surface drifter derived circulation in the northern and middle adriatic sea response to wind regime and season 1 more than 120 satellite tracked drifters were deployed in the northern and middle adriatic nma sea between september 2002 and november 2003 with the purpose of studying the surface circulation at mesoscale to seasonal scale in relation to wind forcing river runoff and bottom topography pseudo eulerian and lagrangian statistics were calculated from the low pass filtered drifter velocity data between september 2002 and december 2003 the structure of the mean circulation is determined with unprecedented high horizontal resolution by the new data in particular mean currents velocity variance and kinetic energy levels are shown to be maximal in the western adriatic current wac separating data into seasons we found that the mean kinetic energy is maximal in fall with high values also in winter while it is significantly weaker in summer high resolution local area model italy winds were used to relate the drifter velocities to the wind fields the surface currents appear to be significantly influenced by the winds the mean flow during the northeasterly bora regime shows an intensification of the across basin recirculating currents in addition the wac is strongly intensified both in intensity and in its offshore lateral extension in the southeasterly sirocco regime northward flow without recirculation dominates in the eastern half of the basin while during northwesterly maestro the wac is enhanced separating the data into low and high po river discharge rates for low wind conditions shows that the wac and the velocity fluctuations in front of the po delta are stronger for high po river runoff lagrangian covariance diffusivity and integral time and space scales are larger in the along basin direction and are maximal in the southern portion of the wac

effects of winter convection on the deep layer of the southern adriatic sea in 2012 1 we analyze aspects concerning the thermohaline changes observed in the near bottom layer of the southern adriatic pit sap in the eastern mediterranean after the arrival of abundant and exceptionally dense water 30 kg m 3 produced in the shallow northern adriatic sea during winter 2012 for this purpose we use temperature t salinity s and current time series collected at the e2m3a deep ocean observatory of the southern adriatic and conductivity temperature depth data obtained both in the southern and middle adriatic from freely drifting profiling floats the dense water produced in the northern adriatic arrived in the central and deepest part of the sap as a series of individual pulses starting on 10 march 2012 while a stronger and prolonged signal that significantly modified the local deep water stratification arrived after 10 april 2012 as a consequence t and s suddenly decreased 0 15 c and 0 015 thus interrupting positive t and s bottom trends observed during the previous 5 years and producing a density increase of 0 02 kg m 3 such variability has been rarely observed in the area we ascribe its occurrence to the concomitance of exceptionally harsh and long lasting bora wind scarce precipitation and low river discharge over the northern adriatic during winter 2011 2012 eventually this newly formed addw reached the strait of otranto during july 2012 its characteristics profoundly differed from those observed in the previous decade hence a noticeable variability in structure and circulation of the abyssal layers of the ionian basin is likely to occur in the near future

process studies on the po river plume north adriatic sea the coastal processes in the adriatic sea and in particular the development and evolution of the po river plume are studied with a three dimensional primitive equation model experiments are performed to examine the buoyancy driven flow and the interaction with topography wind stress and ambient stratification the pathways of particles released from the po are computed to simulate the transport of land drained materials in the absence of wind forcing the po river plume consists of an offshore bulge that occupies most of the north part of the basin and a southward coastal current that is confined within the narrow coastal region along the italian peninsula when all adriatic rivers are included basinwide buoyancy driven cyclonic coastal flow is established that diminishes the seaward removal of po waters and promotes their southward advection through the coastal current wind stress modifies the above winds that are downwelling favorable for the po discharge site like bora restrict offshore plume development enhance the southward coastal current and confine the plume within the narrow western adriatic shelf conversely upwelling favorable winds like scirocco eliminate the baroclinic coastal current and advect low salinity po waters toward the shallow parts of the northern adriatic when preexisting stratification of basin waters is described the density field is influenced by both temperature and salinity during winter when the coastal waters tend to be colder and fresher than offshore waters the cyclonic circulation is sustained owing to input from rivers and particularly the po the intense spatial and temporal variability of wind stress and river runoff and the resulting variability in the circulation of the coastal adriatic sea are elaborated through a realistic simulation during january 1994

