Literatura académica sobre el tema "Surface cloud radiative effect"
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Artículos de revistas sobre el tema "Surface cloud radiative effect"
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Kalisch, J. y A. Macke. "Radiative budget and cloud radiative effect over the Atlantic from ship based observations". Atmospheric Measurement Techniques Discussions 5, n.º 2 (1 de marzo de 2012): 2011–42. http://dx.doi.org/10.5194/amtd-5-2011-2012.
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Abstract. The aim of this study is to determine cloud-type resolved cloud radiative budgets and cloud radiative effects from surface measurements of broadband radiative fluxes over the Atlantic Ocean. Furthermore, based on simultaneous observations of the state of the cloudy atmosphere a radiative closure study has been performed by means of the ECHAM5 single column model in order to identify the models ability to realistically reproduce the effects of clouds on the climate system. An extensive data base of radiative and atmospheric measurements has been established along five meridional cruises of the German research icebreaker POLARSTERN. Besides pyranometer and pyrgeometer for downward broadband solar and thermal radiative fluxes, a sky imager and a microwave radiometer have been utilized to determine cloud fraction and cloud type on the one hand and temperature and humidity profiles as well as liquid water path for warm non-precipitating clouds on the other hand. Averaged over all cruise tracks we obtain a total net (solar + thermal) radiative flux of 144 W m−2 that is dominated by the solar component. In general, the solar contribution is large for cirrus clouds and small for stratus clouds. No significant meridional dependencies were found for the surface radiation budgets and cloud effects. The strongest surface longwave cloud effects were shown in the presence of low level clouds. Clouds with a high optical density induce strong negative solar radiative effects under high solar altitudes. The mean surface net cloud radiative effect is −34 W m−2. For the purpose of quickly estimating the mean surface longwave, shortwave and net cloud effects in moderate, subtropical and tropical climate regimes a new parameterisation was created, considering the total cloud amount and the solar zenith angle. The ECHAM5 single column model provides a surface net cloud effect that is more cooling by 16 W m−2 compared to the radiation observations. This overestimation in solar cooling is mostly caused by the shortwave impact of convective clouds. The latter show a large overestimation in solar cooling of up to 112 W m−2. Mean cloud radiative effects of cirrus and stratus clouds were simulated close to the observations.
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Kalisch, J. y A. Macke. "Radiative budget and cloud radiative effect over the Atlantic from ship-based observations". Atmospheric Measurement Techniques 5, n.º 10 (16 de octubre de 2012): 2391–401. http://dx.doi.org/10.5194/amt-5-2391-2012.
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Abstract. The aim of this study is to determine cloud-type resolved cloud radiative budgets and cloud radiative effects from surface measurements of broadband radiative fluxes over the Atlantic Ocean. Furthermore, based on simultaneous observations of the state of the cloudy atmosphere, a radiative closure study has been performed by means of the ECHAM5 single column model in order to identify the model's ability to realistically reproduce the effects of clouds on the climate system. An extensive database of radiative and atmospheric measurements has been established along five meridional cruises of the German research icebreaker Polarstern. Besides pyranometer and pyrgeometer for downward broadband solar and thermal radiative fluxes, a sky imager and a microwave radiometer have been utilized to determine cloud fraction and cloud type on the one hand and temperature and humidity profiles as well as liquid water path for warm non-precipitating clouds on the other hand. Averaged over all cruise tracks, we obtain a total net (solar + thermal) radiative flux of 144 W m−2 that is dominated by the solar component. In general, the solar contribution is large for cirrus clouds and small for stratus clouds. No significant meridional dependencies were found for the surface radiation budgets and cloud effects. The strongest surface longwave cloud effects were shown in the presence of low level clouds. Clouds with a high optical density induce strong negative solar radiative effects under high solar altitudes. The mean surface net cloud radiative effect is −33 W m−2. For the purpose of quickly estimating the mean surface longwave, shortwave and net cloud effects in moderate, subtropical and tropical climate regimes, a new parameterisation was created, considering the total cloud amount and the solar zenith angle. The ECHAM5 single column model provides a surface net cloud effect that is more cooling by 17 W m−2 compared to the radiation observations. This overestimation in solar cooling is mostly caused by the shortwave impact of convective clouds. The latter show a large overestimation in solar cooling of up to 114 W m−2. Mean cloud radiative effects of cirrus and stratus clouds were simulated close to the observations.
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Lacour, A., H. Chepfer, N. B. Miller, M. D. Shupe, V. Noel, X. Fettweis, H. Gallee, J. E. Kay, R. Guzman y J. Cole. "How Well Are Clouds Simulated over Greenland in Climate Models? Consequences for the Surface Cloud Radiative Effect over the Ice Sheet". Journal of Climate 31, n.º 22 (noviembre de 2018): 9293–312. http://dx.doi.org/10.1175/jcli-d-18-0023.1.
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Using lidar and radiative flux observations from space and ground, and a lidar simulator, we evaluate clouds simulated by climate models over the Greenland ice sheet, including predicted cloud cover, cloud fraction profile, cloud opacity, and surface cloud radiative effects. The representation of clouds over Greenland is a central concern for the models because clouds impact ice sheet surface melt. We find that over Greenland, most of the models have insufficient cloud cover during summer. In addition, all models create too few nonopaque, liquid-containing clouds optically thin enough to let direct solar radiation reach the surface (−1% to −3.5% at the ground level). Some models create too few opaque clouds. In most climate models, the cloud properties biases identified over all Greenland also apply at Summit, Greenland, proving the value of the ground observatory in model evaluation. At Summit, climate models underestimate cloud radiative effect (CRE) at the surface, especially in summer. The primary driver of the summer CRE biases compared to observations is the underestimation of the cloud cover in summer (−46% to −21%), which leads to an underestimated longwave radiative warming effect (CRELW = −35.7 to −13.6 W m−2 compared to the ground observations) and an underestimated shortwave cooling effect (CRESW = +1.5 to +10.5 W m−2 compared to the ground observations). Overall, the simulated clouds do not radiatively warm the surface as much as observed.
