High-frequency atmospherically-induced oscillations in the middle Adriatic coastal area

Temporal and spatial characteristics of the resonant coupling between travelling air pressure disturbances and the middle Adriatic coastal waters are examined using a barotropic numerical model for a one year period (July 2000–July 2001). The model is forced by the travelling air pressure disturbances reconstructed from the 2-min resolution air pressure series measured at Split. Six experiments for the studied period are performed, in order to analyse the influence of the speed and disturbance direction on the resonant coupling. The first group of three experiments uses variable disturbance direction, whereas in the second three, a constant direction is employed during the whole experiment. Disturbance direction for the first group of experiments is computed from the 500-mb geopotential data provided by European Center for Medium Range Weather Forecast (ECMWF), as it is found that all of the past extreme events are correlated with them. Each experiment, with variable and constant disturbance direction, is repeated with three different constant values of 10, 20 and 30 m/s for the disturbance speed. The model verification on the Split sea level data reveals that the model reproduces most of the events but also overestimates/underestimates some of them and creates some false events due to the rigid assumption of a constant disturbance speed. The best agreement with data is obtained in the model runs assuming a disturbance speed of 20 m/s. A number of trapped and edge waves have been modelled at the constrictions and along the coast, in particular on a shoal that lies off Split perpendicular to the channel axis. The importance of the disturbance direction to the energy content is highlighted, particularly close to the shore, where the difference may be significant at 2–3 times on average, up to 30 cm in maximum amplitude

Effects of age on onset time and duration of sensory blockade in ultrasound guided supraclavicular block Abstract

Background and purpose: Involutive changes of brachial plexus occur with aging. The aim of this study was to determine if these changes would effect onset time and duration of sensory blockade in all four distal nerves of brachial plexus in middle aged (65 years). Materials and methods: Middle aged (N=22) and elderly patients (N=22) undergoing upper limb surgery received an ultrasound guided supraclavicular block with a mixture of local anesthetics (50 : 50, 0.5% levobupivacaine, 2% lidocaine). The prospective, observer-blinded study method is a previously validated step-up/step-down sequential model where the local anesthetic volume for each following patient is determined by the outcome of the previous block. The starting volume was 30 ml. Only the blocks with complete sensory blockade in all four regions of distal nerves were analyzed for the onset time and duration of sensory blockade. Results and conclusions: The mean (SD) block onset time was 25.8±0.6 min and the mean (SD) block duration was 151.5±8.9 min in the entire middle aged group. In the entire elderly group, the mean (SD) block onset time was 21±0.82 min and the mean (SD) block duration was 195.75±14.99 min. The difference in both, onset time and duration was significant (P=0.0002, 95%CI 3.352–6.248; P=0.0023, 95% CI 65.63–22.95, respectively). In conclusion, local anesthetics have a faster onset time and longer duration of sensory blockade in elderly due to alterations of peripheral nerves and increased sensitivity to local anesthetics