comparison of model simulated and observed currents in the central adriatic during dart 1 numerical simulations of the adriatic sea were performed with the navy coastal ocean model ncom during the dynamics of the adriatic in real time dart experiments conducted between october 2005 and september 2006 grid resolution was 1 km model forcing included tides surface fluxes from the aire limitee adaptation dynamique developpement international aladin atmospheric model relaxation to a daily satellite sea surface temperature analysis extensive river and runoff discharges and open boundary conditions south of otranto specified from a global model currents predicted by the model were compared with currents from 12 acoustic doppler current profiler adcp moorings located along a line between the gargano peninsula italy and split croatia the nontidal comparisons were performed with detided currents correlations between the model and adcp currents were highest in the western adriatic current wac which flows southeastward along the italian coast lowest correlations were in the interior of the adriatic likely because of instability processes correlations between the aladin winds and the model and adcp currents at the mooring locations were also highest in the wac for november 2005 through august 2006 the model and adcp mean wac transports were 0 321 and 0 304 sv respectively with a temporal correlation of 0 79 comparison of current variance showed best agreement near the italian and croatian coasts in the interior the ncom current variance compared fairly well with that of the adcps for november january but decreased significantly relative to the adcps for february august spectral analyses indicate most of the difference in variance to be at periods exceeding 2 days

frictional properties of shale reservoir rocks 1 we performed laboratory friction experiments on shale samples from three hydrocarbon reservoirs to assess compositional controls on fault slip behavior accompanying hydraulic stimulation the samples span a range of clay and total organic content from 10 to 60 by weight and demonstrate fine scale heterogeneity within each reservoir friction measurements demonstrate strong dependence of strength and rate state constitutive properties on shale composition shale samples with clay and organic content above 30 by weight show coefficient of friction 0 4 and consistently velocity strengthening behavior while those below this threshold show increased strength and velocity weakening behavior this transition in frictional strength and stability suggests a change in the shale grain packing framework from rigid clast supported to clay mineral and organic matter supported measurements of gouge dilatancy further support these relationships showing a negative correlation with clay and organic content critical slip evolution distance exhibits similar dependence on composition implying common micromechanical mechanisms for the observed transition in frictional behavior we performed microstructural characterization of the experimental samples and observe changes in the gouge load bearing framework and shear localization features consistent with these mechanical data while these results can be applied generally to infer slip stability on faults in clay bearing sedimentary rock we employ the experimental data to place constraints on microearthquake magnitudes and the occurrence of slow shear slip on preexisting faults during hydraulic stimulation in shale reservoirs

dynamics of dip slip faulting explorations in two dimensions dynamic models of earthquake rupture and slip are a powerful method by which to investigate the physics of earthquakes owing to both conceptual and computational constraints dynamic earthquake models have largely been limited to cases with geometrical symmetry such as faults in unbounded media or vertical faults however there are both observational and theoretical reasons to believe that nonvertical dip slip faults behave differently from faults with more symmetrical geometries previous observations have shown greater ground motion from thrust reverse faults than normal faults and higher ground motion on hanging walls than on footwalls in the present work two dimensional dynamic simulations of thrust reverse and normal earthquakes show precisely these effects and also elucidate their causes for typical nonvertical dip slip faults the breakdown of symmetry with respect to the free surface allows radiated seismic waves to reflect off the free surface and to hit the fault again altering the stress field on the fault this process can lead to time dependent normal stress and a feedback between the friction rupture processes and seismic radiation this interaction leads to thrust reverse faults producing much higher fault and ground motion than normal faults with the same geometry and stress magnitudes the asymmetric geometry also directly leads to higher motion on the hanging walls of such faults than on the footwalls simulations show that these effects occur for a variety of dip angles but only for faults that either intersect or closely approach the free surface the results emphasize the strong effect that the free surface can have on the dynamics of fault rupture and slip