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Alkama, Ramdane, Patrick C. Taylor, Lorea Garcia-San Martin, Herve Douville, Gregory Duveiller, Giovanni Forzieri, Didier Swingedouw y Alessandro Cescatti. "Clouds damp the radiative impacts of polar sea ice loss". Cryosphere 14, n.º 8 (21 de agosto de 2020): 2673–86. http://dx.doi.org/10.5194/tc-14-2673-2020.
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Abstract. Clouds play an important role in the climate system: (1) cooling Earth by reflecting incoming sunlight to space and (2) warming Earth by reducing thermal energy loss to space. Cloud radiative effects are especially important in polar regions and have the potential to significantly alter the impact of sea ice decline on the surface radiation budget. Using CERES (Clouds and the Earth's Radiant Energy System) data and 32 CMIP5 (Coupled Model Intercomparison Project) climate models, we quantify the influence of polar clouds on the radiative impact of polar sea ice variability. Our results show that the cloud short-wave cooling effect strongly influences the impact of sea ice variability on the surface radiation budget and does so in a counter-intuitive manner over the polar seas: years with less sea ice and a larger net surface radiative flux show a more negative cloud radiative effect. Our results indicate that 66±2% of this change in the net cloud radiative effect is due to the reduction in surface albedo and that the remaining 34±1 % is due to an increase in cloud cover and optical thickness. The overall cloud radiative damping effect is 56±2 % over the Antarctic and 47±3 % over the Arctic. Thus, present-day cloud properties significantly reduce the net radiative impact of sea ice loss on the Arctic and Antarctic surface radiation budgets. As a result, climate models must accurately represent present-day polar cloud properties in order to capture the surface radiation budget impact of polar sea ice loss and thus the surface albedo feedback.
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Stapf, Johannes, André Ehrlich, Evelyn Jäkel, Christof Lüpkes y Manfred Wendisch. "Reassessment of shortwave surface cloud radiative forcing in the Arctic: consideration of surface-albedo–cloud interactions". Atmospheric Chemistry and Physics 20, n.º 16 (26 de agosto de 2020): 9895–914. http://dx.doi.org/10.5194/acp-20-9895-2020.
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Abstract. The concept of cloud radiative forcing (CRF) is commonly applied to quantify the impact of clouds on the surface radiative energy budget (REB). In the Arctic, specific radiative interactions between microphysical and macrophysical properties of clouds and the surface strongly modify the warming or cooling effect of clouds, complicating the estimate of CRF obtained from observations or models. Clouds tend to increase the broadband surface albedo over snow or sea ice surfaces compared to cloud-free conditions. However, this effect is not adequately considered in the derivation of CRF in the Arctic so far. Therefore, we have quantified the effects caused by surface-albedo–cloud interactions over highly reflective snow or sea ice surfaces on the CRF using radiative transfer simulations and below-cloud airborne observations above the heterogeneous springtime marginal sea ice zone (MIZ) during the Arctic CLoud Observations Using airborne measurements during polar Day (ACLOUD) campaign. The impact of a modified surface albedo in the presence of clouds, as compared to cloud-free conditions, and its dependence on cloud optical thickness is found to be relevant for the estimation of the shortwave CRF. A method is proposed to consider this surface albedo effect on CRF estimates by continuously retrieving the cloud-free surface albedo from observations under cloudy conditions, using an available snow and ice albedo parameterization. Using ACLOUD data reveals that the estimated average shortwave cooling by clouds almost doubles over snow- and ice-covered surfaces (−62 W m−2 instead of −32 W m−2), if surface-albedo–cloud interactions are considered. As a result, the observed total (shortwave plus longwave) CRF shifted from a warming effect to an almost neutral one. Concerning the seasonal cycle of the surface albedo, it is demonstrated that this effect enhances shortwave cooling in periods when snow dominates the surface and potentially weakens the cooling by optically thin clouds during the summertime melting season. These findings suggest that the surface-albedo–cloud interaction should be considered in global climate models and in long-term studies to obtain a realistic estimate of the shortwave CRF to quantify the role of clouds in Arctic amplification.
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de Szoeke, Simon P., Sandra Yuter, David Mechem, Chris W. Fairall, Casey D. Burleyson y Paquita Zuidema. "Observations of Stratocumulus Clouds and Their Effect on the Eastern Pacific Surface Heat Budget along 20°S". Journal of Climate 25, n.º 24 (15 de diciembre de 2012): 8542–67. http://dx.doi.org/10.1175/jcli-d-11-00618.1.
