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1
Singh, Bhawan, and Richard Taillefer. "Le bilan énergétique et le gel au sol : une analyse statistique." Géographie physique et Quaternaire 38, no. 2 (November 29, 2007): 135–47. http://dx.doi.org/10.7202/032548ar.
Повний текст джерелаАнотація:
RÉSUMÉ Des mesures régulières détaillées des composantes du bilan radiatif et énergétique et des régimes thermiques et hydrique du sol jusqu'à 5 m de profondeur ont été prises entre les mois d'août 1979 et août 1980 dans une forêt de pins près du lac Hélène, Jamésie. Les analyses statistiques faites sur ces mesures indiquent que la température du sol et, par conséquent, le gel à l'intérieur du sol s'expliquent par les échanges d'énergie radiative et calorifique près de la surface et par l'accumulation de la neige sur la surface. Pour des périodes de temps choisies, les températures du sol sont faiblement corrélées avec le rayonnement solaire (K ↓ ), le flux de chaleur dans le sol (QG) et la température de l'air (TAIR). Lorsque les cumuls de ces variables (∑K ↓, ∑QG et ∑TAIR) ainsi que l'épaisseur de la neige (EPAIS) sont utilisés, les corrélations sont plus fortes. En ce qui a trait à la profondeur du gel, la corrélation est la plus forte avec EPAIS, ∑QG, ∑TAIR et ∑K ↓, en ordre d'importance. D'ailleurs ces variables expliquent plus de 99% de la variance de la profondeur du gel dans le sol.
2
Cantat, Olivier, and Alexandre Follin. "Les singularités thermiques d’un espace périurbain dans une agglomération de dimension moyenne : le cas de Caen durant l’hiver 2018/2019." Climatologie 17 (2020): 3. http://dx.doi.org/10.1051/climat/202017003.
Повний текст джерелаАнотація:
L’analyse comparative des données météorologiques de la station rurale de Carpiquet avec une station expérimentale en périphérie de la ville de Caen a permis de montrer la présence en hiver d’un léger îlot de chaleur péri-urbain (ICPU) (moyenne de +0,4°C). Il est caractérisé par un maximum d’intensité en fin d’après-midi et début de soirée (+0,8°C) et des écarts faibles le reste du temps. Derrière cette image moyenne, une analyse du continuum temporel au pas de temps journalier puis horaire a mis en exergue des comportements différenciés selon les types de temps. Le caractère le plus original des résultats est la présence certes rare, mais significative en termes d’intensité, d’un îlot de fraîcheur péri-urbain (IFPU). Il se forme de nuit par temps clair et calme et se prolonge dans la matinée, jusqu’à présenter un maximum d’intensité vers 9 h UTC. Cette inversion par rapport au schéma classique de fonctionnement des îlots de chaleur urbain (ICU) s’explique par un mode d’occupation du sol favorable à la formation d’une poche froide par rayonnement nocturne, favorisée par l’absence totale de vent (effet de barrage du bâti et de la végétation) et par la faible densité urbaine, alors que sur la campagne ces mécanismes de refroidissement sont atténués par la persistance d’un léger flux. Cet IFPU résiste et s’intensifie en début de matinée, jusqu’à temps que le soleil et la turbulence de l’air ne viennent échauffer et disperser cette pellicule d’air froid plus dense. Ici, les conditions stationnelles semblent donc primer sur les effets purement urbains car l’agglomération de Caen ne présente pas une masse suffisante pour créer une « bulle chaude » jusque dans ses quartiers périphériques quand un type de temps radiatif s’impose.
3
Buckus, Raimondas, Aleksandras Chlebnikovas, Birute Strukcinskiene, Rimantas Stukas, Donatas Austys, Jacek Caban, Marcin Bogucki, et al. "Simulating the Dispersion of the Energy Flux Density of the Electromagnetic Field Generated by Antennas for Mobile Communications." Electronics 11, no. 15 (August 4, 2022): 2431. http://dx.doi.org/10.3390/electronics11152431.
Повний текст джерелаАнотація:
The last two decades have faced a significantly increased number of telecommunication antennas emitting electromagnetic radiation in residential areas. The theoretical simulation of the dispersion of the energy flux density of the electromagnetic field has been performed applying the physical peculiarities of the waves generating electromagnetic radiation. Having evaluated studies on simulation, the visual representation of the spread of electromagnetic radiation has been carried out according to the results obtained applying the AutoCad package. A comparison of the simulated value of the energy flux density radiated from antennas for mobile telecommunications with the measured one has disclosed an overlap of 30%. The simulation of the energy flux density showed that, in the close proximity zone (under a distance of 30 m), antennas radiate values within the range 10–10,000 µW/cm2. At a distance larger than 30 m, the values of energy flux density fluctuate from 10 to 0.001 µW/cm2.
4
Pomraning, G. C. "Multimode flux-limited diffusion theory." Laser and Particle Beams 10, no. 2 (June 1992): 239–51. http://dx.doi.org/10.1017/s0263034600004389.
Повний текст джерелаАнотація:
We present a diffusion approximation describing the flow of thermal radiation that preserves several important features of the underlying equation of radiative transfer. Specifically, this diffusion description: (1) is flux limited; (2) reduces to the correct transport weak gradient limit; (3) allows correct and simultaneous exponential growth and Decay for a certain class of problems; (4) gives correct transport results for certain contiguous half-space problems; and (5) allows the radiative flux and the gradient of the radiation energy density to point in independent directions. This treatment extends and generalizes earlier flux-limited diffusion approximations that are widely used in radiation–hydrodynamics calculations.
5
Perovich, Donald K. "Sunlight, clouds, sea ice, albedo, and the radiative budget: the umbrella versus the blanket." Cryosphere 12, no. 6 (June 27, 2018): 2159–65. http://dx.doi.org/10.5194/tc-12-2159-2018.
Повний текст джерелаАнотація:
Abstract. The surface radiation budget of the Arctic Ocean plays a central role in summer ice melt and is governed by clouds and surface albedo. I calculated the net radiation flux for a range of albedos under sunny and cloudy skies and determined the break-even value, where the net radiation is the same for cloudy and sunny skies. Break-even albedos range from 0.30 in September to 0.58 in July. For snow-covered or bare ice, sunny skies always result in less radiative heat input. In contrast, leads always have, and ponds usually have, more radiative input under sunny skies than cloudy skies. Snow-covered ice has a net radiation flux that is negative or near zero under sunny skies, resulting in radiative cooling. Areally averaged albedos for sea ice in July result in a smaller net radiation flux under cloudy skies. For May, June, August, and September, the net radiation is smaller under sunny skies.
6
Rosida, NFN, and Indah Susanti. "PENGARUH AEROSOL TERHADAP FLUKS RADIASI NETO DI LAPISAN ATAS ATMOSFER DAN DI PERMUKAAN BERDASAR DATA SATELIT [INFLUENCE OF AEROSOL ON NET RADIATION FLUX AT THE TOP OF ATMOSPHERE AND SURFACE BASED ON SATELLITE]." Jurnal Sains Dirgantara 14, no. 2 (July 21, 2017): 27. http://dx.doi.org/10.30536/j.jsd.2016.v14.a2444.
Повний текст джерелаАнотація:
The direct effects of aerosols on radiation budget in Indonesia have been analyzed based on radiation flux net data from the Clouds and the Earth's Radiant Energy System (CERES) instrument and aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra. Radiation budget calculated including short wave and long-wave radiation. Data from March 2000 until February 2010, processed using Grads version 2 to obtain aerosol radiative forcing value. Net radiation in clean sky, estimated using slope method. The analysis showed high temporal variation of aerosols density in the atmosphere with a value AODmax> 2, which generally causes decreases net radiation flux, so providing a cooling effect. The influence of aerosols on the net radiation flux can be very clearly seen in the case of forest fires. AOD in 2006 increased and caused radiation flux anomalies ranging from -9 watt/m-2 to -14 watts/m-2, with the largest decline occurred in the surface. From all the data period, aerosol radiative forcing at TOA level (ARFTOA) on Indonesia was -0.49 watt/m-2 and aerosol radiative forcing at the surface level (ARFSurf) on Indonesia was -17.72 watt/m-2, that influence to the Indonesian climate condition.
7
JHA, T. N. "Characteristics of radiative and non-radiative energy fluxes over monsoon trough zone." MAUSAM 52, no. 3 (January 11, 2022): 581–92. http://dx.doi.org/10.54302/mausam.v52i3.1729.
