10m wind buoy
120814759
Development and evaluation of a new regional coupled atmosphere ocean model in the North Sea and Baltic Sea
A new regional coupled model system for the North Sea and the Baltic Sea is developed, which is composed of the regional setup of ocean model NEMO, the Rossby Centre regional climate model RCA4, the sea ice model LIM3 and the river routing model CaMa Flood. The performance of this coupled model system is assessed using a simulation forced with ERA Interim reanalysis data at the lateral boundaries during the period 1979 2010. Compared to observations, this coupled model system can realistically simulate the present climate. Since the active coupling area covers the North Sea and Baltic Sea only, the impact of the ocean on the atmosphere over Europe is small. However, we found some local, statistically significant impacts on surface parameters like 2 m air temperature and sea surface temperature (SST) A precipitation SST correlation analysis indicates that both coupled and uncoupled models can reproduce the air sea relationship reasonably well. However, the coupled simulation gives slightly better correlations even when all seasons are taken into account. The seasonal correlation analysis shows that the air sea interaction has a strong seasonal dependence. Strongest discrepancies between the coupled and the uncoupled simulations occur during summer. Due to lack of air sea interaction, in the Baltic Sea in the uncoupled atmosphere standalone run the correlation between precipitation and SST is too small compared to observations, whereas the coupled run is more realistic. Further, the correlation analysis between heat flux components and SST tendency suggests that the coupled model has a stronger correlation. Our analyses show that this coupled model system is stable and suitable for different climate change studies.
Shiyu Wang Christian Dieterich Ralf Doscher Anders Hoglund Robinson Hordoir H E Markus Meier Patrick Samuelsson Semjon Schimanke
135344609
The Development and Proliferation of Summer Algal Blooms in the Oligo/Poly Haline Portion of the Chesapeake Bay Observational and Numerical Modeling Studies
Back River is located along the western shoreline of the upper Chesapeake Bay and is about 8 miles in length and 2 3 meters in average depth. Each summer, algal blooms with chlorophyll a concentration exceeding 100 mg/L are regularly observed in Back River. This excessive primary production, exhibited by the high chlorophyll a concentrations, is among the highest in the Chesapeake Bay and its tributaries. In order to explain the unusual phenomenon, a field survey was conducted in the low salinity water of Back River by Boynton and Ceballos (2014) which suggested that pH values exceeding 8.5 on average can trigger a release of phosphorus from the sediment. Based on the observation and related studies, a hypothesis was formulated that a pH mediated feedback mechanism may exist in this system by which elevated phytoplankton growth can enhance pH and the increased pH, in turn, can trigger a phosphorus release from the sediment in Back River where phosphorus is normally limited. A numerical modeling approach was used to verify the hypothesis. In this study, we developed a dynamic pH model with four state variables and coupled it into "integrated compartment model" (ICM) water quality model with 19 state variables. The coupled model is then set up in the upper Chesapeake Bay including Back River. The calibrated model gives reasonable results for hydrodynamics and water quality variables. For testing our hypothesis, we applied the pH model kinetics in Back River and compared with the scenario "with" and "without" it. The results show a positive feedback loop interacting among phytoplankton, total inorganic carbon, pH and phosphate, which verifies that the effect of pH on sediment phosphorus release is important to sustain the high phytoplankton biomass during summer.
Zhengui Wang
53943058
Measurement Characteristics of Near Surface Currents from Ultra Thin Drifters, Drogued Drifters, and HF Radar
Concurrent measurements by satellite tracked drifters of different hull and drogue configurations and coastal high frequency radar reveal substantial differences in estimates of the near surface velocity. These measurements are important for understanding and predicting material transport on the ocean surface as well as the vertical structure of the near surface currents. These near surface current observations were obtained during a field experiment in the northern Gulf of Mexico intended to test a new ultra thin drifter design. During the experiment, thirty small cylindrical drifters with 5 cm height, twenty eight similar drifters with 10 cm hull height, and fourteen drifters with 91 cm tall drogues centered at 100 cm depth were deployed within the footprint of coastal High Frequency (HF) radar. Comparison of collocated velocity measurements reveals systematic differences in surface velocity estimates obtained from the different measurement techniques, as well as provides information on properties of the drifter behavior and near surface shear. Results show that the HF radar velocity estimates had magnitudes significantly lower than the 5 cm and 10 cm drifter velocity of approximately 45% and 35% respectively. The HF radar velocity magnitudes were similar to the drogued drifter velocity. Analysis of wave directional spectra measurements reveals that surface Stokes drift accounts for much of the velocity difference between the drogued drifters and the thin surface drifters except during times of wave breaking.
Remote. Sens.
Steven L Morey Nicolas Wienders Dmitry S Dukhovskoy Mark A Bourassa
11298627
On Shipboard Marine X Band Radar Near Surface Current 'Calibration'
AbstractThe ocean wave signatures within conventional noncoherent marine X band radar (MR) image sequences can be used to derive near surface current information. On ships, an accurate near real time record of the near surface current could improve navigational safety. It could also advance understanding of air sea interaction processes. The standard shipboard MR near surface current estimates were found to have large errors (of the same order of magnitude as the signal) that are associated with ship speed and heading. For acoustic Doppler current profilers (ADCPs) ship heading errors are known to induce a spurious cross track current that is proportional to the ship speed and the sine of the error angle. Conventional mechanical gyrocompasses are very reliable heading sensors, but they are too inaccurate for shipboard ADCPs. Within the ADCP community, it is common practice to correct the gyrocompass measurements with the help of multiantenna carrier phase differential GPS systems. This study shows how a
Bjorn Lund Hans Graber Katrin Gisela Hessner Neil J Williams
56267055
Observations of the Transfer of Energy and Momentum to the Oceanic Surface Boundary Layer beneath Breaking Waves
AbstractMeasurements just beneath the ocean surface demonstrate that the primary mechanism by which energy from breaking waves is transmitted into the water column is through the work done by the covariance of turbulent pressure and velocity fluctuations. The convergence in the vertical transport of turbulent kinetic energy (TKE) balances the dissipation rate of TKE at first order and is nearly an order of magnitude greater than the sum of the integrated Eulerian and Stokes shear production. The measured TKE transport is consistent with a simple conceptual model that assumes roughly half of the surface flux of TKE by wave breaking is transmitted to depths greater than the significant wave height. During conditions when breaking waves are inferred, the direction of momentum flux is more aligned with the direction of wave propagation than with the wind direction. Both the energy and momentum fluxes occur at frequencies much lower than the wave band, consistent with the time scales associated with wave break.