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Abstract Widespread stratocumulus clouds were observed on nine transects from seven research cruises to the southeastern tropical Pacific Ocean along 20°S, 75°–85°W in October–November of 2001–08. The nine transects sample a unique combination of synoptic and interannual variability affecting the clouds; their ensemble diagnoses longitude–vertical sections of the atmosphere, diurnal cycles of cloud properties and drizzle statistics, and the effect of stratocumulus clouds on surface radiation. Mean cloud fraction was 0.88, and 67% of 10-min overhead cloud fraction observations were overcast. Clouds cleared in the afternoon [1500 local time (LT)] to a minimum of fraction of 0.7. Precipitation radar found strong drizzle with reflectivity above 40 dBZ. Cloud-base (CB) heights rise with longitude from 1.0 km at 75°W to 1.2 km at 85°W in the mean, but the slope varies from cruise to cruise. CB–lifting condensation level (LCL) displacement, a measure of decoupling, increases westward. At night CB–LCL is 0–200 m and increases 400 m from dawn to 1600 LT, before collapsing in the evening. Despite zonal gradients in boundary layer and cloud vertical structure, surface radiation and cloud radiative forcing are relatively uniform in longitude. When present, clouds reduce solar radiation by 160 W m−2 and radiate 70 W m−2 more downward longwave radiation than clear skies. Coupled Model Intercomparison Project phase 3 (CMIP3) simulations of the climate of the twentieth century show 40 ± 20 W m−2 too little net cloud radiative cooling at the surface. Simulated clouds have correct radiative forcing when present, but models have ~50% too few clouds.
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Byrne, Michael P. y Laure Zanna. "Radiative Effects of Clouds and Water Vapor on an Axisymmetric Monsoon". Journal of Climate 33, n.º 20 (15 de octubre de 2020): 8789–811. http://dx.doi.org/10.1175/jcli-d-19-0974.1.
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AbstractMonsoons are summertime circulations shaping climates and societies across the tropics and subtropics. Here the radiative effects controlling an axisymmetric monsoon and its response to climate change are investigated using aquaplanet simulations. The influences of clouds, water vapor, and CO2 on the axisymmetric monsoon are decomposed using the radiation-locking technique. Seasonal variations in clouds and water vapor strongly modulate the axisymmetric monsoon, reducing net precipitation by approximately half. Warming and moistening of the axisymmetric monsoon by seasonal longwave cloud and water vapor effects are counteracted by a strong shortwave cloud effect. The shortwave cloud effect also expedites onset of the axisymmetric monsoon by approximately two weeks, whereas longwave cloud and water vapor effects delay onset. A conceptual model relates the timing of monsoon onset to the efficiency of surface cooling. In climate change simulations CO2 forcing and the water vapor feedback have similar influences on the axisymmetric monsoon, warming the surface and moistening the region. In contrast, clouds have a negligible effect on surface temperature yet dominate the monsoon circulation response. A new perspective for understanding how cloud radiative effects shape the monsoon circulation response to climate change is introduced. The radiation-locking simulations and analyses advance understanding of how radiative processes influence an axisymmetric monsoon, and establish a framework for interpreting monsoon–radiation coupling in observations, in state-of-the-art models, and in different climate states.
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Becker, Sebastian, André Ehrlich, Michael Schäfer y Manfred Wendisch. "Airborne observations of the surface cloud radiative effect during different seasons over sea ice and open ocean in the Fram Strait". Atmospheric Chemistry and Physics 23, n.º 12 (23 de junio de 2023): 7015–31. http://dx.doi.org/10.5194/acp-23-7015-2023.
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Abstract. This study analyses the cloud radiative effect (CRE) obtained from near-surface observations of three airborne campaigns in the Arctic north-west of Svalbard: Airborne measurements of radiative and turbulent FLUXes of energy and momentum in the Arctic boundary layer (AFLUX, March/April 2019), Arctic CLoud Observations Using airborne measurements during polar Day (ACLOUD, May/June 2017), and Multidisciplinary drifting Observatory for the Study of Arctic Climate – Airborne observations in the Central Arctic (MOSAiC-ACA, August/September 2020). The surface CRE quantifies the potential of clouds to modify the radiative energy budget at the surface and is calculated by combining broadband radiation measurements during low-level flight sections in mostly cloudy conditions with radiative transfer simulations of cloud-free conditions. The significance of surface albedo changes due to the presence of clouds is demonstrated, and this effect is considered in the cloud-free simulations. The observations are discussed with respect to differences of the CRE between sea ice and open-ocean surfaces and between the seasonally different campaigns. The results indicate that the CRE depends on cloud, illumination, surface, and thermodynamic properties. The solar and thermal-infrared (TIR) components of the CRE, CREsol and CRETIR, are analysed separately, as well as combined for the study of the total CRE (CREtot). The inter-campaign differences of CREsol are dominated by the seasonal cycle of the solar zenith angle, with the strongest cooling effect in summer. The lower surface albedo causes a stronger solar cooling effect over open ocean than over sea ice, which amounts to −259 W m−2 (−108 W m−2) and −65 W m−2 (−17 W m−2), respectively, during summer (spring). Independent of campaign and surface type, CRETIR is only weakly variable and shows values around 75 W m−2. In total, clouds show a negative CREtot over open ocean during all campaigns. In contrast, over sea ice, the positive CREtot suggests a warming effect of clouds at the surface, which neutralizes during mid-summer. Given the seasonal cycle of the sea ice distribution, these results imply that clouds in the Fram Strait region cool the surface during the sea ice minimum in late summer, while they warm the surface during the sea ice maximum in spring.
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Harrop, Bryce E. y Dennis L. Hartmann. "The Relationship between Atmospheric Convective Radiative Effect and Net Energy Transport in the Tropical Warm Pool". Journal of Climate 28, n.º 21 (30 de octubre de 2015): 8620–33. http://dx.doi.org/10.1175/jcli-d-15-0151.1.