application of the coherent to incoherent intensity ratio to estimation of ocean surface roughness from high frequency shallow water propagation measurements for acoustic propagation through a shallow ocean channel or waveguide the coherence between different transmissions is controlled primarily by the roughness of the ocean surface and to a lesser degree by fluctuations in the volume in this study the coherent to incoherent intensity ratio ctir is defined as a way to quantify the coherence between multipath transmissions and ocean surface rms wave height and wind speed a theory that connects the ctir and the coherent surface reflection coefficient is developed using both kirchhoff and small slope approximations as rough surface scattering models the ctirs have been evaluated over a period of several days using broad band experimental results from shallow water deployment of source and receiver arrays that span most of the water column estimates of wind speed and rms wave height obtained using these ctir calculations are compared with environmental measurements to demonstrate the validity of the theory

surface current patterns in the northern adriatic extracted from high frequency radar data using self organizing map analysis 1 a network of high frequency hf radars was installed in the northern adriatic in the second half of 2007 aimed to measure surface currents in the framework of the north adriatic surface current mapping nascum project this study includes a detailed analysis of current measurements from february to august 2008 a period in which three radars were simultaneously operational current patterns and temporal evolutions of different physical processes were extracted by using self organizing map som analysis the analysis focused on subtidal frequency band and extracted 12 different circulation patterns on a 4 3 rectangular som grid the som was also applied on a joint data set that included contemporaneous surface wind data obtained from the operational hydrostatic mesoscale meteorological model aladin hr the strongest currents were recorded during energetic bora episodes being recognized by several current patterns and having the characteristic downwind flow with magnitudes exceeding 35 cm s at some grid points another characteristic wind the sirocco was represented by three current patterns while the remaining current structures were attributed to weak winds and the residual thermohaline circulation a strong resemblance has been found between som patterns extracted from hf radar data only and from combined hf radar and wind data sets revealing the predominant wind influence to the surface circulation structures and their temporal changes in the northern adriatic these results show the som analysis being a valuable tool for extracting characteristic surface current patterns and forcing functions

moment tensors and micromechanical models abstract a numerical modelling approach that simulates cracking and failure in rock and the associated seismicity is presented and a technique is described for quantifying the seismic source mechanisms of the modelled events the modelling approach represents rock as an assemblage of circular particles bonded together at points of contact the connecting bonds can break under applied stress forming cracks and fractures in the modelled rock if numerical damping is set to reproduce realistic levels of attenuation then energy is released when the bonds break and seismic source information can be obtained as damage occurs a technique is described by which moment tensors and moment magnitudes can be calculated for these simulated seismic events the technique basically involves integrating around the source and summing the components of force change at the surrounding particle contacts to obtain the elements of the moment tensor matrix the moment magnitude is then calculated from the eigenvalues of the moment tensor the modelling approach is tested by simulating a well controlled experiment in which a tunnel is excavated in highly stressed granite while microseismicity is recorded the seismicity produced by the model is compared to the actual recorded seismicity underground the model reproduces the spatial and temporal distribution of seismicity observed around the tunnel and also the magnitudes of the events a direct comparison between the actual and simulated moment tensors is not performed due to the two dimensional nature of the model however qualitative comparisons are presented and it is shown that the model produces intuitively realistic source mechanisms the ability to obtain seismic source information from the models provides a unique means for model validation through comparison with actual recorded seismicity once it is established that the model is performing in a realistic manner it can then be used to examine the micromechanics of cracking failure and the associated seismicity and to help resolve the non uniqueness of the geophysical interpretation this is demonstrated by examining in detail the mechanics of one of the modelled seismic events by observation of the time dependence of the moment tensor and by direct examination of the particle motions at the simulated source

