Papers by Alastair Jenkins
Coastwatch: Integrating satellite SAR imagery in an operational system for monitoring coastal currents, wind, surfactants and oil spills
Elsevier eBooks, 2002
This paper describes the ongoing efforts at the Nansen Environmental and Remote Sensing Center (N... more This paper describes the ongoing efforts at the Nansen Environmental and Remote Sensing Center (NERSC) to integrate Synthetic Aperture Radar (SAR) imagery into an operational coastal monitoring system. The capabilities of the SAR to image ocean waves, internal waves, bathymetry, eddies, fronts, natural film, oil slicks and wind in the marine boundary layer, have previously been demonstrated. In order to
Zenodo (CERN European Organization for Nuclear Research), Apr 15, 1998
WP2 report Development of improved EO data products iii 5 Summary of results COASTMON ENV4-CT96-0... more WP2 report Development of improved EO data products iii 5 Summary of results COASTMON ENV4-CT96-0360 Metocean and coastal zone monitoring using satellite radar April WP2 report Development of improved EO data products iv References 76 COASTMON ENV4-CT96-0360 Metocean and coastal zone monitoring using satellite radar April 1999 WP2 report Development of improved EO data products 1 Executive summary The overall objective of COASTMON is to explore and test methods for use of synthetic aperture radar (SAR) and other new satellite data, and their integration with geographical information systems (GIS), in monitoring meteorological and oceanographic conditions in regions of heavy sea tra c, to improve navigational safety, to aid coastal zone management (CZM), and to improve utilization of satellite observations in the user community. The project consists of four major Work Packages: 1. Identi cation of gaps be t ween existing monitoring techniques for environmental conditions in coastal regions and requirements from the users. 2. Development of improved EO data products (wind, waves, currents, shallow water bathymetry, pollution, etc.) which include use of satellite data. 3. User demonstration in di erent test areas in Norway, Ireland and the Netherlands where satellite data will beobtained, analyzed and used together with other met-ocean data. 4. User assessment and recommendation for future use of satellite data in coastal regions. This report presents the results of the studies in WP2. The aim of the products is to provide useful information for many di erent users such as weather forecasting services, coastal and harbour authorities with responsibilities for ship tra c, coastal management, etc., po llution authorities, sheries and aquaculture, o shore industry, navy and coast guard, marine research and resources management, shipping and ferry companies, energy companies, coastal engineering rms, local government and planning authorities, leisure activities and education. The work focused on ve types of products: (1) high resolution wind elds from SAR, (2) spectral wave data from SAR, (3) wind and wave climatology from altimeter, (4) shallow water bathymetric charts, and (5) a group of SAR-derived products which map features such as currents, fronts and oil spills. In addition, the potential bene ts of synergetic use of EO techniques in the analysis of selected ocean parameters was investigated, such as sea surface height and circulation features. The main results of this Work Package are as follows: Develop and test an algorithm for deriving wind speed from SAR images were re ned and used in the project, and comparison with modelled wind elds. A new algorithm for deriving spectral wave data from SAR image spectra was developed, and adapted to work for SAR image mode data. Both this new algorithm as well as earlier algorithms were tested in Norwegian and Irish coastal areas and compared with buoy data. A planning tool for marine operators and emergency response units was augmented with monthly statistics of wind and waves, which were integrated with a GIS at ARGOSS. Data from this system (CLAMS) were also made available online, through the Internet. The GIS based Wave Atlas for Ireland was also further developed in the project, allowing comparison of wave height data obtained from a numerical model (WAM) and remote sensing data (altimeter). The Bathymetry Assessment System (BAS) was enhanced and integrated with the Cork GIS for demonstrations in Irish waters. The inclusion of auxiliary data from the GIS helped the BAS users determine suitable locations for applying the bathymetry algorithm. COASTMON ENV4-CT96-0360 Metocean and coastal zone monitoring using satellite radar April 1999 WP2 report Development of improved EO data products COASTMON ENV4-CT96-0360 Metocean and coastal zone monitoring using satellite radar April 1999 WP2 report Development of improved EO data products 3 COASTMON ENV4-CT96-0360 Metocean and coastal zone monitoring using satellite radar April 1999 WP2 report Development of improved EO data products 7 COASTMON ENV4-CT96-0360 Metocean and coastal zone monitoring using satellite radar
The rotation of the Earth and processes near the air-sea interface: Some aspects of the work of V. W. Ekman and its consequences. Paper submitted to Proceedings, Conference "Climate Change in High Latitudes", Bergen
The climatic conditions in the Arctic, and observations of the wind-induced drift of ice made in ... more The climatic conditions in the Arctic, and observations of the wind-induced drift of ice made in connexion with Nansen's "Fram" expedition, led to the discovery one hundred years ago, by Vilhelm Bjerknes' pupil, V. W. Ekman, of the importance of the Earth's rotation in limiting the depth of the wind-induced shear current in the ocean. This paper provides a review of the impact of some aspects of Ekman's theory and other work on climate-related processes in the Nordic Seas and at high latitudes elsewhere. Such aspects include the Ekman spiral - the helical rotation of the velocity vector, in atmospheric and oceanic boundary layers, and the resultant Ekman pumping: vertical motions in the water column associated with the divergence of the flow in the surface layer in the presence of a rotational wind stress field. These effects are important in the presence of sea ice, because of the great differences in drag coefficient between ice-covered and open-water are...
