In this project, a relatively high resolution coupled ocean-atmosphere GCM SINTEX-FRCGC (SINTEX-F... more In this project, a relatively high resolution coupled ocean-atmosphere GCM SINTEX-FRCGC (SINTEX-F1: ECHAM4.6 AGCM + OPA8.2 OGCM + OASIS2.4 Coupler) has been developed under the EU-Japan collaborative framework. The ensemble seasonal prediction experiments using SINTEX-F have demonstrated high prediction skills for both ENSO and IOD. The model realistically predicted the 1994 IOD event at 3 seasons lead. This is first
A one-dimensional ecosystem numerical model is used to simulate the ecosystem changes that could ... more A one-dimensional ecosystem numerical model is used to simulate the ecosystem changes that could have occurred in the open ocean areas of the Eastern Mediterranean Sea during the Climatic Optimum interval (9500–6000 B.P., Mercone et al. [Mercone, D., Thomson, J., Croudace, I.W., Siani, G., Paterne, M., Troelstra, S., 2000. Duration of S1, the most recent sapropel in the eastern Mediterranean Sea, as indicated by accelerator mass spectrometry radiocarbon and geochemical evidence. Paleoceanography 15, 336–347]). In this period the S1 sapropel was deposited. S1 is the most recent sapropel in the succession of organic carbon-rich layers intercalated in normal Neogene sedimentary sequences. Different theories have been invoked in order to explain the deposition of this peculiar layer. Our simulations seem to indicate that the modified thermohaline circulation, supplying oxygen only in the first 500 m of the water column, is responsible for the sapropel deposition when higher productivity is allowed in the euphotic zone. The model shows the importance in this process of bacteria that consume oxygen by decomposing the Particulate Organic Matter (POM) produced in the upper water column. The sinking velocity of POM partially regulates the timescale of the occurrence of anoxia at the bottom and in the whole water column, allowing the relatively rapid onset of sapropel deposition.
ABSTRACT Dry summers over the eastern Mediterranean are characterized by strong descent anchored ... more ABSTRACT Dry summers over the eastern Mediterranean are characterized by strong descent anchored by long Rossby waves, which are forced by diabatic heating associated with summer monsoon rainfall over South Asia. The large-scale teleconnection between rising and subsiding air masses is referred to as the "monsoon-desert mechanism.'' This study evaluates the ability of the phase 5 of the Coupled Model Intercomparison Project (CMIP5) models in representing the physical processes involved in this mechanism. An evaluation of statistics between summer climatologies of monsoon diabatic heating and that of vertical velocity over the eastern Mediterranean suggests a linear relationship. Despite large spatial diversity in monsoon heating, descent over the Mediterranean is coherently located and realistic in intensity. To measure the sensitivity of descent to the diversity in the horizontal and vertical distribution of monsoon heating, a series of linear atmosphere model experiments are performed. It is shown that column-integrated heating over both the Bay of Bengal and the Arabian Sea provides the largest descent with a more realistic spatial pattern. In the vertical, CMIP5 models underestimate the diabatic heating at upper levels, while they overestimate it at lower levels, resulting in a weaker forced response and weaker associated descent over the Mediterranean. A moist static energy budget analysis applied to CMIP5 suggests that most models capture the dominant role of horizontal temperature advection and radiative fluxes in balancing descent over the Mediterranean. Based on the objective analysis herein, a subset of models is identified that captures the teleconnection for reasons consistent with observations. The recognized processes vary at interannual time scales as well, with imprints of severe weak/strong monsoons noticeable over the Mediterranean.