shear and tensile earthquakes caused by fluid injection 1 we apply rock mechanics concepts to the seismological observations in order to explain why during hydraulic injection some events display tensile and some shear deformation the presence of non shear components depends on the differential stress and the fracture orientation with respect to the 1 direction provided the slip vector is parallel to the traction we define four types of earthquakes according to the ratio of the shear and tensile components assuming a griffith failure envelope hybrid events containing both shear and tensile components can occur for fractures striking within 22 5 of 1 we argue that pure tensile fractures striking parallel to 1 are unlikely in the presence of natural fractures the low shear traction of tensile events also implies their small stress drops by applying the analysis to two different data sets soultz sous forets and cotton valley we show that different orientations of natural fractures and differential stress in the targeted formations made each region favorable for different non dc components in the injection induced seismicity

scales and variability of the sea surface temperature distribution in the adriatic sea 1 scales and variability of the adriatic sea surface temperature sst distribution in the period january 1991 to december 2000 are studied by means of 8 day composite 4 km resolution sst data scales of the sst are defined as scales of the sst autocorrelation function assuming an exponential correlation model scales of the sst are quantified as e folding times and distances of the sst autocorrelation function variability in the sst is analyzed through empirical orthogonal function eof analysis from summer to winter spatial scales of the sst in the along basin direction remain unchanged while in the across basin direction they decrease resulting in scales that are slightly shorter 10 15 in winter than in summer the spatial distribution of temporal scales displays two patterns the first characterized by low values is located in the northern part of the basin and along the italian coast and the second characterized by high values covers the rest of the basin the sst variability is dominated by the annual signal which explains 45 of the overall variance the main structures of the adriatic circulation leave their signature on the first three eofs whose spatial variability occurs on wavelengths longer than 200 km in the along basin direction and in the across basin direction in the band 25 50 km and at 80 and 100 km eof coefficients are characterized by oscillating components with periods of 20 days to 6 months

coupled ocean atmosphere nested modeling of the adriatic sea during winter and spring 2001 1 realistic simulations of the adriatic sea for over 125 days are conducted using the navy coastal ocean model with atmospheric forcing provided by the coupled ocean atmosphere mesoscale prediction system coamps is a registered trademark of the naval research laboratory coamps in two separate simulations of the adriatic a nested 2 km resolution ocean model is forced by the inner 4 km and outer 36 km nests of the atmospheric model two meteorological stations and two acoustic doppler current profiler observation sites are used to evaluate modeled atmosphere and ocean velocity fields for 28 january 4 june 2001 modeled observed correlations of atmospheric 10 m velocity are greater than 0 85 for both resolution models oceanic 5 and 25 m current fluctuations from both simulations generally match the magnitude and orientation of the observations the 4 km resolution atmospheric model is differentiated from the 36 km resolution model by its ability to resolve the small scale flow structures of the bora wind and by its better agreement with observed wind velocity statistics the ocean simulation forced by the 4 km resolution model is distinguished from the one forced by the 36 km resolution model by its ability to reproduce the expected double gyre circulation in the northern adriatic and by its ability to better capture the magnitude and shape of the observed depth dependent velocity correlation with wind at the deeper site though the 36 km forced ocean model agrees better with many observed velocity statistics the 4 km forced ocean model produces the highest correlations with observations exceeding 0 78 at subsurface depths that are most strongly correlated with winds

modeling dynamic rupture in a 3d earthquake fault model we propose a fourth order staggered grid finite difference method to study dynamic faulting in three dimensions the method uses an implementation of the boundary conditions on the fault that allows the use of general friction models including slip weakening and rate dependence because the staggered grid method defines stresses and particle velocities at different grid points we preserve symmetry by implementing a two grid row thick fault zone slip is computed between points located at the borders of the fault zone while the two components of shear traction on the fault are forced to be symmetric inside the fault zone we study the properties of the numerical method comparing our simulations with well known properties of seismic ruptures in 3d among the properties that are well modeled by our method are full elastic wave interactions frictional instability rupture initiation from a finite initial patch spontaneous rupture growth at subsonic and supersonic speeds as well as healing by either stopping phases or rate dependent friction we use this method for simulating spontaneous rupture propagation along an arbitrarily loaded planar fault starting from a localized asperity on circular and rectangular faults the shape of the rupture front is close to elliptical and is systematically elongated in the in plane direction of traction drop this elongation is due to the presence of a strong shear stress peak that moves ahead of the rupture in the in plane direction at high initial stresses the rupture front becomes unstable and jumps to super shear speeds in the direction of in plane shear another interesting effect is the development of relatively narrow rupture fronts due to the presence of rate weakening friction the solutions for the thick fault boundary conditions scale with the slip weakening distance do and are stable and reproducible for do greater than about 4 in terms of 2t t ax finally a comparison of scalar and vector boundary conditions for the friction shows that slip is dominant along the direction of the prestress with the largest deviations in slip rate direction occurring near the rupture front and the edges of the fault

