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International audience; The year-to-year variability in the timing, duration, and spatial extent of the surface phytoplankton bloom over the winter-spring period is examined in the southern Adriatic Sea using Sea-viewing Wide Field-of-view Sensor (SeaWiFS)-derived chlorophyll images for three years (1998, 1999, and 2000). Each year's image time series shows that blooms were intermittent and differed in onset, duration, and intensity with relatively low values observed in 2000. The relation between atmospheric forcing and interannual variability of the bloom timing and intensity is investigated using a coupled physical-biological model. The simulations focus on the effect of cumulative buoyancy loss on convective depths and its implications on surface nutrient availability, chlorophyll concentrations, and other ecosystem components during the study period. We test the hypothesis that the south Adriatic bloom is essentially controlled by the local winter climatic conditions (i.e., maximum convective depth), as suggested by recent findings, rather than the available nutrient pool at the intermediate depths (200-800 m), which also varies from year to year. For all three years the simulations produced convective depths that were in good agreement with in situ observations. However, the fluctuations in SeaWiFS phytoplankton biomass could be reproduced only if the particular year's nutrient pool was also taken into account. Thus the most probable explanation for the low SeaWiFS phytoplankton biomass observed in 2000 is the reduced nutrient pool because of the return from the transient phase to the pretransient regime of the Mediterranean Sea. Our results indicate that the south Adriatic bloom is a complex phenomenon and cannot simply be explained by interannual changes in convective depth.

Different methods for the extrapolation of vertical profiles from sea surface measurements are presented. The techniques, called Coupled Pattern Reconstruction (CPR) and multivariate EOF Reconstruction (mEOF-R) base on the multivariate analysis of the variability of vertical profiles from hydrographic data and on the hypothesis that only few modes are needed to explain most of the variance/covariance of the fields. The CPR and mEOF-R methods have been applied and tested on the data collected during SYMPLEX survey in a selected area of the Mediterranean sea (the Channel of Sicily), also using simultaneous altimeter measurements as surface input.

Three different data sets of numerical drifters are obtained with degrading the time sampling (1 day, 1 month and 1 year) of the Eulerian velocity field computed from a Mediterranean general circulation model. The Finite-Scale Lyapunov Exponent (FSLE) technique is used to characterize, for each of the three data sets, Lagrangian dispersion properties in relation to the time resolution of the field. In particular, we are interested in measuring th eunpredictability of trajectories due to the uncertainly in the knowledge of the velocity field. Our data analysis indicates that surface relative dispersion of the Mediterranean Sea has two regimes; exponential spreading due to chaotic advection at small scales (~mesoscale) and super-diffusion at larger scales (up to ~sub-basin scales). In this scenario, it is shown that trajectory evolution is most sensitive to the time sampling of the field at small spatial scales, while, at scales larger than (~100 km, it is essentially independent from the details of the models. Also, FSLE is employed to visualize the geographical regions characterized by high Lagrangian unpredictability. The relation of FSLE with common oceangraphic observables (e.g., local shear, velocity variance) is duscussed. © 2002 Published by Elsevier Science Ltd.

An empirical method to estimate the solar incoming radiation has been improved using AVHRR-NOAA14 data in the framework of the ARTIST experiment. This method, using several bulk formulas, gives an estimation of the incoming solar radiation and results are compared with the surface-based and aircraft-based measurements. The first step of the method is the development of a cloud detection algorithm for the area and for the period of interest. The area is the Arctic Ocean near the Svalbard Islands and the period is from 15 March to 16 April 1998, the transition period form winter to sprint and in this particular case from the Polar Night to a period of quite normal insolation. Several bulk formulas, right for the Polar condition, are tested comparing the estimate insolation fluxes with the direct measurements made with a pyranometer mounted aboard the Polar2 aircraft and another pyranometer at the research base at Ny-Alesund. The comparison could define the best parameterization for the available data.