In this paper we describe a mesoscale data assimilation experiment in the Middle Adriatic Sea. In... more In this paper we describe a mesoscale data assimilation experiment in the Middle Adriatic Sea. In order to perform dynamical forecasts we provide a quasigeostrophic numerical model with a set of initial fields regularly gridded via an objective analysis technique. Maps of this initial condition show a surface intensified jet meandering around a cyclonic eddy at the thermocline and deep
ABSTRACT This work explores the impact of orbital parameters and greenhouse gas concentrations on... more ABSTRACT This work explores the impact of orbital parameters and greenhouse gas concentrations on the climate of marine isotope stage (MIS) 7 glacial inception and compares it to that of MIS 5. The authors use a coupled atmosphere–ocean general circulation model to simulate the mean climate state of six time slices at 115, 122, 125, 229, 236, and 239 kyr, representative of a climate evolution from interglacial to glacial inception conditions. The simulations are designed to separate the effects of orbital parameters from those of greenhouse gas (GHG). Their results show that, in all the time slices considered, MIS 7 boreal lands mean annual climate is colder than the MIS 5 one. This difference is explained at 70% by the impact of the MIS 7 GHG. While the impact of GHG over Northern Hemisphere is homogeneous, the difference in temperature between MIS 7 and MIS 5 due to orbital parameters differs regionally and is linked with the Arctic Oscillation. The perennial snow cover is larger in all the MIS 7 experiments compared to MIS 5, as a result of MIS 7 orbital parameters, strengthened by GHG. At regional scale, Eurasia exhibits the strongest response to MIS 7 cold climate with a perennial snow area 3 times larger than in MIS 5 experiments. This suggests that MIS 7 glacial inception is more favorable over this area than over North America. Furthermore, at 239 kyr, the perennial snow covers an area equivalent to that of MIS 5 glacial inception (115 kyr). The authors suggest that MIS 7 glacial inception is more extensive than MIS 5 glacial inception over the high latitudes.
Journal of Atmospheric and Oceanic Technology, 2014
ABSTRACT AbstractOptimally modeling background-error horizontal correlations is crucial in ocean ... more ABSTRACT AbstractOptimally modeling background-error horizontal correlations is crucial in ocean data assimilation. In this paper, we investigate the impact of releasing the assumption of uniform background-error correlations in a global ocean variational analysis system. Spatially varying horizontal correlations are introduced in the recursive filter operator, which is used for modeling horizontal covariances in the CMCC analysis system. The horizontal correlation length-scales (HCLSs) were defined on the full three-dimensional model space, and computed from both a dataset of monthly anomalies with respect to the monthly climatology and through the so-called NMC method. Different formulas for estimating the correlation length-scale are also discussed and applied to the two forecast error datasets. The new formulation is tested within a 12-year period (2000-2011) in the 1/2 degree resolution system. The comparison with the data assimilation system using uniform background-error horizontal correlations indicates
A data assimilation system has been developed for the Adriatic Sea. It is based on the Nemo ocean... more A data assimilation system has been developed for the Adriatic Sea. It is based on the Nemo ocean model with the horizontal resolution of 2km and 120 levels, and on the OceanVar data assimilation scheme. In two experiments we assimilate satellite observations of Sea Level Anomaly and in situ observations of temperature and salinity. In one experiment we exclude the coastal observations of temperature and salinity in selected areas of the Adriatic Sea. By comparing the analyses from the two experiments we find that the information from coastal observations may be maintained in the data assimilation system for a long time. The differences in the estimates of the state of the Adriatic Sea may be amplified with respect to initial differences even in remote areas of the Adriatic Sea and several months after the observations are made.
