摘要 :
We present the first measurements of the absolute albedos of hohlraums made from gold or from high-Z mixtures. The measurements are performed over the range of radiation temperatures (70-100 eV) expected during the foot of an indi...
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We present the first measurements of the absolute albedos of hohlraums made from gold or from high-Z mixtures. The measurements are performed over the range of radiation temperatures (70-100 eV) expected during the foot of an indirect-drive temporally- shaped ignition laser pulse, where accurate knowledge of the wall albedo (i.e. soft x-ray wall re-emission) is most critical for determining capsule radiation symmetry. We find that the gold albedo agrees well with calculations using the super transition array opacity model, potentially providing additional margin for ICF ignition.
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The overarching goals of this project are to understand the role of sea ice-albedo feedback on sea ice predictability, to improve how sea-ice albedo is modeled and how sea ice predictions are initialized, and then to evaluate how ...
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The overarching goals of this project are to understand the role of sea ice-albedo feedback on sea ice predictability, to improve how sea-ice albedo is modeled and how sea ice predictions are initialized, and then to evaluate how these improvements influence inherent sea ice predictability.
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The scattering of astronomical light by the Earth-Moon system is a subject of much importance, ranging from surface properties of the Moon and the backscatter albedo of the Earth's atmosphere to the solar radiation constant and is...
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The scattering of astronomical light by the Earth-Moon system is a subject of much importance, ranging from surface properties of the Moon and the backscatter albedo of the Earth's atmosphere to the solar radiation constant and issues of global warming. Moonshine is the term for sunlight reflected by the Moon and illuminating portions of the Earth. Earthshine is the reciprocal, being that portion of sunlight reflected by the Earth and illuminating the Moon. The latter is the basis for astronomical scattering studies of the dark portion of a crescent Moon as well as for measuring attributes of the Earth's atmospheric albedo. By symmetry, the two terms are interchanged under reciprocity for an Earth-based optical observer O. However, for a Moon-based observer the reciprocity fails (a broken symmetry). The reason is that the Moon has no appreciable atmosphere and is directly bombarded by a charged particle flux of cosmic rays (CRs) and solar wind material, while the Earth's surface is not. The consequence is that the lunar surface has a small CR albedo which is absent from the Earth's surface (althouth it is present at the top of Earth's atmosphere as a neutron albedo, a property since corroborated by AMS). Therefore, a lunar-based observer standing in the dark of the Moon does not see Earthshine, but rather Earthshine plus CR albedo. On the far side of the Moon where there is no Earthshine, the same observer still sees CR albedo. The effect is a local one not noticed by remote sensing from Earth or spacecraft, although transient optical events on the Moon have been discussed for centuries. A thermal albedo also exists as part of the photon radiation emitted by the Earth or Moon, and is one method for arriving at a planetary temperature at thermal equilibrium. Nevertheless, it is infrared and does not contribute to the optical luminescence of the Moon, whereas Earthshine and CR albedo do.
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摘要 :
Land surface albedo is an important parameter in describing the radiative properties of the earth's surface as it represents the amount of incoming solar radiation that is reflected from the surface. The amount and type of vegetat...
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Land surface albedo is an important parameter in describing the radiative properties of the earth's surface as it represents the amount of incoming solar radiation that is reflected from the surface. The amount and type of vegetation of the surface dramatically alters the amount of radiation that is reflected; for example, croplands that contain leafy vegetation will reflect radiation very differently than blacktop associated with urban areas. In addition, since vegetation goes through a growth, or phenological, cycle, the amount of radiation that is reflected changes over the course of a year. As a result, albedo is both temporally and spatially dependant upon global location as there is a distribution of vegetated surface types and growing conditions. Land surface albedo is critical for a wide variety of earth system research projects including but not restricted to remote sensing of atmospheric aerosol and cloud properties from space, ground-based analysis of aerosol optical properties from surface-based sun/sky radiometers, biophysically-based land surface modeling of the exchange of energy, water, momentum, and carbon for various land use categories, and surface energy balance studies. These projects require proper representation of the surface albedo's spatial, spectral, and temporal variations, however, these representations are often lacking in datasets prior to the latest generation of land surface albedo products.
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The study presents a scene independent algorithm for estimating broadband planetary (top-of-atmosphere) albedo using NOAA/AVHRR narrowband satellite data. Initial results from a radiative transfer model investigation are given, fo...
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The study presents a scene independent algorithm for estimating broadband planetary (top-of-atmosphere) albedo using NOAA/AVHRR narrowband satellite data. Initial results from a radiative transfer model investigation are given, followed by empirical coefficients which were deduced through multivariant regression analysis of Nimbus-7/ERB broadband data and/NOAA-7/AVHRR narrowband data. Planetary scenes were grouped into five major categories. Strong variations in the two channel AVHRR narrowband albedo observations were noted for different scene classifications which emphasize the potential error in using a single AVHRR channel 1 (0.58-0.68 micrometer) albedo determination as has historically been done. The results presented should allow improved albedo calculations when one is limited to AVHRR narrowband data.
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