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Abstract Reanalysis data and radiation budget data are used to calculate the role of the atmospheric cloud radiative effect in determining the magnitude of horizontal export of energy by the tropical atmosphere. Because tropical high clouds result in net radiative heating of the atmosphere, they increase the requirement for the atmosphere to export energy from convective regions. Increases in upper-tropospheric water vapor associated with convection contribute about a fifth of the atmospheric radiative heating anomaly associated with convection. Over the warmest tropical oceans, the radiative effect of convective clouds and associated water vapor is roughly two-thirds the value of the atmospheric energy transport. Cloud radiative heating and atmospheric heat transport increase at the same rate with increasing sea surface temperature, suggesting that the increased energy export is supplied by the radiative heating associated with convective clouds. The net cloud radiative effect at the top of the atmosphere is insensitive to changes in SST over the warm pool. Principal component analysis of satellite-retrieved cloud data reveals that the insensitivity of the net cloud radiative effect to SST is the result of changes in cloud amount offsetting changes in cloud optical thickness and cloud-top height. While increasing upward motion makes the cloud radiative effect more negative, that decrease is offset by reductions in outgoing longwave radiation owing to increases in water vapor.
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Degünther, M. y R. Meerkötter. "Effect of remote clouds on surface UV irradiance". Annales Geophysicae 18, n.º 6 (30 de junio de 2000): 679–86. http://dx.doi.org/10.1007/s00585-000-0679-5.
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Abstract. Clouds affect local surface UV irradiance, even if the horizontal distance from the radiation observation site amounts to several kilometers. In order to investigate this effect, which we call remote clouds effect, a 3-dimensional radiative transfer model is applied. Assuming the atmosphere is subdivided into a quadratic based sector and its surrounding, we quantify the influence of changing cloud coverage within this surrounding from 0% to 100% on surface UV irradiance at the sector center. To work out this remote clouds influence as a function of sector base size, we made some calculations for different sizes between 10 km × 10 km and 100 km × 100 km. It appears that in the case of small sectors (base size < 20 km × 20 km) the remote clouds effect is highly variable: Depending on cloud structure, solar zenith angle and wavelength, the surface UV irradiance may be enhanced up to 15% as well as reduced by more than 50%. In contrast, for larger sectors it is always the case that enhancements become smaller by 5% if sector base size exceeds 60 km × 60 km. However, these values are upper estimates of the remote cloud effects and they are found only for special cloud structures. Since these structures might occur but cannot be regarded as typical, different satellite observed cloud formations (horizontal resolution about 1 km × 1 km) have also been investigated. For these more common cloud distributions we find remote cloud effects to be distinctly smaller than the corresponding upper estimates, e.g., for a sector with base size of 25 km × 25 km the surface UV irradiance error due to ignoring the actual remote clouds and replacing their influence with periodic horizontal boundary conditions is less than 3%, whereas the upper estimate of remote clouds effect would suggest an error close to 10%.Key words: Atmospheric composition and structure (transmission and scattering of radiation) - Meteorology and atmospheric dynamics (radiative process)
Tesis sobre el tema "Surface cloud radiative effect"
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Arouf, Assia. "Surface longwave cloud radiative effect derived from space lidar observations : application in the Arctic". Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS173.
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Les nuages jouent un rôle important dans la régulation du bilan énergétique à la surface de la Terre. Par exemple, ils absorbent le rayonnement tellurique émis par la surface de la Terre et le réémettent vers la surface, réchauffant ainsi cette dernière. Ce réchauffement peut être quantifié au travers de l’effet radiatif des nuages (Cloud Radiative Effect (CRE)) infrarouge (LongWave (LW)) à la surface. Cependant, il n’est pas bien connu en tout point du globe et sa variabilité instantané et interdécennale est mal connue. En effet, il dépend fortement de la distribution verticale des nuages qui n’est pas bien restitué à l’échelle globale. Dans cette thèse, nous proposons de restituer le CRE LW à la surface sur 13 ans (2008 − 2020) sur tout le globe en utilisant les observations du lidar Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). A partir de calculs de transfert radiatif 1D, nous établissons des paramétrisations linéaires entre le CRE LW à la surface et des propriétés nuageuses dont l’altitude des nuages. En combinant les paramétrisations avec les observations nuages, nous restituons le CRE LW à la surface, à l’échelle mensuelle (2° × 2°) et instantané à la pleine résolution horizontale de CALIPSO (90 m/330 m). Nous avons trouvé que les nuages réchauffent la surface de 27.0 W/m2 sur la période 2008−2020 à l’échelle globale. Le CRE LW à la surface est particulièrement important dans les régions polaires, où les nuages peuvent avoir un effet sur la fonte des glaces. En colocalisant instantanément le CRE LW à la surface et les observations de la banquise dans les régions où la concentration de la banquise Arctique varie, nous avons montré que les grandes valeurs du CRE LW à la surface (> 80 W/m2 ) sont beaucoup plus fréquentes au-dessus des océans ouverts que de la banquise en fin d’automne. Nos résultats suggèrent que les nuages peuvent retarder la reconstruction de la banquise plus tard dans la saisonClouds play an important role in regulating Earth’s energy budget at the surface. For example, clouds absorb thermal radiation emitted by Earth’s surface and reemit it toward the surface and warming the surface. This can be quantified through surface LongWave (LW) Cloud Radiative Effect (CRE). However, surface LW CRE on a global scale is not well retrieved and its instantaneous and interdecadal variability is poorly known. Indeed, it depends highly on vertical cloud distribution, which is poorly documented globally. In this thesis, we propose to retrieve the surface LW CRE over 13 years (2008 − 2020) at a global scale using Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) spaceborne lidar observations. From 1D radiative transfer computations, we establish linear parametrizations between surface LW CRE and cloud properties including cloud altitude. Combining the parametrizations with the cloud observations, we derive two datasets of surface LW CRE, at monthly–2° × 2° gridded scale and instantaneously at full CALIPSO horizontal resolution (90 m cross-track; 330 m along orbit-track). We found that clouds warm the surface by 27.0 W/m2 over the 2008 − 2020 time period at a global scale. Surface LW CRE is particularly important in polar regions such that clouds may have an effect on ice melting. By instantaneously co-locating surface cloud warming and sea ice observations in regions where sea ice varies, we showed that large surface cloud warming values (> 80 W/m2 ) are much more frequent over open water than over sea ice during late Fall. Our results suggest that clouds may delay sea ice freeze-up later into the Fall
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Marty, Christoph. "Surface radiation, cloud forcing and greenhouse effect in the Alps /". Zürich, 2000. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13609.