A new method to estimate radiation budgets at air-sea interface by means of AVHRR data has been developed and tested in the framework of the Arctic Radiation and Turbulence Interaction Study (ARTIST). Main goal of the ARTIST project is assess the effects of clouds and of Arctic Haze on the radiative fluxes at the surface and in the atmospheric column in the European Arctic. One month of Advanced Very High Resolution Radiometer (AVHRR) data relative to the period March - April 1998 has been processed and analyzed in order to evaluate short and long wave radiation budgets in the Arctic Sea during the experiment. Remote sensing data (NOAA 14 satellite) have been acquired at the Tromso station and then processed at the Istituto Fisica dell'Atmosfera (IFA) to produce maps of surface albedo and brightness temperature of the experiment's zone. These maps were used to develop a new cloud detection algorithm for the region. Image pixels then have been classified as ice, clouds or water. The method was applied to 151 available AVHRR scenes. The pixels classification performance was verified against the analysis of an expert in satellite image. The cloud classification results to be quite accurate. In fact 99 images are classified as 'very good' by the expert and 37 images the accuracy is a little lower. The radiation budgets are then estimated using several available empirical formulae for clear sky and overcast conditions. The results were compared with in situ measurements made during the ARTIST experiment in order to define the best parameterization of the fluxes. The best estimates of shortwave incoming radiation results from the Bennet (1982) formula for clear sky condition with the Laevastu (1960) correction for overcast condition. The more accurate estimate of incoming long wave radiation in clear sky has been obtained using the Swinbank (1963) parameterization. Finally, averaged map of total radiation budget are calculated for the time period of the ARTIST experiment in the Arctic region.

The monitoring of organic matter, suspended or dissolved in the water column, is relevant for the study of the aquatic environment. Actually, the Dissolved Organic Matter (DOM) represents a major reservoir of reactive carbon in the global carbon cycle, thus influencing significantly the marine ecosystem. Due to the strong absorption in the near ultraviolet, DOM reduces considerably the extinction path of solar light in the water column, affecting phytoplankton population and its vertical distribution. The measurement of the DOM absorption coefficient has to be regarded as a good parameter for the monitoring of water quality. This paper deals with the measurements carried out during the oceanographic campaign 'Marine Fronts,' which took place in the Western Mediterranean Sea and Atlantic Ocean from July 14 to August 5, 1998. In this measurement campaign, a high spectral resolution fluorescence lidar (FLIDAR) was installed on the rear-deck of the O/V 'Urania,' acquiring remote fluorescence spectra both in ship motion and in stations. A particular attention was devoted to the monitoring of DOM distribution in the different water masses in marine frontal areas. The lidar data were compared and integrated with SST satellite data and biological samplings. The results show that FLIDAR data agree with satellite imagery, particularly for marine front detection. The comparison with water sample data gave indications for retrieving the DOM absorption coefficient directly from fluorescence remote spectra. In addition, a protein like fluorescence band was detected in the measurements carried out on total suspended matter filtered from the water samplings.