simulation of the northern adriatic circulation during winter 2003 1 numerical simulations of the adriatic sea were conducted with the navy coastal ocean model during the adriatic circulation experiment in the fall and winter of 2002 2003 and results were compared with observations the ocean model used a 1 km resolution grid over the entire adriatic sea model forcing included atmospheric fluxes from the coupled ocean atmosphere mesoscale prediction system coamps tides boundary conditions from a global model and freshwater river and runoff inflows model tidal elevation showed good agreement with international hydrographic organization station data and model tidal currents showed good agreement with tidal currents determined from acoustic doppler current profiler adcp measurements detided model currents showed good agreement with adcp currents with rms errors along the principal variance axes ranging from 6 to 12 9 cm s and correlations ranging from 0 16 to 0 81 correlations between model and adcp currents along the minor variance axes were generally low comparison of the model simulated temperature and salinity profiles during january and february with conductivity temperature depth measurements indicated that the model captured some of the spatial structure of the observed fields the model response to several bora wind events in january and february showed a recurring pattern of cyclonic and anticyclonic gyres that generally agreed with observations and reflected the pattern of wind stress curl from the coamps wind stress forcing during strong bora forcing two large cyclonic circulation gyres form in the northern adriatic with a smaller anticyclonic circulation between them near the istrian peninsula additionally a couple of large meanders frequently occur within the eastern adriatic current southeast of kvarner bay and these meanders sometimes close to form small gyres

hydraulic fracturing controlled dynamics of microseismic clouds 1 several dynamic processes related to propagation of hydraulic fracture modify the stress state in rocks and therefore they are relevant for triggering of microseismicity for instance these are the creation of a new fracture volume fracturing fluid loss and its infiltration into reservoir rocks as well as diffusion of the injection pressure into the pore space of surrounding rocks and inside the fracture using real data we show that some of these processes can be seen from features of spatio temporal distributions of the induced microseismicity especially the initial stage of fracture volume opening as well as the back front of the induced seismicity starting to propagate after termination of the fluid injection can be well identified and used for reservoir engineering

extreme cooling and dense water formation estimates in open and coastal regions of the adriatic sea during the winter of 2012 generation of dense waters in the adriatic sea during an extreme cooling event in the winter of 2012 including its preconditioning and spreading phases have been investigated using the one way coupled roms and the aladin hr modeling system both climatological and real river fluxes are used in the simulations aside from the convenient dense water formation areas located at the northernmost adriatic shelf we found that a similar amount of dense water with slightly lower density was formed in the eastern and deeper adriatic coastal area which was subjected to extreme heat losses up to 2000 w m2 during peak cooling periods this part of the adriatic has been known for extreme cooling during wintertime bora outbreaks nevertheless no ocean model study has previously reproduced dense water formation in this area the most likely reason for that was an overestimate of river discharges introduced to ocean models from newly available data we estimated that the contribution of eastern adriatic rivers between the neretva river and rijeka bay is more than six times lower than what has been previously documented transport of dense water toward the middle adriatic had a peak value of about 0 6 sv while the speed of initial bottom density current surpassed 40 50 cm s which is several times faster than past events different pathways of the dense water toward the middle and south adriatic depressions have also been documented the contribution of the eastern coastal adriatic area to the overall north adriatic dense water formation has been quantified and discussed for average and low freshwater load conditions indicating that this part of the adriatic is a common place for dense water generation