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Schäfer, Michael, Eike Bierwirth, André Ehrlich, Evi Jäkel y Manfred Wendisch. "Three-dimensional radiative effects in Arctic boundary layer clouds above ice edges". Universität Leipzig, 2015. https://ul.qucosa.de/id/qucosa%3A16651.
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Based on airborne spectral imaging observations, three-dimensional (3-D) radiative effects between Arctic boundary layer clouds and highly variable Arctic surfaces have been identified and quantified. A method is presented to discriminate sea ice and open water in cloudy conditions based on airborne upward radiance measurements in the visible spectral range. This separation simultaneously reveals that the transition of radiance between open water and sea ice is not instantaneous in cloudy conditions but horizontally smoothed. In general, clouds reduce the nadir radiance above bright surfaces in the vicinity of open water, while the nadir radiance above open sea is enhanced compared to situations with clouds located above sea ice surfaces. With the help of the observations and 3-D radiative transfer simulations, this effect was
quantified. This affected distance deltaL was found to depend on both cloud and sea ice properties. For a low level cloud at 0-200 m altitude, as observed during the Arctic field campaign Vertical Distribution of Ice in Arctic Clouds (VERDI) in 2012, an increase of the cloud optical thickness from tau = 1 to tau = 10 leads to a decrease of deltaL from 600 to 250 m. An increase in cloud base altitude or cloud geometrical thickness results in an increase of deltaL. Furthermore, the impact of these 3-D-radiative effects on a retrieval of cloud optical properties was investigated. The enhanced brightness of a dark pixel next to an ice edge results in uncertainties of up to 90 % in retrievals of tau and up to 30 % in retrievals of the effective radius reff. With the help of detlaL quantified here, an estimate of the distance to the ice edge is given where the retrieval uncertainties due to 3D-effects are negligible.Mit Hilfe flugzeuggetragener abbildender spektraler Beobachtungen wurden 3-D Strahlungseffekte zwischen arktischen Grenzschichtwolken sowie der hochvariablen arktischen Bodenoberfläche identifiziert und quantifiziert. Eine Methode zur Differenzierung von Meereis und offener Wasserflächen, auf Grundlage flugzeuggetragener Messungen der aufwärtsgerichteten Strahldichte im sichtbaren Spektralbereich, während bewölkter Bedingungen wird vorgestellt. Diese Differenzierung zeigt gleichzeitig auf, dass die Strahldichtereduzierung beim Übergang vom Meereis zu den offenen Wasserflächen nicht unmittelbar erfolgt, sondern horizontal geglättet ist. Allgemein verringern Wolken in der Umgebung von Eiskanten die Nadir-Strahldichte über den hellen Eisflächen und erhöhen sie über dunklen Meeresoberflächen. Mit Hilfe von 3-D Strahlungstransferrechnungen wurde dieser Effekt quantifiziert. Die Reichweite dieses Effektes wird sowohl von den Wolken- als auch den Oberflächeneigenschaften beeinflusst. Für eine flache Wolke zwischen 0 und 200 m, so wie sie während der arktischen Feldkampagne Vertical Distribution of Ice in Arctic Clouds (VERDI), 2012 beobachtet werden konnte, führt eine Erhöhung der wolkenoptischen Dicke von tau = 1 zu tau = 10 zu einer Verringerung in deltaL von 600 zu 250 m. Zudem führt eine Erhöhung der Wolkenhöhe und ihrer geometrischen Dicke zu einer Zunahme von deltaL. Anschließend wurde der Einfluss dieser 3-D Strahlungseffekte auf die Ableitungsergebnisse von tau untersucht. Die Aufhellung eines dunkleren Pixels neben der Eiskante führt zu Unsicherheiten von bis zu 90 % bei der Ableitung von . Beim effektiven Radius zu bis zu 30 %. DeltaL ist ein Maß mit Hilfe dessen die Entfernung zur Eiskante bestimmt werden kann, ab welcher die Unsicherheiten bezüglich der 3-D Effekte vernachlässigt werden können.
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Viúdez, i. Mora Antoni. "Atmospheric downwelling longwave radiation at the surface during cloudless and overcast conditions. Measurements and modeling". Doctoral thesis, Universitat de Girona, 2011. http://hdl.handle.net/10803/31841.