ABSTRACT The global marine biogeochemical system is an integral part of the Earth system and carb... more ABSTRACT The global marine biogeochemical system is an integral part of the Earth system and carbon cycle. Like many other fields, as computer power improves so also has the trend towards using higher resolution in an effort to capture a greater proportion of the real world in the models. In the framework of the EU-FP7 GreenSeas project we examine this approach by performing two simulations of the global marine biogeochemical system, one at 2 degree resolution (LO-res), and the other at 1/4 degree resolution (HI-res) using the PELAGOS model, a coupling between NEMO and the BFM. Both the LO-res and HI-res simulations are set up with the same initial conditions, forcing and biogeochemical parameterizations, allowing us to perform a direct inter-comparison of the two, with a special focus on the Atlantic ocean. We examine how resolving more of the physical features affects the biogeochemical system, in particular how differences in the resolved horizontal, vertical motions and the mixed layer depth are reflected in the plankton biomass, the nutrient availability and community structure. While the global large-scale oceanographic features (fronts, gyres, etc) are captured in both the LO-res and HI-res simulations, differences in the mesoscale flow structures, and in particular the resolved vertical physics in the HI-res simulation, drive very different behaviour in the biogeochemical system. These differences in the physics drive what is a spun-up biogeochemical system in the LO-res simulation into a new regime in the HI-res simulation, where overall there is greater nutrient availability and much higher total primary production. Overall this approach identify the importance of resolving the vertical dynamics in marine biogeochemical models and opens up the question of the sensitivity of the parameterizations to the resolved scales. Keywords: Atlantic ocean, resolution, biogeochemical, models
In this project, a relatively high resolution coupled ocean-atmosphere GCM SINTEX-FRCGC (SINTEX-F... more In this project, a relatively high resolution coupled ocean-atmosphere GCM SINTEX-FRCGC (SINTEX-F1: ECHAM4.6 AGCM + OPA8.2 OGCM + OASIS2.4 Coupler) has been developed under the EU-Japan collaborative framework. The ensemble seasonal prediction experiments using SINTEX-F have demonstrated high prediction skills for both ENSO and IOD. The model realistically predicted the 1994 IOD event at 3 seasons lead. This is first
A one-dimensional ecosystem numerical model is used to simulate the ecosystem changes that could ... more A one-dimensional ecosystem numerical model is used to simulate the ecosystem changes that could have occurred in the open ocean areas of the Eastern Mediterranean Sea during the Climatic Optimum interval (9500–6000 B.P., Mercone et al. [Mercone, D., Thomson, J., Croudace, I.W., Siani, G., Paterne, M., Troelstra, S., 2000. Duration of S1, the most recent sapropel in the eastern Mediterranean Sea, as indicated by accelerator mass spectrometry radiocarbon and geochemical evidence. Paleoceanography 15, 336–347]). In this period the S1 sapropel was deposited. S1 is the most recent sapropel in the succession of organic carbon-rich layers intercalated in normal Neogene sedimentary sequences. Different theories have been invoked in order to explain the deposition of this peculiar layer. Our simulations seem to indicate that the modified thermohaline circulation, supplying oxygen only in the first 500 m of the water column, is responsible for the sapropel deposition when higher productivity is allowed in the euphotic zone. The model shows the importance in this process of bacteria that consume oxygen by decomposing the Particulate Organic Matter (POM) produced in the upper water column. The sinking velocity of POM partially regulates the timescale of the occurrence of anoxia at the bottom and in the whole water column, allowing the relatively rapid onset of sapropel deposition.
ABSTRACT Dry summers over the eastern Mediterranean are characterized by strong descent anchored ... more ABSTRACT Dry summers over the eastern Mediterranean are characterized by strong descent anchored by long Rossby waves, which are forced by diabatic heating associated with summer monsoon rainfall over South Asia. The large-scale teleconnection between rising and subsiding air masses is referred to as the "monsoon-desert mechanism.'' This study evaluates the ability of the phase 5 of the Coupled Model Intercomparison Project (CMIP5) models in representing the physical processes involved in this mechanism. An evaluation of statistics between summer climatologies of monsoon diabatic heating and that of vertical velocity over the eastern Mediterranean suggests a linear relationship. Despite large spatial diversity in monsoon heating, descent over the Mediterranean is coherently located and realistic in intensity. To measure the sensitivity of descent to the diversity in the horizontal and vertical distribution of monsoon heating, a series of linear atmosphere model experiments are performed. It is shown that column-integrated heating over both the Bay of Bengal and the Arabian Sea provides the largest descent with a more realistic spatial pattern. In the vertical, CMIP5 models underestimate the diabatic heating at upper levels, while they overestimate it at lower levels, resulting in a weaker forced response and weaker associated descent over the Mediterranean. A moist static energy budget analysis applied to CMIP5 suggests that most models capture the dominant role of horizontal temperature advection and radiative fluxes in balancing descent over the Mediterranean. Based on the objective analysis herein, a subset of models is identified that captures the teleconnection for reasons consistent with observations. The recognized processes vary at interannual time scales as well, with imprints of severe weak/strong monsoons noticeable over the Mediterranean.
