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As integration of solar power into the national electric grid rapidly increases, it becomes imperative to improve forecasting of this highly variable renewable resource. Thus, a team of researchers from [...]

Emissions of carbon dioxide (C[O.sub.2]) and other greenhouse gases (GHGs) continue to rise. The effects of climate change are becoming ever more apparent. Yet prospects for reducing global emissions of [...]

Continental lacustrine laminites deposited in low latitudes have been examined from the Devonian and Torridonian (Mesoproterozoic) strata of northern Scotland to investigate the consistency of sunspot periodicity through geological time. The thicknesses of 2448 annual laminae were measured from the Middle Devonian (c. 388 Ma) Achanarras Limestone Member, Lower Caithness Flagstone Group, and of 2821 laminae from the Mesoproterozoic (1.2 Ga) Poll a'Mhuilt Member of the Stoer Group. Time-series analysis resolved periodicities of 13.8 and 13.9 years in the complete Devonian and Mesoproterozoic datasets respectively. When sedimentological variance was considered and the data were examined as evolutive spectra those sections consisting of the most robust data consistently yielded periodicities between 8.6 and 13.7 years for the Devonian section and 9.2 and 10.6 years for the Mesoproterozoic section. These correspond well to Schwabe cycles. Evidence for the presence of the longer Hale cycles (20 years) was also recognized in the Devonian time series. The sunspot periodicities identified within the Devonian and Mesoproterozoic show little variance from published examples from the Quaternary and Eocene and therefore provide evidence for the consistency of solar processes and solar--atmospheric interactions for the past 1.2 Ga. doi: 10.1144/0016-76492009-105.

Mg-based multilayers, including SiC/Mg, Co/Mg, [B.sub.4]C/Mg, and Si/Mg, are investigated for solar imaging and a He II calibration lamp at a 30.4 nm wavelength. These multilayers were fabricated by a magnetron sputtering method and characterized by x-ray reflection. The reflectivities of these multilayers were measured by synchrotron radiation. Near-normal-incidence reflectivities of Co/Mg and SiC/Mg multilayer mirrors are as high as 40.3% and 44.6%, respectively, while those of [B.sub.4]C/Mg and Si/Mg mirrors are too low for application. The measured results suggest that SiC/Mg, Co/Mg multilayers are promising for a 30.4nm wavelength. OCIS codes: 310.1620, 230.4170, 040.7480, 340.6720, 350.6090.

This paper focuses on two shortcomings of radiative transfer codes commonly used in climate models. The first aspect concerns the partitioning of solar versus infrared spectral energy. In most climate models, the solar spectrum comprises wavelengths less than 4 [micro]m with all incoming solar energy deposited in that range. In reality, however, the solar spectrum extends into the infrared, with about 12 W [m.sup.-2] in the 4-1000-[micro]m range. In this paper a simple method is proposed wherein the longwave radiative transfer equation with solar energy input is solved. In comparison with the traditional method, the new solution results in more solar energy absorbed in the atmosphere and less at the surface. As mentioned in a recent intercomparison of the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) and line-by-line (LBL) radiation models, most climate model radiation schemes neglect shortwave absorption by methane. However, the shortwave radiative forcing at the surface due to C[H.sub.4] since the preindustrial period is estimated to exceed that due to C[O.sub.2]. The authors show that the C[H.sub.4] shortwave effect can be included in a correlated k-distribution model, with the additional flux being accurately simulated in comparison with LBL models. Ten-year GCM simulations are presented, showing the detailed climatic effect of these changes in radiation treatment. It is demonstrated that the inclusion of solar flux in the infrared range produces a significant amount of extra warming in the atmosphere, specifically (i) in the tropical stratosphere where the warming can exceed 1 K [day.sup.-1], and (ii) near the tropical tropopause layer. Additional GCM simulations show that inclusion of C[H.sub.4] in the shortwave calculations also produces a warming of the atmosphere and a consequent reduction of the upward flux at the top of the atmosphere. DOI: 10.1175/2010JAS3282.1

Solar radiation data are essential for the work of energy planners, engineers, and agricultural scientists. However, most solar radiation recording stations measure only global radiation in China. It is, therefore, necessary to elaborate correlations between the rarely available diffuse radiation and other climatic data. In the present study, 10-year data (1995-2004) of daily global diffuse solar radiation and sunshine duration obtained at Beijing meteorological station of China was analyzed to guide future projects. Nine models correlating the diffuse fraction ([K.sub.d]) with both the clearness index ([K.sub.t]) and percentage possible sunshine (S/[S.sub.0]) and each variable separately were tested. The accuracy of the correlations is performed in terms of the two widely used statistical indicators, mean bias error, and root mean square error. The results indicate that the correlations relating [K.sub.d] with both [K.sub.t] and S/[S.sub.0] are more reliable than using each variable separately and Model 9 is preferred for its accuracy. The recorded data of Zhengzhou meteorological station are compared with the corresponding values predicted by Model 9 of Beijing. Model 9 provides predictions very close to the measured values of Zhengzhou. Therefore, it may be concluded that Model 9 can be used for estimating diffuse solar radiation for locations of semiwet region of the north of China where only global solar radiation and sunshine duration are available. DOI: 10.1061/(ASCE)0733-9402(2009)135:4(107) CE Database subject headings: Solar radiation; Data analysis; Solar energy; China.

