Gulf Of Genoa Research Articles

A 40 year objective climatology of surface cyclones in the Mediterranean region: spatial and temporal distribution

AbstractA climatological analysis of the synoptic scale cyclones that occur in the Mediterranean region is carried out for an extended period of 40 years (1958–1997). The cyclones are identified with the aid of an objective method based on grid point values, available every 6 h. The study of the seasonal and diurnal variations of the frequency of cyclonic occurrences, with respect to the value of the central pressure, revealed that the major cyclonic centres appear to be different in frequency and location, reflecting the different triggering mechanisms. In the western Mediterranean region, the frequency of occurrence is higher in winter, more so for the intense cyclones, with no substantial diurnal difference in the Gulf of Genoa, and with a preference during the night in southern Italy. The Cyprus centre reveals diurnal variability in location, especially in the cold period, in accordance with the triggering mechanism, being associated principally with weak and moderate cyclones. In northwestern Africa, there appears to be two marked regions of high cyclonic frequency, not only in spring, but also in summer and autumn. The extremely high frequency of cyclonic occurrences in summer in the Mediterranean basin is attributed mainly to the generation of weak thermal lows. The number of rapidly deepening cyclones within 12 h and 24 h increases from the south to the north part of Mediterranean, being mostly favoured near the lee of Alps and the Gulf of Venice, occurring mainly after 06:00 co‐ordinated universal time (UTC). Copyright © 2001 Royal Meteorological Society

Objective Climatology of Cyclones in the Mediterranean Region

Abstract An objective cyclone detection and tracking analysis is performed over an 18-yr period, for the Mediterranean basin. The high-resolution (1.125° × 1.125° grid) European Centre for Medium-Range Weather Forecasts data used in this study proved to be particularly suitable for the detection and tracking techniques and to identify subsynoptic-scale Mediterranean lows, which have often been underestimated in previous studies. The major characteristics of Mediterranean cyclones are examined and compared with other Northern Hemisphere depressions. Both cyclogenesis and cyclolysis regions are identified in the domain of study. In addition, characteristics of Mediterranean depressions, such as cyclone duration and intensity, as well as their persistence throughout the year, are shown to be quite variable for different formation areas. Overall, the regions where cyclogenesis is mainly controlled by topography, like the Gulf of Genoa and south of the Atlas Mountains, seem to generally account for the most in...

SAR detection and characterization of sea surface slicks

In this paper we demonstrate SAR system capability for detecting and characterizing marine surface slicks. During an aircraft measurement campaign over the Gulf of Genoa (Italy), a multi-frequency SAR system, operating in P-, L- and C-bands, explored a sea area heavily covered by slicks. At the same time in situ measurements were performed with an interferential microwave probe, installed on board a small boat, capable of measuring high resolution sea spectra up to frequencies of capillary waves. By plotting SAR pixel intensity versus sea wave Bragg frequency we obtained wide portions of the sea spectrum region affected by the surface film damping. Spectra derived from SAR imagery and from gauge data present comparable slopes and furthermore the ratio between clean to slicked water spectrum obtained with the two techniques were surprisingly similar. This demonstrates the multi-frequency SAR systems ability to detect and characterize sea surface films assuming the Bragg mechanism in the radar backscatter. The outlined analysis suggests a simple methodology to monitor coastal water quality by using airborne SAR.

Total and organic mercury concentrations in offshore crustaceans of the Ligurian Sea and their relations to the trophic levels

Total mercury and organic mercury were measured in five crustaceans representative of an offshore pelagic food web in the Gulf of Genoa, Italy: Meganycthiphanes norvegica, Gennadas elegans, Pasiphaea sivado, Pasiphaea multidentata and Aristeus antennatus. According to their predator-prey relationships, they represent three trophic levels in the Ligurian Sea. The concentrations of total and organic mercury increase with the trophic levels and with the weight of the specimens (except in G. elegans and in females of A. antennatus). However, at higher trophic levels the specimens are also larger. Only in P. sivado, do levels of inorganic mercury increase significantly (P = 0.001) with the size of the specimens. The ratio between organic mercury and total mercury did not increase with the trophic level.