Повний текст джерелаАнотація:
In order to describe behaviour of radiative and non-radiative erergy fluxes in the surface layer, computation of net radiation, sensible, latent and heat soil flux has been done using hourly global radiation, slow response data of MONTBLEX-90 and surface observation of Varanasi and Jodhpur during rainy and non-rainy days in July 1990. Daily and hourly ground temperature is calculated solving one dimensional heat conduction equation and soil heat flux is computed using force restored method .Outgoing Longwave Radiation (OLR) is calculated by Stefan-Boltzrnann law of radiation and the largest diurnal variability was found over dry convective zone. Results show that OLR from the ground lies in the range 473.0-537.6 Wm-2 at Jodhpur and 497.4 -548.4 Wm-2 at Varanasi during generally cloudy day. The dip in OLR is increascd by 10% with increase of relative humidity and cloudiness. Daily mean of the largest downward soil heat flux are found as 206.4 and 269.4 Wm-2 at Varanasi and Jodhpur respectively during cloudy day. About 40-50% of net radiation is imparted to soil heat flux at Varanasi and Jodhpur. Sum of the hourly non- radiative energy fluxes has not been balanced by net radiation while daily cumulative value of the fluxes balances the net radiation during non-rainy day.
8
Wang, Zhenhua, Shikui Dong, Zhihong He, Lei Wang, Weihua Yang, and Bengt Ake Sunden. "Numerical analysis of radiative heat transfer in an inhomogeneous and non-isothermal combustion system considering H2O/CO2/CO and soot." International Journal of Numerical Methods for Heat & Fluid Flow 27, no. 9 (September 4, 2017): 1967–85. http://dx.doi.org/10.1108/hff-03-2016-0127.
Повний текст джерелаАнотація:
Purpose H2O, CO2 and CO are three main species in combustion systems which have high volume fractions. In addition, soot has strong absorption in the infrared band. Thus, H2O, CO2, CO and soot may take important roles in radiative heat transfer. To provide calculations with high accuracy, all of the participating media should be considered non-gray media. Thus, the purpose of this paper is to study the effect of non-gray participating gases and soot on radiative heat transfer in an inhomogeneous and non-isothermal system. Design/methodology/approach To solve the radiative heat transfer, the fluid flow as well as the pressure, temperature and species distributions were first computed by FLUENT. The radiative properties of the participating media are calculated by the Statistical Narrow Band correlated K-distribution (SNBCK), which is based on the database of EM2C. The calculation of soot properties is based on the Mie scattering theory and Rayleigh theory. The radiative heat transfer is calculated by the discrete ordinate method (DOM). Findings Using SNBCK to calculate the radiative properties and DOM to calculate the radiative heat transfer, the influence of H2O, CO2, CO and soot on radiation heat flux to the wall in combustion system was studied. The results show that the global contribution of CO to the radiation heat flux on the wall in the kerosene furnace was about 2 per cent, but that it can reach up to 15 per cent in a solid fuel gasifier. The global contribution of soot to the radiation heat flux on the wall was 32 per cent. However, the scattering of soot has a tiny influence on radiation heat flux to the wall. Originality/value This is the first time H2O, CO2, CO and the scattering of soot were all considered simultaneously to study the radiation heat flux in combustion systems.
9
Knight, I. K., and A. L. Sullivan. "A semi-transparent model of bushfire flames to predict radiant heat flux." International Journal of Wildland Fire 13, no. 2 (2004): 201. http://dx.doi.org/10.1071/wf03047.
Повний текст джерелаАнотація:
The radiation emitted by a body is related through the Stefan-Boltzmann equation to the temperature of the emitting element. In the case of flame, the emitting elements are carbon particles. Existing models of bushfire flame radiation assume, however, that the flame radiates as a surface with an emissivity of 1 (i.e. a blackbody). This is only true when the flame is thick enough to provide a continuous wall of radiating carbon particles. In this paper we propose a semi-physical model of radiant heat flux from bushfire flame that calculates the emissivity of the flame front based on its geometry and the optical properties of the flame. This model is calibrated using conservation of energy principles and empirical information about the radiant heat energy as a percentage of total energy of the flame. Comparisons are made with the flames generated by a propane-fuelled bushfire flame front simulator.
10
Golkarfard, Vahid, Seyyed Abdolreza Gandjalikhan Nassab, and Amir Babak Ansari. "Simulation of Solid Particles in Combined Conduction, Convection and Radiation Gas Flow over a Backward-Facing Step in a Duct." Applied Mechanics and Materials 110-116 (October 2011): 5276–82. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.5276.
Повний текст джерелаАнотація:
A numerical simulation procedure for studying deposition of aerosol particles in a laminar convection flow of radiating gas over a backward-facing step including the effect of thermal force is developed. In the gas flow, all of the heat transfer mechanisms consisting of conduction, convection and radiation take place simultaneously. Behavior of solid particles is studied numerically based on an Eulerian–Lagrangian method. Two dimensional Navier-Stokes and energy equations are solved using CFD techniques, while the radiating transfer equation (RTE) is solved by discrete ordinate method (DOM) for calculating radiative heat flux distribution. The objective of this research is to study the effect of Reynolds number variation and also radiation on thermophoretic deposition of particles. Numerical results show a decrease in deposition percent by increasing in Reynolds number and the radiation effect is negligible. The results are compared with the existing experimental and numerical data and good agreement is found.
11
Budaev, Bair V., and David B. Bogy. "The role of EM wave polarization on radiative heat transfer across a nanoscale gap." Journal of Applied Physics 132, no. 5 (August 7, 2022): 054903. http://dx.doi.org/10.1063/5.0094382.
Повний текст джерелаАнотація:
This work presents a novel study of radiative heat transfer between closely separated plates based on an extension of Planck’s spectrum of thermal radiations to systems with a steady heat flux. This extension together with electromagnetic wave theory is chosen specifically to avoid the commonly used so-called fluctuation dissipation theory, which is also limited to equilibrium systems. The spectrum of thermal radiation with a heat flux is described by the introduction of an analog of a chemical potential, which creates a bias toward the direction of heat transfer. This is the first comprehensive study of radiative heat transfer based on the generalization of Planck’s spectrum for systems with a heat flux, which eliminates contradictions arising when a heat flux is described in terms of the laws limited to equilibrium systems. The total heat flux is split into fluxes carried by waves with different frequencies, directions of propagation, and polarizations. This simplifies the analysis because due to the stochastic independence, the energy fluxes of such waves are additive, and this also reveals that the heat carrying capacity of radiation with the parallel polarization is significantly higher than that of the perpendicularly polarized radiation. This suggests that the rate of radiative heat transfer may be noticeably increased by the control of the polarization of thermal radiation.
12
Smith, Karen L., Michael Previdi, and Lorenzo M. Polvani. "The Antarctic Atmospheric Energy Budget. Part II: The Effect of Ozone Depletion and its Projected Recovery." Journal of Climate 26, no. 24 (December 2, 2013): 9729–44. http://dx.doi.org/10.1175/jcli-d-13-00173.1.
Повний текст джерелаАнотація:
Abstract In this study the authors continue their investigation of the atmospheric energy budget of the Antarctic polar cap (the region poleward of 70°S) using integrations of the Whole Atmosphere Community Climate Model from the years 1960 to 2065. In agreement with observational data, it is found that the climatological mean net top-of-atmosphere (TOA) radiative flux is primarily balanced by the horizontal energy flux convergence over the polar cap. On interannual time scales, changes in the net TOA radiative flux are also primarily balanced by changes in the energy flux convergence, with the variability in both terms significantly correlated (positively and negatively, respectively) with the southern annular mode (SAM). On multidecadal time scales, twentieth-century stratospheric ozone depletion produces a negative trend in the net TOA radiative flux due to a decrease in the absorbed solar radiation within the atmosphere–surface column. The negative trend in the net TOA radiative flux is balanced by a positive trend in energy flux convergence, primarily in austral summer. This negative (positive) trend in the net TOA radiation (energy flux convergence) occurs despite a positive trend in the SAM, suggesting that the effects of the SAM on the energy budget are overwhelmed by the direct radiative effects of ozone depletion. In the twenty-first century, ozone recovery is expected to reverse the negative trend in the net TOA radiative flux, which would then, again, be balanced by a decrease in the energy flux convergence. Therefore, over the next several decades, ozone recovery will, in all likelihood, mask the effect of greenhouse gas warming on the Antarctic energy budget.
13
Liu, Cheng, Evgeni Fedorovich, Jianping Huang, Xiao-Ming Hu, Yongwei Wang, and Xuhui Lee. "Impact of Aerosol Shortwave Radiative Heating on Entrainment in the Atmospheric Convective Boundary Layer: A Large-Eddy Simulation Study." Journal of the Atmospheric Sciences 76, no. 3 (March 1, 2019): 785–99. http://dx.doi.org/10.1175/jas-d-18-0107.1.