M E Scully John H Trowbridge Alexander W Fisher
52088370
An Enhanced PIRATA Dataset for Tropical Atlantic Ocean Atmosphere Research
AbstractThe Prediction and Research Moored Array in the Tropical Atlantic (PIRATA) provides measurements of the upper ocean and near surface atmosphere at 18 locations. Time series from many moorings are nearly 20 years in length. However, instrumental biases, data dropouts, and the coarse vertical resolutions of the oceanic measurements complicate their use for research. Here an enhanced PIRATA dataset (ePIRATA) is presented for the 17 PIRATA moorings with record lengths of at least seven years. Data in ePIRATA are corrected for instrumental biases, temporal gaps are filled using supplementary datasets, and the subsurface temperature and salinity time series are mapped to a uniform 5 m vertical grid. All original PIRATA data that pass quality control and that do not require bias correction are retained without modification, and detailed error estimates are provided. The terms in the mixed layer heat and temperature budgets are calculated and included, with error bars. As an example of ePIRATA's applicati.
Gregory R Foltz C Schmid R Lumpkin
130167344
OBSERVATIONS OF INTERTIDAL BAR WELDING ALONG A HIGH ENERGY, DISSIPATIVE COASTLINE
Field observations during summer 2014 in Newport, OR, USA indicate the importance of intertidal sandbar welding for shoreline recovery and growth. Over a two month period of low energy wave conditions subtidal and intertidal sandbars migrated onshore by approximately 1 m/day. There was 19 m/m of sediment added to the system above mean low water and the shoreline prograded by an average of 17 m along the 2.2 km stretch of coast during the experiment.
Nicholas Cohn Dylan Anderson Peter Ruggiero
51833941
Wave Statistics for the Middle Adriatic Sea
The paper presents the methodology and results of the sea state statistics development for the middle Adriatic Sea. The study is based on the World Waves Atlas containing data of sea states in the Adriatic Sea calibrated using different satellite missions and numerical wave model simulations during the period of past 23 years. Wave scatter diagram and wave rose at the location in the middle Adriatic Sea are derived from the data. The 3 parametric Weibull distribution and the log normal distribution for significant wave height and peak spectral periods respectively, are fitted through the data in the World Waves Atlas. Based on available data, the relation between wind speed and wave height is established by regression analysis. Comparison of the relationship between the significant wave height and peak spectral period is performed between the data from the World Waves Atlas and the Tabain's wave spectrum, frequently used for sea states in the Adriatic Sea. Finally, the most probable extreme sea states for different return periods are calculated and results are compared with another relevant study for the long term prediction of sea states in the Adriatic Sea.
Andrea Farkas Josko Parunov Marko Katalinic
25506293
Effects of light polarization and waves slope statistics on the reflectance factor of the sea surface.
Above water radiometry depends on estimates of the reflectance factor r of the sea surface to compute the in situ water leaving radiance. The Monte Carlo code for ocean color simulations MOX is used in this study to analyze the effect of different environmental components on r values. A first aspect is examining the reflectance factor without and by accounting for the sky radiance polarization. The influence of the sea surface statistics at discrete grid points is then considered by presenting a new scheme to define the variance of the waves slope. Results at different sun elevations and sensor orientations indicate that the light polarization effect on r simulations reduces from ~17 to ~10% when the wind speed increases from 0 to 14m s 1. An opposite tendency characterizes the modeling of the sea surface slope variance, with r differences up to ~12% at a wind speed of 10m s 1. The joint effect of polarization and the the sea surface statistics displays a less systematic dependence on the wind speed, with differences in the range ~13 to ~18% The r changes due to the light polarization and the variance of the waves slope become more relevant at sky viewing geometries respectively lower and higher than 40deg with respect to the zenith. An overall compensation of positive and negative offsets due to light polarization is finally documented when considering different sun elevations. These results address additional investigations which, by combining the modeling and experimental components of marine optics, better evaluate specific measurement protocols for collecting above water radiometric data in the field.
Optics express
Davide D'Alimonte Tamito Kajiyama
122804332
A Horizon Tracking Method for Shipboard Video Stabilization and Rectification*
AbstractAn algorithm is presented for the stabilization and rectification of digital video from floating platforms. The method relies on a horizon tracking technique that was tested under a variety of lighting and sea state conditions for 48 h of video data over 12 days during a research cruise in the North Pacific Ocean. In this dataset, the horizon was correctly labeled in 92% of the frames in which it was present. The idealized camera model assumes pure pitch and roll motion, a flat sea surface, and an unobstructed horizon line. Pitch and roll are defined along the camera look direction rather than in traditional ship coordinates, such that the method can be used for any heading relative to the ship. The uncertainty in pitch and roll is estimated from the uncertainties of the horizon finding method. These errors are found to be of the order 0.6deg in roll and 0.3deg in pitch. Errors in rectification are shown to be dominated by the uncertainty in camera height, which may change with the heave motion of a f.
Michael Schwendeman Jim Thomson