ABOUT INVARIANCE OF ANGLE NOISE DISTRIBUTION PARAMETERS BY AN ARBITRARY N-POINT GEOMETRIC MODEL TO VIEWING ANGLE

2019 ◽  
pp. 32-35
Author(s):  
V. V. Artyushenko ◽  
A. V. Nikulin
Keyword(s):  
Regular Polygon ◽  
Geometric Model ◽  
Sea Surface ◽  
Noise Distribution ◽  
Viewing Angle ◽  
Distributed Objects ◽  
Software Complex ◽  
The Earth ◽  
Distribution Parameters ◽  
Equal Power

In this article we consider a problem of reliable modeling of echo signals and angle noise of distributed objects using twodimensional geometric models with random statistically unrelated signals. The conditions that ensure the invariance of distribution parameters of the angle noise generated by an arbitrary N-point configuration of a two-dimensional geometric model are obtained. In the particular case of a model whose emitters are supplied with signals of equal power, the conditions of invariance are reduced to the location of the model points on the plane in the form of a regular polygon. These results can be used to synthesize mathematical models used for simulating reflections from distributed objects and for developing a hardware-software complex for the simulation of electromagnetic fields reflected from the Earth surface, atmospheric inhomogeneities, the sea surface, etc.

scholarly journals Modelling a Spectral Index to Detect Dispersed Oil in a Seawater Column Depending on the Viewing Angle: Gulf of Gdańsk Case Study

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5352
Author(s):  
Emilia Baszanowska ◽  
Zbigniew Otremba ◽  
Jacek Piskozub
Keyword(s):  
Optical Properties ◽  
Spectral Index ◽  
Sea Surface ◽  
Viewing Angle ◽  
Gulf Of Gdańsk ◽  
Water Emulsion ◽  
Dispersed Oil ◽  
Oil Concentration ◽  
Gulf Of Gdansk ◽  
Oil In Water Emulsion

This paper analyzes the digital modelling of radiance reflectance of the sea surface when the water column is polluted by oil-in-water emulsion. A method tracking the fate of two billion virtual solar photons was applied to obtain the angular distribution of bottom-up radiance for a plane of sunlight striking the sea surface. For the calculations, the inherent optical properties of seawater characteristic for the Gulf of Gdańsk (southern Baltic Sea) were used. The analyses were performed for two types of oils with extremely different optical properties for an oil concentration of 10 ppm and for a roughened sea surface with a wind speed of 2 m/s. The spectral index for oil detection in seawater for different viewing angles was determined based on the results obtained for reflectance at eight wavelengths in the range of 412–676 nm for viewing angle in the range from 80° to 0°, both on the side of incidence of direct sunlight and on the opposite side. The resulting calculated spectral indexes for different wavelength combinations indicated significant dependence on the viewing angle.

scholarly journals Marine iodine emissions in a changing world

2021 ◽  
Vol 477 (2247) ◽  
pp. 20200824
Author(s):  
Lucy J. Carpenter ◽  
Rosie J. Chance ◽  
Tomás Sherwen ◽  
Thomas J. Adams ◽  
Stephen M. Ball ◽  
...  
Keyword(s):  
Air Quality ◽  
Radiative Forcing ◽  
Sea Surface ◽  
Biogeochemical Cycle ◽  
Surface Ocean ◽  
The Past ◽  
The Earth ◽  
Tropospheric Photochemistry ◽  
Fresh Perspective ◽  
Global Cycle

Iodine is a critical trace element involved in many diverse and important processes in the Earth system. The importance of iodine for human health has been known for over a century, with low iodine in the diet being linked to goitre, cretinism and neonatal death. Research over the last few decades has shown that iodine has significant impacts on tropospheric photochemistry, ultimately impacting climate by reducing the radiative forcing of ozone (O 3 ) and air quality by reducing extreme O 3 concentrations in polluted regions. Iodine is naturally present in the ocean, predominantly as aqueous iodide and iodate. The rapid reaction of sea-surface iodide with O 3 is believed to be the largest single source of gaseous iodine to the atmosphere. Due to increased anthropogenic O 3 , this release of iodine is believed to have increased dramatically over the twentieth century, by as much as a factor of 3. Uncertainties in the marine iodine distribution and global cycle are, however, major constraints in the effective prediction of how the emissions of iodine and its biogeochemical cycle may change in the future or have changed in the past. Here, we present a synthesis of recent results by our team and others which bring a fresh perspective to understanding the global iodine biogeochemical cycle. In particular, we suggest that future climate-induced oceanographic changes could result in a significant change in aqueous iodide concentrations in the surface ocean, with implications for atmospheric air quality and climate.

scholarly journals A global vertical datum defined by the conventional geoid potential and the Earth ellipsoid parameters

