scholarly journals XBT, ARGO Float and Ship-Based CTD Profiles Intercompared under Strict Space-Time Conditions in the Mediterranean Sea: Assessment of Metrological Comparability

2020 ◽  
Vol 8 (5) ◽  
pp. 313
Author(s):  
Andrea Bordone ◽  
Francesca Pennecchi ◽  
Giancarlo Raiteri ◽  
Luca Repetti ◽  
Franco Reseghetti
Keyword(s):  
Mediterranean Sea ◽  
Space Time ◽  
Ocean Dynamics ◽  
Experimental Comparison ◽  
Argo Data ◽  
Argo Floats ◽  
Depth Sensors ◽  
Space And Time ◽  
Post Process ◽  
The Mediterranean

Accurate measurement of temperature and salinity is a fundamental task with heavy implications in all the possible applications of the currently available datasets, for example, in the study of climate changes and modeling of ocean dynamics. In this work, the reliability of measurements obtained by oceanographic devices (eXpendable BathyThermographs, Argo floats and Conductivity-Temperature-Depth sensors) is analyzed by means of an intercomparison exercise. As a first step, temperature profiles from XBT probes, deployed by commercial ships crossing the Ligurian and Tyrrhenian seas during the Ship of Opportunity Program (SOOP), were matched with profiles from Argo floats quasi-collocated in space and time. Attention was then paid to temperature/salinity profiling Argo floats. Since Argo floats usually are not recovered and should last up to five years without any re-calibration, their onboard sensors may suffer some drift and/or offset. In the literature, refined methods were developed to post-process Argo data, in order to correct the response of their profiling CTD sensors, in particular adjusting the salinity drift. The core of this delayed-mode quality control is the comparison of Argo data with reference climatology. At the same time, the experimental comparison of Argo profiles with ship-based CTD profiles, matched in space and time, is still of great importance. Therefore, an overall comparison of Argo floats vs. shipboard CTDs was performed, in terms of temperature and salinity profiles in the whole Mediterranean Sea, under space-time matching conditions as strict as possible. Performed analyses provided interesting results. XBT profiles confirmed that below 100 m depth the accordance with Argo data is reasonably good, with a small positive bias (close to 0.05 °C) and a standard deviation equal to about 0.10 °C. Similarly, side-by-side comparisons vs. CTD profiles confirmed the good quality of Argo measurements; the evidence of a drift in time was found, but at a level of about E−05 unit/day, so being reasonably negligible on the Argo time-scale. XBT, Argo and CTD users are therefore encouraged to take into account these results as a good indicator of the uncertainties associated with such devices in the Mediterranean Sea, for the analyzed period, in all the climatological applications.

scholarly journals Novel metrics based on Biogeochemical Argo data to improve the model uncertainty evaluation of the CMEMS Mediterranean marine ecosystem forecasts

Ocean Science ◽  
2019 ◽  
Vol 15 (4) ◽  
pp. 997-1022 ◽  
Author(s):  
Stefano Salon ◽  
Gianpiero Cossarini ◽  
Giorgio Bolzon ◽  
Laura Feudale ◽  
Paolo Lazzari ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Reference Data ◽  
Robust Statistics ◽  
Marine Ecosystem ◽  
Global Ocean ◽  
Argo Data ◽  
Argo Floats ◽  
Biogeochemical Models ◽  
The Mediterranean

Abstract. The quality of the upgraded version of the Copernicus Marine Environment Monitoring Service (CMEMS) biogeochemical operational system of the Mediterranean Sea (MedBFM) is assessed in terms of consistency and forecast skill, following a mixed validation protocol that exploits different reference data from satellite, oceanographic databases, Biogeochemical Argo floats, and literature. We show that the quality of the MedBFM system has been improved in the previous 10 years. We demonstrate that a set of metrics based on the GODAE (Global Ocean Data Assimilation Experiment) paradigm can be efficiently applied to validate an operational model system for biogeochemical and ecosystem forecasts. The accuracy of the CMEMS biogeochemical products for the Mediterranean Sea can be achieved from basin-wide and seasonal scales to mesoscale and weekly scales, and its level depends on the specific variable and the availability of reference data, the latter being an important prerequisite to build robust statistics. In particular, the use of the Biogeochemical Argo floats data proved to significantly enhance the validation framework of operational biogeochemical models. New skill metrics, aimed to assess key biogeochemical processes and dynamics (e.g. deep chlorophyll maximum depth, nitracline depth), can be easily implemented to routinely monitor the quality of the products and highlight possible anomalies through the comparison of near-real-time (NRT) forecasts skill with pre-operationally defined seasonal benchmarks. Feedbacks to the observing autonomous systems in terms of quality control and deployment strategy are also discussed.