Phytoplankton communities in the Ross Sea, Antarctica, are characterized by the haptophyte Phaeocvstis antarctica Karsten, which dominates deep mixed layers, and diatoms, including Fragilariopsis cylindrus Grunow, that thrive in shallower mixed layers. To investigate whether differences in photoprotective strategies explain these distributions, photosynthetic parameters, pigments, and fluorescence properties were measured in cultures grown under several irradiance regimes and during acclimation to increased irradiance. In P. antarctica, cellular concentrations of all pigments declined with increasing growth irradiance under continuous light, but xanthophyll cycle pigment concentrations increased with increasing irradiance under dynamic conditions without changes in chlorophyll. In contrast, F. cylindrus exhibited declines in chlorophyll cell J with increasing irradiance under both continuous and dynamic conditions, but xanthophyll cycle [cell.sup.-1] i pigments increased under continuous irradiance and declined under dynamic irradiance. P. antarctica did not exhibit non-photochemical quenching (NPQ) unless exposed to irradiance in excess of the mean growth irradiance. F. cvlindrus exhibited NPQ in response to lower irradiances but displayed less photoinhibitory quenching than P. antarctica after exposure to very high irradiance. Inhibitor experiments suggest that both taxa rely upon xanthophyll cycle photoprotection to maintain photosynthetic performance but only P. antarctica relies heavily upon protein synthesis, presumably for D1 protein repair. F cylindrus can thrive in shallow mixed layers because its high capacity for heat dissipation minimizes photoinhibition. P. antarctica utilizes xanthophyll cycle photoprotection to a lesser degree, but is able to dominate deeper mixed layers by effectively repairing the photodamage incurred when it is mixed to the surface.

Dry methane reforming with carbon dioxide in a directly irradiated particle receiver seeded with carbon black is presented in this study. Carbon particles were entrained in the reacting gases and acted as heat transfer and reaction surface. The reactions were not catalyzed by a metal catalyst. The molar ratio between the entrained carbon particles and the working gases (Ar, C[O.sub.2], and C[H.sub.4]) was 4-7 mmol carbon/mol gas. The temperature of the reforming experiments varied from 750[degrees]C to 1450[degrees]C with C[O.sub.2]/C[H.sub.4] ratios varying from 1:1 to 1:6. Experimental results show that methane reacts at lower temperatures than expected for its thermal decomposition; this indicates that the decomposing reaction is enhanced by the presence of the carbon black particles. At 1170[degrees]C 90% of the methane reacted in the receiver during a residence time of 0.3 s. The reaction between carbon dioxide and carbon black is .faster than is documented in the literature, but the reaction rate does not seem to change if only carbon dioxide and carbon black are present in the receiver, compared with experiments where methane is also part of the gas mixture. The experimental results indicate that a high solar flux, i.e., about 2500 kW/[m.sup.2] or higher, significantly accelerates the reaction rate of methane decomposition. Total or partial blockage of the solar radiation reduced the yield by about 50%, compared with tests when the receiver was exposed to the full solar radiation flux, at the same operating temperature. [DOI: 10.1115/1.3090823]

A new type of convex Fresnel lens for linear photovoltaic concentration systems is presented. The lens designed with this method reaches 100% of geometrical optical efficiency, and the ratio (Aperture area)/(Receptor area) is up to 75% of the theoretical limit. The main goal of the design is high uniformity of the radiation on the cell surface for each input angle inside the acceptance. The ratio between the maximum and the minimum irradiance on points of the solar cell is less than 2. The lens has been designed with the simultaneous multiple surfaces (SMS) method of nonimaging optics, and ray tracing techniques have been used to characterize its performance for linear symmetry systems. OCIS codes: 220.3630, 220.4298, 220.1770, 220.2740.

The role of aerosols in climate and climate change is one of the factors that is least understood at the present. Aerosols' direct interaction with solar radiation is a well understood mechanism that affects Earth's net radiative forcing. However, quantifying its magnitude is more problematic because of the temporal and spatial variability of aerosol particles. To enhance our understanding of the radiative effects of aerosols on the global climate, Singapore has joined the AERONET (Aerosol Robotic Network) worldwide network by contributing ground-based direct Sun measurements performed by means of a multiwavelength Sun-photometer instrument. Data are collected on an hourly basis, then are uploaded to be fully screened and quality assured by AERONET. We use a one year data record (level 1.5/2.0) of measured columnar atmospheric optical depth, spanning from November 2006 to October 2007, to study the monthly and seasonal variability of the aerosol optical depth and the Angstrom exponent. We performed independent retrievals of these parameters (aerosol optical depth and Angstrom exponent) by using the photometer's six available bands covering the near-UV to near-IR (380-1080 nm). As a validation, our independent retrievals were compared with AERONET 1.5/2.0 level direct Sun product. OCIS codes: 010.1100, 010.0280.