A new perspective on oil slick detection from space by NOAA satellites

In this paper an extension of the Split Window Technique algorithm, to account for small surface emissivity variations, is presented. This algorithm has been used, along with an adaptive filtering pattern recognition approach, in order to detect oil spills on the sea surface under the assumptions of thermal equilibrium between the oil polluted areas and the surrounding water, of weak horizontal sea surface temperature gradients (i.e., <1°C) in the area of interest and of a horizontal uniform atmospheric water vapour distribution over the discharged area. AVHRR/2 data acquired both on the Gulf of Genoa in April 1991 during an oil pollution episode following the wreck of the Haven tanker and on the Persian Gulf during war operations in January-February 1991 were considered. Comparing satellite retrieved polluted areas with in situ observations available in literature and high spatial resolution satellite observations (Landsat and SPOT), the algorithm has proved to supply satisfactory results in detecting oil contaminated areas.

Arguments for the pre‐rift uplift and rift propagation in the Ligurian‐Provencal Basin (northwestern Mediterranean) In the light of Pyrenean Provencal Orogeny

The Cenozoic Provencal orogeny and the subsequent opening of the Ligurian‐Provencal basin were caused by a geodynamic mechanism that originated in the Cretaceous. It is evident from the arguments presented that (1) regional doming preceded rifting of the continental margin and this uplift widened and/or migrated during the ensuing opening of the Ligurian‐Provencal basin; (2) clastic sedimentation on the Provencal platform was initiated during the early Cenomanian; (3) deformation in the Provencal block, which varies from Late Cretaceous to Miocene, reflects a migration of the north‐south compression from west to east accross the block; (4) the Languedoc‐Provencal fold belt was initiated during the Eocene as a result of tectonic uplift and sinistral displacement of the Paleozoic basement toward the north. Significant geologic features of the region associated with these events include (1) similarities in shape of the Languedoc virgation and the Provencal thrust front with the shape of geophysical features over the Golfe du Lion; (2) the unusual width of the young, stretched continental margin in the Golfe du Lion; (3) the distinctive V‐shaped form of the Ligurian oceanic crust; and (4) the concordance in age of the earliest post‐rift deposits, which increasingly young toward the east, and magnetic anomalies that parallel the basin axis. These events and structures are attributed to the uplift of a Paleozoic block situated to the south in the Golfe du Lion and previously buried under the Mesozoic cover. The development of this crustal uplift since upper Aptian, and its northeastwards migration and/or gradual widening account for both sedimentary events and tectonic deformation that occurred on the Provencal platform until upper Eocene, and the later stage of rifting and formation of the Provencal margin. In the Ligurian‐Provencal basin, the synthesis of marine data as well as relevant terrestrial data indicates that rifting propagated towards the Gulf of Genoa, while the Corsica‐Sardinia block rotated to the southeast.

Total mercury, organic mercury, copper, manganese, selenium, and zinc in Sarda sarda from the gulf of Genoa

The total mercury content of the Atlantic bonito ( Sarda sarda) increases with increasing size of the specimen, as shown by other authors for other marine organisms (Renzoni et al., 1973; Buffoni et al., 1982; Bernhard and Andreae, 1984; Thibaud, 1986). Organic mercury content also increase with the size of the specimen, whereas inorganic mercury remains constant, which is in agreement with the prediction made on another species of Sgombridae (Bernhard, 1985). This kind of mercury partitioning has not, to our knowledge, been reported for other species of fish. It is interesting to note that the mercury concentration in the gonads also increases with the size of the specimen. A very small difference between the total mercury content of white and dark muscle was observed, while for selenium, zinc, copper, and manganese the concentrations are lower in white muscle than in dark muscle.

Aerial observations of stratospheric descent in a Gulf of Genoa cyclone

The structure of a cyclone in the Gulf of Genoa on April 24, 25, 1982 is examined using an enhanced rawinsonde network, data from four ALPEX research flights, and satellite ozone and water vapor observations. This particular cyclone had, as a precursor, a mesoscale upper level vortex which approached the Alps from the north at a rate of about 400 km/6 hours. This small cyclone had a roughly axisymmetric tropopause fold. Cold air below the cyclone prevented it from having a surface pressure signature. Upon encountering the Alps, the cold air appeared to be deflected, allowing the cyclone reaching the Gulf of Genoa to extend to the surface. Aircraft data at thep≈447 mb level reveal a small volume of stratospheric air slightly ahead of the vortex center. This air is marked by high ozone concentration, low water vapor mixing ratio, and high relative vorticity. The boundaries of this region are very well defined with a horizontal scale of about 20 km, but with some evidence of advection and mixing processes. Satellite derived maps of vertically integrated ozone (TOMS) agree with the aircraft data regarding the position of the ozone maximum. Satellite images in the water vapor band /6.7 μm) also agree with the aircraft data, and provide some information on the time evolution of the stratospheric intrusion.

