6,909 research outputs found
Earth reflector type classification based on multispectral remote sensing image
Earth’s reflectivity is one of the key parameters of climate change, Earth’s radiation budget research and so on. It is determined by the characteristic of Earth atmosphere components. Earth atmosphere components vary strongly in
both spatially and temporally, thus complete spatial mosaics and/or richer time series information are needed. In this study, we developed an Earth Reflector Type Index (ERTI) to discriminate major Earth atmosphere components: clouds, cloud-free ocean, bare and vegetated land. Results show that the probability of the ERTI method with selected thresholds
being able to discriminate between cloudy and cloud-free scenes is about 82%. ERTI can be used to interpret global Earth’s reflectivity and its temporal variation.Accepted manuscrip
A theory of microwave apparent temperature over the ocean
In the microwave region combined active (scatterometer) and passive (radiometer) remote sensors over the ocean show promise of providing surface wind speeds and weather information to the oceanographer and meteorologist. This has aroused great interest in the investigation of the scattering of waves from the sea surface. A composite surface scattering theory is investigated. The two-scale scattering theory proposed by Semyonov was specifically extended to compute the emmision and scattering characteristics of ocean surfaces. The effects of clouds and rain on the radiometer and scatterometer observations are also investigated using horizontally stratified model atmospheres with rough sea surfaces underneath. Various cloud and rain models proposed by meteorologist were employed to determine the rise in the microwave temperature when viewing downward through these model atmospheres. For heavy rain-fall rates the effects of scattering on the radiative transfer process are included
Ocean color spectrum calculations
The development is considered of procedures for measuring a number of subsurface oceanographic parameters using remotely sensed ocean color data. It is proposed that the first step in this effort should be the development of adequate theoretical models relating the desired oceanographic parameters to the upwelling radiances to be observed. A portion of a contributory theoretical model is shown to be described by a modified single scattering approach based upon a simple treatment of multiple scattering. The resulting quasi-single scattering model can be used to predict the upwelling distribution of spectral radiance emerging from the sea. The shape of the radiance spectrum predicted by this model for clear ocean water shows encouraging agreement with measurments made at the edge of the Sargasso Sea off Cape Hatteras
Influence of aerosols, clouds, and sunglint on polarization spectra of Earthshine
Ground-based observations of the Earthshine, i.e., the light scattered by
Earth to the Moon, and then reflected back to Earth, simulate space
observations of our planet and represent a powerful benchmark for the studies
of Earth-like planets. Earthshine spectra are strongly linearly polarized,
owing to scattering by molecules and small particles in the atmosphere of the
Earth and surface reflection, and may allow us to measure global atmospheric
and surface properties of planet Earth. Aims. We aim to interpret already
published spectropolarimetric observations of the Earthshine by comparing them
with new radiative transfer model simulations including a fully realistic
three-dimensional (3D) surface-atmosphere model for planet Earth. We used the
highly advanced Monte Carlo radiative transfer model MYSTIC to simulate
polarized radiative transfer in the atmosphere of the Earth without
approximations regarding the geometry, taking into account the polarization
from surface reflection and multiple scattering by molecules, aerosol
particles, cloud droplets, and ice crystals. We have shown that Earth
spectropolarimetry is highly sensitive to all these input parameters, and we
have presented simulations of a fully realistic Earth atmosphere-surface model
including 3D cloud fields and two-dimensional (2D) surface property maps. Our
modeling results show that scattering in high ice water clouds and reflection
from the ocean surface are crucial to explain the continuum polarization at
longer wavelengths as has been reported in Earthshine observations taken at the
Very Large Telescope in 2011 (3.8 % and 6.6 % at 800 nm, depending on which
part of Earth was visible from the Moon at the time of the observations). We
found that the relatively high degree of polarization of 6.6 % can be
attributed to light reflected by the ocean surface in the sunglint region
Radiative transfer in a spherical, emitting, absorbing and anisotropically scattering medium
The atmospheres of planets (including Earth) and the outer layers of stars
have often been treated in radiative transfer as plane-parallel media, instead
of spherical shells, which can lead to inaccuracy, e.g. limb darkening. We give
an exact solution of the radiative transfer specific intensity at all points
and directions in a finite spherical medium having arbitrary radial spectral
distribution of: source (temperature), absorption, emission and anisotropic
scattering. The power and efficiency of the method stems from the spherical
numerical gridding used to discretize the transfer equations prior to matrix
solution: the wanted ray and the rays which scatter into it both have the same
physico-geometric structure. Very good agreement is found with an isotropic
astrophysical benchmark (Avrett & Loeser, 1984). We introduce a specimen
arbitrary forward-back-side phase scattering function for future comparisons.
