Statistical characteristics of Doppler velocity shift in artificial slick on sea surface

2019 ◽  
Author(s):  
Aleksey V. Ermoshkin ◽  
Aleksandr A. Molkov ◽  
Ivan A. Kapustin
Keyword(s):  
Sea Surface ◽  
Statistical Characteristics ◽  
Doppler Velocity ◽  
Velocity Shift

The distribution of sun glints sizes on the sea surface

2011 ◽  
Vol 3 (2) ◽  
Author(s):  
Rauf Gardashov
Keyword(s):  
Experimental Study ◽  
Spatial Resolution ◽  
Total Curvature ◽  
Digital Camera ◽  
Fortran Program ◽  
Theoretical Distribution ◽  
Sea Surface ◽  
Statistical Characteristics ◽  
Statistical Distributions ◽  
Natural Experiments

AbstractThe problem is studied both theoretically and experimentally. Statistical distributions of the total curvature and the reciprocal to the total curvature at the specular points (SP) of a random Gaussian uniform sea surface are discussed. The theoretical distribution and its asymptotes are completely investigated. The validity of the theoretical distribution is verified by numerical simulations and natural experiments. In the experimental study of this distribution, Sun glint images taken with a high time and spatial resolution digital camera are used. Those images are developed by using a specially-designed Fortran program which calculates the statistical characteristics of the glints. The experimentally derived distribution of the glint areas is compared with the theoretical distribution. The main causes (origins) of small divergence between the theoretical and experimental results are discussed.

scholarly journals VLT and E-ELT spectrographs & fundamental-constants

2009 ◽  
Vol 5 (H15) ◽  
pp. 326-326
Author(s):  
Paolo Molaro
Keyword(s):  
Fine Structure ◽  
Equivalence Principle ◽  
Structure Constant ◽  
Rate Of Change ◽  
Fine Structure Constant ◽  
Doppler Velocity ◽  
Fundamental Constants ◽  
Velocity Shift ◽  
Theoretical Predictions

The fundamental dimensionless physical constants cannot be predicted by theory but can only be measured experimentally. And so it is of their possible variation where there are several theoretical predictions but unfortunately with little theoretical guidance on the expected rate of change. The role of fundamental constants in the representation of nature as well as the implications of their variability for the Equivalence Principle and cosmology have been highlighted in many contributions at this conference (cfr K. Olive and J.P Uzan, these proceedings). Measuring the variability of the fine structure constant α or the electron-to-proton ratio μ by means of absorption lines implies the measurement of a tiny variation of the position of one or a few lines with regard to other lines which are taken as reference. For the fine structure constant the relation between its change and the doppler velocity shift is:

scholarly journals Detection of Multi-pixel Low Contrast Object on a Real Sea Surface

2021 ◽  
Author(s):  
Victor Golikov ◽  
Oleg Samovarov ◽  
Daria Chernomorets ◽  
Marco Rodriguez-Blanco
Keyword(s):  
Spectral Characteristics ◽  
False Alarm Probability ◽  
Sea Surface ◽  
Statistical Characteristics ◽  
Statistical Parameters ◽  
Low Contrast ◽  
Video Images ◽  
Floating Object ◽  
The Difference ◽  
Floating Objects

The video images captured at long range usually have low contrast floating objects of interest on a sea surface. A comparative experimental study of the statistical characteristics of reflections from floating objects and from the agitated sea surface showed the difference in the correlation and spectral characteristics of these reflections. The functioning of the recently proposed modified matched subspace detector (MMSD) is based on the separation of the observed data spectrum on two subspaces: relatively low and relatively high frequencies. In the literature the MMSD performance has been evaluated in generally and moreover using only a sea model (additive Gaussian background clutter). This paper extends the performance evaluating methodology for low contrast object detection and moreover using only the real sea dataset. This methodology assumes an object of low contrast if the mean and variance of the object and the surrounding background are the same. The paper assumes that the energy spectrum of the object and the sea are different. The paper investigates a scenario in which an artificially created model of a floating object with specified statistical parameters is placed on the surface of a real sea image. The paper compares the efficiency of the classical Matched Subspace Detector (MSD) and MMSD for detecting low-contrast objects on the sea surface. The article analyzes the dependence of the detection probability at a fixed false alarm probability on the difference between the statistical means and variances of a floating object and the surrounding sea.

scholarly journals Structure of the Field of the Colored Dissolved Organic Matter Concentration in the Kerch Strait

2021 ◽  
Vol 28 (5) ◽  
Author(s):  
P. D. Lomakin ◽  
A. I. Chepyzhenko ◽  
A.A. Chepyzhenko ◽  
◽  
◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Concentration Distribution ◽  
Vertical Structure ◽  
Concentration Field ◽  
Sea Surface ◽  
Statistical Characteristics ◽  
Colored Dissolved Organic Matter ◽  
Typical Structure ◽  
Kerch Strait