The Remote Sensing Group at the University of Arizona has developed multispectral ground-viewing radiometers that use light-emitting diodes as detectors. This work describes the optical design, electrical design, and laboratory calibration of a three-channel radiometer that operates in the visible and near-infrared region of the spectrum. The optical and electrical design of the radiometer is introduced, and then the calibration and characterization of the radiometer are described. Laboratory measurements include the spectral responsivity for each channel of the radiometer, the temperature dependence of the total responsivity for each channel, system linearity, field of view, and finally, the absolute radiometric calibration. A solar-radiation-based calibration is used to determine the absolute responsivity. OCIS codes: 230.0040, 230.3670, 280.4788, 280.4991.

The surface and edge emissions from dye-filled and dye-topped polycarbonate and polymethyl methacrylate luminescent solar concentrators were measured. We demonstrate that about 40-50% of the absorbed light energy (and 50-70% of the photons) is lost through the top and bottom surfaces of the filled waveguide. In most cases the escape cone losses are greater at the top than the bottom surface. OCIS codes: 350.6050, 350.5500, 310.2785, 260.2510, 230.7390, 160.5470.

The visibility of stars, planets, diffraction coronas, halos, and rainbows during the partial and total phases of a solar eclipse is studied. The limiting magnitude during various stages of the partial phase is presented. The sky radiance during totality with respect to noneclipse conditions is revisited and found to be typically 1/4000. The corresponding limiting magnitude is +3.5. At totality, the signal-to-background ratio of diffraction coronas, halos, and rainbows has dropped by a factor of 250. It is found that diffraction coronas around the totally eclipsed Sun may nevertheless occur. Analyses of lunar halo observations during twilight indicate that bright halo displays may also persist during totality. Rainbows during totality seem impossible. OCIS codes: 010.2940, 010.1290, 350.1260.

Land surface albedo determines the repartition of downwelling solar radiation into components that are either reflected back to the atmosphere or absorbed by the surface. As more sophisticated soil--vegetation--atmosphere transfer schemes are being implemented in numerical meteorological models, it will become increasingly important to accurately characterize the spatial and temporal albedo variations. Within the scope of the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Satellite Application Facility for Land Surface Analysis, we have developed a daily albedo product, which is derived in near real time from observations provided by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) instrument onboard the geostationary satellites of the Meteosat Second Generation series. The basic algorithm concept comprises an atmospheric correction scheme, the inversion of a linear semiempirical model of the bidirectional reflectance distribution function, the angular integration of the bidirectional reflectance distribution function to obtain spectral albedo, and the application of suitable conversion relations to derive broadband albedo estimates. The reflectance model inversion is performed each day based on the available set of clear-sky observations. In addition, constraints on the model parameters are taken into account in the inversion process. By specifying these constraints according to the previous model output in a recursive manner, a complete spatial coverage of the resulting albedo maps is achieved while, at the same time, preserving a high temporal resolution. This paper primarily concentrates on the description of the methodology. In addition, examples for the obtained albedo maps and time series, as well as the first validation results, are presented. Index Terms--Geostationary satellites, land surface modeling, near real time, operational processing, surface albedo.

The phenomenon of sunglint, well known in satellite remote sensing, lacks a fundamental characterization under controlled laboratory conditions. Exploiting an apparatus specifically assembled for the purpose, we examine the signal collected by a photopolarimeter, pointed at a wavy water surface with measurable statistics and illuminated by a laser source. We also analyze the wave slope distributions, retrieved with an imaging system, and correlate them with the time series of glints. More particularly, we investigate the link between the occurrence of glints and that of the slopes from which they originate. In this context, the results obtained by applying the Hilbert-Huang transform technique to the slope time series are compared with those obtained through a traditional Fourier transform. This novel study first identifies the individual atomic glints as Fresnel reflection originating from a single wave facet. It then discusses the periodic character of a sequence of glints generated by a gravity wave state, as opposed to the erratic behavior of glints typical of capillary wave states. In mixed gravity-capillary conditions, it is shown that the glint properties are governed mainly by the capillary regime. OCIS codes: 120.6660, 010.0280, 010.4450.