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Atmospheric downwelling longwave radiation is an important component of the terrestrial energy budget; since it is strongly related with the greenhouse effect, it remarkably affects the climate. In this study, I evaluate the estimation of the downwelling longwave irradiance at the terrestrial surface for cloudless and overcast conditions using a one-dimensional radiative transfer model (RTM), specifically the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART). The calculations performed by using this model were compared with pyrgeometer measurements at three different European places: Girona (NE of the Iberian Peninsula), Payerne (in the East of Switzerland), and Heselbach (in the Black Forest, Germany). Several studies of sensitivity based on the radiative transfer model have shown that special attention on the input of temperature and water content profiles must be held for cloudless sky conditions; for overcast conditions, similar sensitivity studies have shown that, besides the atmospheric profiles, the cloud base height is very relevant, at least for optically thick clouds. Also, the estimation of DLR in places where radiosoundings are not available is explored, either by using the atmospheric profiles spatially interpolated from the gridded analysis data provided by European Centre of Medium-Range Weather Forecast (ECMWF), or by applying a real radiosounding of a nearby site. Calculations have been compared with measurements at all sites. During cloudless sky conditions, when radiosoundings were available, calculations show differences with measurements of -2.7 ± 3.4 Wm-2 (Payerne). While no in situ radiosoundings are available, differences between modeling and measurements were about 0.3 ± 9.4 Wm-2 (Girona). During overcast sky conditions, when in situ radiosoundings and cloud properties (derived from an algorithm that uses spectral infrared and microwave ground based measurements) were available (Black Forest), calculations show differences with measurements of -0.28 ± 2.52 Wm2. When using atmospheric profiles from the ECMWF and fixed values of liquid water path and droplet effective radius (Girona) calculations show differences with measurements of 4.0 ± 2.5 Wm2. For all analyzed sky conditions, it has been confirmed that estimations from radiative transfer modeling are remarkably better than those obtained by simple parameterizations of atmospheric emissivity.La radiació infrarroja a l’atmosfera és una component important del balanç energètic del planeta; en estar fortament relacionada amb l’efecte hivernacle influeix de manera remarcable en el clima. En aquest estudi s’avalua la bondat de les estimacions de la irradiància infrarroja incident en superfície (DLR) fetes amb un model unidimensional de transferència radiativa, el Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART), per a condicions de cel serè o bé completament ennuvolat. Els càlculs realitzats amb aquest model han estat comparats amb mesures de pirgeòmetre realitzades en tres emplaçaments a Europa: Girona (NE de la Península Ibèrica), Payerne (a l’est de Suïssa), i Heselbach (a la Selva Negra, Alemanya). Els estudis de sensibilitat fets amb el model de transferència radiativa han mostrat l’especial importància que tenen els perfils atmosfèrics de temperatura i contingut d’aigua en absència de núvols; per cels completament ennuvolats l’estudi de sensibilitat mostra que, a banda dels perfils atmosfèrics esmentats, l’altura de la base dels núvols és molt rellevant. S’ha estimat la DLR per indrets on no es disposava de radiosondatges, substituint-los bé per un radiosondatge proper, o bé per perfils interpolats espacialment en l’anàlisi del model de predicció meteorològica de l’European Centre of Medium-Range Weather Forecast (ECMWF). Els càlculs han estat comparats amb mesures per tots els llocs. Per condicions de cel serè, i quan es disposa de radiosondatge, els càlculs mostren una diferència amb les mesures de -2.7 ± 3.4 Wm-2 (Payerne). Quan no es disposa d’aquests perfils, la diferència entre les modelitzacions i les mesures és de 0.3 ± 9.4 Wm-2 (Girona). Per condicions de cel cobert, quan es disposa del radiosondatge i les propietats dels núvols (derivades a partir d’un algoritme que empra mesures espectrals en infraroig i en la banda de microones en superfície, Selva Negra), els càlculs mostren una diferència amb les mesures de -0.28 ± 2.52 Wm-2. Quan es fan servir els perfils del ECMWF i es fixa el valor de la columna d’aigua líquida i el radi efectiu de les gotes d’aigua (Girona) els càlculs mostren una diferència amb les mesures de 4.0 ± 2.5 Wm-2. També s’ha confirmat per totes les condicions estudiades que les estimacions amb el model de transferència radiativa són notablement millors que les obtingudes amb parametritzacions senzilles de l’emissivitat atmosfèrica.
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Spadanuda, Enrica. "Surface cloud radiative forcing from broadband radiation measurements on the Antarctic plateau". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10201/.
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Surface based measurements systems play a key role in defining the ground truth for climate modeling and satellite product validation. The Italian-French station of Concordia is operative year round since 2005 at Dome C (75°S, 123°E, 3230 m) on the East Antarctic Plateau. A Baseline Surface Radiation Network (BSRN) site was deployed and became operational since January 2006 to measure downwelling components of the radiation budget, and successively was expanded in April 2007 to measure upwelling radiation. Hence, almost a decade of measurement is now available and suitable to define a statistically significant climatology for the radiation budget of Concordia including eventual trends, by specifically assessing the effects of clouds and water vapor on SW and LW net radiation. A well known and robust clear sky-id algorithm (Long and Ackerman, 2000) has been operationally applied on downwelling SW components to identify cloud free events and to fit a parametric equation to determine clear-sky reference along the Antarctic daylight periods (September to April). A new model for surface broadband albedo has been developed in order to better describe the features the area. Then, a novel clear-sky LW parametrization, based on a-priori assumption about inversion layer structure, combined with daily and annual oscillations of the surface temperature, have been adopted and validated. The longwave based method is successively exploited to extend cloud radiative forcing studies to nighttime period (winter). Results indicated inter-annual and intra-annual warming behaviour, i.e. 13.70 W/m2 on the average, specifically approaching neutral effect in summer, when SW CRF compensates LW CRF, and warming along the rest of the year due prevalentely to CRF induced on the LW component.
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Li, Xianming. "The effect of gas-surface interactions on radiative ignition of PMMA". Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/15888.
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Monteiro, Manuel Conceição Gonçalves. "Forçamento radiativo à superficie e no topo da atmosfera provocado por nuvens sobre a Região de Évora : Cloud radiative forcing to the surface and in the top of the atmosphere provoked for clouds on the region of Évora". Master's thesis, Universidade de Évora, 2004. http://hdl.handle.net/10174/14850.
