940s and 1950s, based on the combined use of real-time data and modelling systems that can extend the information from observations in space and time. Operational science is based on a sound knowledge of the dynamics and processes for the space/timescales of interest and operational meteorology and oceanography have started to implement these principles to weather and ocean forecasting activities. In the past 20 years, operational meteorology has become a reality with a network of in situ and satellite observations that has made the weather forecast capable of extending the theoretical limit of predictability of the atmosphere (only one-two days theoretically, now forecasts are useful for more than fi ve days on average). Today meteorological observations are mainly used in their assimilated form even if observations are still collected for specifi c process-oriented studies. Recently the meteorological re-analysis projects (Gibson et al., 1997; Kalnay et al., 1996) have released a wealth of data to be understood and analysed. Th ese data sets are coherent and approximately continuous (daily), fi lling the observational gaps in space and time with a dynamical interpolation scheme. Th e model and the real-time observations are fused in one best estimate of the state of the system by data-assimilation techniques that have been developed to a great degree of sophistication in recent years (Lorenc, 2002). Th e re-analysis data are now forming the basic reference data set to understand climate variability in the atmosphere and upper oceans. Ch20.indd 73Ch20.indd 733 3/7/07 9:58:01 AM Habwatch 734 Dynamical interpolation/extrapolation of observational data for operational forecasting in the ocean began to be investigated at the beginning of the 1980s and the fi rst successful forecasts were carried out in the open ocean (Robinson and Leslie, 1985). Th ese exercises required real-time data that were initially collected with rapid ship surveys realizing adaptive sampling schemes and collecting a combination of traditional recoverable and expendable instruments (CTD, XBTs). At the same time but in a totally independent way, shelf scale and coastal real-time data from moored and drifting sensors such as meteorological buoys and sea-level stations started to be used for shelf scale storm surge operational forecasting (Prandle, 2002). Operational oceanography is now building on this experience and considers real-time measurements from opportunity platforms and satellites in a manner very similar to operational meteorology. Th is chapter aims to show the use of real-time observations in a state-of-the-art ocean-predicting system realized in the Mediterranean. We discuss the pre-processing schemes required to properly assimilate the observations into an operational nowcasting/ forecasting system, elucidate the role and impact of diff erent observations in the assimilation system and show the use of real-time data to evaluate quality of the modelling system. We start with the description of the Mediterranean Forecasting System (MFS) real-time observing system and pre-processing quality control in Section 20.2, we then describe the modelling and assimilation system in relation to the impact of diff erent real-time observations in Section 20.3. In Section 20.4 we evaluate the consistency, quality and accuracy of the forecasting system using model-data intercomparison and Section 20.5 offers conclusion

Forecast and analysis assessment through skill scores

International audienceThis paper describes a first comprehensive evaluation of the quality of the ten days ocean forecasts produced by the Mediterranean ocean Forecasting System (MFS). Once a week ten days forecasts are produced. The forecast starts on Tuesday at noon and the prediction is released on Wednesday morning with less then 24 hr delay. In this work we have considered 22 ten days forecasts produced from the 16 August 2005 to the 10 January 2006. All the statistical scores have been done for the Mediterranean basin and for 13 regions in which the Mediterranean sea has been subdivided. The forecast evaluation is given here in terms of root mean square (rms) values. The main skill score is computed as the root mean square of the difference between forecast and analysis (FA) and forecast and persistence (FP), where the persistence is defined as the average of the day of the analysis corresponding to the first day of the forecast. A second skill score (SSP) is defined as the ratio between rms of FA and FP, giving the percentage of accuracy of the forecast with respect to the persistence (Murphy 1993). The rms of FA is always better than FP and the FP rms error is double than the rms of FA. It is found that in the surface layers the error growth is controlled mainly by the atmospheric forcing inaccuracies while at depth the forecast errors could be due to adjustments of the data assimilation scheme to the data insertion procedure. The predictability limit for our ocean forecast seems to be 5?6 days connected to atmospheric forcing inaccuracies and to the data availability for assimilation

sensitivity of the mediterranean sea level to atmospheric pressure and free surface elevation numerical formulation in nemo

Abstract. The sensitivity of the dynamics of the Mediterranean Sea to atmospheric pressure and free surface elevation formulation using NEMO (Nucleus for European Modelling of the Ocean) was evaluated. Four different experiments were carried out in the Mediterranean Sea using filtered or explicit free surface numerical schemes and accounting for the effect of atmospheric pressure in addition to wind and buoyancy fluxes. Model results were evaluated by coherency and power spectrum analysis with tide gauge data. We found that atmospheric pressure plays an important role for periods shorter than 100 days. The free surface formulation is important to obtain the correct ocean response for periods shorter than 30 days. At frequencies higher than 15 days−1 the Mediterranean basin's response to atmospheric pressure was not coherent and the performance of the model strongly depended on the specific area considered. A large-amplitude seasonal oscillation observed in the experiments using a filtered free surface was not evident in the corresponding explicit free surface formulation case, which was due to a phase shift between mass fluxes in the Gibraltar Strait and at the surface. The configuration with time splitting and atmospheric pressure always performed best; the differences were enhanced at very high frequencies

A high resolution free surface model of the Mediterranean Sea

International audienceThis study describes a new model implementation for the Mediterranean Sea which has the presently highest vertical resolution over the Mediterranean basin. The resolution is of 1/16°×1/16° in horizontal and 71 unevenly spaced vertical levels. This model has been developed in the frame of the EU-MFSTEP project and it is the operational forecast model presently used at the basin scale. For the first time in the Mediterranean, the model considers an implicit free surface and this characteristics enhances the model capability to simulate the sea surface height variability. In this study we show the calibration/validation experiments done before and after the model has been used for forecasting. The first experiment consist of six years of a simulation forced by a perpetual year forcing and the other experiment is a simulation from January 1997 to December 2004, forcing the model with 6 h atmospheric forcing fields from ECMWF. For the first time the model Sea Level Anomaly is compared with SLA and with ARGO data to provide evidence of the quality of the simulation. The results show that this model is capable to reproduce most of the variability of the general circulation in the Mediterranean Sea even if some basic model inadequacies stand out and should be corrected in the near future