Abstract: The aim of this work has been to obtain a typical annual time a function by the application of a calculation procedure based on a Fourier analysis to global solar radiation data of nine years at Helwan Egypt from June 1991 to August 1999. This function allows us to estimate the most probable values of the horizontal daily global solar radiation for every day of the year at Helwan Egypt. It is confirmed that the harmonic model presents an important percentage with 98% confidence bounds. The applied method permits its application to the new measurements of solar radiation that are being carried out, This will be necessary because of the number of years used in this study. Key Words: Statistical Analysis -Global Solar Radiation -Fourier transforms, INTRODUCTION The Solar radiation data needed for effective research into solar energy utilization. The physical and statistical routes to solar metrology related to each other. The parameters, which govern a [...]

Geoengineering (the intentional modification of Earth's climate) has been proposed as a means of reducing C[O.sub.2]-induced climate warming while greenhouse gas emissions continue. Most proposals involve managing incoming solar radiation such that future greenhouse gas forcing is counteracted by reduced solar forcing. In this study, we assess the transient climate response to geoengineering under a business-as-usual C[O.sub.2] emissions scenario by using an intermediate-complexity global climate model that includes an interactive carbon cycle. We find that the climate system responds quickly to artificially reduced insolation; hence, there may be little cost to delaying the deployment of geoengineering strategies until such a time as 'dangerous' climate change is imminent. Spatial temperature patterns in the geoengineered simulation are comparable with preindustrial temperatures, although this is not true for precipitation. Carbon sinks in the model increase in response to geoengineering. Because geoengineering acts to mask climate warming, there is a direct C[O.sub.2]-driven increase in carbon uptake without an offsetting temperature-driven suppression of carbon sinks. However, this strengthening of carbon sinks, combined with the potential for rapid climate adjustment to changes in solar forcing, leads to serious consequences should geoengineering fail or be stopped abruptly. Such a scenario could lead to very rapid climate change, with warming rates up to 20 times greater than present-day rates. This warming rebound would be larger and more sustained should climate sensitivity prove to be higher than expected. Thus, employing geoengineering schemes with continued carbon emissions could lead to severe risks for the global climate system. carbon cycle | climate change | geoengineering | climate forcing | managing solar radiation

The aim of this research is to investigate the theoretical usefulness of a solar chimney with thermal inertia applied to the Mediterranean climates, offering nocturnal ventilation benefits. A mathematical dynamical model is proposed to evaluate the energy performance of a solar chimney with 24 cm concrete wall as storage surface for solar radiation. The results obtained with the proposed model are coherent with several models response and experiments reported on solar chimneys. As well, the difference of the proposed model to others is the incorporation of an unsteady state and the inclusion of thermal inertia. The results show that for a 2 m height and width of air channel of 14.5 cm, 0.011 kg/s air mass flow rate is obtained for 450 W/[m.sup.2]. The 24 cm thickness concrete wall, reaches its greater temperature 2 h later with respect to the maximum ambient temperature, maintaining its temperature over the beginning of the night, so nocturnal ventilation is achieved. The model shows the interest in continuing investigating on this cooling techniques and to built a solar chimney with thermal inertia for future experimental research.

Thermal comfort of people occupying indoor spaces depends, to a large extent, on the direct component of solar radiation incident on the human body. In turn, even the diffuse component of the solar radiation could affect the thermal sensations of people. Despite this evidence, at the present there is a lack in the availability of simple and reliable methods capable of taking into account the influence of the solar radiation on thermal balance in the human body. In this work a comprehensive method is presented for the computation of the mean radiant temperature of people in thermal moderate indoor environments in the presence of solar radiation. The effects produced on the amount of solar radiation entering rooms in the presence of shadowing devices are also analysed. Finally, an application of the method is provided for a non-parallelepiped room equipped with a south window: results are shown in terms of the mean radiant temperature. A simple evaluation of thermal comfort conditions, referring to the present international standards, is also provided. The model can be easily linked to the computerized methods for analyzing the thermal behaviour of buildings, and is intended as a support for the thermal comfort evaluation methods. Keywords: Thermal comfort; Solar radiation; Moderate thermal environments; Buildings indoor quality

A detailed three-dimensional computational fluid dynamics (CFD) analysis on gas-particle flow and heat transfer inside a solid-particle solar receiver, which utilizes freefalling particles for direct absorption of concentrated solar radiation, is presented. The two-way coupled Euler-Lagrange method is implemented and includes the exchange of heat and momentum between the gas phase and solid particles. A two-band discrete ordinate method is included to investigate radiation heat transfer within the particle cloud and between the cloud and the internal surfaces of the receiver The direct illumination energy source that results from incident solar radiation was predicted by a solar load model using a solar ray-tracing algorithm. Two kinds of solid-particle receivers, each having a different exit condition for the solid particles, are modeled to evaluate the thermal performance of the receiver Parametric studies, where the particle size and mass flow rate are varied, are made to determine the optimal operating conditions. The results also include detailed information for the gas velocity, temperature, particle solid volume fraction, particle outlet temperature, and cavity efficiency. [DOI: 10.1115/1.2716418]