Ugniježđeno modeliranje istočno-jadranskih obalnih voda

The middle Adriatic coastal area was numerically modeled with a 1 km resolution in order to simulate temperature, salinity and currents. The model employed was a modification of the Princeton Ocean Model (POM), forced with surface momentum, heat and water fluxes and discharges from four rivers: Jadro, Žrnovnica, Cetina and Neretva. The coastal model was nested into the whole-Adriatic model having a 5 km resolution, using a simple off-line one-way nesting technique. Results of a three-year long experiment with perpetual atmospheric and river forcing were characterized by a strong annual signal, in reasonable agreement with temperature and salinity data taken at permanent oceanographic stations along the Split-Gargano transect. Current reversal obtained between the islands of Hvar and Vis in summer also agreed with previous measurements. The simulation also revealed the way Dalmatian islands – in particular Lastovo and Vis – influence the East Adriatic Current prevailing in winter, with wakes being formed behind the islands and jets among them. Comparison of an interannual simulation with corresponding measurements showed good agreement for temperature, whereas a discrepancy in salinity was related to the model being forced with climatological water fluxes. Experimental forecasts, produced over a six-month period, enabled some experience to be gained in operational oceanography, but also pointed to an additional problem – the model overmixing when the wind forcing is pronounced. Moreover, low spatial resolution of atmospheric forcing was suspected of reducing the quality of current forecasts for some wind directions.Obalno područje srednjeg Jadrana numerički je modelirano s rezolucijom od 1 km radi simuliranja temperature, saliniteta i struja. Upotrijebljeni model predstavljao je modifikaciju Princetonskog Oceanskog Modela (POM), kontroliranog površinskom izmjenom impulsa, topline i vlage te dotokom četiri rijeke: Jadra, Žrnovnice, Cetine i Neretve. Model obalnog područja povezan je s jadranskim modelom rezolucije 5 km, upotrebom jednostavnog načina gniježđenja. Rezultate trogodišnjeg eksperimenta izvedenog uz ponavljajuće atmosfersko i riječno djelovanje obilježio je jak godišnji signal, u prilično dobrom suglasju s temperaturnim i salinitetnim podacima prikupljenima na stalnim oceanografskim postajama uzduž profila Split-Gargano. Obrat struja dobiven u području između Hvara i Visa tijekom ljeta također je prethodno dokumentiran mjerenjima. Simulacija je uz to pokazala da dalmatinski otoci – napose Lastovo i Vis – utječu na istočno-jadransku struju zimi, dovodeći do pojave brazda iza otoka i mlazeva među njima. Usporedba rezultata simulacije višegodišnje promjenjivosti s odgovarajućim podacima ukazala je na dobro slaganje temperature, dok je relativno veliko odstupanje saliniteta bilo uzrokovano klimatološkim protocima vlage koji su nametnuti modelu. Eksperimen-talne prognoze, izdavane za razdoblje od šest mjeseci, omogućile su stjecanje iskustva u području operativne oceanografije, ali su upozorile i na jedan dodatni problem – pretjerano miješanje modelirano u situacijama u kojima je vjetar izražen. Osim toga, niska prostorna rezolucija upotrijebljenih atmosferskih polja po svoj je prilici nepovoljno utjecala na prognoze strujnog polja za neke smjerove vjetra

Bora-induced currents corresponding to different synoptic conditions above the Adriatic

International audienceThe Bora wind field is characterised by strong vorticity and divergence. Several numerical experiments, in which an oceanographic model was forced with northeasterly winds having climatological alongshore variability, were performed in order to study the influence of spatial variability in the bora wind field on the surface currents in the northern Adriatic. Numerical model results showed that during bora episodes with lower speeds and fast offshore decay surface currents along transect Rovinj - Po River are predominantly in the downwind direction. On the other hand, during bora episodes with strong intensity and slow offshore decay, a cyclonic gyre due to the pronounced bora alongshore variability is formed in the northernmost part of the Adriatic Sea and the studied transect is influenced by the counter currents. Moreover, bora having a high speed and a short offshore range produces the same effect in the eastern part of the Rovinj - Po River transect as low-speed bora characterised by slow offshore decay. Eulerian current measurements performed in the northern Adriatic during bora episodes characterised by different synoptic conditions supported the numerical model findings. Surface currents during the bora episode of 8-11 February 1984 were directed downwind, whereas during the episode of 12-19 February 1984 they were directed upwind. The first episode was characterised by a deep bora layer with cyclonic activity over the western Mediterranean and Genoa Bay, whereas the second one was accompanied by temperature inversion and a southwesterly tropospheric wind above a shallow bora layer. According to the hydraulic theory developed by Smith (1985), an observed descent of isentropes during the second bora episode led to the stronger acceleration in the bora layer and its larger offshore extent. Different offshore bora decays during studied events were confirmed by a comparison of the wind data originating from the meteorological stations positioned on the opposite Adriatic coasts

Protoci na granici atmosfera-more i termohalina promjenjivost ADRICOSM poligona Pelješac-Vis-Drvenik