long period long duration seismic events during hydraulic stimulation of shale and tight gas reservoirs part 1 waveform characteristics abstractlong period long duration lpld seismic events are relatively low amplitude signals that have been observed during hydraulic fracturing in several shale gas and tight gas reservoirs these events are similar in appearance to tectonic tremor sequences observed in subduction zones and transform fault boundaries lpld events are predominantly composed of s waves but weaker p waves have also been identified in some cases microearthquakes are observed during the events based on the similarity with tectonic tremors and our observations of several impulsive s wave arrivals within the lpld events we interpret the lpld events as resulting from the superposition of slow shear slip events on relatively large faults most large lpld waveforms appear to start as a relatively slower low amplitude precursor lacking clear impulsive arrivals we estimate the energy carried by the larger lpld events to be 1000 times greater than a mw 2 microseismic event that is typical of the events that occur during hyd

stress estimated using microseismic clusters and its relationship to the fracture system of the hijiori hot dry rock reservoir a method for estimating the in situ stress state by analyzing microseismic clusters induced by hydraulic injections is proposed the method is based on focal mechanism analysis supplemented with microseismic doublet analysis the latter is used to discriminate between the fault plane and the auxiliary planes of the focal mechanism solution the method was applied to estimate the stress field within the hijiori hot dry rock geothermal reservoir and yielded results which were consistent with other estimates the mechanics of permeability creation within the reservoir during major hydraulic injections was then examined by evaluating the interaction of the inferred stress field with the natural fracture system the characteristics of the latter were determined by integrating information obtained from core samples acoustic borehole televiewer images and pressure temperature and spinner logs the results indicated that the observed microseismicity and orientation dependent permeability characteristics of the fracture population are well explained by shear failure inferred from coulomb s friction theory it is also shown that the growth direction of the reservoir is strongly controlled by the distribution of favorably oriented pre existing fractures and their interaction with the stress field

adcp observations of the western adriatic slope current during winter of 2001 abstract data from an acoustic doppler current profiler adcp mooring maintained during the winter of 2001 in 57 m of water near senigallia italy are used to describe the winter conditions of the western adriatic current in the northern adriatic sea wind and water temperature measurements from the acqua alta tower in 19 m water depth off venice and winds from a 4 km resolution reanalysis model coamps are used to interpret the adcp data especially with respect to currents generated by bora winds at the adcp site mean depth average current for the winter deployment period was 10 4 cm s toward 140 roughly aligned with local bathymetric contours both mean currents and fluctuations about the means were highly barotropic during the winter southeastward along shore mean currents increased slightly 1 8 cm s with depth between 7 and 47 m following a nearly linear trend offshore cross slope mean currents only increased 2 0 cm s deep in the water column between 35 and 51 m current variability was dominated by four bursts of currents in which flow toward the southeast greatly increased these bursts followed bora winds the timing of which was identified by measured winds at the acqua alta tower depth averaged de tided currents exceeded 30 cm s during all four events and reached 45 cm s during one event correlations between these along shore currents and simulated wind stress from the coamps model were calculated over the whole north adriatic the cross covariance between currents and wind stress had a spatial pattern similar to the bora wind itself reaching maxima along the northern adriatic coast off the southern tip of istria and near ilovik island 14 5 n 44 4 e wind stress in these regions had stronger correlation with currents at the mooring than did wind stress anywhere near the mooring bottom water at the mooring was too warm for it to have been north adriatic dense water except perhaps for a brief pulse of cold water associated with the third current burst on april 1st

the oceanographic tower acqua alta activity and prediction of sea states at venice abstract the oceanographic tower acqua alta was constructed in early 1970 in the adriatic sea some 20 km from venice the main objective was to obtain information about the meteomarine conditions off the venice lagoon where the old town is threatened by ever more severe floodings the paper describes the tower and its instrumentation and summarizes the experience and results of activities relevant to coastal engineering this encompasses modelling of wind field storm surge and wind generated waves various types of models have been applied to and validated for the adriatic sea and in particular for the coastline of the venice lagoon this includes application of long term statistics of extreme wave heights specific studies of the influence of bottom friction and wind gustiness on waves are presented as well as measurements of kinematics of wind generated waves further a short discussion of white capping is included finally some information about the management of the tower is given