The potential role of solar variations in modulating recent climate has been debated for many decades and recent papers suggest that solar forcing may be less than previously believed. Because solar variability before the satellite period must be scaled from proxy data, large uncertainty exists about phase and magnitude of the forcing. We used a coupled climate system model to determine whether proxy-based irradiance series are capable of inducing climatic variations that resemble variations found in climate reconstructions, and if part of the previously estimated large range of past solar irradiance changes could be excluded. Transient simulations, covering the published range of solar irradiance estimates, were integrated from 850 AD to the present. Solar forcing as well as volcanic and anthropogenic forcing are detectable in the model results despite internal variability. The resulting climates are generally consistent with temperature reconstructions. Smaller, rather than larger, long-term trends in solar irradiance appear more plausible and produced modeled climates in better agreement with the range of Northern Hemisphere temperature proxy records both with respect to phase and magnitude. Despite the direct response of the model to solar forcing, even large solar irradiance change combined with realistic volcanic forcing over past centuries could not explain the late 20th century warming without inclusion of greenhouse gas forcing. Although solar and volcanic effects appear to dominate most of the slow climate variations within the past thousand years, the impacts of greenhouse gases have dominated since the second half of the last century.

Solar radiation is characterized by short fluctuations introduced by passing clouds. An analysis of these fluctuations with regard to solar energy applications should focus on the instantaneous clearness index. Its probability distribution for a given mean clearness index is, as a first approximation, independent from the season and partly also from the site. This is verified for four annual datasets from three different sites. An analysis of fluctuations in solar radiation must focus on their amplitude, persistence, and frequency of occurrence rather than their location in time. The Fourier analysis cannot satisfactorily provide this information since time series of the instantaneous clearness index exhibit no periodicity. Instead, a localized spectral analysis based on wavelet bases rather than on periodic-ones has been applied. This analysis allows the decomposition of the fluctuating clearness index signal into a set of orthonormal subsignals. Each of them represents one specific scale of persistence of the fluctuation. The annual mean square values of all subsignals have been analysed, permitting the allocation of the signal's power content to the different scales of persistence of a fluctuation. These annual mean values agree well for the different datasets, indicating the existence of statistically significant mean square values of the fluctuations as a function of their persistence. The analysis offers a valuable tool for the estimation of power flow fluctuations introduced by direct solar energy systems. With further elaboration it may be applied by power system operators for network planning in distribution grids with a high density of embedded generation. Keywords: Fluctuations; Spectral analysis; Wavelets; Clearness index; Solar radiation

Sun glint obscures the radiance originating from within the water, but it also mirrors the solar radiance after transmission through the atmosphere. The difference between a glint-contaminated pixel and a nearby nonglint pixel from a spectral image prior to atmospheric correction yields a direct estimate of the spectral transmission of solar radiance which can then be used both to confirm atmospheric models and to retrieve an estimate of remote sensing reflectance. Index Terms--Atmospheric transmission, radiative transfer, remote sensing reflectance, spectral imaging, sun glint, sun glitter.

The photocatalytic degradation of four reactive dyes using Ti[O.sub.2] was investigated in suspended and immobilized systems under solar irradiation. Batch degradation experiments were carried out at initial concentrations ranging from 25 to 100 mg [1.sup.-1] and at a catalyst loading of 0.5-1 g [1.sup.-1]. The studies on batch photocatalytic degradation of four dyes, showed about 30-70% colour removal depending on the initial dye concentration, dye structure (functional group and reactivity of dyes) and the amount of catalyst. The thin film immobilized surface photoreactor was able to give nearly 90-98% colour removal depending on the initial concentration and exposure time. Flow rate has noticeable effect on colour removal particularly at higher concentration (100 mg [1.sup.-1]). High colour removals obtained with solar radiation indicated effectiveness of this process and its potential for practical application. Keywords: Photocatalysis; Ti[O.sub.2]; Thin film; Photoreactor; Catalyst immobilization; AOP; Dye degradation; Decolourization; Solar/UV irradiation

The thermal performances of vacuum glazings employing coatings with emittance between 0.02 and 0.16 were simulated using a three-dimensional finite volume model. Physical samples of vacuum glazings with hard and soft coatings with emittance of 0.04, 0.12 and 0.16 were fabricated and their thermal performance characterised experimentally using a guarded hot box calorimeter. Good agreement was found between experimental and theoretical thermal performances for both a vacuum glazing with a soft coating (emittance 0.04) and those with hard coatings (emittance 0.12 and 0.16). Simulations showed that for a low value of emittance (e.g. 0.02), the use of two low-emittance coatings gives limited improvement in thermal performance of the glazing system. The use of a single high performance low-emittance coating in a vacuum glazing has been shown to provide excellent performance. Keywords: Vacuum glazing; Low-emittance coating; Thermal performance; Insolation