scholarly journals A high-resolution free-surface model of the Mediterranean Sea

Ocean Science ◽  
2008 ◽  
Vol 4 (1) ◽  
pp. 1-14 ◽  
Author(s):  
M. Tonani ◽  
N. Pinardi ◽  
S. Dobricic ◽  
I. Pujol ◽  
C. Fratianni
Keyword(s):  
Free Surface ◽  
Mediterranean Sea ◽  
General Circulation ◽  
Forecast Model ◽  
Surface Model ◽  
Argo Data ◽  
Basic Model ◽  
Basin Scale ◽  
Before And After ◽  
The Mediterranean

Abstract. This study describes a new model implementation for the Mediterranean Sea with what is currently the highest vertical resolution over the Mediterranean basin. The resolution is of 1/16°×1/16° in the horizontal and has 72 unevenly spaced vertical levels. This model has been developed in the frame of the EU-MFSTEP project and is the operational forecast model currently used at the basin scale. The model considers an implicit free surface and this characteristic enhances the model's capability to simulate the sea surface height variability and the net transport at the Strait of Gibraltar. In this study we show the calibration/validation experiments performed before and after the model was used for forecasting. The first experiment consists of a six-year 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. The model Sea Level Anomaly has been compared for the first time with satellite SLA and with ARGO data to provide evidence of the quality of the simulation. The results show that this model is capable of reproducing most of the variability of the general circulation in the Mediterranean Sea. However, some basic model inadequacies stand out and should be corrected in the near future.

scholarly journals Modelling Present and Future Climate in the Mediterranean Sea: A Focus on Sea-Level Change

2021 ◽  
Author(s):  
Gianmaria Sannino ◽  
Adriana Carillo ◽  
Roberto Iacono ◽  
Ernesto Napolitano ◽  
Massimiliano Palma ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Sea Level ◽  
Ocean Dynamics ◽  
Scenario Simulation ◽  
Surface Salinity ◽  
Western Basin ◽  
Regional Patterns ◽  
Adequate Treatment ◽  
Level Information ◽  
The Mediterranean

Abstract We present results of three simulations of the Mediterranean Sea climate: a hindcast, a historical run, and a RCP8.5 scenario simulation reaching the year 2100. The simulations are performed with MED16, a new, tide-including implementation of the MITgcm model, which covers the Mediterranean - Black Sea system with a resolution of 1/16°, further increased at the Gibraltar and Turkish Straits. Validation of the hindcast simulation against observations and numerical reanalyses has given excellent results, proving that the model is also capable of reproducing near-shore sea level variations. Moreover, the spatial structure of the elevation field compares well with altimetric observations, especially in the Western basin, due to the use of improved sea level information at the Atlantic lateral boundary and to the adequate treatment of the complex, hydraulically driven dynamics across the Gibraltar Strait.Under the RCP8.5 future scenario, the temperature is projected to generally increase while the surface salinity decreases in the portion of the Mediterranean affected by the penetration of the Atlantic stream, and increases elsewhere. The warming of sea waters results in the partial inhibition of deep-water formation.The scenario simulation allows for a detailed characterization of the regional patterns of future sea level, arising from ocean dynamics, and indicates a relative sinking of the Mediterranean with respect to the Atlantic more pronounced than the current one. Explicit tidal forcing and an accurate resolution of the Gibraltar Strait are proved to be key features in the designing of numerical simulations for the Mediterranean Sea.

scholarly journals On the mesoscale monitoring capability of Argo floats in the Mediterranean Sea