Повний текст джерелаАнотація:
AbstractEntrainment is critical to the development of the atmospheric convective boundary layer (CBL), but little is known about how entrainment is impacted by the aerosol radiative effect. An aerosol radiation transfer model is used in conjunction with large-eddy simulation (LES) to quantify the impact of aerosol shortwave radiative heating on entrainment and thermodynamics of an idealized dry CBL under aerosol-loading conditions. An entrainment equation is derived within the framework of a zero-order model (ZOM) with the aerosol radiative heating effect included; the equation is then examined against the LES outputs for varying aerosol optical depths (AODs) and free-atmosphere stratification scenarios. The results show that the heat flux profiles become more nonlinear in shape as compared to the case of the clean (no aerosol pollution) CBL, with the degree of nonlinearity being highly dependent on the AOD of the layer for the given type of radiation-absorbing aerosols. As AOD increases, less solar radiation reaches the surface and thus the surface heat flux becomes smaller, and both actual (LES) and ZOM-derived entrainment flux ratios decrease. This trend is opposite to the clean CBL where the LES-predicted flux ratios show an increasing trend with diminishing surface heat flux, while the ZOM-calculated flux ratio remains constant. The modified dimensionless entrainment rate closely follows the −1 power law with a modified Richardson number. The study suggests that including the aerosol radiative effect may improve numerical air quality predictions for heavy-air-pollution events.
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Atashafrooz, M., and SA Gandjalikhan Nassab. "Simulation of three-dimensional laminar forced convection flow of a radiating gas over an inclined backward-facing step in a duct under bleeding condition." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 227, no. 2 (May 17, 2012): 332–45. http://dx.doi.org/10.1177/0954406212447657.
Повний текст джерелаАнотація:
This study presents a numerical analysis of three-dimensional laminar forced convection flow of a radiating gas over an inclined backward-facing step in a rectangular duct under bleeding condition. The fluid is treated as a gray, absorbing, emitting, and scattering medium. The three-dimensional Cartesian coordinate system is used to solve the governing equations which are the conservations of mass, momentum, and energy. These equations are solved numerically using the computational fluid dynamic techniques to obtain the temperature and velocity fields, while the blocked-off method is employed to simulate the incline surface. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. Since the gas is considered as a radiating medium, besides the convective and conductive terms in the energy equation, the radiative term also presented. For computation of this term, the radiative transfer equation is solved numerically by the discrete ordinates method to find the divergence of radiative heat flux distribution inside the radiating medium. By this numerical procedure, the role of radiation heat transfer on convection flow of a radiating gas which has many engineering applications (for example in heat exchangers and combustion chambers) is studied in detail. Beside, the effects of bleeding coefficient, albedo coefficient, optical thickness, and the radiation–conduction parameter on heat transfer behavior of the system are investigated. Comparison of numerical results with the available data published in the open literature shows a good agreement.
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Ansaria, Amir, and Nassaba Gandjalikhan. "Forced convection of radiating gas over an inclined backward facing step using the blocked-off method." Thermal Science 17, no. 3 (2013): 773–86. http://dx.doi.org/10.2298/tsci110112132a.
Повний текст джерелаАнотація:
The present work investigates the laminar forced convection flow of a radiating gas over an inclined backward facing step (BFS) in a horizontal duct. The momentum and energy equations are solved numerically by the CFD techniques to obtain the velocity and temperature fields. Since, the twodimensional Cartesian coordinate system is used to solve the governing equations; the flow over inclined surface is simulated by considering the blocked-off region in regular grid. Discretized forms of the governing equations in the (x,y) plane are obtained by the control volume method and solved using the SIMPLE algorithm. The fluid is treated as a gray, absorbing, emitting and scattering medium. Therefore, all of the convection, conduction and radiation heat transfer mechanisms take place simultaneously in the gas flow. For computation of the radiative term in the gas energy equation, the radiative transfer equation (RTE) is solved numerically by the discrete ordinates method (DOM) to find the radiative heat flux distribution inside the radiating medium. In the numerical results, effects of inclination angle, optical thickness, scattering albedo and the radiation-conduction parameter on the heat transfer behavior of the convection flow are investigated. This research work is a new one in which a combined convection-radiation thermal system with a complex flow geometry is simulate by efficient numerical techniques.
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Wu, Wei, and Yangang Liu. "A new one-dimensional radiative equilibrium model for investigating atmospheric radiation entropy flux." Philosophical Transactions of the Royal Society B: Biological Sciences 365, no. 1545 (May 12, 2010): 1367–76. http://dx.doi.org/10.1098/rstb.2009.0301.
Повний текст джерелаАнотація:
A new one-dimensional radiative equilibrium model is built to analytically evaluate the vertical profile of the Earth's atmospheric radiation entropy flux under the assumption that atmospheric longwave radiation emission behaves as a greybody and shortwave radiation as a diluted blackbody. Results show that both the atmospheric shortwave and net longwave radiation entropy fluxes increase with altitude, and the latter is about one order in magnitude greater than the former. The vertical profile of the atmospheric net radiation entropy flux follows approximately that of the atmospheric net longwave radiation entropy flux. Sensitivity study further reveals that a ‘darker’ atmosphere with a larger overall atmospheric longwave optical depth exhibits a smaller net radiation entropy flux at all altitudes, suggesting an intrinsic connection between the atmospheric net radiation entropy flux and the overall atmospheric longwave optical depth. These results indicate that the overall strength of the atmospheric irreversible processes at all altitudes as determined by the corresponding atmospheric net entropy flux is closely related to the amount of greenhouse gases in the atmosphere.
17
Miller, Mark A., Virendra P. Ghate, and Robert K. Zahn. "The Radiation Budget of the West African Sahel and Its Controls: A Perspective from Observations and Global Climate Models." Journal of Climate 25, no. 17 (April 27, 2012): 5976–96. http://dx.doi.org/10.1175/jcli-d-11-00072.1.
Повний текст джерелаАнотація:
Abstract Continuous measurements of the shortwave (SW), longwave (LW), and net cross-atmosphere radiation flux divergence over the West African Sahel were made during the year 2006 using the Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) and the Geostationary Earth Radiation Budget (GERB) satellite. Accompanying AMF measurements enabled calculations of the LW, SW, and net top of the atmosphere (TOA) and surface cloud radiative forcing (CRF), which quantifies the radiative effects of cloud cover on the column boundaries. Calculations of the LW, SW, and net cloud radiative effect (CRE), which is the difference between the TOA and surface radiative flux divergences in all-sky and clear-sky conditions, quantify the radiative effects on the column itself. These measurements were compared to predictions in four global climate models (GCMs) used in the Intergovernmental Panel for Climate Change Fourth Assessment Report (IPCC AR4). All four GCMs produced wet and dry seasons, but reproducing the SW column radiative flux divergence was problematic in the GCMs and SW discrepancies translated into discrepancies in the net radiative flux divergence. Computing cloud-related quantities from the measurements produced yearly averages of the SW TOA CRF, surface CRF, and CRE of ~−19, −83, and 47 W m−2, respectively, and yearly averages of the LW TOA CRF, surface CRF, and CRE of ~39, 37, and 2 W m−2. These quantities were analyzed in two GCMs and compensating errors in the SW and LW clear-sky, cross-atmosphere radiative flux divergence were found to conspire to produce somewhat reasonable predictions of the net clear-sky divergence. Both GCMs underestimated the surface LW and SW CRF and predicted near-zero SW CRE when the measured values were substantially larger (~70 W m−2 maximum).
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Damm, David L., and Andrei G. Fedorov. "Spectral Radiative Heat Transfer Analysis of the Planar SOFC." Journal of Fuel Cell Science and Technology 2, no. 4 (April 5, 2005): 258–62. http://dx.doi.org/10.1115/1.2041667.
Повний текст джерелаАнотація:
Thermo-mechanical failure of components in planar-type solid oxide fuel cells (SOFCs) depends strongly on the local temperature gradients at the interfaces of different materials. Therefore, it is of paramount importance to accurately predict the temperature fields within the stack, especially near the interfaces. Because of elevated operating temperatures (of the order of 1000K or even higher), radiation heat transfer could become a dominant mode of heat transfer in the SOFCs. In this study, we extend our recent work on radiative effects in solid oxide fuel cells [J. Power Sources, 124, No. 2, pp. 453–458] by accounting for the spectral dependence of the radiative properties of the electrolyte material. The measurements of spectral radiative properties of the polycrystalline yttria-stabilized zirconia electrolyte we performed indicate that an optically thin approximation can be used for treatment of radiative heat transfer. To this end, the Schuster–Schwartzchild two-flux approximation is used to solve the radiative transfer equation for the spectral radiative heat flux, which is then integrated over the entire spectrum using an N-band approximation to obtain the total heat flux due to thermal radiation. The divergence of the total radiative heat flux is then incorporated as a heat sink into a three-dimensional thermo-fluid model of a SOFC through the user-defined function utility in the commercial FLUENT computational fluid dynamics software. The results of sample calculations are reported and compared against the base line cases when no radiation effects are included and when the spectrally gray approximation is used for treatment of radiative heat transfer.