Common indicators used to examine the potential for utilising natural radiation of urban forms include the sky view factor ([V.sub.s]), the height to width ratio and the urban horizon angle. These indicators are conveniently related to one another. In comparing simulations of sky view factor with those of simulated solar irradiation, which itself relates well to illumination, this paper tests the effectiveness of all three--based on analysis of three existing Swiss districts. From this, it is concluded that the absence of treatment of direct solar radiation, sky anisotropy or reflected radiation seriously impairs the ability of the [V.sub.s]-related indicators to offer meaningful insights regarding natural radiation potential in the localised case. Predictions of annual irradiation from aggregations of [V.sub.s] also perform badly, but the aggregate [V.sub.s] does correlate reasonably well with irradiation so that judgements of overall radiation availability may be made with some confidence. Keywords: Urban morphology; Radiation availability; Comparisons

Reaction between tantalum (Ta) and carbon (graphite or amorphous carbon) in tap-compacted powder mixture state under solar radiation heating was investigated. Although mono-carbide TaC is the final equilibrium product at 1600[degrees]C under presence of excess carbon, formation of sub-carbide [Ta.sub.2]C as the interim product was detected under certain circumstances. After 30 min reaction at 1600 [degrees]C reached by solar radiation heating, Ta powders compacted with graphite powders by pressing into pellet were fully converted to TaC but loosely tap-compacted powder mixtures of Ta and graphite yielded [Ta.sub.2]C coexisted with TaC. On the other hand, Ta powders tap-compacted with amorphous carbon were fully converted to TaC under the comparable reaction condition reflecting the high reactivity and chemical carbon activity of amorphous carbon compared with those of graphite (reference state of carbon). Keywords: Tantalum sub-carbide; Tantalum mono-carbide; Solar furnace

The launch of the Geostationary Earth Radiation Budget (GERB) instrument onboard the Meteostat 8 allows a diurnal sampling of the Earth's Radiation Budget for the first time, providing a unique and important addition to polar-orbiting measurements. However, preliminary data from the GERB instrument exhibit systematic asymmetry in the short-wave (SW) flux diurnal variation. Such asymmetries are not found in the Clouds and the Earth's Radiant Energy System angular distribution models used to convert the directional broad-band GERB SW radiances to fluxes. Comparison between angularly matched estimations of reflected SW flux at the top of the atmosphere from the Spinning Enhanced Visible and Infra Red Imager (SEVIRI) and GERB data indicates that the SEVIRI spectral modeling could be a major issue. In addition, the results indicate that other factors such as the GERB SW geolocation, the GERB detector spectral response functions, the GERB nominal footprint resolution, and cloud cover could also potentially have an influence on the diurnal evolution of the GERB SW fluxes, as they can erroneously impact on the GERB SW correction factor. Index Terms--Remote sensing, satellites, solar energy, solar radiation.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.05.011 Byline: C.N. Foley (a), L.R. Nittler (a), T.J. McCoy (b), L.F. Lim (c), M.R.M. Brown (b)(d), R.D. Starr (e), J.I. Trombka (c) Keywords: Asteroids; composition; Solar radiation; Meteorites; Spectroscopy; Asteroids; surfaces Abstract: The NEAR mission to 433 Eros provided detailed data on the geology, mineralogy, and chemistry of this S-class asteroid [McCoy, T.J., Robinson, M.S., Nittler, L.R., Burbine, T.H., 2002. Chem. Erde 62, 89-121; Cheng, A.F., 1997. Space Sci. Rev. 82, 3-29] with a key science goal of understanding the relationship between asteroids and meteorites [Cheng, A.F., 1997. Space Sci. Rev. 82, 3-29; Gaffey, M.J., Burbine, T.H., Piatek, J.L., Reed, K.L., Chaky, D.A., Bell, J.F., Brown, R.H., 1993a. Icarus 106, 573-602]. Previously reported major element data revealed a bulk surface similar to that of ordinary chondrites, with the notable exception of sulfur, which was highly depleted [Trombka, J.I., and 23 colleagues, 2000. Science 289, 2101-2105; Nittler, L.R., and 14 colleagues, 2001. Meteorit. Planet. Sci. 36, 1673-1695]. The origin of this sulfur deficiency, and hence the fundamental nature of the asteroid's surface, has remained controversial. We report a new analysis of NEAR X-ray spectrometer data, indicating that Eros has Cr/Fe, Mn/Fe, and Ni/Fe ratios similar to ordinary chondrite meteorites of type LL or L. Chondritic levels of Cr, Mn, and Ni argue strongly against a partial melting explanation for the sulfur depletion. Instead, our results provide definitive evidence that Eros is a primitive body with composition and mineralogy similar to ordinary chondrites, but with a surface heavily modified by interactions with the solar wind and micrometeorites, processes collectively termed space weathering. Author Affiliation: (a) Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015-1305, USA (b) Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560-0119, USA (c) NASA Goddard Spaceflight Center, Bldg. 2, Code 691, Greenbelt, MD 20771, USA (d) Department of Geological Sciences, Arizona State University, Tempe, AZ 85287-1404, USA (e) Department of Physics, The Catholic University of America, Washington, DC 20064, USA Article History: Received 27 January 2006; Revised 11 May 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2005.09.022 Byline: Enno Bahlmann (a), Ralf Ebinghaus (a), Wolfgang Ruck (b) Keywords: Mercury; Laboratory flux chamber; Air/surface exchange; Soil temperature; Solar radiation Abstract: Recent measurements at different locations suggest that the emission of mercury from soils may play a more pronounced role in the global mercury cycle as suggested by global emission inventories and global mercury cycling models. For up scaling and modelling of mercury emissions from soils a comprehensive assessment of the processes controlling the emission of mercury from soils is imperative. We have developed a laboratory flux measurement system (LFMS) to study the effect of major environmental variables on the emission of mercury under controlled conditions. We have investigated the effects of turbulent mixing, soil temperature and solar radiation on the emission of mercury from soils. The emission of mercury from soils is constant over time under constant experimental conditions. The response of the mercury emission flux to variations of the atmospheric transfer parameters such as turbulence requires a rapid adjustment of the equilibrium that controls the Hg.sup.o concentration in the soil air. It has been shown that the light-induced flux is independent of the soil temperature and shows a strong spectral response to UV-B. Author Affiliation: (a) GKSS Research Centre Geesthacht, Institute for Coastal Research, Max-Planck-Str. 1, D-21502 Geesthacht, Germany (b) University of Lueneburg, Institute for Ecology and Environmental Chemistry, Scharnhorst-Str. 1, D-21335 Lueneburg, Germany Article History: Received 11 May 2004; Revised 2 March 2005; Accepted 30 September 2005

