The surface albedo of the earth in the near ultraviolet (330–340 nm)

Frederick, John E.; Abrams, R. B.

doi:10.1016/0034-4257(81)90031-6

Cited by 7 publications

(2 citation statements)

References 9 publications

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“…The minimum cloud reflectivities are 51.5 _+ 16.2% for low clouds and 76 _+ 13.5% for high clouds. This is in agreement with the values of Frederick and Abrams [1981] who found a typical average cloud albedo to lie in the range 50-60% from AE-E satellite measurements taken at 330-340 nm. Model simulations with the Monte Carlo method carried out by Los et al [1997] showed that at cloud top photodissociation rate coefficients (and hence actinic flux) may be 300% higher than in clear-sky conditions.…”

Section: Introductionsupporting

confidence: 92%

Measurements of the diffuse UV sky radiance during broken cloud conditions

Weihs¹,

Webb²,

Hutchinson³

et al. 2000

J. Geophys. Res.

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Abstract. Sky radiance distributions pertaining to surface UV have been investigated under clear-sky and broken cloud conditions. Comparison between the measured clear-sky distribution and either a radiative transfer model or an empirical function showed reasonable agreement in each case. The radiance distribution measurements performed during broken cloud conditions were then investigated and compared to the clear-sky radiance. Radiances from cloudy sky locations were either higher (by up to 2.5 times) or lower (with minimum values that were 8% of the clear-sky radiances) than the clear-sky case. It has been shown that clouds have an enhancing effect on the ground UV radiance at locations with scattering angles between 30 ø and 60 ø and a sight zenith angle less than 30 ø, or with scattering angles greater than 60 ø irrespective of the sight zenith angle. These results represent an advance toward the accurate description and modeling of ground UV under broken cloud conditions. IntroductionUltraviolet (UV) radiation belongs to the part of the electromagnetic spectrum between X ray at 10 nm and the visible at 400 nm. The UV consists of three regions, the UV-C (below 280 nm), UV-B (280-320 nm), and the UV-A (320-400 nm) [Huffman, 1992]. Ozone and oxygen completely absorb the UV-C radiation in the upper and middle atmosphere. The various factors that influence ground UV-B and UV-A radiation, in order of decreasing importance, are the solar zenith angle, which determines the optical path length, the total column ozone (which mainly affects UV-B), cloud cover, the aerosol loading of the atmosphere, surface albedo, gaseous pollutants, the Sun-Earth distance, and the air pressure. Ozone depletion and clouds are two of these factors that have re-

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Section: Introductionsupporting

confidence: 92%

Measurements of the diffuse UV sky radiance during broken cloud conditions

Weihs¹,

Webb²,

Hutchinson³

et al. 2000

J. Geophys. Res.

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“…Furthermore, a generic planar ground topography with a relatively low surface albedo of 0.03 (compare e.g. Frederick and Abrams 1981) was assumed in all scenarios.…”

Section: Scenario Descriptions and Resultsmentioning

confidence: 99%

Radiative transfer corrections for accurate spectroscopic measurements of volcanic gas emissions

et al. 2009

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There is widespread use of passive remote sensing techniques to quantify trace gas column densities in volcanic plumes utilizing scattered sunlight as a light source. Examples include passive DOAS, COSPEC, and the SO 2 camera. In order to calculate trace gas concentrations or volcanic emission fluxes, knowledge about the optical path through the plume is necessary. In the past, a straight photon path through the plume has always been assumed although it was known that this is not always true. Here we present the results of model studies conducted specifically to quantify the effects of realistic radiative transfer in and around volcanic plumes on ground-based remote sensing measurements of SO 2 . The results show that measurements conducted without additional information on average photon paths can be inaccurate under certain conditions, with possible errors spanning more than an order of magnitude. Both over and underestimation of the true column density can occur. Actual errors depend on parameters such as distance between instrument and plume, plume SO 2 concentration, plume aerosol load, as well as aerosol conditions in the ambient atmosphere. As an example, a measurement conducted with an SO 2 camera is discussed, the results of which can only be correctly interpreted if realistic radiative transfer is considered. Finally, a method is presented which for the first time allows the retrieval of actual average photon paths in spectroscopic (i.e. DOAS) measurements of adequate resolution. By allowing for a wavelength dependent column density during the evaluation of DOAS measurements, we show how radiative transfer effects can be corrected using information inherently available in the measured spectra, thus greatly enhancing the accuracy of DOAS measurements of volcanic emissions.

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The interstellar medium and the glacial eras during the Pleistocene

1988

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We study the hypothetical conditions for interstellar clouds dense enough to produce glaciations on the Earth. A simple differential formula (adequate to give lower limits to dust absorption) is used to relate mean temperatures and visual albedos today and during the glacial eras. For this, the geological and oceanographical records of the Pleistocene are used. The temperature decays are associated to an absorption of the solar light in visual magnitudes mu. As the effective albedo, integrated in all wavelengths are lower than the corresponding visual value, the adoption of a visual scale leads to an underestimation of the actual amount of dust. A minimum dust absorption Am0 = 0.02 mag, necessary to start a glacial era is then obtained. This should mean interstellar clouds with dust densities of 4100 mag. PC-' and sizes of 0.3 pc or more, taking into account the time span of the glacial eras and the mean velocity of the Sun with respect to the LSR. Such clouds were never observed and are uncompatible with what is known from the interstellar medium: the 'glaciation clouds' should be clouds with densities 50-100 times above the tolerable value for gravitational stability; on the other hand, the necessary number of clouds per cubic parsec should produce the collapse of the galactic disc as a whole. From a comparative analysis of the temperatures of the other planets it seems to be that the actual thermal temperatures in their surfaces depend less than one expects from the visual albedos. From this it is raised the suspicion that the cause of the ice ages was the Sun itself.

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The surface albedo of the earth in the near ultraviolet (330–340 nm)

Cited by 7 publications

References 9 publications

Measurements of the diffuse UV sky radiance during broken cloud conditions

Measurements of the diffuse UV sky radiance during broken cloud conditions

Radiative transfer corrections for accurate spectroscopic measurements of volcanic gas emissions

The interstellar medium and the glacial eras during the Pleistocene

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