2020 ◽  
Author(s):  
Hadi Amin ◽  
Lars E. Sjöberg ◽  
Mohammad Bagherbandi
Keyword(s):  
Gravity Field ◽  
Satellite Altimetry ◽  
Input Data ◽  
Equipotential Surface ◽  
Sea Surface ◽  
Dynamic Topography ◽  
The Earth ◽  
Degree Harmonic ◽  
Mean Sea Surface ◽  
Zero Degree

<p>According to the classical Gauss–Listing definition, the geoid is the equipotential surface of the Earth’s gravity field that in a least-squares sense best fits the undisturbed mean sea level. This equipotential surface, except for its zero-degree harmonic, can be characterized using the Earth’s Global Gravity Models (GGM). Although nowadays, the satellite altimetry technique provides the absolute geoid height over oceans that can be used to calibrate the unknown zero-degree harmonic of the gravimetric geoid models, this technique cannot be utilized to estimate the geometric parameters of the Mean Earth Ellipsoid (MEE). In this study, we perform joint estimation of W<sub>0</sub>, which defines the zero datum of vertical coordinates, and the MEE parameters relying on a new approach and on the newest gravity field, mean sea surface, and mean dynamic topography models. As our approach utilizes both satellite altimetry observations and a GGM model, we consider different aspects of the input data to evaluate the sensitivity of our estimations to the input data. Unlike previous studies, our results show that it is not sufficient to use only the satellite-component of a quasi-stationary GGM to estimate W<sub>0</sub>. In addition, our results confirm a high sensitivity of the applied approach to the altimetry-based geoid heights, i.e. mean sea surface and mean dynamic topography models. Moreover, as W<sub>0</sub> should be considered a quasi-stationary parameter, we quantify the effect of time-dependent Earth’s gravity field changes as well as the time-dependent sea-level changes on the estimation of W<sub>0</sub>. Our computations resulted in the geoid potential W<sub>0 </sub>= 62636848.102 ± 0.004 m<sup>2</sup>s<sup>-2</sup> and the semi-major and –minor axes of the MEE, a = 6378137.678 ± 0.0003 m and b = 6356752.964 ± 0.0005 m, which are 0.678 and 0.650 m larger than those axes of the GRS80 reference ellipsoid, respectively. Moreover, a new estimation for the geocentric gravitational constant was obtained as GM = (398600460.55 ± 0.03) × 10<sup>6</sup> m<sup>3</sup>s<sup>-2</sup>.</p>

scholarly journals RFI and Remote Sensing of the Earth From Space

2019 ◽  
Vol 08 (01) ◽  
pp. 1940001 ◽  
Author(s):  
David M. Le Vine
Keyword(s):  
Remote Sensing ◽  
Soil Moisture ◽  
Surface Temperature ◽  
Microwave Remote Sensing ◽  
Atmospheric Temperature ◽  
Passive Microwave ◽  
Sea Surface ◽  
Radio Frequency Interference ◽  
Passive Microwave Remote Sensing ◽  
The Earth

Passive microwave remote sensing of the Earth from space provides information essential for understanding the Earth’s environment and its evolution. Parameters such as soil moisture, sea surface temperature and salinity, and profiles of atmospheric temperature and humidity are measured at frequencies determined by the physics (e.g. sensitivity to changes in desired parameters) and by the availability of suitable spectrum free from interference. Interference from man-made sources (radio frequency interference) is an impediment that in many cases limits the potential for accurate measurements from space. A review is presented here of the frequencies employed in passive microwave remote sensing of the Earth from space and of the associated experience with RFI and contemporary approaches to address the problem.

scholarly journals CONNECTION OF ANGULAR DIMENSIONS OF SIMULATED DISTRIBUTED OBJECTS WITH PARAMETERS OF DISTRIBUTION OF THEIR ANGULAR NOISE

2019 ◽  
pp. 36-41
Author(s):  
V. V. Artyushenko ◽  
A. V. Nikulin
Keyword(s):  
Mathematical Modeling ◽  
Angular Size ◽  
Distributed Objects ◽  
Statistical Nature ◽  
Distributed Object ◽  
Distribution Parameters

Fluctuations of the apparent center of radiation near their expectation during the irradiation of distributed objects with probing signals from radar stations have been observed by scientists for many decades. An expression describing the statistical nature of such fluctuations is known in the literature. These fluctuations are called angular noise. With all this, there is still no expression connecting the angular dimensions of the object and the distribution parameters of its angular noise. This expression is necessary to predict the angular size of distributed objects in problems of simulating reflections from them. In the article, the problem indicated above is solved in two ways. When using the first method, it is possible to obtain an unambiguous relationship between the angular size of the object and the distribution parameters of its angular noise, but for each new object it is necessary to re-derive this relationship, which is not always possible. When using the second method, the probability is used with which the fluctuating apparent center of radiation of a signal reflected from a distributed object falls within the boundaries of this object. This method has no disadvantage of the first one. The results presented in this article were confirmed by means of mathematical modeling.