Different methods may be used for measurement of very high solar irradiance on large areas, all of them are based on one or several heat flux sensors. The most common gages used for this purpose are the Gardon type, which are usually calibrated using a black body at a certain temperature as the radiant source. An alternative way to calibrate these sensors based on a thermal balance is presented in this article. The agreement between both methodologies confirms the validity of the black body calibration procedure and the potential of the calorimetry to calibrate heat flux sensors. However, with the proposed method, the uncertainty in estimating the calibration constant of these sensors is reduced from 3% to less than 2%. This procedure calibrates these sensors to measure properly under concentrated solar radiation. Keywords: High solar irradiance; Heat flux measurement; Calorimeter; Radiometer

The NEAR mission to 433 Eros provided detailed data on the geology, mineralogy, and chemistry of this S-class asteroid [McCoy, T.J., Robinson, M.S., Nittler, L.R., Burbine, T.H., 2002. Chem. Erde 62, 89-121; Cheng, A.F., 1997. Space Sci. Rev. 82, 3-29] with a key science goal of understanding the relationship between asteroids and meteorites [Cheng, A.F., 1997. Space Sci. Rev. 82, 3-29: Gaffey, M.J., Burbine, T.H., Piatek, J.L., Reed, K.L., Chaky, D.A., Bell, J.F., Brown, R.H., 1993a. Icarus 106, 573-602]. Previously reported major element data revealed a bulk surface similar to that of ordinary chondrites, with the notable exception of sulfur, which was highly depleted [Trombka, J.I., and 23 colleagues, 2000. Science 289, 2101-2105: Nittler, L.R., and 14 colleagues, 2001. Meteorit. Planet. Sci. 36, 1673-1695]. The origin of this sulfur deficiency, and hence the fundamental nature of the asteroid's surface, has remained controversial. We report a new analysis of NEAR X-ray spectrometer data, indicating that Eros has Cr/Fe, Mn/Fe, and Ni/Fe ratios similar to ordinary chondrite meteorites of type LL or L. Chondritic levels of Cr, Mn, and Ni argue strongly against a partial melting explanation for the sulfur depletion. Instead, our results provide definitive evidence that Eros is a primitive body with composition and mineralogy similar to ordinary chondrites, but with a surface heavily modified by interactions with the solar wind and micrometeorites, processes collectively termed space weathering. Keywords: Asteroids, composition; Solar radiation; Meteorites; Spectroscopy; Asteroids, surfaces

A numerical model called 'NEOPLANTA' for estimating solar UV irradiance and UV index under cloud-free conditions is being developed and tested at the University of Novi Sad in Serbia. In this paper, the model features, calculation procedure, and input parameters are described. Effects of the absorption of UV radiation by [O.sub.3] S[O.sub.2] and N[O.sub.2] and absorption and scattering by aerosol as well as the air molecules in the atmosphere are included. The performance of the model has been tested with respect to its capability of UV index, which is a weighted integral between 280 and 400 nm of the solar irradiance reaching the ground. For this test 10-day data measured during the spring and summer in 2003, 2004, and 2005 are used. Data are recorded by the Yankee UVB-1 biometer located at the Novi Sad university campus (45.33[degrees]N, 19.85[degrees]E; 84 m MSL). Error analyses indicate that the modeled values agree well with the observations.