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Makarieva, A. M., V. G. Gorshkov, and T. Pujol. "Height of convective layer in planetary atmospheres with condensable and non-condensable greenhouse substances." Atmospheric Chemistry and Physics Discussions 3, no. 6 (December 16, 2003): 6701–20. http://dx.doi.org/10.5194/acpd-3-6701-2003.
Повний текст джерелаАнотація:
Abstract. Convection reduces greenhouse effect by transporting a certain amount of non-radiative dynamic energy to the upper atmosphere, where this energy dissipates and radiates into space without interaction with greenhouse substances in the lower atmosphere. In this paper we show that the height of the convective layer zc is finite and independent of atmospheric optical thickness τs at large values of the latter. We derive an analytical formula for zc at large values of τs for condensable and non-condensable greenhouse substances. The formula obtained yields reasonable quantitative estimates of the observed height of convective layer on Venus and at low latitudes on Earth, where atmospheric thickness of water vapor is maximum. The dissipative power of dynamic convective processes is limited by the incoming flux of solar radiation. Height of convective layer being finite, values of optical depth at the top of the convective layer and at the mean height of convective energy dissipation increase proportionally to the atmospheric optical thickness, while the contribution of convective energy fluxes to formation of the outgoing flux of thermal radiation proportionally diminishes. As far as optical thickness of condensable greenhouse substances grows exponentially with increasing surface temperature, the obtained results lead to the conclusion that the outgoing thermal radiation into space in the presence of convection tends exponentially to zero with increasing surface temperature, instead of reaching a finite plateau as suggested by earlier radiative-convective studies.
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Hoch, S. W., P. Calanca, R. Philipona, and A. Ohmura. "Year-Round Observation of Longwave Radiative Flux Divergence in Greenland." Journal of Applied Meteorology and Climatology 46, no. 9 (September 1, 2007): 1469–79. http://dx.doi.org/10.1175/jam2542.1.
Повний текст джерелаАнотація:
Abstract Longwave radiative flux divergence within the lowest 50 m of the atmospheric boundary layer was observed during the Eidgenössische Technische Hochschule (ETH) Greenland Summit experiment. The dataset collected at 72°35′N, 38°30′W, 3203 m MSL is based on longwave radiation measurements at 2 and 48 m that are corrected for the influence of the supporting tower structure. The observations cover all seasons and reveal the magnitude of longwave radiative flux divergence and its incoming and outgoing component under stable and unstable conditions. Longwave radiative flux divergence during winter corresponds to a radiative cooling of −10 K day−1, but values of −30 K day−1 can persist for several days. During summer, the mean cooling effect of longwave radiative flux divergence is small (−2 K day−1) but exhibits a strong diurnal cycle. With values ranging from −35 K day−1 around midnight to 15 K day−1 at noon, the heating rate due to longwave radiative flux divergence is of the same order of magnitude as the observed temperature tendency. However, temperature tendency and longwave radiative flux divergence are out of phase, with temperature tendency leading the longwave radiative flux divergence by 3 h. The vertical variation of the outgoing longwave flux usually dominates the net longwave flux divergence, showing a strong divergence at nighttime and a strong convergence during the day. The divergence of the incoming longwave flux plays a secondary role, showing a slight counteracting effect. Fog is frequently observed during summer nights. Under such conditions, a divergence of both incoming and outgoing fluxes leads to the strongest radiative cooling rates that are observed. Considering all data, a correlation between longwave radiative flux divergence and the temperature difference across the 2–48-m layer is found.
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Khemani, Kamal, and Pradeep Kumar. "Radiative heat transfer calculation for mixture of gases using full spectrum k-distribution method." Journal of Physics: Conference Series 2116, no. 1 (November 1, 2021): 012065. http://dx.doi.org/10.1088/1742-6596/2116/1/012065.
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Abstract The full spectrum k-distribution method is used to obtain radiative heat flux and divergence of radiative heat flux for two test cases, containing mixture of CO 2 and H 2 O at different concentration and temperature keeping pressure constant. The k-distribution for mixture of gases is obtained from individual gas k-distribution using three different mixing models, viz., superposition, multiplication and hybrid model. Further, the radiative transfer equation (RTE) is solved by the finite volume discrete ordinate method (FVDOM) to obtain the radiative flux and the radiation source term. The results obtained were compared with the FSK from spectral addition and LBL method. The multiplication mixing model provides better accuracy compared to other mixing models considered in the present study.
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Miller, Nathaniel B., Matthew D. Shupe, Christopher J. Cox, David Noone, P. Ola G. Persson, and Konrad Steffen. "Surface energy budget responses to radiative forcing at Summit, Greenland." Cryosphere 11, no. 1 (February 13, 2017): 497–516. http://dx.doi.org/10.5194/tc-11-497-2017.
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Abstract. Greenland Ice Sheet surface temperatures are controlled by an exchange of energy at the surface, which includes radiative, turbulent, and ground heat fluxes. Data collected by multiple projects are leveraged to calculate all surface energy budget (SEB) terms at Summit, Greenland, for the full annual cycle from July 2013 to June 2014 and extend to longer periods for the radiative and turbulent SEB terms. Radiative fluxes are measured directly by a suite of broadband radiometers. Turbulent sensible heat flux is estimated via the bulk aerodynamic and eddy correlation methods, and the turbulent latent heat flux is calculated via a two-level approach using measurements at 10 and 2 m. The subsurface heat flux is calculated using a string of thermistors buried in the snow pack. Extensive quality-control data processing produced a data set in which all terms of the SEB are present 75 % of the full annual cycle, despite the harsh conditions. By including a storage term for a near-surface layer, the SEB is balanced in this data set to within the aggregated uncertainties for the individual terms. November and August case studies illustrate that surface radiative forcing is driven by synoptically forced cloud characteristics, especially by low-level, liquid-bearing clouds. The annual cycle and seasonal diurnal cycles of all SEB components indicate that the non-radiative terms are anticorrelated to changes in the total radiative flux and are hence responding to cloud radiative forcing. Generally, the non-radiative SEB terms and the upwelling longwave radiation component compensate for changes in downwelling radiation, although exact partitioning of energy in the response terms varies with season and near-surface characteristics such as stability and moisture availability. Substantial surface warming from low-level clouds typically leads to a change from a very stable to a weakly stable near-surface regime with no solar radiation or from a weakly stable to neutral/unstable regime with solar radiation. Relationships between forcing terms and responding surface fluxes show that the upwelling longwave radiation produces 65–85 % (50–60 %) of the total response in the winter (summer) and the non-radiative terms compensate for the remaining change in the combined downwelling longwave and net shortwave radiation. Because melt conditions are rarely reached at Summit, these relationships are documented for conditions of surface temperature below 0 °C, with and without solar radiation. This is the first time that forcing and response term relationships have been investigated in detail for the Greenland SEB. These results should both advance understanding of process relationships over the Greenland Ice Sheet and be useful for model validation.
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Zhang, Chong, Zhongnong Zhang, and Chun Lou. "Thermodynamic Irreversibility Analysis of Thermal Radiation in Coal-Fired Furnace: Effect of Coal Ash Deposits." Materials 16, no. 2 (January 13, 2023): 799. http://dx.doi.org/10.3390/ma16020799.
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In this paper, a three-dimensional (3-D) high-temperature furnace filled with a gas-solid medium was investigated, and the radiative transfer equation and the radiative entropy transfer equation in the chamber were applied in order to analyze the effect of coal deposits on thermal radiation. The heat flux on the walls of the furnace and the entropy generation rate were determined due to the irreversibility of the radiative heat transfer process in the furnace. Furthermore, the effect of ash deposits on the wall surface on the irreversibility of the radiation heat transfer process was investigated. The numerical results show that when burning bituminous and sub-bituminous coal, ash deposits in the furnace led to a 48.2% and 63.2% decrease in wall radiative heat flux and a 9.1% and 12.4% decrease in the radiative entropy rate, respectively. The ash deposits also led to an increase in the entropy generation number and a decrease in the thermodynamic efficiency of the radiative heat transfer process in the furnace.