2016 ◽  
Author(s):  
Antonio Sánchez-Román ◽  
Simón Ruiz ◽  
Ananda Pascual ◽  
Baptiste Mourre ◽  
Stéphanie Guinehut
Keyword(s):  
Mediterranean Sea ◽  
Large Scale ◽  
Spatial Scales ◽  
Altimeter Data ◽  
Simulation Experiments ◽  
Argo Data ◽  
Sea Level Anomalies ◽  
The Mediterranean ◽  
Observing System Simulation Experiment ◽  
Initial Objective

Abstract. In this work an Observing System Simulation Experiment (OSSE) approach is used to investigate the Argo array spatial sampling necessary in the Mediterranean Sea to recover the mesoscale signal as seen by altimetry. The monitoring of the mesoscale features is not an initial objective of the Argo network. However, it is an interesting question in the perspective of future network extensions in order to improve the ocean state estimates. A quality assessment of the performances of the altimeter product is carried out to quantify the differences between Argo and altimetry needed to conduct the simulation experiments. The method used here to evaluate the altimeter data is based on the comparison of Sea Level Anomalies (SLA) from altimetry and Dynamic Height Anomalies (DHA) referred to both 400 and 900 dbar computed from the in-situ Argo network. A standard deviation of the differences between SLA and DHA of 4.92 cm is obtained when comparing altimetry and Argo data referred to 400 dbar. The simulation experiments show that a configuration similar to the current Argo array in the Mediterranean (with a spatial resolution of 2° × 2°) is only able to recover the large-scale signals of the basin. On the contrary, the SLA field reconstructed from a 0.75° x 0.75° Argo network can retrieve most of the mesoscale signal. Such an Argo array of around 450 floats in the Mediterranean Sea would be enough to recover the SLA field with an RMSE of 3 cm for spatial scales higher than 150 km, similar to those captured by the altimetry.

scholarly journals Improved near real time surface wind resolution over the Mediterranean Sea

Ocean Science ◽  
2007 ◽  
Vol 3 (2) ◽  
pp. 259-271 ◽  
Author(s):  
A. Bentamy ◽  
H.-L. Ayina ◽  
P. Queffeulou ◽  
D. Croize-Fillon ◽  
V. Kerbaol
Keyword(s):  
Wind Speed ◽  
Mediterranean Sea ◽  
Real Time ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Remotely Sensed ◽  
Wind Fields ◽  
Remotely Sensed Data ◽  
Space And Time ◽  
The Mediterranean

Abstract. Several scientific programs, including the Mediterranean Forecasting System Toward Environmental Predictions (MFSTEP project), request high space and time resolutions of surface wind speed and direction. The purpose of this paper is to focus on surface wind improvements over the global Mediterranean Sea, based on the blending near real time remotely sensed wind observations and ECMWF wind analysis. Ocean surface wind observations are retrieved from QuikSCAT scatterometer and from SSM/I radiometers available at near real time at Météo-France. Using synchronous satellite data, the number of remotely sensed data available for each analysis epoch (00:00 h; 06:00 h; 12:00 h; 18:00 h) is not uniformly distributed as a function of space and time. On average two satellite wind observations are available for each analysis time period. The analysis is performed by optimum interpolation (OI) based on the kriging approach. The needed covariance matrixes are estimated from the satellite wind speed, zonal and meridional component observations. The quality of the 6-hourly resulting blended wind fields on 0.25° grid are investigated trough comparisons with the remotely sensed observations as well as with moored buoy wind averaged wind estimates. The blended wind data and remotely wind observations, occurring within 3 h and 0.25° from the analysis estimates, compare well over the global basin as well as over the sub-basins. The correlation coefficients exceed 0.95 while the rms difference values are less than 0.30 m/s. Using measurements from moored buoys, the high-resolution wind fields are found to have similar accuracy as satellite wind retrievals. Blended wind estimates exhibit better comparisons with buoy moored in open sea than near shore.

scholarly journals A high resolution free surface model of the Mediterranean Sea

2007 ◽  
Vol 4 (1) ◽  
pp. 213-244 ◽  
Author(s):  
M. Tonani ◽  
N. Pinardi ◽  
S. Dobricic ◽  
I. Pujol ◽  
C. Fratianni
Keyword(s):  
Free Surface ◽  
Mediterranean Sea ◽  
General Circulation ◽  
Forecast Model ◽  
Surface Model ◽  
Argo Data ◽  
Basin Scale ◽  
Before And After ◽  
The Mediterranean ◽  
First Time

Abstract. This 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.