Nilsson et al. have recently shown how a velocity field in geostrophic and hydrostatic balance in... more Nilsson et al. have recently shown how a velocity field in geostrophic and hydrostatic balance in an f -plane may be diagnosed from prescribed distributions of buoyancy and wind stress, in a basin with closed isobaths. I extend their analysis to cover basins with more complex depth contours, treating in particular the behavior of the flow in the presence of a saddle point.
The Seventeenth International Offshore and Polar Engineering Conference, Jul 1, 2007
To estimate fluxes of momentum, heat and mass between the atmosphere and the ocean, one must meas... more To estimate fluxes of momentum, heat and mass between the atmosphere and the ocean, one must measure simultaneously the vertical component of the fluid velocity and variables representative of the concentration of the relevant quantity. Measurement platforms which move with the sea surface are often employed, which may lead to systematic biases in the flux estimates, proportional to the square of the wave height or measurement platform displacement amplitude. Such biases may be corrected for by using suitable modifications of the Reynolds eddy-covariance flux formulae. We give an example using a simple flow field over monochromatic waves and indicate how it may be extended for more complex situations.
The global climate system, the ecology of the biosphere, biogeochemical cycling, human society an... more The global climate system, the ecology of the biosphere, biogeochemical cycling, human society and macroeco-nomics are all very complex processes. The modelling and prediction of these systems is very resource-intensive and subject to considerable uncertainty, for two main rea-sons: (1) there are generally insufficent data available to estimate model parameters; (2) the model dynamics are often inherently unstable. Nevertheless, there are some general principles which may be used to constrain the behaviour of such com-plex systems. One such principle is based on the ideas of thermodynamics and statistical mechanics. An iso-lated system in thermodynamic equilibrium will tend to a state of maximum entropy, subject to constraints involving the total energy, chemical composition, etc. This is obviously not the case for the coupled climate-biogeochemical-economic system, which is very much in a non-equilibrium state. However, it has been shown that under certain circumstances, the most p...
L'utilisation d'un mod�le de pr�vision de vague pour forcer un mod�le de courant superficiel
Ocean Dyn, 1989
Connecting Physical-Biological Interactions to Recruitment Variability, Ecosystem Dynamics, and the Management of Exploited Stocks
ABSTRACT
The statistics of sea state duration (persistence) have been found to be dependent upon the recor... more The statistics of sea state duration (persistence) have been found to be dependent upon the recording interval \Delta t. Such behavior can be explained as a consequence of the fact that the graph of a time series of an environmental parameter such as the significant wave height has an irregular, "fractal" geometry. The mean duration, \bar\tau, can have a power-law
Boundary-Layer Meteorology, 2006
A non-local parameterisation of shear turbulence is proposed, which includes a dimensionless mult... more A non-local parameterisation of shear turbulence is proposed, which includes a dimensionless multiplicative constant as the sole tunable parameter. Analytical and numerical solutions in the case of plane Couette flow exhibit sheared velocity profiles with logarithmic behaviour near the boundaries, and the classical logarithmic flow profile is reproduced for a semi-infinite domain. We also prove that the families of analytical solutions obtained are locally unique: if the velocity is a strictly-increasing function of the distance from the boundary, a small perturbation of the velocity profile must be of the same functional form as the basic flow.