Purpose. Using the data obtained in the expeditions, 2001–2014, the authors intend to identify the typical features of vertical structure of the colored dissolved organic matter (fDOM) concentration field in the Kerch Strait, to type the fDOM(z) profiles, to zone the region under consideration according to a given set of the qualitative features, and also to determine the features of statistical characteristics of the fDOM concentration distribution on the sea surface layer for the water areas with a typical structure. Methods and Results. The typing was carried out by the method of visual expert assessment of the curves of vertical distribution of concentration of the considered value. It was based on analyzing the fDOM(z) profile shapes. To reveal the boundaries of the areas with typical stratification of the fDOM content field, the thermohaline field structure was analyzed. Three types of water vertical structure were identified; they differed in the fDOM(z) profile shape and in statistical indices of empirical distribution of this substance concentration on the sea surface. These are the Azov Sea and the Black Sea types peculiar to the Azov and Black seas waters not contaminated by dissolved organic matter, and the type, the structure of which identifies the waters containing the anthropogenic component in the concentration field of the analyzed value. The latter type is characterized by a special intrusive shape of the fDOM(z) profile. For each of the identified stratification types, the histograms of the fDOM concentration distribution on the sea surface were calculated. Conclusions. The fDOM(z) profiles were typed. The Kerch Strait water area was zoned in accordance with a given set of the preliminary revealed qualitative features. The boundaries of the areas with typical stratification and their displacements were determined. It is shown that each structure type has its own statistical distribution of concentration of the considered value on the sea surface

scholarly journals Measuring ocean surface velocities with the KuROS and KaRADOC airborne near-nadir Doppler radars: a multi-scale analysis in preparation of the SKIM mission

2019 ◽  
Author(s):  
Louis Marié ◽  
Fabrice Collard ◽  
Frédéric Nouguier ◽  
Lucia Pineau-Guillou ◽  
Danièle Hauser ◽  
...  
Keyword(s):  
Wave Height ◽  
Theoretical Estimate ◽  
Phase Speed ◽  
Sea Surface ◽  
Doppler Velocity ◽  
Measured Velocity ◽  
Actual Measurement ◽  
Ka Band ◽  
Measurement Geometry ◽  
Ku Band

Abstract. Surface currents are poorly known over most of the oceans. Satellite-borne Doppler Waves and Current Scatterometers (DWCS) can be used to fill this observation gap. The Sea surface KInematics Multiscale (SKIM) proposal, is the first satellite concept built on a DWCS design at near-nadir angles, and now one of the two candidates to become the 9th mission of the European Space Agency Earth Explorer program. As part of the detailed design and feasibility studies (phase A) funded by ESA, airborne measurements were carried out with both a Ku-Band and a Ka-Band Doppler radars looking at the sea surface at near nadir-incidence in a real-aperture mode, i.e. in a geometry and mode similar to that of SKIM. The airborne radar KuROS was deployed to provide simultaneous measurements of the radar backscatter and Doppler velocity, in a side-looking configuration, with an horizontal resolution of about 5 to 10 m along the line of sight and integrated in the perpendicular direction over the real-aperture 1-way 3-dB footprint diameter (about 580 m). The KaRADOC system has a much narrower beam and footprint that only about 45 m in diameter. The experiment took place in November 2018 off the French Atlantic coast, with sea states representative of the open ocean and a well known tide-dominated current regime. The data set is analyzed to explore the contribution of non-geophysical velocities to the measurement and how the geophysical part of the measured velocity combines wave-resolved and wave-averaged scales. We find that the measured Doppler velocity contains a characteristic wave phase speed, called here C0 that is analogous to the Bragg phase speed of coastal High Frequency radars that use a grazing measurement geometry, with little variations ΔC associated to changes in sea state. The Ka-band measurements at an incidence of 12° are 10 % lower than the theoretical estimate C0 ~ 2.4 m/s for typical oceanic conditions defined by a wind speed of 7 m/s and a significant wave height of 2 m. For Ku-band the measured data is 30 % lower than the theoretical estimate 2.8 m/s. ΔC is of the order of 0.2 m/s for a 1 m change in wave height, and cannot be confused with a 1 m/s change in tidal current. The actual measurement of the current velocity from an aircraft at 4 to 18° incidence angle is, however, made difficult by uncertainties on the measurement geometry, which are much reduced in satellite measurements.

scholarly journals Low-Frequency Sea Surface Radar Doppler Echo

2018 ◽  
Author(s):  
Yury Yu. Yurovsky ◽  
Vladimir N. Kudryavtsev ◽  
Semyon A. Grodsky ◽  
Bertrand Chapron
Keyword(s):  
Cross Section ◽  
Modulation Transfer Function ◽  
Low Frequency ◽  
Sea Surface ◽  
Doppler Velocity ◽  
Modulation Transfer ◽  
Low Frequencies ◽  
Wave Range ◽  
Wave Slope ◽  
Backscatter Cross Section

Observed sea surface Ka-band normalized radar backscatter cross section (NRCS) and Doppler velocity (DV) exhibit energy at low frequencies (LF) below the surface wave range. It is shown that non-linearity in NRCS-wave slope Modulation Transfer Function (MTF) and inherent NRCS averaging within the footprint account for the NRCS and DV LF variance with the exception of VV NRCS for which almost half of the LF variance is attributable to wind fluctuations. Although the distribution of radar DV is quasi-Gaussian suggesting virtually little impact of non-linearity, the LF DV variations arise due to footprint averaging of correlated local DV and non-linear NRCS. Numerical simulations demonstrate that MTF non-linearity weakly affects traditional linear MTF estimate (less than 10% for |MTF|< 20). Thus the linear MTF is a good approximation to evaluate the DV averaged over large footprints typical of satellite observations.

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