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Book, Jeffrey W.
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- PublicationOpen AccessSueper-Ensemble techniques: application to surface drift prediction during the DART06 and MREA07 campaigns(2009-11)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Vanderbulcke, L.; GeoHydrodynamics and Environmental Research, University of Liege, Belgium ;Beckers, J.-M.; GeoHydrodynamics and Environmental Research, University of Liege, Belgium ;Lenartz, F.; GeoHydrodynamics and Environmental Research, University of Liege, Belgium ;Barth, A.; GeoHydrodynamics and Environmental Research, University of Liege, Belgium ;Poulain, P.-M.; stituto Nazionale di Oceanografia Sperimentale (OGS), Trieste, Italy ;Aidonindis, M.; ServiceIdrographique et Oceanographique de la marine, 13 rue du Chatelier, 29200 Brest, France ;Meyrat, J.; ServiceIdrographique et Oceanographique de la marine, 13 rue du Chatelier, 29200 Brest, France ;Ardhuin, F.; ServiceIdrographique et Oceanographique de la marine, 13 rue du Chatelier, 29200 Brest, France ;Fratianni, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Tonani, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Torrisi, L.; Servizio Meteorologico (Aeronautica Militare), Italy ;Pasquini, S.; Servizio Meteorologico (Aeronautica Militare), Italy ;Chiggiato, J.; ARPA Emilia Romagna, Servizio Idro Meteorologico, Bologna ;Tudor, M.; DHMZ Meteorological and Hydrological Service, Zagreb, Croatia ;Book, J.; US Naval Research Lab., 4555 Overlook Ave, SW, Washington, DC 20375 ;Martin, P.; US Naval Research Lab., 4555 Overlook Ave, SW, Washington, DC 20375 ;Allard, R.; US Naval Research Lab., 4555 Overlook Ave, SW, Washington, DC 20375 ;Peggion, G.; US Naval Research Lab., 4555 Overlook Ave, SW, Washington, DC 20375 ;Rixen, M.; NATO/SACLANT Undersea Research Centre, La Spezia, Italy; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The prediction of the drift of floating objects is an important task, with applications such as marine transport, pollutant dispersion, and search-and-rescue activities. But forecasting surface drift is also very challenging, because it depends in a complex way on various interacting factors such as the wind, the ocean surface current, and the wave field. Furthermore, although each of the cited factors can be fore- casted by deterministic models, the latter all suffer from limitations, resulting in imperfect predictions. In the present study, we try and predict the drift of buoys launched during the DART06 (Dynamics of the Adriatic sea in Real-Time 2006) and MREA07 (Maritime Rapid Environmental Assessment 2007) sea trials, using the so-called hyper-ensemble technique: different models are combined in order to minimize departure from independent observations during a training period; the ob- tained combination is then used in forecasting mode. We review and try out different hyper-ensemble techniques, going from simple ensemble mean to techniques based on data assimilation, which dynamically update the model’s weights in the combi- nation when new observations become available. We show that the latter methods alleviate the need of fixing the training length a priori, as older information is au- tomatically discarded, and hence they lead to better results. Moreover, they allow to determine a characteristic time during which the model weights are more or less stable, which allows to predict how long the obtained combination will be valid in forecasting mode.282 253 - PublicationOpen AccessTurbulence variability in the upper layers of the Southern Adriatic Sea under a variety of atmospheric forcing conditions(2012-02)
; ; ; ; ; ;Carniel, Sandro; CNR-ISMAR ;Kantha, L.H.; Univ. of Colorado ;Book, J.W.; NRL Stennis, USA ;Prandks, H.; ISW Germany ;Sclavo, Mauro; CNR-ISMAR; ; ; ; As part of the DART06B observational campaign in late August 2006, a microstructure profiler was deployed to make turbulence measurements in the upper layers of the Southern Adriatic Sea. Of the nearly 300 total casts, 163 were made near Station B90, where various moorings were deployed in the 90 m deep water column to measure water column properties and meteorological and surface wave conditions. We were able to measure turbulence properties in the upper layers under a variety of atmospheric forcing conditions that included strong wind forcing, night-time convection, mixed convection and wind forcing, weak wind forcing and strong insolation. The