OGCM's numerical experiments for climatic studies can be performed only after testing their capability to well represent the today ocean circulation. In order to improve the model results we assimilated satellite SST (from NOAA-AVHRR sensors) by means of a nudging method. Daily 1987 - 1992 NASA Pathfinder SST have been interpolated in time and space by means of an objective analysis algorithm to fill gaps in the time series. These data were analyzed to investigate the main variability of the Mediterranean SST field. The 1988 data was selected to be assimilated in the OGCM. To relate more closely the assimilation of the SST data to the physics of the air-sea interaction, here we propose a new parameterization of the surface relaxation time. Actually the use of realistic surface forcing strongly contribute to reproduce the correct hydrological values of the Mediterranean water masses, the right energetic basin budgets and the mesoscale features of the Mediterranean circulation.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Upper ocean dynamics is characterized by a strong variability, at different scales, both in direction and structure of the flow. Mesoscale variability, which is ubiquitous in the world ocean, is often the dominant component in the variance spectrum of velocity with relevant implications on water mass mixing and transformation and on the carbon transfer in the marine food web. Mesoscale activity is manifested through the formation of instabilities, meanders and eddies. Eddies generate either a doming of isopycnals (cyclones) or a central depression (anticyclones). This in turn modifies, among the others, nutrient and organism distributions in the photic zone eventually enhancing or depressing photosynthetic activity and other connected biological responses. The mechanism is similar to what has been thoroughly studied for the warm and cold core rings but at different spatial and temporal scales. The enhancement of phytoplankton growth and the modification of photosynthetic parameters has been shown to occur in situ by means of a modulated fluorescence probe. More recently, an attempt to estimate the magnitude of this specific forcing on nutrient fluxes and primary production has also been conducted at different scales by modeling exercises, though with contrasting estimates the relative importance concerns. Because phytoplankton growth takes place when light, nutrients and cells are found at the same place, the increase in primary production favored by mesoscale eddies cannot be easily predicted. The incident light, the seasonality, the life-time of the structure, its intensity etc. can all influence the final yield. In addition, it has still to be determined which component of the community reacts faster and takes advantage of the new nutrients and how efficiently the new carbon is channeled in the food web. For what remote sensing is concerned, the detectability form the space of such structures is certainly dependent on the depth at which the upward distortion of isopycnals takes places. It can be supposed that a change in bio-optical signature of the whole structure could occur because of the 3-D dynamics of the eddy. If this holds true, then color remote sensing coupled with sea level topography and sea surface temperature should be a powerful tool to track such transient structures. The ALT-SYMPLEX program has been designed to better understand the relationship between short living eddies and carbon transfer in the food web. This is based on several experiments aimed to integrate remote sensing data (ocean color and surface topography) and in situ data in order to evaluate the relationship between surface and sub-surface physical dynamics and its relations on chemical and biological aspects in presence of mesoscale features.

Two years of TOPEX/POSEIDON altimeter data have successfully been used to study the mesoscale field in the Mediterranean and to investigate the seasonal and year-to-year variability of the sea level and eddy statistics in this basin. The mesoscale field described by TOPEX/POSEIDON revealed a strong, but subbasin dependent, seasonal signal. Year-to-year variations are also evident in terms of both intensity and position of the main mesoscale features. Crossover analysis indicated the existence of a meridional transport of eddy momentum away from the Algerian current due to the northward migration of mesoscale eddies. A comparison between mesoscale features detected by the altimeter and contemporaneous features observed using advanced very high resolution radiometer (AVHRR) sea surface temperature has been made for the following Mediterranean subbasins: the Algerian basin, the Levantine basin, and the Tyrrhenian Sea. The results definitively prove the direct relation between sea level anomalies and the Mediterranean eddy field. Copyright 1998 by the American Geophysical Union.

Seasonal and interannual variability of the sea surface temperature field in the Adriatic Sea is analyzed using a five years time series of daily AVHRR (advanced very high resolution radiometer) data. The data used are the 9 km resolution sea surface temperature maps obtained in the framework of the Pathfinder project. This spatial resolution allowed analysis of only basin and sub-basin scale features. Average monthly sea surface temperature maps for the entire studied period (1987 - 1991) are discussed. The analysis shows the absence of any permanent surface feature in the Adriatic Sea. The cyclonic circulation of the south Adriatic Sea is marked by a surface temperature minimum that recurrently appears in late autumn or early winter, i.e. in the preconditioning and deep water formation phase. During autumn the surface inflow of Ionian water is observed while the Adriatic outflow is more evident in winter. Results of an EOF analysis suggest that the intensity of the western coastal cold water plume and the north Adriatic thermal front vary from year to year. Other sub-basin features like the south Adriatic gyre also display year-to-year variability.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