Texto completoResumen
Nesta tese investigou-se o papel desempenhado pelas nuvens no balanço radiativo local observado à superfície da Terra. Para tal foram determinados os forçamentos radiativos de pequeno comprimento de onda, de grande comprimento de onda e referentes à banda espectral total devido às nuvens. Recorrendo a imagens de satélite, determinou-se os forçamentos radiativos devido às nuvens, no topo da atmosfera. Foram consideradas as situações de cobertura total de nuvens, ou seja, correspondendo à nebulosidade máxima, N=8. O estudo foi feito de modo a poder contemplar situações distintas de cobertura de nuvens, correspondentes a diferentes tipos de nuvens para a região de Évora. A partir das medidas dos fluxos de radiação solar e da radiação infravermelha observados, desde há vários anos no Centro Geofísico de Évora, com radiómetro de banda larga foi possível determinar, quer o balanço da radiação (solar global, infravermelha ou total, isto é, a soma das duas) como o forçamento radiativo global local à superfície devido à presença de nuvens que cobrem totalmente o céu, sobre o local de observação (Évora). A partir do conhecimento dos forçamentos radiativos devido às nuvens simultaneamente no topo de atmosfera e à superfície foi possível determinar o forçamento radiativo na atmosfera devido às nuvens. O conhecimento do forçamento radiativo na atmosfera devido às nuvens e a sua evolução ao longo de um certo período de tempo permitir-nos-ão ter informação sobre a evolução da energia que é absorvida ou retirada da atmosfera ao longo desse intervalo de tempo.
/*** Abstract - The present thesis consists of the role played by clouds in the local radiative balance observed at Earth surface. They had been determined both the radiative forcing of short and long wave related to the total spectral band provoked by clouds. The clouds radiative forcing in the top of atmosphere was determined by satellite images. The situation of total cloud covering had been corresponding to the maximum cloudiness N=8. The study was made in order to be able to contemplate distinct situations of clouds covering corresponding differents clouds types in Évora region. From the measures of solar radiation and infrared radiation fluxes observed for many years in the Geophysical Centre of Évora , with radiometer of broadband was possible to determine the radiation balance (solar global , infrared or total) as the local global radiative forcing at surface due to cloud presence that covers total sky in Évora region. lt was possible to determine the cloud radiative forcing in the atmosphere by the knowledge simultaneously of the clouds radiative in the top of atmosphere and at the surface. The knowledge of clouds radiative forcing in the atmosphere and its evolution throughout a certain period of time will allow us to have information on the evolution of the energy that absorbed or removed form the atmosphere during this interval of time.
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Xie, Yu. "The effect of ice crystal surface roughness on the retrieval of ice cloud microphysical and optical properties". Texas A&M University, 2003. http://hdl.handle.net/1969.1/5970.
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The effect of the surface roughness of ice crystals is not routinely accounted for in
current cloud retrieval algorithms that are based on pre-computed lookup libraries. In this
study, we investigate the effect of ice crystal surface roughness on the retrieval of ice
cloud effective particle size, optical thickness and cloud-top temperature. Three particle
surface conditions, smooth, moderately rough and deeply rough, are considered in the
visible and near-infrared channels (0.65 and 3.75 õm). The discrete ordinates radiative
transfer (DISORT) model is used to compute the radiances for a set of optical
thicknesses, particle effective sizes, viewing and illumination angles, and cloud
temperatures. A parameterization of cloud bi-directional reflectances and effective
emittances is then developed from a variety of particle surface conditions. This
parameterization is applied in a 3-channel retrieval method for Moderate Resolution
Imaging Spectroradiometer (MODIS) data at 0.65, 3.75, and 10.8 õm. Cloud optical
properties are derived iteratively for each pixel that contains ice clouds. The impact of ice
crystal surface roughness on the cloud parameter retrievals is examined by comparing the
results for particles with smooth surfaces and rough surfaces. Retrieval results from two
granules of MODIS data indicate that the retrieved cloud optical thickness is significantly reduced if the parameterization for roughened particles is used, as compared with the case
of smooth particles. For the retrieval of cloud effective particle size, the inclusion of the
effect of surface roughness tends to decrease the retrieved effective particle size if ice
crystals are small. The reversed result is noticed for large ice crystals. It is also found that
surface roughness has a very minor effect on the retrieval of cloud-top temperatures.
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Voogt, James Adrian. "Validation of an urban canyon radiation model for nocturnal long-wave radiative fluxes and the effect of surface geometry on cooling in urban canyons". Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27679.
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The urban canyon radiation model of Arnfield (1976, 1982) is validated using measurements of long-wave fluxes taken within a scale urban canyon constructed from concrete building blocks. A custom-designed traversing system allowed miniature radiometers to be automatically moved around the perimeter of a canyon cross-section thereby providing for the validation of individual model grid-points.
Measured model input consists of surface temperatures obtained using fine wire themocouples, incident long-wave radiation at the canyon top, and emissivity of canyon materials. Tests were conducted to establish the expected accuracy and precision of the input data. Surface temperature data were filtered to remove a noise component. A probable error analysis of all measured model input and validation data is made.
Sensitivity tests of the model to variations in input data are presented. Surface temperature is the dominant control under the conditions tested. Model-calculated view-factors are shown to be in error for adjacent corner points and are replaced with view-factors calculated using equations derived from the Nusselt Unit Sphere method (Steyn, pers. comm.)