scholarly journals Middle Jurassic-Early Cretaceous high-latitude sea-surface temperatures from the Southern Ocean

2011 ◽  
Vol 7 (2) ◽  
pp. 1339-1361 ◽  
Author(s):  
H. C. Jenkyns ◽  
L. Schouten-Huibers ◽  
S. Schouten ◽  
J. S. Sinninghe Damsté
Keyword(s):  
Southern Ocean ◽  
Early Cretaceous ◽  
Middle Jurassic ◽  
Climatic Conditions ◽  
Sea Surface ◽  
Polar Regions ◽  
Polar Ice ◽  
Surface Conditions ◽  
The Earth

Abstract. Although a division of the Phanerozoic climatic modes of the Earth into "greenhouse" and "icehouse" phases is widely accepted, whether or not polar ice developed during the relatively warm Jurassic and Cretaceous Periods is still under debate. In particular, there is a range of isotopic and biotic evidence that favours the concept of discrete "cold snaps", marked particularly by migration of certain biota towards lower latitudes. Extension of the use of the palaeotemperature proxy TEX86 back to the middle Jurassic indicates that relatively warm sea-surface conditions (26–30 °C) existed from this interval (~160 Ma) to the Early Cretaceous (~115 Ma) in the Southern Ocean. The Jurassic and Cretaceous "cold snaps" represent falls of only a few degrees. Belemnite δ18O data give palaeotemperatures that are consistently lower by ~14 °C than does TEX86 and these molluscs likely record conditions below the thermocline. Such long-term warm climatic conditions would only be compatible with the existence of continental ice if appreciable areas of high altitude existed on Antarctica, and/or in other polar regions, during the Mesozoic Era.

Observed reduction in low-level clouds over the northeastern Pacific attributed to increase in sea surface temperatures

2021 ◽  
Author(s):  
Hendrik Andersen ◽  
Jan Cermak ◽  
Lukas Zipfel
Keyword(s):  
Radiant Energy ◽  
Energy System ◽  
Reanalysis Data ◽  
Sea Surface ◽  
Data Sets ◽  
Sea Surface Temperatures ◽  
Low Level ◽  
The Earth ◽  
Surface Temperatures ◽  
Northeastern Pacific

<p>In this contribution, a significant reduction of low-level marine clouds (LLCs) in the northeastern Pacific is found over a 20-year period in satellite observations and attributed to increasing sea surface temperatures (SSTs).</p><p>LLCs play a key role for the Earth’s energy balance, however, their response to climatic changes is not clear, yet. Here, 20 years of Clouds and the Earth’s Radiant Energy System (CERES) cloud observations are analyzed together with reanalysis data sets in multivariate-regression and machine-learning frameworks to link an observed decrease of LLCs in the subtropical northern Pacific to changes in environmental factors. In the analyses, the observed LCC trend is explained almost exclusively by an increase in SSTs, but counteracted to some extent by increased low-level moisture availability. The influence of other factors such as estimated inversion strength, local winds and aerosols is investigated in the statistical frameworks but found to be negligible when compared to the effect of SST changes. The results provide observational evidence for the low-cloud feedback that back model findings of reduced LCC due to increased SSTs in a changing climate.</p>

SIMULATION OF REFLECTIONS FROM SURFACE-DISTRIBUTED OBJECTS ON EXAMPLE OF FRAGMENT OF UNDERLYING SURFACE

2019 ◽  
pp. 22-26
Author(s):  
M. A. Stepanov
Keyword(s):  
Real Time ◽  
Electromagnetic Waves ◽  
Geometric Model ◽  
Angular Position ◽  
Underlying Surface ◽  
Distributed Objects ◽  
Spherical Coordinate ◽  
Flight Mode ◽  
Straight Line ◽  
Low Altitude

The paper considers the problem of the synthesis of a low-point model of the relief of the underlying surface. The model can be used to conduct semi-null simulation when the radar is operating in low-altitude flight mode. A method for defining a relief in the form of a piecewise broken approximation is proposed. An algorithm is presented that allows real-time, for a given relief, to calculate for each of the elements of the resolution in range its angular position and angular dimensions. These parameters determine the expectation of the angular noise and the width of their probability density, respectively. The ability to work in real time is provided using a straight line in a spherical coordinate system when defining the relief. The recommendations on the choice of a geometric model from the previously justified family are given. The synthesized models provide a given form of the correlation functions of angular noise and adequately replace reflections from distributed objects. Geometric models can be used as the basis for matrix simulators of reflected electromagnetic waves.

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