TOPEX/Poseidon and ERS-1 altimeter data have successfully been used to study the mesoscale field in the Mediterranean Sea and to investigate the seasonal variability of the Sea Level and eddy statistics in this basin. The comparison between the two altimeter performance is very good and underline importance to combine the information of TOPEX/Poseidon and ERS-1 to study the Mediterranean mesoscale eddy field. Sea level anomalies maps every five days were produced using the both data sets by means of sub-optimal interpolation. A comparison between mesoscale features detected by the two altimeters and contemporaneous features observed using Sea Surface Temperature maps definitively proves the direct relation between sea level anomalies and the Mediterranean eddy field. The data collected ERS-SYMPLEX cruise have been used to verify the performance of ERS-1/2 and TOPEX/POSEIDON altimeters in the Mediterranean Sea. The ERS-SYMPLEX experiment has been carried out in the channel of Sicily during spring 1996 in order to make a direct comparison between SLA from ERS1/2 and TOPEX/POSEIDON altimeters and in situ data. During the cruise CTD and XBT casts have been done in the central and eastern regions of the channel, and particularly densely along selected altimeters' tracks at the same time of the satellite pass. Sea level anomalies have been computed and compared with the dynamic heights and with the main circulation features resulting from SYMPLEX cruise. The results definitively prove the capability of the two altimeters to correctly detect both basin and mesoscale features of the Mediterranean circulation. Collinear analysis along a repeated T/P track has also suggested potential use of SLA in order to detect barotropic component of currents in the channel of Sicily.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

TOPEX/Poseidon and ERS-1 altimeter data have successfully been used to demonstrate the capability of these altimeters to study the mesoscale field in the MEditerranean Sea and to investigate the seasonal variability of the Sea Level and eddy statistics in this basin. The analysis reveals a strong, but sub-basin dependent, seasonal signal. A comparison between mesoscale features detected by the two altimeters and contemporaneous features observed using Sea Surface Temperature maps definitively proves the direct relation between sea level anomalies and the MEditerranean eddy field. The comparison between the two altimeter performance is very good and underline importance to combine the information of TOPEX/Poseidon and ERS-1 to study the Mediterranean mesoscale eddy field.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Moored temperature signals, tide gauge data and CTD profiles measured on the Sicilian continental shelf are studied. EOF decomposition and cross spectral analysis of the moored temperature data and analysis of the CTD profiles provide information on the hydrological characteristics in the area. Power and line spectral analysis of the moored temperature signals are discussed; major results are that (1) a tidally generated, topographically trapped baroclinic wave with diurnal period dominates the dynamics at all depths below the surface mixed layer. The analysis of the tide gauge data allows for evaluating the role of the barotropic tide. (2) Contrary to what usually happens in the Mediterranean Sea, the semidiurnal tide is always weaker than the diurnal component. This behavior is ascribed to the presence of an amphidromic point of the M 2 tide in the vicinity of the thermistor chain. (3) A weak inertial wave component, possibly important in the seasonal evolution of the average stratification, is recognizable in the line spectra; and (4) the power spectra of temperature oscillations display a power law behaviorP(ω) ≈ ω -1.8 in the frequency range of internal wave activity.

Large amplitude internal waves were observed north and south of the Strait of Messina during two different periods. A comparison between the two sets of data is made. The behaviour of the shape of the waves is analysed from the physical parameters and two possible interpretations of these waves are given. The mechanism of formation related to the tide in the Strait is also discussed.

Hydrological observations in the Ligurian Sea, north-western part of the Mediterranean Sea, are discussed. They show a steady cyclonic circulation. At theboundary of this circulation meanders and small eddies are rather frequent, in particular North of the Corsica Island. Their presence is in agreement with satellite data. In this paper also a number of simple baroclinic instability models are also considered, in an attempt to explain these current fluctuations.

We study a process of thermocline erosion measured in the Channel of Sicily in the period 16 November–December 1985. Evidence is presented that the transition from Summer to Winter stratification has been an impulsive process. We show that the erosion of the seasonal thermocline and the deepening of the surface mixed layer were stimulated by the action of two strong atmospheric perturbations. Possible relations between mixing events and internal wave breaking are discussed.

We compare recent observations of internal waves and currents generated by tidal mixing inside the strait of Messina, with classical measurements made in 1922–1923 by Francesco Vercelli. A peculiar front South of Capo Vaticano in southern Tyrrhenian Sea is described. Its relation with the turbulence due to the breaking of internal nonlinear waves generated by the inside the Strait of Messina is discussed. We recall that this last phenomenon is novel as far as the Mediterranean Sea is concerned.