In this paper we describe a mesoscale data assimilation experiment in the Middle Adriatic Sea. In... more In this paper we describe a mesoscale data assimilation experiment in the Middle Adriatic Sea. In order to perform dynamical forecasts we provide a quasigeostrophic numerical model with a set of initial fields regularly gridded via an objective analysis technique. Maps of this initial condition show a surface intensified jet meandering around a cyclonic eddy at the thermocline and deep
ABSTRACT This work explores the impact of orbital parameters and greenhouse gas concentrations on... more ABSTRACT This work explores the impact of orbital parameters and greenhouse gas concentrations on the climate of marine isotope stage (MIS) 7 glacial inception and compares it to that of MIS 5. The authors use a coupled atmosphere–ocean general circulation model to simulate the mean climate state of six time slices at 115, 122, 125, 229, 236, and 239 kyr, representative of a climate evolution from interglacial to glacial inception conditions. The simulations are designed to separate the effects of orbital parameters from those of greenhouse gas (GHG). Their results show that, in all the time slices considered, MIS 7 boreal lands mean annual climate is colder than the MIS 5 one. This difference is explained at 70% by the impact of the MIS 7 GHG. While the impact of GHG over Northern Hemisphere is homogeneous, the difference in temperature between MIS 7 and MIS 5 due to orbital parameters differs regionally and is linked with the Arctic Oscillation. The perennial snow cover is larger in all the MIS 7 experiments compared to MIS 5, as a result of MIS 7 orbital parameters, strengthened by GHG. At regional scale, Eurasia exhibits the strongest response to MIS 7 cold climate with a perennial snow area 3 times larger than in MIS 5 experiments. This suggests that MIS 7 glacial inception is more favorable over this area than over North America. Furthermore, at 239 kyr, the perennial snow covers an area equivalent to that of MIS 5 glacial inception (115 kyr). The authors suggest that MIS 7 glacial inception is more extensive than MIS 5 glacial inception over the high latitudes.
Journal of Atmospheric and Oceanic Technology, 2014
ABSTRACT AbstractOptimally modeling background-error horizontal correlations is crucial in ocean ... more ABSTRACT AbstractOptimally modeling background-error horizontal correlations is crucial in ocean data assimilation. In this paper, we investigate the impact of releasing the assumption of uniform background-error correlations in a global ocean variational analysis system. Spatially varying horizontal correlations are introduced in the recursive filter operator, which is used for modeling horizontal covariances in the CMCC analysis system. The horizontal correlation length-scales (HCLSs) were defined on the full three-dimensional model space, and computed from both a dataset of monthly anomalies with respect to the monthly climatology and through the so-called NMC method. Different formulas for estimating the correlation length-scale are also discussed and applied to the two forecast error datasets. The new formulation is tested within a 12-year period (2000-2011) in the 1/2 degree resolution system. The comparison with the data assimilation system using uniform background-error horizontal correlations indicates
A data assimilation system has been developed for the Adriatic Sea. It is based on the Nemo ocean... more A data assimilation system has been developed for the Adriatic Sea. It is based on the Nemo ocean model with the horizontal resolution of 2km and 120 levels, and on the OceanVar data assimilation scheme. In two experiments we assimilate satellite observations of Sea Level Anomaly and in situ observations of temperature and salinity. In one experiment we exclude the coastal observations of temperature and salinity in selected areas of the Adriatic Sea. By comparing the analyses from the two experiments we find that the information from coastal observations may be maintained in the data assimilation system for a long time. The differences in the estimates of the state of the Adriatic Sea may be amplified with respect to initial differences even in remote areas of the Adriatic Sea and several months after the observations are made.