resulting dataset provides a kaleidoscope of turbulence properties and turbulent mixing above, below and in the strong pycnocline present at a depth of 15 to 25 m in the coastal waters of the Southern Adriatic Sea during late summer. A slightly modified scaling of the dissipation rate of turbulence kinetic energy in the mixed layer (ML), based on the observed friction velocity u* and the surface buoyancy flux Jb0, reproduces the measured values reasonably well. In the interior, below the ML, the dissipation rate scales like , where LT is the Thorpe scale and N is the buoyancy frequency. Analysis of velocity and density profile measurements from Station B90 and the nearby station B75 suggest that anticyclonic eddies and near-inertial waves can interact in these coastal waters to produce significant horizontal advective density fluxes in the pycnocline.287 219 - PublicationRestrictedImproved ocean prediction skill and reduced uncertainty in the coastal region from multi-model super-ensembles(2009)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ;The use of Multi-model Super-Ensembles (SE) which optimally combine different models, has been shown to significantly improve atmospheric weather and climate predictions. In the highly dynamic coastal ocean, the presence of small-scales processes, the lack of real-time data, and the limited skill of operational models at the meso-scale have so far limited the application of SE methods. Here, we report results from state-of-the-art super-ensemble techniques in which SEPTR (a trawl-resistant bottom mounted instrument platform transmitting data in near real-time) temperature profile data are combined with outputs from eight ocean models run in a coastal area during the Dynamics of the Adriatic in Real-Time (DART) experiment in 2006. New Kalman filter and particle filter based SE methods, which allow for dynamic evolution of weights and associated uncertainty, are compared to standard SE techniques and numerical models. Results show that dynamic SE are able to significantly improve prediction skill. In particular, the particle filter SE copes with non-Gaussian error statistics and provides robust and reduced uncertainty estimates.61 1 - PublicationRestrictedTracking bottom waters in the Southern Adriatic Sea applying seismic oceanography techniques(2012)
; ; ; ; ; ;Carniel, S.; CNR-ISMAR ;Bergamasco, A.; CNR-ISMAR ;Book, J. W.; NRL ;Hobbs, R. W.; Univ. of Durham ;Sclavo, M.; CNR-ISMAR; ; ; ; We present the first results from the Seismic Oceanography (SO) cruise ADRIASEISMIC where we successfully imaged thermohaline fine structures in the shallow water environment (50-150 m) of the southern Adriatic Sea during March 2009 using a compact two GI-gun seismic source. The SO observations are complemented with traditional oceanographic and micro-structure measurements and show that SO can operate over almost the entire water column except (in our experimental layout) for the uppermost 50 m. After processing to enhance the signal-to-noise ratio, the seismic reflection data have a vertical resolution of ~10 m and a horizontal resolution of ~100 m and provide a laterally continuous map of significant thermohaline boundaries that cannot be achieved with conventional physical oceanography measurements alone. ADRIASEISMIC specifically targeted structures in shallow waters, namely along the western margin of the southern Adriatic Sea, between the Gargano peninsula and the Bari canyon, and imaged the Northern Adriatic Dense Water (NAdDW), a bounded cold and relatively dense water mass flowing from the northern Adriatic Sea. The seismic data acquired in Bari canyon and offshore of the Gargano promontory show many regions of strongly reflecting shallow structures, and the incorporation of XBTs measurements with these data demonstrate that they can be interpreted in terms of temperature structures and gradients. In the Gargano region several warm water intrusive structures are mapped along with the offshore transitional edge of cold waters of strong NAdDW influence. In Bari Canyon, waters with NAdDW influence are further mapped extending over the shelf and off the slope into a 5 km long tongue extending offshore between depths of 200-300 m. More generally, even though neither cascading nor open-ocean deep convection process appeared to be evident during March 2009, the SO approach was able to map details of thermal features not resolved by even closely spaced XBT measurements.305 56