One month of Meteosat IR data has been used to study the upwelling phenomenon along the northwest coasts of Africa. The analysis has shown the presence of a cold water strip along the coastline (1500 km long and (100÷200) km wide) characterized by a sea surface temperature of almost 3°C lower than the surroundings. The synoptic view offered by Meteosat evidentiated the simultaneous presence of two zones of the upwelling regime characterized by a different behaviour: the C. Bojador zone where the oscillations of the cross-shore thermal gradient measured by satellite follow quite well the daily variation of the large-scale meteorological forcings and the C. Ghir zone where the phenomenon is not always present and is more related to local forcings and coastal geometry. The general features resulting from our study are in agreement with the results of in situ previous measurements.

Physical phenomena occurring in the area of the Strait of Messina, related to the current and interface rising on the sill are analyzed on the basis of recent experimental observations. The measurements of the interface time evolution on the sill have revealed for the first time the presence of turbulent columnar disturbances. The formation of a peculiar front in the Gulf of Gioia, in the southern Tyrrhenian Sea, is described as the result of turbulent mixing due to the breaking of nonlinear internal waves on the shelf of this Gulf, directly oriented toward the Strait of Messina where these waves are generated.

Advanced Very High Resolution Radiometer (AVHRR) and Sea viewing Wide Field of view Sensor (SeaWiFS) data from January 1998 to June 1999 are used to examine spatial and temporal variability of sea surface temperature (SST) and apparent chlorophyll (AChl) in the Adriatic Sea. Flows long the Albanian coast and the Italian can be distinguished year-round in the monthly averaged AChl, but only in the colder months in the monthly averaged SST's. The AChl averaged fields supply less information on circulation features away from coastal boundaries and where conditions are generally oligotrophic except for the early spring bloom in the Southern Adriatic Gyre. The winter-spring SST and chlorophyll distributions are very different between the two years, particularly in the Northern Adriatic shelf and the Southern Adriatic Gyre. It is hypothesized that this difference may be related to dense water formation that occurs only in the northern and southern Adriatic Seas. The time series of daily SST indicate that dense water formation was favored in 1999 by episodes of cooler winter temperatures in the southern gyre (less than 13.5 degrees Celsius) and on the northern Adriatic shelf. Blooms in 1999 may have been delayed due to surface replacement flows driven by sinking of dense water.

[1] In this article we study the effect of high-frequency surface momentum and heat fluxes in the numerical simulation of some key ocean processes ofthe Mediterranean thermohaline circulation. The lack of synoptic and reliable heat and freshwater flux data sets is bypassed using the relaxation approach both for the salinity and temperature surface fields. We propose a parameterization of the heat fluxes in which the temperature-restoring coefficient depends on wind intensity and regime and in which the use of simuoultaneous satellite daily sea surface temperature (SST) estimates as a restoring field is required. The consistency of the proposed parameterization and of its numerical implementation with the previous oceanic boundary layer studies has been verified trough the analysis of the Saunders’ proportionality constant. This parameterization coupling simultaneous surface heat fluxes and wind trough the skin-bulk temperature difference, recovers the high variability of the air-sea exchanges of the extreme events in the Mediterranean Sea. The effect of highfrequency surface momentum and heat fluxes is studied comparing results from two differentexperimentsforcedwithmonthlyanddailysurfacewindandsatelliteSSTdatasets. Thesecomparisonsshowtherelevanceofhigh-frequencyforcingintherepresentationofthe dynamical processes relative to the intermediate water mass transformation and horizontal advection as well as in the deep water formation in the northwestern Mediterranean Sea. INDEX TERMS: 4504 Oceanography: Physical: Air/sea interactions (0312); 4255 Oceanography: General: Numerical modeling; 4243 Oceanography: General: Marginal and semienclosed seas; KEYWORDS: air/ interaction, numerical modeling, Mediterranean, satellite, circulation