ABSTRACT The global marine biogeochemical system is an integral part of the Earth system and carb... more ABSTRACT The global marine biogeochemical system is an integral part of the Earth system and carbon cycle. Like many other fields, as computer power improves so also has the trend towards using higher resolution in an effort to capture a greater proportion of the real world in the models. In the framework of the EU-FP7 GreenSeas project we examine this approach by performing two simulations of the global marine biogeochemical system, one at 2 degree resolution (LO-res), and the other at 1/4 degree resolution (HI-res) using the PELAGOS model, a coupling between NEMO and the BFM. Both the LO-res and HI-res simulations are set up with the same initial conditions, forcing and biogeochemical parameterizations, allowing us to perform a direct inter-comparison of the two, with a special focus on the Atlantic ocean. We examine how resolving more of the physical features affects the biogeochemical system, in particular how differences in the resolved horizontal, vertical motions and the mixed layer depth are reflected in the plankton biomass, the nutrient availability and community structure. While the global large-scale oceanographic features (fronts, gyres, etc) are captured in both the LO-res and HI-res simulations, differences in the mesoscale flow structures, and in particular the resolved vertical physics in the HI-res simulation, drive very different behaviour in the biogeochemical system. These differences in the physics drive what is a spun-up biogeochemical system in the LO-res simulation into a new regime in the HI-res simulation, where overall there is greater nutrient availability and much higher total primary production. Overall this approach identify the importance of resolving the vertical dynamics in marine biogeochemical models and opens up the question of the sensitivity of the parameterizations to the resolved scales. Keywords: Atlantic ocean, resolution, biogeochemical, models
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Papers by Simona Masina
ocean areas of the Eastern Mediterranean Sea during the Climatic Optimum interval (9500–6000 B.P., Mercone et al. [Mercone, D.,
Thomson, J., Croudace, I.W., Siani, G., Paterne, M., Troelstra, S., 2000. Duration of S1, the most recent sapropel in the eastern
Mediterranean Sea, as indicated by accelerator mass spectrometry radiocarbon and geochemical evidence. Paleoceanography 15,
336–347]). In this period the S1 sapropel was deposited. S1 is the most recent sapropel in the succession of organic carbon-rich
layers intercalated in normal Neogene sedimentary sequences. Different theories have been invoked in order to explain the
deposition of this peculiar layer. Our simulations seem to indicate that the modified thermohaline circulation, supplying oxygen
only in the first 500 m of the water column, is responsible for the sapropel deposition when higher productivity is allowed in the
euphotic zone. The model shows the importance in this process of bacteria that consume oxygen by decomposing the Particulate
Organic Matter (POM) produced in the upper water column. The sinking velocity of POM partially regulates the timescale of the
occurrence of anoxia at the bottom and in the whole water column, allowing the relatively rapid onset of sapropel deposition.
ocean areas of the Eastern Mediterranean Sea during the Climatic Optimum interval (9500–6000 B.P., Mercone et al. [Mercone, D.,
Thomson, J., Croudace, I.W., Siani, G., Paterne, M., Troelstra, S., 2000. Duration of S1, the most recent sapropel in the eastern
Mediterranean Sea, as indicated by accelerator mass spectrometry radiocarbon and geochemical evidence. Paleoceanography 15,
336–347]). In this period the S1 sapropel was deposited. S1 is the most recent sapropel in the succession of organic carbon-rich
layers intercalated in normal Neogene sedimentary sequences. Different theories have been invoked in order to explain the
deposition of this peculiar layer. Our simulations seem to indicate that the modified thermohaline circulation, supplying oxygen
only in the first 500 m of the water column, is responsible for the sapropel deposition when higher productivity is allowed in the
euphotic zone. The model shows the importance in this process of bacteria that consume oxygen by decomposing the Particulate
Organic Matter (POM) produced in the upper water column. The sinking velocity of POM partially regulates the timescale of the
occurrence of anoxia at the bottom and in the whole water column, allowing the relatively rapid onset of sapropel deposition.