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Kylling, A., A. R. Webb, R. Kift, G. P. Gobbi, L. Ammannato, F. Barnaba, A. Bais, et al. "Spectral actinic flux in the lower troposphere: measurement and 1-D simulations for cloudless, broken cloud and overcast situations." Atmospheric Chemistry and Physics 5, no. 7 (August 3, 2005): 1975–97. http://dx.doi.org/10.5194/acp-5-1975-2005.
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Abstract. In September 2002, the first INSPECTRO campaign to study the influence of clouds on the spectral actinic flux in the lower troposphere was carried out in East Anglia, England. Measurements of the actinic flux, the irradiance and aerosol and cloud properties were made from four ground stations and by aircraft. The radiation measurements were modelled using the uvspec model and ancillary data. For cloudless conditions, the measurements of the actinic flux were reproduced by 1-D radiative transfer modelling within the measurement and model uncertainties of about ±10%. For overcast days, the ground-based and aircraft radiation measurements and the cloud microphysical property measurements are consistent within the framework of 1-D radiative transfer and within experimental uncertainties. Furthermore, the actinic flux is increased by between 60-100% above the cloud when compared to a cloudless sky, with the largest increase for the optically thickest cloud. Correspondingly, the below cloud actinic flux is decreased by about 55-65%. Just below the cloud top, the downwelling actinic flux has a maximum that is seen in both the measurements and the model results. For broken clouds the traditional cloud fraction approximation is not able to simultaneously reproduce the measured above-cloud enhancement and below-cloud reduction in the actinic flux.
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McDONALD, N. ROBB. "The decay of cyclonic eddies by Rossby wave radiation." Journal of Fluid Mechanics 361 (April 25, 1998): 237–52. http://dx.doi.org/10.1017/s0022112098008696.
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It is argued that because shallow water cyclones on a β-plane drift westward at a speed equal to an available Rossby wave phase speed, they must radiate energy and cannot, therefore, be steady. The form of the Rossby wave wake accompanying a quasi-steady cyclone is calculated and the energy flux in the radiated waves determined. Further, an explicit expression for the radiation-induced northward drift of the cyclone is obtained. A general method for determining the effects of the radiation on the radius and amplitude of the vortex based on conservation of energy and potential vorticity is given. An example calculation for a cyclone with a ‘top-hat’ profile is presented, demonstrating that the primary effect of the radiation is to decrease the radius of the vortex. The dimensional timescale associated with the decay of oceanic vortices is of the order of several months to a year.
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Vicquelin, R., Y. F. Zhang, O. Gicquel, and J. Taine. "Effects of radiation in turbulent channel flow: analysis of coupled direct numerical simulations." Journal of Fluid Mechanics 753 (July 25, 2014): 360–401. http://dx.doi.org/10.1017/jfm.2014.368.
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AbstractThe role of radiative energy transfer in turbulent boundary layers is carefully analysed, focusing on the effect on temperature fluctuations and turbulent heat flux. The study is based on direct numerical simulations (DNS) of channel flows with hot and cold walls coupled to a Monte-Carlo method to compute the field of radiative power. In the conditions studied, the structure of the boundary layers is strongly modified by radiation. Temperature fluctuations and turbulent heat flux are reduced, and new radiative terms appear in their respective balance equations. It is shown that they counteract turbulence production terms. These effects are analysed under different conditions of Reynolds number and wall temperature. It is shown that collapsing of wall-scaled profiles is not efficient when radiation is considered. This drawback is corrected by the introduction of a radiation-based scaling. Finally, the significant impact of radiation on turbulent heat transfer is studied in terms of the turbulent Prandtl number. A model for this quantity, based on the new proposed scaling, is developed and validated.
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de Boer, G., W. D. Collins, S. Menon, and C. N. Long. "Using surface remote sensors to derive radiative characteristics of Mixed-Phase Clouds: an example from M-PACE." Atmospheric Chemistry and Physics 11, no. 23 (December 2, 2011): 11937–49. http://dx.doi.org/10.5194/acp-11-11937-2011.
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Abstract. Measurements from ground-based cloud radar, high spectral resolution lidar and microwave radiometer are used in conjunction with a column version of the Rapid Radiative Transfer Model (RRTMG) and radiosonde measurements to derive the surface radiative properties under mixed-phase cloud conditions. These clouds were observed during the United States Department of Energy (US DOE) Atmospheric Radiation Measurement (ARM) Mixed-Phase Arctic Clouds Experiment (M-PACE) between September and November of 2004. In total, sixteen half hour time periods are reviewed due to their coincidence with radiosonde launches. Cloud liquid (ice) water paths are found to range between 11.0–366.4 (0.5–114.1) gm−2, and cloud physical thicknesses fall between 286–2075 m. Combined with temperature and hydrometeor size estimates, this information is used to calculate surface radiative flux densities using RRTMG, which are demonstrated to generally agree with measured flux densities from surface-based radiometric instrumentation. Errors in longwave flux density estimates are found to be largest for thin clouds, while shortwave flux density errors are generally largest for thicker clouds. A sensitivity study is performed to understand the impact of retrieval assumptions and uncertainties on derived surface radiation estimates. Cloud radiative forcing is calculated for all profiles, illustrating longwave dominance during this time of year, with net cloud forcing generally between 50 and 90 Wm−2.
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Flamant, G., J. D. Lu, and B. Variot. "Radiation Heat Transfer in Fluidized Beds: A Comparison of Exact and Simplified Approaches." Journal of Heat Transfer 116, no. 3 (August 1, 1994): 652–59. http://dx.doi.org/10.1115/1.2910919.
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Radiation heat transfer at heat exchanger walls in fluidized beds has never been examined through a complete formulation of the problem. In this paper a wall-to-bed heat transfer model is proposed to account for particle convection, gas convection, and radiation exchange in a variable porosity medium. Momentum, energy, and intensity equations are solved in order to determine the velocity, temperature, radiative heat flux profiles and heat transfer coefficients. The discrete-ordinates method is used to compute the radiative intensity equation and the radiative flux divergence in the energy equation. Both the gray and the non-gray assumptions are considered, as well as dependent and independent scattering. The exact solution obtained is compared with several simplified approaches. Large differences are shown for small particles at high temperature but the simplified solutions are valid for large particle beds. The dependency of radiative contribution on controlling parameters is discussed.
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Menart, J. A., and HaeOk Skarda Lee. "Nongray Gas Analyses for Reflecting Walls Utilizing a Flux Technique." Journal of Heat Transfer 115, no. 3 (August 1, 1993): 645–52. http://dx.doi.org/10.1115/1.2910735.
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A flux formulation for a planar slab of molecular gas radiation bounded by diffuse reflecting walls is developed. While this formulation is limited to the planar geometry, it is useful for studying approximations necessary in modeling nongray radiative heat transfer. The governing equations are derived by considering the history of multiple reflections between the walls. Accurate solutions are obtained by explicitly accounting for a finite number of reflections and approximating the spectral effects of the remaining reflections. Four approximate methods are presented and compared using a single absorption band of H2O. All four methods reduce to an identical zeroth-order formulation, which accounts for all reflections approximately but does handle nonreflected radiation correctly. A single absorption band of CO2 is also considered using the best-behaved approximation for higher orders. A zeroth-order formulation is sufficient to predict the radiative transfer accurately for many cases considered. For highly reflecting walls, higher order solutions are necessary for better accuracy. Including all the important bands of H2O, the radiative source distributions are also obtained for two different temperature and concentration profiles.
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Kuai, Le, Kevin W. Bowman, Kazuyuki Miyazaki, Makoto Deushi, Laura Revell, Eugene Rozanov, Fabien Paulot, et al. "Attribution of Chemistry-Climate Model Initiative (CCMI) ozone radiative flux bias from satellites." Atmospheric Chemistry and Physics 20, no. 1 (January 8, 2020): 281–301. http://dx.doi.org/10.5194/acp-20-281-2020.