Extreme wave statistics from time-series data
Journal of Physical Oceanography, 2003
Surface wave equations appropriate to three-dimensional ocean models apparently have not been pre... more Surface wave equations appropriate to three-dimensional ocean models apparently have not been presented in the literature. It is the intent of this paper to correct that deficiency. Thus, expressions for vertically dependent radiation stresses and a definition of the Doppler velocity for a vertically dependent current field are obtained. Other quantities such as vertically dependent surface pressure forcing are derived for inclusion in the momentum and wave energy equations. The equations include terms that represent the production of turbulence energy by currents and waves. These results are a necessary precursor for three-dimensional ocean models that handle surface waves together with wind-and buoyancy-driven currents. Although the third dimension has been added here, the analysis is based on the assumption that the depth dependence of wave motions is provided by linear theory, an assumption that is the basis of much of the wave literature.
Quantitative Estimation of Upper Ocean Air-Sea Interaction Processes using Tandem (ERS-1/2 SAR) and Synergetic Instrument Combinations
8-Bits Data Storage Electronic System for Sea-surface Measurements
On the Occurrence of Surface Slicks in the Oceans
ABSTRACT
Intercomparison of SAR imaging models for upper ocean current boundaries
IGARSS '98. Sensing and Managing the Environment. 1998 IEEE International Geoscience and Remote Sensing. Symposium Proceedings. (Cat. No.98CH36174), 1998
ABSTRACT A review and intercomparison has been performed for numerical simulation models which ai... more ABSTRACT A review and intercomparison has been performed for numerical simulation models which aim to predict the SAR signatures of upper ocean current frontal features. The specific models whose performance is compared in detail are (i) The ERIM Ocean Model (EOM), developed by the Environmental Research Institute of Michigan and the Naval Research Laboratory, and (ii) the University of Hamburg Satellite Oceanography Group Composite Surface Model (UHSO). Both models compute the two-dimensional spectrum of surface waves, including their interaction with wind and the current field by means of an assumed relaxation to an equilibrium wind-wave spectrum. The EOM model computes the radar backscatter using tilted Bragg scattering plus specular reflection. The UHSO model does not account for specular reflection, but it includes the effect of hydrodynamic modulation of the Bragg waves by longer waves, which leads to an upwind/downwind asymmetry of the backscattered power. As a basis for the comparison, ocean current and meteorological observations from the COAST WATCH '95 experiment, conducted off the south-western coast of Norway, were used together with SAR data obtained under the ESA ERS-1/2 Tandem AO program
COAST WATCH -95: ERS-1I2 SAR Applications of Mesoscale Upper Ocean and Atmospheric Boundary Layer Processes off the Coast of Norway
The ERS SAR sensors have demonstrated their capability for imaging ocean waves, internal waves, u... more The ERS SAR sensors have demonstrated their capability for imaging ocean waves, internal waves, underwater topography, eddies, fronts, natural slicks, oil slicks, and atmospheric fea tures in the marine boundary layer such as wind. In order to quantify the mesoscale upper ocean and atmo spheric boundary layer processes, a tandem ERS-I/2 ESA AO experiment was carried out off the south-western coast of Nor way during the month of September 1995. A unique integrated data set was collected, including extensive SAR coverage in the ERS-l/2 tandem mode, an extensive set of oceanographic and meteorological variables from the RIV Hakon Mosby of the University of Bergen, metocean parameters from state-of-the art metocean buoys, and natural slick sampling with a radio controlled "mini research vessel ". Analysis from this very comprehensive integrated experi ment is reported, quantifying coastal jets, ocean fronts, natural slicks, wind velocity, wind fronts and rain showers fro...
Coastwatch: Integrating satellite SAR imagery in an operational system for monitoring coastal currents, wind, surfactants and oil spills
Elsevier Oceanography Series, 2002
This paper describes the ongoing efforts at the Nansen Environmental and Remote Sensing Center (N... more This paper describes the ongoing efforts at the Nansen Environmental and Remote Sensing Center (NERSC) to integrate Synthetic Aperture Radar (SAR) imagery into an operational coastal monitoring system. The capabilities of the SAR to image ocean waves, internal waves, bathymetry, eddies, fronts, natural film, oil slicks and wind in the marine boundary layer, have previously been demonstrated. In order to
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Papers by Alastair Jenkins