[1] The Channel of Sicily, which represents the only connection between the western and the eastern Mediterranean Sea, can be described as a three-layer system, where fresher water of Atlantic origin (Modified Atlantic Water) flows eastward in the upper layer, Levantine Intermediate Water (LIW) leaves the eastern basin at around 250–350 m, and an outflow of Transitional Ionian Deep Water (TIDW) is identified below the LIW. Synoptic Mesoscale Plankton Experiment data, collected during four surveys in the Channel of Sicily, show that LIW and TIDW are subject to major modifications when crossing the eastern sill. A significant Bernoulli aspiration is found there, and the bottom water at the sill is composed of modified deep Ionian waters coming from >800 m. An analysis of the water mass composition proves that LIW mixes essentially with TIDW, and that the TIDW flow through the channel must be larger than the expected 0.5 Sv. The presence of a secondary circulation related to the bottom boundary layer is demonstrated to be the primary factor leading to the dilution and cooling of LIW.

The 1996 Altimeter/Synoptic Mesoscale Plancton Experiment (ALT/SYMPLEX) was specifically designed to perform in situ measurements simultaneous with the passage of TOPEX/POSEIDON (T/P) and ERS 2 over selected tracks in the central and eastern Sicily Channel. This experiment made it possible to have, for the first time, a validation of altimetry with in situ data over the Mediterranean, where weak dynamics results in a modest sea elevation, rarely exceeding 10 cm. Historical infrared and altimetric satellite data were first analyzed in order to study the variability of the circulation in the area. The comparative and integrative analysis of simultaneous satellite data and in situ measurements permitted investigation of the relation between the altimeter-derived surface topography and the three-dimensional structure of the sea. The Pearson correlation coefficients between altimeter data and dynamic heights along track resulted to be 0.72-0.89 (T/P) and 0.88 (ERS 2) when using conventional repeat track analysis. For T/P, a correlation value of 0.87 was found for time differences computed basing on a collinear analysis technique. This analysis also led to the identification of a strong barotropic component of the velocity field located near the Sicilian continental shelf, where it is responsible for approximately 60% of the signal.

During the last decades, scientific community has been investigating both biological and hydrographic processes that affect fisheries. Such an interdisciplinary and synergic approach is nowadays giving a fundamental contribution, in particular, in connecting the dots between hydrographic phenomena and biomass variability and distribution of small pelagic fish. Here we estimate impacts of hydrographic fluctuations on small pelagic fishery, focusing on the inter-annual variability that characterizes connectivity between spawning and recruiting areas for the European anchovy (Engraulis encrasicolus, Linnaues 1758), in the Northern side of the Sicily Channel (Mediterranean Sea). Results show that coastal transport dynamics of a specific year largely affect the biomass recorded the following year. Our work, moreover, quantifies the specific monetary impacts on landings of European anchovy fishery due to hydrodynamics variability, connecting biomass fluctuations with fishery economics in a highly dynamic and exploited marine environment as the Sicily Channel. In particular, we build a model that attributes a monetary value to the hydrographic phenomena (i.e., cross-shore vs. alongshore eggs and larvae transport), registered in the FAO Geographical Sub-Area (GSA) 16 (Southern Sicily). This allows us to provide a monetary estimation of catches, derived from different transport dynamics. Our results highlight the paramount importance that hydrographic phenomena can have over the socio-economic performance of a fishery.

Diurnal warming of the sea surface temperature (SST) is often observed in the spring and summer Advanced Very High Resolution Radiometer (AVHRR) imagery of the Mediterranean Sea. It masks SST features of oceano-graphic interest. Diurnally warmed regions, where low wind conditions prevail, exhibit smooth surface and thus are characterized by low reflected solar radiation except for specular reflection of the visible solar radiation. Utilization of this correlation through clustering of diurnally warmed areas in an infrared-visible histogram permits discrimination from areas where the SST is representative of the underlying bulk temperature.

The time series of satellite infrared AVHRR data from 1985 to 2005 has been used to produce a daily series of optimally interpolated SST maps over the regular grid of the operational MFSTEP OGCM model of the Mediterranean basin. A complete validation of this OISST (Optimally Interpolated Sea Surface Temperature) product with in situ measurements has been performed in order to exclude any possibility of spurious trends due to instrumental calibration errors/shifts or algorithms malfunctioning related to local geophysical factors. The validation showed that satellite OISST is able to reproduce in situ measurements with a mean bias of less than 0.1°C and RMSE of about 0.5°C and that errors do not drift with time or with the percent interpolation error.