87:6570 Total mercury, organic mercury, copper, manganese, selenium, and zinc in Sarda sarda from the Gulf of Genoa : Capelli, R., V. Minganti and M. Bernhard, 1987. Sci. total Environment, 63:83–99. Istituto di Chimica Generale, Univ. di Genova, Genova, Italy

87:6570 Total mercury, organic mercury, copper, manganese, selenium, and zinc in Sarda sarda from the Gulf of Genoa : Capelli, R., V. Minganti and M. Bernhard, 1987. Sci. total Environment, 63:83–99. Istituto di Chimica Generale, Univ. di Genova, Genova, Italy

Limited Area Energetics of Genoa Cyclogenesis

The energetics of a frontal depression initially formed in the Gulf of Genoa is studied. The partition of available potential energy and kinetic energy into zonal and eddy components is adopted. The energy equations, as developed for an open area of the atmosphere, are applied over a region enclosing the synoptic-scale disturbance in study. The period covering stages of the development of the depression is from 1200 GMT 15 January to 1200 GMT 17 January 1981. Vertical distributions of components of the energy equations are presented and discussed. Also, the energy balance over the region in terms of an energy cycle is presented.

Some laboratory models of flow past the Alpine/Pyrenees mountain complex

A series of laboratory experiments have been conducted to simulate the dynamical effects of the flow over and around a model Alpine/Pyrenean topography. The experimental study has employed a linearly salt-stratified rotating water channel through which the model topography is towed. Data have been collected for ranges of the similarity parameters (Rossby, Burger, Ekman and Froude numbers and the topography height to fluid depth ratio) which accord with their atmospheric values; only four of these parameters are independent. The ratio of the fluid depth to topography width need not be simulated because it does not appear as an independent parameter in the leading terms of the governing equations and boundary conditions. The results demonstrate the effects of flow direction on the horizontal motion patterns at various heights and numerous system parameter combinations. Vortex shedding is shown to occur for parameter ranges similar to those appropriate for the atmosphere; an empirical relation between the Strouhal and Rossby numbers is obtained and it is shown that the shedding periods is approximately twice the inertial period. The experiments demonstrate the flow splitting occurs in the vicinity of Geneva for both westerly and northwesterly flow. The importance of the Froude number in controlling the conditions under which fluid flows over or around the topography is illustrated, and the occurrence of lee waves for different values of the Froude and Rossby numbers (and different locations and flow directions) is described. Finally, it is shown that the advection of a parent cyclone from west to east along a path north of the Alps can generate a cyclone in the lower levels of the atmosphere in the vicinity of the Gulf of Genoa. It is suggested that these dynamical effects may play a role in triggering a lee cyclone which then might grow by other physical processes.

Several location methods for underwater shots in the Gulf of Genoa (Western Mediterranean): Structural implications

During the EGT survey, 50 underwater shots were detonated on a N-S section through the Gulf of Genoa running from the northern margin (44.12°N) towards Corsica (42.90°N) along the 9°E meridian. The aim of this work is, in a first stage, to establish the propagation model of regional phases in this region and. consequently, to improve the location of epicentres, and afterwards, to refine our structural knowledge of this complex crustal area. The relocation of these shots was carried out with arrival times of seismic signals recorded at land stations. We have used different location methods all of which led to similar crustal models. They reveal a low P n-velocity area in the northern Ligurian Sea and in the Gulf of Genoa, with a 20 km thick crust. In the southern part, approximately south of latitude 43°7N, a 4 km thick oceanic crust covered by 8 km of sediments is clearly confirmed. Using these models, a significant improvement of epicentre locations was obtained. These improvements to propagation models lead to the two main structural conclusions: 1. (1) in the southern part of the investigated area, the spread of an oceanic-type domain as far as the foot of the continental margin, 2. (2) a sharp transition between the two domains of different stretching rate — the northern one. with a Moho depth of about 20 km, and the southern one, with an average Moho depth of about 14 km. These observations substantiate the presence of a transform margin between the rifted Gulf of Genoa and the oceanic-type Ligurian Basin.