Thermohaline properties in the east Adriatic coastal area were measured bi-weekly during the cold season of 2002/2003 and weekly in the warm season of 2003 at 14 stations. The collected data set has space and time coverage suitable for comparison with general thermohaline climatology of the region. Temporal salinity changes registered during the experiment show strong departures from the typical annual cycle in which salinity follows average surface water flux variability. Throughout the experiment, high salinity values were measured as a consequence of prolonged bora events in the cold period, and unusual spring-summer atmospheric conditions. Due to the anomalously long and strong heating season, corresponding surface temperatures were also higher than the long-term averages. Surface heat and water fluxes were calculated for the research period, and were compared with climatological values originating from meteorological stations in the ADRICOSM polygon.Tijekom razdoblja listopad 2002. – rujan 2003. u području istočne obale Jadranskog mora, unutar poligona Pelješac-Vis-Drvenik, kao dio projekta ADRICOSM (Integrirano upravljajnje obalnom zonom Jadranskoga mora), obavljena su vrlo intenzivna mjerenja termohalinih osobina vodenog stupca na 14 postaja. Tijekom zimskog razdoblja mjerilo se jednom u dva tjedna, a kasnije jednom tjedno. Dobra prostorno-vremenska pokrivenost podacima omogućila je usporedbu s klimatološkim vrijednostima. Pokazano je kako su promjene saliniteta u ovom razdoblju znatno odstupale od prosjeka. Tijekom istraživanja uočen je iznadprosječno visoki salinitet koji je bio posljedica jakih i dugotrajnih epizoda bure u hladnom dijelu godine te neuobičajenih atmosferskih uvjeta tijekom razdoblja proljeće-ljeto 2003. Kao posljedica neuobičajeno duge i intenzivne sezone grijanja temperatura mora također je bila iznadprosječna. Procesi na granici atmosfera-more također su pokazali znatna odstupanja od klimatoloških vrijednosti

Numerička analiza cirkulacije u sjevernom Jadranu za vrijeme dvije uzastopne epizode bure

The north Adriatic circulation during two successive bora episodes was studied using single point current measurements and results of the Princeton Ocean Model (POM). Surface currents recorded at the gas field Ivana positioned in the central part of the northern Adriatic were directed downwind during the bora episode of 8-11 February 1984, whereas during the next bora period of 12-16 February 1984 they were directed upwind. The observed current reversal was reproduced in the numerical experiment controlled by air-sea fluxes and river inflows. Atmospheric forcing for the POM model was estimated from high resolution Mesoscale Model 5 (MM5) surface fields, while river discharges were introduced in the simulations as source terms of zero salinity in the continuity equation. The baseline experiment with realistic forcings, atmospheric and riverine, related the current reversal to displacements of the bora induced gyres. Sensitivity studies revealed a dominant role of the wind stress curl for the vorticity in the current field and showed the relevance of the changing wind divergence for the cross-shore circulation variability and accompanied current reversal. Additional numerical experiments emphasized even more the role of the spatial wind variability for the recorded flow and also stressed the importance of the model domain size for the numerical results.Površinsko strujanje u sjevernom Jadranu za vrijeme trajanja dvije uzastopne epizode bure analizirano je na temelju strujomjernih podatka i rezultata numeričkog modela Princeton Ocean Model (POM). Površinske struje zabilježene na plinskom polju Ivana smještenom u centralnom dijelu sjevernog Jadrana bile su u smjeru vjetra za vrijeme prve epizode bure od 8. do 11. veljače 1984., dok su za vrijeme slijedeće epizode bure od 12. do 16. veljače bile suprotnog smjera od vjetra. Zabilježeni obrat struje reproduciran je u numeričkom eksperimentu u kojem je oceanografski model kontroliran površinskom napetošću vjetra, protocima topline i riječnim dotocima. Atmosfersko prisilno djelovanje za POM model izračunato je na temelju prizemnih polja iz meteorološkog mod- ela Mesoscale Model 5 (MM5), dok je djelovanje sjevernojadranskih rijeka uvedeno u numeričke eksperimente kao izvor slatke vode u jednadžbi kontinuiteta. Rezultati osnovnog eksperimenta s realističnim prisilnim djelovanjima, atmosferskim i riječnim, povezali su obrat površinske struje naplinskom polju Ivana s pomacima burom induciranih vrtloga. Analize osjetljivosti numeričkih rezul -tata ukazale su na dominantnu ulogu rotora vjetra za vrtložnost u strujnom polju, dok je promjenjiva divergencija u polju vjetra utjecala na varijabilnost struja u smjeru okomitom na obalu te tako dovela do obrata površinske cirkulacije na poziciji plinskog polja Ivana. Dodatni numerički eksperimenti još su više naglasili važnost prostorne varijabilnosti vjetra za zabilježeni obrat struje, a također su pokazali i važnost veličine modelske domene za dobivene rezultate