reservoir characterization using oil production induced microseismicity clinton county kentucky abstract microseismic monitoring tests were conducted from 1993 to 1995 in the seventy six oil field clinton county kentucky oil is produced from low porosity fractured carbonate rocks at 3 no injection operations were conducted gross changes in production rate correlate with event rate event rate lags changes in production rate by 2 to 3 weeks hypocenters and first motion data have revealed previously undetected low angle thrust faults above and below the currently drained depth intervals production history well logs and drill tests indicate that the seismically active faults or fractures are previously drained intervals that have subsequently recovered to hydrostatic pressure via brine invasion storage capacity computed for one of these drained fractures implies that total oil production represents about 20 of total pore volume correlation of older production intervals and well log porosity anomalies with the seismically active faults indicate that the oil reservoir in the study area is primarily a set of compartmentalized low angle thrust faults although low angle fracture sets have not previously been considered in the exploration and development of the area the mapped thrust faults are consistent with other investigators interpretations of oil associated with secondary fracture sets occurring along deeper seated wrench fault structures stress determined from composite focal mechanisms indicates a near surface

the adriatic sea general circulation part ii baroclinic circulation structure abstract in the second part of the paper dedicated to the adriatic sea general circulation the horizontal structure of the hydrographic parameters and dissolved oxygen fields is described on a seasonal timescale maps of temperature and salinity climatological fields reveal the enhanced seasonal variability of the adriatic sea which at the surface is associated with the major dilution effects of river runoff the density and derived dynamic height fields show for the first time the baroclinic geostrophic structure of the general circulation winter is dominated by compensation effects between temperature and salinity fronts along the western coastline the resulting baroclinic circulation is weak and suggests the presence of barotropic current components not accessible by the dataset spring and summer seasons have the smallest spatial scales in the temperature and salinity fields and stronger subbasin scale gyres and current systems which have been classified in a schematic representation of the circu

impact of the spatial distribution of the atmospheric forcing on water mass formation in the mediterranean sea the impact of the atmospheric forcing on the winter ocean convection in the mediterranean sea was studied with a high resolution ocean general circulation model the major areas of focus are the levantine basin the aegean cretan sea the adriatic sea and the gulf of lion two companion simulations differing by the horizontal resolution of the atmospheric forcing were compared the first simulation med16 era40 was forced by air sea fields from era40 which is the ecmwf reanalysis the second simulation med16 ecmwf was forced by the ecmwf analyzed surface fields that have a horizontal resolution twice as high as those of era40 the analysis of the standard deviations of the atmospheric fields shows that increasing the resolution of the atmospheric forcing leads in all regions to a better channeling of the winds by mountains and to the generation of atmospheric mesoscale patterns comparing the companion ocean simulation results with available observations in the adriatic sea and in the gulf of lion shows that med16 ecmwf is more realistic than med16 era40 in the eastern mediterranean although deep water formation occurs in the two experiments the depth reached by the convection is deeper in med16 ecmwf in the gulf of lion deep water formation occurs only in med16 ecmwf this larger sensitivity of the western mediterranean convection to the forcing resolution is investigated by running a set of sensitivity experiments to analyze the impact of different time space resolutions of the forcing on the intense winter convection event in winter 1998 1999 the sensitivity to the forcing appears to be mainly related to the effect of wind channeling by the land orography which can only be reproduced in atmospheric models of sufficient resolution thus well positioned patterns of enhanced wind stress and ocean surface heat loss are able to maintain a vigorous gyre circulation favoring efficient preconditioning of the area at the beginning of winter and to drive realistic buoyancy loss and mixing responsible for strong convection at the end of winter