In this work we test the compatibility between the theoretical parameters of a nonlinear wave model and the quantitative information that one can deduce from satellite-derive0 data. The theoretical parameters are obtained by applying an inverse problem to the solution of the Cauchy problem for the Korteweg-de Vries equation. Our results are applied to the case of internal wave patterns elaborated from two different satellite sensors at the south of Messina (the thematic mapper) and at the north of Messina (the synthetic aperture radar).

If climate services are to lead to effective use of climate information in decision-making to enable the transition to a climate-smart, climate-ready world, then the question of trust in the products and services is of paramount importance. The Copernicus Climate Change Service (C3S) has been actively grappling with how to build such trust: provision of demonstrably independent assessments of the quality of products, which was deemed an important element in such trust-building processes. C3S provides access to essential climate variables (ECVs) from multiple sources to a broad set of users ranging from scientists to private companies and decision-makers. Here we outline the approach undertaken to coherently assess the quality of a suite of observation- and reanalysis-based ECV products covering the atmosphere, ocean, land, and cryosphere. The assessment is based on four pillars: basic data checks, maturity of the datasets, fitness for purpose (scientific use cases and climate studies), and guidance to users. It is undertaken independently by scientific experts and presented alongside the datasets in a fully traceable, replicable, and transparent manner. The methodology deployed is detailed, and example assessments are given. These independent scientific quality assessments are intended to guide users to ensure they use tools and datasets that are fit for purpose to answer their specific needs rather than simply use the first product they alight on. This is the first such effort to develop and apply an assessment framework consistently to all ECVs. Lessons learned and future perspectives are outlined to potentially improve future assessment activities and thus climate services., Bulletin of the American Meteorological Society, 103 (9), ISSN:0003-0007, ISSN:1520-0477

Direct measurements of infrared budget and meteorological parameters at sea were carried out in the western Mediterranean Sea during different seasons in the years 1989–1992. The spatial and time distribution of this data set allows us to perform an exhaustive test on the most widely used infrared budget bulk formulas. An underestimation of about 30 W/m2 is systematically observed, confirming previous results obtained by a limited data set. This discrepancy is independent of the time of the year and location of measurements, indicating an inability of the bulk formulas to reproduce the infrared Mediterranean budget. The completeness of the data set enables us to determine a new relation between infrared budget and meteorological parameters. Alternative expressions, to be used accordingly with the available data sets, are presented here.

The aim of this chapter is to introduce the main topics in the Mediterranean circulation research and to give a general description of the Mediterranean Sea variability. Its scope is to provide information that is important for a comprehensive view of the most relevant issues concerning climate, which is a coupling between atmosphere and sea. The chapter describes data, research results, and key findings that have been reported in the most recent literature about the Mediterranean Sea circulation. The issue about sea level is considered in Chapter 4. The chapter also includes, in its concluding section, a discussion of the main open issues in Mediterranean Sea research.

Two field experiments named WISE (WInd and Salinity Experiment) were sponsored by the European Space Agency (ESA) to better understand the wind and sea state effects on the L-band brightness temperatures. They took place at the Casablanca oil rig located in the North Mediterranean Sea, 40 km off shore the Ebro river delta: WISE 2000 from November 25 to December 18, 2000, and continued during the January 9 to 16, 2001, and WISE 2001 from October 23 to November 22, 2001. During the spring of 2003, under Spanish National funds, a third field experiment named FROG (Foam, Rain, Oil slicks and GPS reflectometry) took place at the Ebro river delta, to measure the phenomena that were not completely understood during the WISE field experiments, mainly the effect of foam and rain. In order to achieve the objectives of the WISE field experiments the LAURA L-band fully polarimetric radiometer from the Technical University of Catalonia (UPC) was mounted on the Casablanca oil-rig at the 32 meters deck above the sea surface, pointing to the North and North-West, in the direction of the dominant winds. In this paper we present the results of the first study to determine the relationship between the brightness temperature and the sea state.