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Abstract. The top-of-atmosphere (TOA) outgoing longwave flux over the 9.6 µm ozone band is a fundamental quantity for understanding chemistry–climate coupling. However, observed TOA fluxes are hard to estimate as they exhibit considerable variability in space and time that depend on the distributions of clouds, ozone (O3), water vapor (H2O), air temperature (Ta), and surface temperature (Ts). Benchmarking present-day fluxes and quantifying the relative influence of their drivers is the first step for estimating climate feedbacks from ozone radiative forcing and predicting radiative forcing evolution. To that end, we constructed observational instantaneous radiative kernels (IRKs) under clear-sky conditions, representing the sensitivities of the TOA flux in the 9.6 µm ozone band to the vertical distribution of geophysical variables, including O3, H2O, Ta, and Ts based upon the Aura Tropospheric Emission Spectrometer (TES) measurements. Applying these kernels to present-day simulations from the Chemistry-Climate Model Initiative (CCMI) project as compared to a 2006 reanalysis assimilating satellite observations, we show that the models have large differences in TOA flux, attributable to different geophysical variables. In particular, model simulations continue to diverge from observations in the tropics, as reported in previous studies of the Atmospheric Chemistry Climate Model Intercomparison Project (ACCMIP) simulations. The principal culprits are tropical middle and upper tropospheric ozone followed by tropical lower tropospheric H2O. Five models out of the eight studied here have TOA flux biases exceeding 100 mW m−2 attributable to tropospheric ozone bias. Another set of five models have flux biases over 50 mW m−2 due to H2O. On the other hand, Ta radiative bias is negligible in all models (no more than 30 mW m−2). We found that the atmospheric component (AM3) of the Geophysical Fluid Dynamics Laboratory (GFDL) general circulation model and Canadian Middle Atmosphere Model (CMAM) have the lowest TOA flux biases globally but are a result of cancellation of opposite biases due to different processes. Overall, the multi-model ensemble mean bias is -133±98 mW m−2, indicating that they are too atmospherically opaque due to trapping too much radiation in the atmosphere by overestimated tropical tropospheric O3 and H2O. Having too much O3 and H2O in the troposphere would have different impacts on the sensitivity of TOA flux to O3 and these competing effects add more uncertainties on the ozone radiative forcing. We find that the inter-model TOA outgoing longwave radiation (OLR) difference is well anti-correlated with their ozone band flux bias. This suggests that there is significant radiative compensation in the calculation of model outgoing longwave radiation.
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Nashine, Prerana, and Ashok Kumar Satapathy. "Transient Radiation Coupled With Conduction Heat Transfer in a One Dimensional Slab." Applied Mechanics and Materials 619 (August 2014): 94–98. http://dx.doi.org/10.4028/www.scientific.net/amm.619.94.
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The present research work views over a solution of radiative transport problem along with conduction in one perspective piece and in the existence of participating media. The radiative transfer equations are developed for anisotropically scattering, absorbing, emitting medium and the equation is being discretized using finite volume method. Heat flux and the incident radiation effects have been computed at three different time step. Transient radiation along with transient conduction is solved and the radiative effect has been measured using radiative transfer equation while the conduction term has been measured using conduction equation.
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Kremens, R. L., M. B. Dickinson, and A. S. Bova. "Radiant flux density, energy density and fuel consumption in mixed-oak forest surface fires." International Journal of Wildland Fire 21, no. 6 (2012): 722. http://dx.doi.org/10.1071/wf10143.
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Closing the wildland fire heat budget involves characterising the heat source and energy dissipation across the range of variability in fuels and fire behaviour. Meeting this challenge will lay the foundation for predicting direct ecological effects of fires and fire–atmosphere coupling. In this paper, we focus on the relationships between the fire radiation field, as measured from the zenith, fuel consumption and the behaviour of spreading flame fronts. Experiments were conducted in 8 × 8-m outdoor plots using preconditioned wildland fuels characteristic of mixed-oak forests of the eastern United States. Using dual-band radiometers with a field of view of ~18.5 m2 at a height of 4.2 m, we found a near-linear increase in fire radiative energy density over a range of fuel consumption between 0.15 and 3.25 kg m–2. Using an integrated heat budget, we estimate that the fraction of total theoretical combustion energy density radiated from the plot averaged 0.17, the fraction of latent energy transported in the plume averaged 0.08, and the fraction accounted for by the combination of fire convective energy transport and soil heating averaged 0.72. Future work will require, at minimum, instantaneous and time-integrated estimates of energy transported by radiation, convection and soil heating across a range of fuels.
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Dübal, Hans-Rolf, and Fritz Vahrenholt. "Radiative Energy Flux Variation from 2001–2020." Atmosphere 12, no. 10 (October 5, 2021): 1297. http://dx.doi.org/10.3390/atmos12101297.
Повний текст джерелаАнотація:
Radiative energy flux data, downloaded from CERES, are evaluated with respect to their variations from 2001 to 2020. We found the declining outgoing shortwave radiation to be the most important contributor for a positive TOA (top of the atmosphere) net flux of 0.8 W/m2 in this time frame. We compare clear sky with cloudy areas and find that changes in the cloud structure should be the root cause for the shortwave trend. The radiative flux data are compared with ocean heat content data and analyzed in the context of a longer-term climate system enthalpy estimation going back to the year 1750. We also report differences in the trends for the Northern and Southern hemisphere. The radiative data indicate more variability in the North and higher stability in the South. The drop of cloudiness around the millennium by about 1.5% has certainly fostered the positive net radiative flux. The declining TOA SW (out) is the major heating cause (+1.42 W/m2 from 2001 to 2020). It is almost compensated by the growing chilling TOA LW (out) (−1.1 W/m2). This leads together with a reduced incoming solar of −0.17 W/m2 to a small growth of imbalance of 0.15 W/m2. We further present surface flux data which support the strong influence of the cloud cover on the radiative budget.
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Seaton, M. J. "Atomic Opacities." International Astronomical Union Colloquium 146 (1994): 265–70. http://dx.doi.org/10.1017/s0252921100021382.
Повний текст джерелаАнотація:
LetIv(r, θ) be the intensity of radiation of frequencyv, at a distancerfrom the centre of a star and in a direction making an angleθto the outward normal. In a plane-parallel approximation the equation of radiative transfer iswhere𝛋vis the opacity andjvthe emissivity. The net outward flux of radiant energy isand the flux integrated over all frequencies is
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Wen, Guoyong, Alexander Marshak, Si-Chee Tsay, Jay Herman, Ukkyo Jeong, Nader Abuhassan, Robert Swap, and Dong Wu. "Changes in the surface broadband shortwave radiation budget during the 2017 eclipse." Atmospheric Chemistry and Physics 20, no. 17 (September 9, 2020): 10477–91. http://dx.doi.org/10.5194/acp-20-10477-2020.
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Abstract. While solar eclipses are known to greatly diminish the visible radiation reaching the surface of the Earth, less is known about the magnitude of the impact. We explore both the observed and modeled levels of change in surface radiation during the eclipse of 2017. We deployed a pyranometer and Pandora spectrometer instrument to Casper, Wyoming, and Columbia, Missouri, to measure surface broadband shortwave (SW) flux and atmospheric properties during the 21 August 2017 solar eclipse event. We performed detailed radiative transfer simulations to understand the role of clouds in spectral and broadband solar radiation transfer in the Earth's atmosphere for the normal (non-eclipse) spectrum and red-shift solar spectra for eclipse conditions. The theoretical calculations showed that the non-eclipse-to-eclipse surface flux ratio depends strongly on the obscuration of the solar disk and slightly on the cloud optical depth. These findings allowed us to estimate what the surface broadband SW flux would be for hypothetical non-eclipse conditions from observations during the eclipse and further to quantify the impact of the eclipse on the surface broadband SW radiation budget. We found that the eclipse caused local reductions of time-averaged surface flux of about 379 W m−2 (50 %) and 329 W m−2 (46 %) during the ∼3 h course of the eclipse at the Casper and Columbia sites, respectively. We estimated that the Moon's shadow caused a reduction of approximately 7 %–8 % in global average surface broadband SW radiation. The eclipse has a smaller impact on the absolute value of surface flux reduction for cloudy conditions than a clear atmosphere; the impact decreases with the increase in cloud optical depth. However, the relative time-averaged reduction of local surface SW flux during a solar eclipse is approximately 45 %, and it is not sensitive to cloud optical depth. The reduction of global average SW flux relative to climatology is proportional to the non-eclipse and eclipse flux difference in the penumbra area and depends on cloud optical depth in the Moon's shadow and geolocation due to the change in solar zenith angle. We also discuss the influence of cloud inhomogeneity on the observed SW flux. Our results not only quantify the reduction of the surface solar radiation budget, but also advance the understanding of broadband SW radiative transfer under solar eclipse conditions.
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Fukao, Shinji, Jun Kondo, Yoshikazu Nakanishi, Yoshiaki Ito, and Shinzo Yoshikado. "Excitation of X-Rays Using Polarized LiNbO3 Single Crystal." Key Engineering Materials 301 (January 2006): 205–10. http://dx.doi.org/10.4028/www.scientific.net/kem.301.205.
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The radiation of X-rays using the electric charge generated by a temperature change of a LiNbO3 single crystal has been investigated. When the LiNbO3 single crystal was placed in a conductive cylindrical pipe made of graphite, aluminum or copper, the photon flux of the radiated X-rays was dependent on the type of conductive material used. Depending on the type of materials on which the crystal was placed, the photon flux of the radiated X-rays increased with decreasing work function of the material.