The effect of preparation method on the photocatalytic degradation of phenol using zinc oxides under solar radiation was studied in batch reactors. Zinc oxide was prepared by different methods by varying precipitating agents and the source of precursors and microwave irradiation time and characterized by XRD, surface area, acid sites and crystallite sizes. The photocatalytic reactions were carried out by varying the reaction conditions such as preparation methods, microwave irradiation time, activation temperature, solar irradiation time, catalyst amount, substrate concentration etc. Under optimization conditions, it was found that 15 min microwave irradiated sample shows 88% phenol (0.6 g/1 dose) degradation at pH 5.0 and 4 h reaction time under sunlight. Zinc oxide samples prepared by microwave irradiation and calcined at 573 K exhibit highest surface area, acid sites and lowest crystallite sizes and show highest activity towards photocatalytic oxidation of phenol. Keywords: Photocatalytic degradation; Microwave irradiation; Hydrozincite; Solar radiation

The QinetiQ atmospheric radiation model (QARM) is a comprehensive model of the energetic radiation in the atmosphere. In this paper we report on the improvement and validation activities for this model. The improvements include the implementation of two additional cosmic ray models, new response matrix, dose rate and flight dose calculation facilities. Tests/validations of the model have been carried out at individual component level as well as at system level. We will also report on the web interface developed to allow easy access to the model. Index Terms--Atmosphere, cosmic rays, modelling, Monte Carlo, radiation, solar particles.

Evidence is presented that solar particle events are a self-organized critical phenomenon. Using daily and monthly fluences of solar protons measured by the IMP-8 and GOES satellite instrumentation over a 28-year period, long-term correlation of events, fractal characteristics and power function behavior for the density functions of fluence magnitudes and waiting times are demonstrated. The implications are that it is not possible to predict the time of occurrence and magnitude of solar particle events within narrow limits. Index Terms--Fractal, rescaled range, self-organized criticality, solar particle event.

We determine the solar constant experimentally using two independent techniques that allow us to study the dependence of the solar irradiation on the zenith angle and the characteristics of the light extinction in the atmosphere. Our result for the solar luminosity agrees within 7% of the accepted value. This value can be used to estimate the luminosity or power radiated by the Sun. The experiment is inexpensive and conceptually easy to perform and understand.

Unexpected diurnal discrepancies between high-quality spectroradiometers were observed during the 2000 Nordic Ozone Group Intercomparison campaign. The spectral ratios of the irradiances showed a diurnal variation of ~2-9%. This cannot be explained by the nonideal angular response of the instruments' input optics in one plane (cosine effect). Instead, by using a radiative transfer model, we show that differences in the angular response in four azimuth planes have the potential to bias the measured data by up to 4.4% (azimuth effect). Other relevant factors are also discussed and quantified and are shown to be significant when diurnal changes in radiation are explained by environmental factors, or when measured data are compared with model or satellite data. Again, intercomparison campaigns have the potential to reveal errors that would otherwise remain undetected. OCIS codes: 260.7190, 120.6200, 120.5630.

In this technical note authors propose new expressions to calculate the diffuse irradiance coming from the horizon brightness band on a tilted plane. As in the model of Perez, it is assumed that the radiance from this band is a constant. New expressions are more exact than previous ones as they eliminate some of the simplifications considered in the model of Perez. For small slope angles new expressions give irradiance values up to 32.98% higher than with the cited model. Notwithstanding, when slope angle increases obtained differences sharply decrease at the beginning and this decrease becomes practically linear from about 40[degrees] on. Keywords: Radiation estimation; Solar radiation: Modelization

This paper presents a study of the variability of solar radiation in the minute-long time range. The solar climate in Northern Europe is classified in this paper as being either stable, or highly variable, due to stochastic cloud cover inducing fluctuations of the solar irradiance. In general, solar radiation exhibits both positive and negative increments in the radiation during any period. The distribution functions of these increments with respect to their magnitude and duration are investigated, as well the distribution functions of stable intervals during generally variable radiation. The distribution functions are found to be a superposition of two exponential functions with different exponents, which depend on the magnitude of the radiation increments. Keywords: Fluctuation; Solar irradiance; Distribution function

A selection of eight high performance clear sky solar irradiance models is evaluated against a set of 16 independent data banks covering 20 years/stations, altitudes from sea level to 1600 m and a large range of different climates. Their performance evaluated on very clear condition measurements are within 4% in term of standard deviation. The conclusions are that the accuracy of the input parameters such as the turbidity is crucial in the validity of the obtained radiation components, and that the choice of a specific model is secondary. The model selection criteria should be based upon either implementation simplicity, input parameter availability (Linke turbidity or aerosol optical depth) or the capacity of the model to produce spectral radiation. Keywords: Clear sky irradiance; Solar irradiance modeling; Model validation