Modeling new scenarios of ocean dynamics during deglaciation over Southern European Seas (Mediterranean and Black Seas)

2021 ◽  
Author(s):  
Gilles Ramstein ◽  
Tristan Vadsaria ◽  
Laurent Li ◽  
Jean-Claude Dutay ◽  
Sébastien Zaragosi
Keyword(s):  
Mediterranean Sea ◽  
Fresh Water ◽  
Black Sea ◽  
Ocean Dynamics ◽  
The Black Sea ◽  
Nile River ◽  
African Monsoon ◽  
Last Glacial ◽  
The Mediterranean ◽  
The Last Glacial

<p>During quaternary, periodic organic rich layers in the Mediterranean Sea marine sediments also known as sapropels, are not only driven by African monsoon modulation. Superimposed to the main pacing associated with precession cycles (about 21 ka) many sapropels are also impacted by the 100 ka periods associated with the glacial-interglacial cycles. The last occurrence (S1) at the end of the last glacial period and the Early Holocene is an appropriate illustration of this behavior. Recent studies based on long deglaciation simulations with coupled AOGCM pointed out that reaching bottom water anoxia needs a preconditioning, throughout the last deglaciation, driven by North Atlantic Ocean freshening for a few thousand years prior to S1. Here, we investigate another important source of fresh water induced by the melting of Fennoscandian ice sheets (FIS). This run-off freshened the Black Sea, the Marmara Sea and ultimately could have an impact on the stratification and the convection over the Aegean Sea. In order to tackle this issue, we used continental hydrologic perturbation scenarios to drive a high-resolution Mediterranean Sea dynamic circulation model (1/8°) that correctly captures the convection sites and their intensity. In one hand, we rely on hydrologic reconstruction of FIS melting provided by Peltier et al. (JGR, 2015) and Patton, H. et al. (QSR, 2017) in order to derive freshwater flux since the Last Glacial Maximum - that impacted the Black Sea, and likely the Eastern Mediterranean Sea. In the other hand, we build a complete transient scenario accounting for the later enhancement of the African monsoon and we increase fresh water from Nile river. Prescribing such a scenario: first a freshwater increase from FIS during the deglaciation and second a fresh water increase from Nile river, it leads to the shutdown of the Mediterranean Thermohaline Circulation. Our results are in good agreement with Aegean reconstructions (Grant et al, QSR, 2016; Soulet e al. Proc. Natl. Acad. Sci, 3013). The methodology we developed could also be applied to sapropel S5 and S10.</p>

scholarly journals Assessment of the impact of TS assimilation from ARGO floats in the Mediterranean Sea

2006 ◽  
Vol 3 (4) ◽  
pp. 671-700
Author(s):  
A. Griffa ◽  
A. Molcard ◽  
F. Raicich ◽  
V. Rupolo
Keyword(s):  
Mediterranean Sea ◽  
System Simulation ◽  
Optimal Interpolation ◽  
Interpolation Scheme ◽  
Simulation Experiments ◽  
Qualitative Comparison ◽  
Reduced Order ◽  
Argo Floats ◽  
The Mediterranean ◽  
The Impact

Abstract. In this paper, the impact of assimilating Temperature (T) and Salinity (S) profiles from Argo floats in the Mediterranean Sea (MEDARGO) is quantitatively investigated using the Observing System Simulation Experiments (OSSE) approach. The impact of varying the number of floats and their launch positions is considered, using numerical simulations with a MOM model and a reduced-order multivariate Optimal Interpolation scheme (SOFA) for assimilation. Realistic launch positions used during the first MFSTEP phase are considered, as well as ''ideal'' positions that can be envisioned for the future, along the VOS tracks. The most effective float trajectories are identified, showing that frontal regions play a major role, and that it is crucial to maintain a sufficient coverage of them. In addition to this, also a qualitative comparison is performed between the results obtained from MEDARGO floats in ideal conditions and results from ''ideal'' profiles taken along the VOS (Volunteer Observing Ships) tracks, as for the XBT (Expandable Baththermograph) data.

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