Mean length of runs of sea waves recorded in the Gulf of Genoa : Cicconi, Giuseppe, Ignazio Dagnino and Alberto Albert, 1985. Boll. Oceanol. teor. appl., 3(2):103–112

Mean length of runs of sea waves recorded in the Gulf of Genoa : Cicconi, Giuseppe, Ignazio Dagnino and Alberto Albert, 1985. Boll. Oceanol. teor. appl., 3(2):103–112

A wave refraction computation in the Gulf of Genoa

A numerical ray model of surface gravity wave refraction was applied to a coastal area of the Gulf of Genoa. A series of refraction diagrams was computed by means of wave data recorded at a moored oil-platform which operates 1.5 miles off the harbour of Genoa. The numerical calculations provided wave energy concentration effects near the city of Savona where coastal structures and beaches are often damaged during storm surges.p

An experimental verification of a clockwise circulation in the Gulf of Genoa

Current observations carried out in the Gulf of Genoa during the years 1975–76 have shown inversions of the typical alongshore cyclonic flow in association with meteorological frontal systems transiting over the Ligurian Sea. This result agrees with the circulation field computed by a numerical model of the Ligurian basin, which revealed the existence of an anticyclonic gyre in the northwestern part of the Gulf of Genoa in association with southerly winds.

ジェノヴァ低気圧に対する山脈効果

Four cases of cyclogenesis in the Gulf of Genoa (so-called Genoa cyclogeneses) have been simulated using a high resolution prediction model. Integrations are performed for a 48 hour period, using observed boundary conditions, and for each case with and without mountains in the model.It is found that in two of these cases cyclogenesis happens irrespective of the presence of mountains. However, mountains have a strong modifying influence, in ridging at the surface to the northwest and to the southwest of the Alpine obstacle, and at mid-troposphere in ridging in central Europe north of the Alps.Of the two cases in which cyclogenesis does not happen without mountains, in one case a very realistic simulation of the surface development is obtained. In mid-troposphere, although simulated geopotential heights are even less than observed, the intensity of the cutoff process north of the Genoa region is not sufficiently realistic. It is suggested that, therefore, the problem is either in an insufficient intensity of blocking north of the obstacle, or in a process of a more large scale nature.

A numerical verification of a clockwise circulation in the Gulf of Genoa

A numerical verification of a clockwise circulation in the Gulf of Genoa

Numerical Simulation of Lee Cyclogenesis in the Gulf of Genoa

A numerical model framed in isentropic coordinates is applied to the problem of predicting lee cyclogenesis south of the Alps. Since “Genoa cyclones” during their initial stage are mesoscale phenomena, while mid-tropospheric flow configurations conducive to Genoa cyclogenesis are not, a grid nesting approach is followed in the model to capture both large-scale and mesoscale aspects of the problem. The two grids differ in mesh aim by a factor of 4 and interact in a two-way mode. The model is dry and uses a highly simplified surface drag formulation. Twenty-four hour predictions carried out on three occasions of observed cyclogenesis show that the model is capable of simulating cyclonic development approximately in the correct location. However, by slightly underpredicting the development of a high-pressure ridge over the eastern Atlantic the model in two of the three cases fails to build up the lee cyclone to the observed strength.

The Pn velocity under the Gulf of Genoa

Nous avonsetudiela variation en azimut de la vitesse apparente des ondes Pn dans le Sud-Est de la France. Nous avons utiliseles donnees des stations permanentes du Provence pour les seismes situes autour du Golfe de Geˆnes. Les premiers resultats obtenus par Fahlquist semblent avoireteconfirmeet le domaine des faibles vitesses des ondes Pn peutetreetendual' ensemble du golfe de Geˆnes.

Cyclonic activity in Yugoslavia and surrounding areas

A precise statistics of the cyclones in Yugoslavia and surrounding areas for the period 1951–1960 has been made. By that statistics eight different cyclogenetic regions in South Europe have been identified. They are: the Gulf of Genoa, the Tyrrhenian Sea, the Northern Adriatic, the Southern Adriatic, the Aegean Sea, the Black Sea, the Panonean Lowland and the Walachian Plain. Further, some features of cyclonic activity in the cyclogenetic regions such as the frequency of cyclogenesis, as well as the distribution, the duration and the intensity of cyclones have been discussed.