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Li, Hong Mei, Ying Chao Han, and Jing Hui Qiu. "Analytical Investigation of Radiation Characteristic for Radio Frequencies Magnetic Flux Compression Generator." Applied Mechanics and Materials 143-144 (December 2011): 796–99. http://dx.doi.org/10.4028/www.scientific.net/amm.143-144.796.
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Radio frequencies magnetic flux compression generator is capable of producing and radiating ultra high power electromagnetic pulse by compressing magnetic field. As a maneuverable device, radio frequencies magnetic flux compression generator design has been developed and tested, it has been found widespread use in many fields. The radio performance is one of the most important parameters for radio frequencies magnetic flux compression generator. In this paper, the output current and voltage is given based on equivalent circuit model. In a bid to deliberate the radiation characteristic particularly, ring armature is equivalent to loop antenna in the light of electrically small loop antenna theory. The output voltage is used to feed antenna. Through analysis, the values of radiation strengths around radio frequencies magnetic flux compression generator 10 meters 50 meters 100 meters away are given. On the basis of the above analysis and discussion, the radiation characteristic for RF MFCG could be comprehended precisely.
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Trujillo, Francisco J., Tomasz Safinski, and Adesoji A. Adesina. "CFD Analysis of the Radiation Distribution in a New Immobilized Catalyst Bubble Column Externally Illuminated Photoreactor." Journal of Solar Energy Engineering 129, no. 1 (April 28, 2006): 27–36. http://dx.doi.org/10.1115/1.2391013.
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A new externally irradiated photoreactor configuration combining the excellent mass transfer characteristics of a bubble column operation with the separation power of an immobilized catalyst on quartz plates has been investigated using computational fluid dynamics (CFD) simulation. The radiative transport equation (RTE) in conjunction with the Navier-Stokes equations were solved to obtain the light incident radiative flux and the light absorbed by the immobilized titania as a function of the gas superficial velocity, the angle of inclination, and the separating distance between the plates. The model employed water and air as the fluid phases and the results indicated that gas bubbling considerably increased the incident radiation in the gas-liquid mixture enhancing the radiative flux and the absorbed radiation on the titania-coated plates. The CFD results pave the way for the optimization of a solar photocatalytic reactor for the degradation of organic pollutants.
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Vargas, William E. "Two-flux radiative transfer model under nonisotropic propagating diffuse radiation." Applied Optics 38, no. 7 (March 1, 1999): 1077. http://dx.doi.org/10.1364/ao.38.001077.
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Zare, Mehdi, and Sadegh Sadeghi. "Development of hybrid method for coupled conduction-radiation heat transfer in two-dimensional irregular enclosure considering thermo-radiative effects and varying thermal conductivity." International Journal of Numerical Methods for Heat & Fluid Flow 30, no. 4 (April 19, 2019): 1815–37. http://dx.doi.org/10.1108/hff-11-2018-0667.
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Purpose This study aims to perform a comprehensive investigation to model the thermal characteristics of a coupled conduction-radiation heat transfer in a two-dimensional irregular enclosure including a triangular-shaped heat source. Design/methodology/approach For this purpose, a promising hybrid technique based on the concepts of blocked-off method, FVM and DOM is developed. The enclosure consists of several horizontal, vertical and oblique walls, and thermal conductivity within the enclosure varies directly with temperature and indirectly with position. To simplify the complex geometry, a promising mathematical model is introduced using blocked-off method. Emitting, absorbing and non-isotropic scattering gray are assumed as the main radiative characteristics of the steady medium. Findings DOM and FVM are, respectively, applied for solving radiative transfer equation (RTE) and the energy equation, which includes conduction, radiation and heat source terms. The temperature and heat flux distributions are calculated inside the enclosure. For validation, results are compared with previous data reported in the literature under the same conditions. Results and comparisons show that this approach is highly efficient and reliable for complex geometries with coupled conduction-radiation heat transfer. Finally, the effects of thermo-radiative parameters including surface emissivity, extinction coefficient, scattering albedo, asymmetry factor and conduction-radiation parameter on temperature and heat flux distributions are studied. Originality/value In this paper, a hybrid numerical method is used to analyze coupled conduction-radiation heat transfer in an irregular geometry. Varying thermal conductivity is included in this analysis. By applying the method, results obtained for temperature and heat flux distributions are presented and also validated by the data provided by several previous papers.
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Yang, Bin, Yuri Knyazikhin, Donghui Xie, Haimeng Zhao, Junqiang Zhang, and Yi Wu. "Influence of Leaf Specular Reflection on Canopy Radiative Regime Using an Improved Version of the Stochastic Radiative Transfer Model." Remote Sensing 10, no. 10 (October 14, 2018): 1632. http://dx.doi.org/10.3390/rs10101632.
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Interpreting remotely-sensed data requires realistic, but simple, models of radiative transfer that occurs within a vegetation canopy. In this paper, an improved version of the stochastic radiative transfer model (SRTM) is proposed by assuming that all photons that have not been specularly reflected enter the leaf interior. The contribution of leaf specular reflection is considered by modifying leaf scattering phase function using Fresnel reflectance. The canopy bidirectional reflectance factor (BRF) estimated from this model is evaluated through comparisons with field-measured maize BRF. The result shows that accounting for leaf specular reflection can provide better performance than that when leaf specular reflection is neglected over a wide range of view zenith angles. The improved version of the SRTM is further adopted to investigate the influence of leaf specular reflection on the canopy radiative regime, with emphases on vertical profiles of mean radiation flux density, canopy absorptance, BRF, and normalized difference vegetation index (NDVI). It is demonstrated that accounting for leaf specular reflection can increase leaf albedo, which consequently increases canopy mean upward/downward mean radiation flux density and canopy nadir BRF and decreases canopy absorptance and canopy nadir NDVI when leaf angles are spherically distributed. The influence is greater for downward/upward radiation flux densities and canopy nadir BRF than that for canopy absorptance and NDVI. The results provide knowledge of leaf specular reflection and canopy radiative regime, and are helpful for forward reflectance simulations and backward inversions. Moreover, polarization measurements are suggested for studies of leaf specular reflection, as leaf specular reflection is closely related to the canopy polarization.
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Lohmann, U., L. Rotstayn, T. Storelvmo, A. Jones, S. Menon, J. Quaas, A. Ekman, D. Koch, and R. Ruedy. "Total aerosol effect: radiative forcing or radiative flux perturbation?" Atmospheric Chemistry and Physics Discussions 9, no. 6 (November 30, 2009): 25633–61. http://dx.doi.org/10.5194/acpd-9-25633-2009.
Повний текст джерелаАнотація:
Abstract. Uncertainties in aerosol radiative forcings, especially those associated with clouds, contribute to a large extent to uncertainties in the total anthropogenic forcing. The interaction of aerosols with clouds and radiation introduces feedbacks which can affect the rate of rain formation. In former assessments of aerosol radiative forcings, these effects have not been quantified. Also, with global aerosol-climate models simulating interactively aerosols and cloud microphysical properties, a quantification of the aerosol forcings in the traditional way is difficult to properly define. Here we argue that fast feedbacks should be included because they act quickly compared with the time scale of global warming. We show that for different forcing agents (aerosols and greenhouse gases) the radiative forcings as traditionally defined agree rather well with estimates from a method, here referred to as radiative flux perturbations (RFP), that takes these fast feedbacks and interactions into account. Based on our results, we recommend RFP as a valid option to compare different forcing agents, and to compare the effects of particular forcing agents in different models.
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Lohmann, U., L. Rotstayn, T. Storelvmo, A. Jones, S. Menon, J. Quaas, A. M. L. Ekman, D. Koch, and R. Ruedy. "Total aerosol effect: radiative forcing or radiative flux perturbation?" Atmospheric Chemistry and Physics 10, no. 7 (April 6, 2010): 3235–46. http://dx.doi.org/10.5194/acp-10-3235-2010.
Повний текст джерелаАнотація:
Abstract. Uncertainties in aerosol radiative forcings, especially those associated with clouds, contribute to a large extent to uncertainties in the total anthropogenic forcing. The interaction of aerosols with clouds and radiation introduces feedbacks which can affect the rate of precipitation formation. In former assessments of aerosol radiative forcings, these effects have not been quantified. Also, with global aerosol-climate models simulating interactively aerosols and cloud microphysical properties, a quantification of the aerosol forcings in the traditional way is difficult to define properly. Here we argue that fast feedbacks should be included because they act quickly compared with the time scale of global warming. We show that for different forcing agents (aerosols and greenhouse gases) the radiative forcings as traditionally defined agree rather well with estimates from a method, here referred to as radiative flux perturbations (RFP), that takes these fast feedbacks and interactions into account. Based on our results, we recommend RFP as a valid option to compare different forcing agents, and to compare the effects of particular forcing agents in different models.
