Francesco Cioffi

Management strategies for the control of eutrophication processes in Fogliano lagoon (Italy): a long-term analysis using a mathematical model

Abstract Models are developed and used to analyse and test different management strategies aimed at limiting eutrophication processes in Fogliano Lagoon: modification of lagoon hydrodynamics by tidal flow regulation, harvest of algae biomass, reclaim of sediments. Mathematical models, which have been constructed and proposed, simulate, on a multiyear time scale, the main ecological processes responsible for the most important effects of eutrophication: vegetal blooms, summer anoxia. For different management strategies, hydrodynamic fields produced by wind and tide, and three-dimensional concentration fields of significant species in the ecological phenomena, in water and into sediments, are quantified and compared. The species simulated are: in the water column dissolved oxygen, phytoplanktonic biomass, macrophytic biomass, orthophosphate, dissolved organic carbon, particulate organic carbon and hydrogen sulphide; in sediments dissolved oxygen, dissolved organic carbon, particulate organic carbon, orthophosphate, adsorbed phosphorous and hydrogen sulphide. On the basis of the results of the simulations carried out, the best management strategy limiting eutrophication processes in Fogliano lagoon has been pointed out.

A new representation of anoxic crises in hypertrophic lagoons

Abstract A new representation of the causes of anoxia in hypertrophic lagoons is proposed; field measurements show that, in high concentrations of organic matter and high temperature, anoxic crises may be correlated either with the anaerobic mineralization phenomena in the sediment layer or with the turbulent characteristics of the hydrodynamic field produced by external influence (wind, tide). Two different models have been developed which are able to simulate, respectively, the hydrodynamic field in the lagoon and the concentration fields of the biochemical species which are the most important in characterizing the phenomena, i.e., dissolved oxygen, organic carbon, and hydrogen sulphide. The results of the simulations are compared with field measurements to validate the representation of the phenomena. Furthermore the effect of forced recirculation by pumping, in avoiding anoxia in water, is quantified.

Three-dimensional numerical simulation of wind-driven flows in closed channels and basins

F. Cioffi, F. Gallerano And E. Napoli, Journal of Hydraulic Research 2005, 43(3), 290–301In the paper, a fully 3D finite-volume numerical model is developed and employed for the prediction of wind-induced flows in a regular channel and in a square basin with a complex bathymetry. Numerical results are compared with laboratory experiments.Numerical tests are then performed to investigate whether simplifying assumptions about the pressure distribution and the turbulente stresses representation can be employed in the simulation of wind-driven flows. The hydrostatic pressure assumption, resulting in the use of “quasi-3D” models, proved to be reasonably acceptable in order to obtain the vertical profile of the streamwise velocity component away from the boundaries. The quasi-3D model employed, nevertheless, provided incorrect velocity patterns near the upwind and downwind boundaries. The zero-equation turbulence model proposed by Tsanis [J. Hydraul. Div. ASCE 115 (1990) 1113] is also investigated by comparing the parabolic vertical profiles of the eddy viscosity coefficient assumed in this model w...

Large scale climate and rainfall seasonality in a Mediterranean Area: Insights from a non‐homogeneous Markov model applied to the Agro‐Pontino plain

In the context of climate change and variability, there is considerable interest in how large scale climate indicators influence regional precipitation occurrence and its seasonality. Seasonal and longer climate projections from coupled ocean-atmosphere models need to be downscaled to regional levels for hydrologic applications, and the identification of appropriate state variables from such models that can best inform this process is also of direct interest. Here, a Non-Homogeneous Hidden Markov Model (NHMM) for downscaling daily rainfall is developed for the Agro-Pontino Plain, a coastal reclamation region very vulnerable to changes of hydrological cycle. The NHMM, through a set of atmospheric predictors, provides the link between large scale meteorological features and local rainfall patterns. Atmospheric data from the NCEP/NCAR archive and 56-years record (1951-2004) of daily rainfall measurements from 7 stations in Agro-Pontino Plain are analyzed. A number of validation tests are carried out, in order to: 1) identify the best set of atmospheric predictors to model local rainfall; 2) evaluate the model performance to capture realistically relevant rainfall attributes as the inter-annual and seasonal variability, as well as average and extreme rainfall patterns. Validation tests show that the best set of atmospheric predictors are the following: mean sea level pressure, temperature at 1000 hPa, meridional and zonal wind at 850 hPa and precipitable water, from 20°N to 80°N of latitude and from 80°W to 60°E of longitude. Furthermore, the validation tests show that the rainfall attributes are simulated realistically and accurately. The capability of the NHMM to be used as a forecasting tool to quantify changes of rainfall patterns forced by alteration of atmospheric circulation under climate change and variability scenarios is discussed.

Surface Temperature Gradients as Diagnostic Indicators of Midlatitude Circulation Dynamics

AbstractZonal and meridional surface temperature gradients are considered to be determinants of large-scale atmospheric circulation patterns. However, there has been limited investigation of these gradients as diagnostic aids. Here, the twentieth-century variability in the Northern Hemisphere equator-to-pole temperature gradient (EPG) and the ocean–land temperature contrast (OLC) is explored. A secular trend in decreasing EPG and OLC is noted. Decadal and interannual (ENSO-related) variations in the joint distribution of EPG and OLC are identified, hinting at multistable climate states that may be indigenous to the climate or due to changing boundary forcings. The NH circulation patterns for cases in the tails of the joint distribution of EPG and OLC are also seen to be different. Given this context, this paper extends past efforts to develop insights into jet stream dynamics using the Lorenz-1984 model, which is forced directly and only by EPG and OLC. The joint probability distribution of jet stream and...

An experimental study of the turbulence statistics in a lagoon

Simultaneous measurements of three-dimensional velocity components and free-surface elevations were carried out in the lagoon of Fogliano, to investigate the statistical characteristics of turbulence produced in the flow by the action of wind over the free surface. Measurements were made in typical spring–summer environmental conditions, characterized by a gentle sea-breeze wind. Two measurement points were chosen far from the only tidal channel of the lagoon to evidence the role of the wind in generating turbulence. The analysis of velocity data has proved: (1) the presence of a significant oscillatory motion due to wind waves, which affects the entire water column and interferes with the lagoon bottom; (2) an evident degree of anisotropy between larger horizontal and vertical turbulent scales; (3) the existence of a scaling range where the relative scaling exponents, calculated using the Extended Self Similarity, have a scale-independent behavior.

Design and management of hyperintensive aquaculture tanks

In order to identify the optimum design and management criteria for hyperintensive aquaculture rectangular tanks, a hydrodynamic model and a water quality model have been developed. The models allow the simulation of the velocity fields in the tanks and of the concentration evolution, in space and time, of the significant species: dissolved oxygen, phytoplankton and nitrogen compounds. These models can be used to identify both the critical conditions for the survival of the reared aquatic organisms and the pollutant load discharged in the environment from the tanks. The hydrodynamic fields are obtained by solving numerically, on a symmetric vertical plane of the tank, the two-dimensional turbulent motion equations expressed in terms of vorticity and stream function; the eddy viscosity which appears in the motion equations is obtained by solving a standard k-e model. The concentration fields of each chemical and biological species are obtained by solving their mass balance equations, in which the physical,...