1,720,986 research outputs found
FOAM EFFECTS ON ALTIMETER RESPONSE
No full textThe effects of whitecaps foam on the backscattering of
radio waves were taken into consideration as early as
1983 in [1] and [2]. It is well known that foam and
spray play an essential role in determining the
dependence of altimeter wind response, especially for
very high wind velocities; little effort however has been
devoted so far to consider the effect of spatial foam
distribution over the sea surface on the shape of the
backscattered electromagnetic impulse and therefore on
the measurement of Significant Wave Height and on the
E/M bias of the Sea Surface Level. This work presents
some results obtained by implementing a dynamic
distribution algorithm for the whitecap formation and
foam movement on the waves together with an altimeter
simulation model
Wave hindcast resolution reliability for extreme analysis
No full textHere we analyze the wave hindcast reliability for a proper description of wave climate in the Mediterranean Sea. To this aim, 6-hourly 35-years ECMWF (European Center Medium Weather Forecast) wave data at 0.7° resolution grid are compared with those provided by means of a meteocean modelling chain operative at DICCA, University of Genoa (http://www.dicca.unige.it/meteocean/) covering a 34-years temporal span at an hourly frequency on a 0.1° resolution domain. Results reveal not negligible differences in evaluating significant wave heights at peaks; in particular the tendency to underrate values in storm sea conditions performed by ECMWF dataset is here evidenced. This behavior turns directly into not-reliable long-term return level estimates for extreme wave analysis, leading to a weak description of wave climate; conversely, a wave climate robust assessment is of primary importance for maritime design
WAVE FIELD ANALYSIS FROM SAR IMAGES OF ENCLOSED SEAS
No full textWhile Synthetic Aperture Radar (SAR) satellite wave data are routinely applied over the
oceans to extract spectral shapes, their application over enclosed seas is limited by their low
resolution. No spectral information can presently be gathered about wavelengths of less than
about 100 meters, thus limiting their usefulness to a restricted number of situations in
enclosed or semi-enclosed seas where fetch lengths are necessarily limited.
Yet another important SAR application, i.e. the study and the evaluation of bathymetry
effects, can be particularly difficult in enclosed seas because of the sharp variations of the sea
surface conditions due to winds and coastal topography that can be very hard to interpret.
The paper presents some examples of SAR data which highlight the possibility of
extracting useful information even in such difficult circumstances, as long as satellite images
are integrated with other data and with numerical wave simulation.
Two examples are given: the first provides wave field analysis during a heavy storm in
the Tyrrhenian sea during which two ESA ERS satellite passes are available; the second
example deals with a storm in the Persian Golf during which two passes at a day’s distance
(ERS–1 and ERS–2) clearly show shallow bottom effects
Wave hindcast resolution reliability for extreme analysis
No full textHere we analyze the wave hindcast reliability for a proper description of wave climate in the Mediterranean Sea. To this aim, 6-hourly 35-years ECMWF (European Center Medium Weather Forecast) wave data at 0.7° resolution grid are compared with those provided by means of a meteocean modelling chain operative at DICCA, University of Genoa (http://www.dicca.unige.it/meteocean/) covering a 34-years temporal span at an hourly frequency on a 0.1° resolution domain. Results reveal not negligible differences in evaluating significant wave heights at peaks; in particular the tendency to underrate values in storm sea conditions performed by ECMWF dataset is here evidenced. This behavior turns directly into not-reliable long-term return level estimates for extreme wave analysis, leading to a weak description of wave climate; conversely, a wave climate robust assessment is of primary importance for maritime design
A numerical method to analyze the interaction between sea waves and rubble mound emerged breakwaters
No full textThe paper provides some results of a new procedure, developed by MEDUS, to analyze the hydrodynamic aspects of the interactions between maritime emerged breakwaters and waves, by integrating CAD and CFD software.The filtration of the fluid within the interstices of a concrete blocks breakwater is evaluated by integrating the Reynolds Averaged Navier-Stokes equations (RANS) inside the voids rather than making use of the widespread “porous media” approach. The structure is thus modelled, very much like in the real world or in the physical laboratory testing, by overlapping individual three-dimensional elements (Armour in AccropodeTM, Core-locTM or Xbloc®, toe protection and filter layer in stones), and then the computational grid is fitted so as to provide enough computational nodes within the flow paths. This approach is meant to match closely the physical laboratory test procedure, and it is oriented at analyzing the hydrodynamic aspects of the phenomenon (overtopping, breaking, Run-up, reflection) as well as the stability of armour elements. Therefore, for the results' validation, the numerical Run-up and reflection effects on virtual breakwater were compared with some empirical formulas and some similar laboratory tests
On the effects of wave-induced drift and dispersion in the deepwater horizon oil spill
No full textThe objective of this work is to provide an indication of the effects of waveinduced movement of oil on the sea surface in connection with the Deepwater Horizon oil spill. By making use of modeled wave fields, satellite altimeter, and buoy data, mean trajectories and wave-induced oil spreading are computed for some of the storm events which took place during the accident. The effects of mean Stokes' drift are confirmed to be an important element in most situations, causing spill movements of 30 km and more in about 5 days. The diffusion due to random wave movement is also shown to be relevant at least for smaller spills; for large accidents, its effects are less important, but it still has an influence on some aspects of the oil spreading. © 2011 by the American Geophysical Union
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