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Yang, Bolei, and Zhe-Min Tan. "Interactive Radiation Accelerates the Intensification of the Midlevel Vortex for Tropical Cyclogenesis." Journal of the Atmospheric Sciences 77, no. 12 (December 2020): 4051–65. http://dx.doi.org/10.1175/jas-d-20-0094.1.
Повний текст джерелаАнотація:
AbstractInteractive radiation helps accelerate tropical cyclogenesis, but the mechanism is still unclear. Using idealized numerical modeling in the radiative–convective equilibrium framework, it is revealed that interactive radiation can bring forward tropical cyclogenesis by accelerating the development of the midlevel vortex. A strong horizontal longwave radiative warming anomaly in the layer between 6 and 11 km altitudes in the vortex region, caused by large concentration of ice-phased particles at high levels, is critical to the development of the midlevel vortex. This longwave radiative warming anomaly induces more upward water vapor flux (mainly in the nonconvective region) and then results in more latent heating at upper levels and more sublimation and melting cooling at lower levels. This leads to an increase of the vertical diabatic heating gradient, and then the intensification of the midlevel vortex. A stronger upward water vapor flux also produces more condensates at upper levels and further enhances the horizontal longwave radiative warming anomaly in the upper troposphere, constituting a positive feedback, and then accelerates tropical cyclogenesis.
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Zeng, Xiping, Wei-Kuo Tao, Minghua Zhang, Arthur Y. Hou, Shaocheng Xie, Stephen Lang, Xiaowen Li, David O’C Starr, Xiaofan Li, and Joanne Simpson. "An Indirect Effect of Ice Nuclei on Atmospheric Radiation." Journal of the Atmospheric Sciences 66, no. 1 (January 1, 2009): 41–61. http://dx.doi.org/10.1175/2008jas2778.1.
Повний текст джерелаАнотація:
Abstract A three-dimensional cloud-resolving model (CRM) with observed large-scale forcing is used to study how ice nuclei (IN) affect the net radiative flux at the top of the atmosphere (TOA). In all the numerical experiments carried out, the cloud ice content in the upper troposphere increases with IN number concentration via the Bergeron process. As a result, the upward solar flux at the TOA increases whereas the infrared one decreases. Because of the opposite response of the two fluxes to IN concentration, the sensitivity of the net radiative flux at the TOA to IN concentration varies from one case to another. Six tropical and three midlatitudinal field campaigns provide data to model the effect of IN on radiation in different latitudes. Classifying the CRM simulations into tropical and midlatitudinal and then comparing the two types reveals that the indirect effect of IN on radiation is greater in the middle latitudes than in the tropics. Furthermore, comparisons between model results and observations suggest that observational IN data are necessary to evaluate long-term CRM simulations.
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Liska, M. T. P., G. Musoke, A. Tchekhovskoy, O. Porth, and A. M. Beloborodov. "Formation of Magnetically Truncated Accretion Disks in 3D Radiation-transport Two-temperature GRMHD Simulations." Astrophysical Journal Letters 935, no. 1 (August 1, 2022): L1. http://dx.doi.org/10.3847/2041-8213/ac84db.
Повний текст джерелаАнотація:
Abstract Multiwavelength observations suggest that the accretion disk in the hard and intermediate states of X-ray binaries (XRBs) and active galactic nucleus transitions from a cold, thin disk at large distances into a hot, thick flow close to the black hole (BH). However, the formation, structure, and dynamics of such truncated disks are poorly constrained due to the complexity of the thermodynamic, magnetic, and radiative processes involved. We present the first radiation-transport two-temperature general relativistic magnetohydrodynamic (GRMHD) simulations of truncated disks radiating at ∼35% of the Eddington luminosity with and without large-scale poloidal magnetic flux. We demonstrate that when a geometrically thin accretion disk is threaded by large-scale net poloidal magnetic flux, it self-consistently transitions at small radii into a two-phase medium of cold gas clumps floating through a hot, magnetically dominated corona. This transition occurs at a well-defined truncation radius determined by the distance out to which the disk is saturated with magnetic flux. The average ion and electron temperatures in the semiopaque corona reach, respectively, T i ≳ 1010 K and T e ≳ 5 × 108 K. The system produces radiation, powerful collimated jets, and broader winds at the total energy efficiency exceeding 90%, the highest ever energy extraction efficiency from a spinning BH by a radiatively efficient flow in a GRMHD simulation. This is consistent with jetted ejections observed during XRB outbursts. The two-phase medium may naturally lead to broadened iron line emission observed in the hard state.
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Joshi, Ojas, and Pénélope Leyland. "Implementation of Surface Radiation and Fluid-Structure Thermal Coupling in Atmospheric Reentry." International Journal of Aerospace Engineering 2012 (2012): 1–8. http://dx.doi.org/10.1155/2012/402653.
Повний текст джерелаАнотація:
During atmospheric reentry, radiative heating is one of the most important component of the total heat flux. In this paper, we investigate how the thermal radiation coming from the postshock region interacts with the spacecraft structure. A model that takes into account the radiation reflected by the surface is developed and implemented in a solid solver. A partitioned algorithm performs the coupling between the fluid and the solid thermal fields. Numerical simulation of a hollow cone head and a deployed flap region shows the effects of the radiative cooling and the significance of the surface radiation.
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Biehs, Svend-Age. "Magneto-optical control and spin coupling with non-reciprocal surface waves for nanoscale thermotronics -INVITED." EPJ Web of Conferences 238 (2020): 10001. http://dx.doi.org/10.1051/epjconf/202023810001.
Повний текст джерелаАнотація:
Magneto-optical materials have been proposed as promising candidates for an active control of the directionality of nanoscale heat radiation. Here, we discuss the possibility to rectify nanoscale radiative heat fluxes by means of non-reciprocal surface waves and propose a nanoscale heat flux rectifier or diode which can be controlled actively by means of externally applied fields. We furthermore, reveal the spin coupling mechanism behind the observed heat flux rectification
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Smirnov, Sergey, Mikhail Sinkevich, Yuri Antipov, Igor Tsarkov, Sergei Kupreev, and Hassan Khalife. "An Enhanced Calculation Method of the Heat Rejection System of a Free-Piston Stirling Engine (FPSE) Operating on the Moon." Symmetry 14, no. 6 (June 6, 2022): 1168. http://dx.doi.org/10.3390/sym14061168.
Повний текст джерелаАнотація:
In this paper, an enhanced calculation method of a heat rejection system operating on the moon is presented. This was taken into consideration in the developed calculation method and in the propagation of heat fluxes with the radiation of the removed heat. The developed method made it possible to effectively evaluate the capabilities of various refrigerants and choose the radiator parameters and the refrigerant flow regime in a less time-consuming process and with minimal deviations (<5%) compared to the previously developed two-dimensional radiator model by the authors. A comparative analysis was carried out for two refrigerants: helium and liquid ammonia. It has been established that when using liquid ammonia, there are more possibilities for varying the geometric parameters of the radiator. The use of liquid ammonia as a refrigerant made it possible to reduce the power spent on pumping the refrigerant through the radiator. Using helium, the power for pumping the refrigerant was 5.1 W during a turbulent flow Re = 4500. On the other hand, the power for pumping liquid ammonia was 0.27 W. In addition, using liquid ammonia increased the heat flux radiated by the radiator pipe by 3.9 times, which made it to possible to increase the fin width and reduce the length of the radiator pipe.
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Ning, Jia. "Effects of Cropland Expansion on the Regional Land Surface Radiative Energy Balance and Heat Fluxes in Northern China." Applied Sciences 11, no. 4 (February 9, 2021): 1556. http://dx.doi.org/10.3390/app11041556.
Повний текст джерелаАнотація:
Land use change can impact the land surface radiation budget and energy balance by changing surface biophysical processes. Based on satellite remote sensing data and land use data from 2000 to 2015, we quantitatively estimated radiative forcing induced by cropland expansion during the early 21st century in northern China. The results showed that heat flux from the land surface to the atmosphere due to cropland expansion was quite variable in different climate zones. The heat flux increased in humid North China, whereas it decreased in arid Northwest China, semiarid Inner Mongolia, and humid Northeast China. Cropland expansion from woodland areas led to a general decline in the land surface heat flux to the atmosphere, which led to a cooling effect on the climate. The surface heat flux to the atmosphere due to cropland expansion in grassland areas displayed significant variations in different climate zones. The surface heat flux decreased only in humid Northeast China and arid Northwest China. The net surface radiation and latent heat flux both increased when grasslands were changed into cropland, but to different extents, which produced the differences in the surface heat flux to the atmosphere between different zones.