Our method directly and exactly addresses spherical symmetry with anisotropic
scattering, and could be used to study the Earth's climate, nuclear power
(neutron diffusion) and the astrophysics of stars and planets.Comment: 8 pages, 2 figures, spherical radiative transfer: stellar, planetary,
terrestia
Falsification Of The Atmospheric CO2 Greenhouse Effects Within The Frame Of Physics
The atmospheric greenhouse effect, an idea that many authors trace back to
the traditional works of Fourier (1824), Tyndall (1861), and Arrhenius (1896),
and which is still supported in global climatology, essentially describes a
fictitious mechanism, in which a planetary atmosphere acts as a heat pump
driven by an environment that is radiatively interacting with but radiatively
equilibrated to the atmospheric system. According to the second law of
thermodynamics such a planetary machine can never exist. Nevertheless, in
almost all texts of global climatology and in a widespread secondary literature
it is taken for granted that such mechanism is real and stands on a firm
scientific foundation. In this paper the popular conjecture is analyzed and the
underlying physical principles are clarified. By showing that (a) there are no
common physical laws between the warming phenomenon in glass houses and the
fictitious atmospheric greenhouse effects, (b) there are no calculations to
determine an average surface temperature of a planet, (c) the frequently
mentioned difference of 33 degrees Celsius is a meaningless number calculated
wrongly, (d) the formulas of cavity radiation are used inappropriately, (e) the
assumption of a radiative balance is unphysical, (f) thermal conductivity and
friction must not be set to zero, the atmospheric greenhouse conjecture is
falsified.Comment: 115 pages, 32 figures, 13 tables (some typos corrected
Radiation-Hydrodynamics of Hot Jupiter Atmospheres
Radiative transfer in planetary atmospheres is usually treated in the static
limit, i.e., neglecting atmospheric motions. We argue that hot Jupiter
atmospheres, with possibly fast (sonic) wind speeds, may require a more
strongly coupled treatment, formally in the regime of radiation-hydrodynamics.
To lowest order in v/c, relativistic Doppler shifts distort line profiles along
optical paths with finite wind velocity gradients. This leads to flow-dependent
deviations in the effective emission and absorption properties of the
atmospheric medium. Evaluating the overall impact of these distortions on the
radiative structure of a dynamic atmosphere is non-trivial. We present
transmissivity and systematic equivalent width excess calculations which
suggest possibly important consequences for radiation transport in hot Jupiter
atmospheres. If winds are fast and bulk Doppler shifts are indeed important for
the global radiative balance, accurate modeling and reliable data
interpretation for hot Jupiter atmospheres may prove challenging: it would
involve anisotropic and dynamic radiative transfer in a coupled
radiation-hydrodynamical flow. On the bright side, it would also imply that the
emergent properties of hot Jupiter atmospheres are more direct tracers of their
atmospheric flows than is the case for Solar System planets.
Radiation-hydrodynamics may also influence radiative transfer in other classes
of hot exoplanetary atmospheres with fast winds.Comment: 25 pages, 4 figures, accepted for publication in ApJ (minor
revisions
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