Validation results for a range of canyon height-to-width ratios, meteorological conditions and model parameters are presented. Excellent agreement between modelled and measured fluxes is obtained for points on the canyon floor and top. The agreement for fluxes at points on the canyon walls is generally good but is shown to suffer from errors in sensor orientation relative to the canyon walls. Use of the Unsworth and Monteith (1975) radiance distribution improves model performance statistics for incident and net long-wave radiation.
Four different estimates of surface temperature are used as model input in place of the measured values to investigate the differences in the model output. Surface temperature-based estimates are found to be superior to those based upon air temperature. The use of unmodified screen-level air temperatures measured at Vancouver Airport produces the poorest agreement.
The temporal and spatial variation of in-canyon temperatures and radiation are presented for three canyon height-to-width ratios. The canyon geometry is shown to significantly reduce the surface cooling on the canyon floor compared to an open site under ideal radiative cooling conditions. Results are compared to previous results from scale models (Oke, 1981) and field studies (Oke and Maxwell, 1975; Hogstrdm et al., 1978). . Atmospheric controls of incident long-wave radiation, wind speed and direction are also shown to affect the observed cooling.Arts, Faculty of
Geography, Department of
Graduate
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Galloway, Christopher. "Non-radiative processes and vibrational pumping in surface-enhanced raman scattering : a thesis submitted to the Victoria University of Wellington in fulfilment of the requirements for the degree of Doctor of Philosophy in Physics /". ResearchArchive@Victoria e-Thesis, 2010. http://hdl.handle.net/10063/1244.
Texto completoLibros sobre el tema "Surface cloud radiative effect"
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R, Frouin y United States. National Aeronautics and Space Administration., eds. Analysis of long-term cloud cover, radiative fluxes, and sea surface temperature in the eastern tropical Pacific. [Washington, DC: National Aeronautics and Space Administration, 1996.
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R, Frouin y United States. National Aeronautics and Space Administration., eds. Analysis of long-term cloud cover, radiative fluxes, and sea surface temperature in the eastern tropical Pacific. [Washington, DC: National Aeronautics and Space Administration, 1996.
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R, Frouin y United States. National Aeronautics and Space Administration., eds. Analysis of long-term cloud cover, radiative fluxes, and sea surface temperature in the eastern tropical Pacific. [Washington, DC: National Aeronautics and Space Administration, 1996.
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Analysis of long-term cloud cover, radiative fluxes, and sea surface temperature in the eastern tropical Pacific. [Washington, DC: National Aeronautics and Space Administration, 1996.
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Krishnamurti, T. N., H. S. Bedi y V. M. Hardiker. An Introduction to Global Spectral Modeling. Oxford University Press, 1998. http://dx.doi.org/10.1093/oso/9780195094732.001.0001.
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This book is an indispensable guide to the methods used by nearly all major weather forecast centers in the United States, England, Japan, India, France, and Australia. Designed for senior-level undergraduates and first-year graduate students, the book provides an introduction to global spectral modeling. It begins with an introduction to elementary finite-difference methods and moves on towards the gradual description of sophisticated dynamical and physical models in spherical coordinates. Topics include computational aspects of the spectral transform method, the planetary boundary layer physics, the physics of precipitation processes in large-scale models, the radiative transfer including effects of diagnostic clouds and diurnal cycle, the surface energy balance over land and ocean, and the treatment of mountains. The discussion of model initialization includes the treatment of normal modes and physical processes, and the concluding chapter covers the spectral energetics as a diagnostic tool for model evaluation.
Capítulos de libros sobre el tema "Surface cloud radiative effect"
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Randall, David A., Laura D. Fowler y Donald A. Dazlich. "Cloud Effects on the Ocean Surface Energy Budget". En Climate Sensitivity to Radiative Perturbations, 239–49. Berlin, Heidelberg: Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-61053-0_18.
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Dajuma, Alima, Siélé Silué, Kehinde O. Ogunjobi, Heike Vogel, Evelyne Touré N’Datchoh, Véronique Yoboué, Arona Diedhiou y Bernhard Vogel. "Biomass Burning Effects on the Climate over Southern West Africa During the Summer Monsoon". En African Handbook of Climate Change Adaptation, 1515–32. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-45106-6_86.
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AbstractBiomass Burning (BB) aerosol has attracted considerable attention due to its detrimental effects on climate through its radiative properties. In Africa, fire patterns are anticorrelated with the southward-northward movement of the intertropical convergence zone (ITCZ). Each year between June and September, BB occurs in the southern hemisphere of Africa, and aerosols are carried westward by the African Easterly Jet (AEJ) and advected at an altitude of between 2 and 4 km. Observations made during a field campaign of Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa (DACCIWA) (Knippertz et al., Bull Am Meteorol Soc 96:1451–1460, 2015) during the West African Monsoon (WAM) of June–July 2016 have revealed large quantities of BB aerosols in the Planetary Boundary Layer (PBL) over southern West Africa (SWA).This chapter examines the effects of the long-range transport of BB aerosols on the climate over SWA by means of a modeling study, and proposes several adaptation and mitigation strategies for policy makers regarding this phenomenon. A high-resolution regional climate model, known as the Consortium for Small-scale Modelling – Aerosols and Reactive Traces (COSMO-ART) gases, was used to conduct two set of experiments, with and without BB emissions, to quantify their impacts on the SWA atmosphere. Results revealed a reduction in surface shortwave (SW) radiation of up to about 6.5 W m−2 and an 11% increase of Cloud Droplets Number Concentration (CDNC) over the SWA domain. Also, an increase of 12.45% in Particulate Matter (PM25) surface concentration was observed in Abidjan (9.75 μg m−3), Accra (10.7 μg m−3), Cotonou (10.7 μg m−3), and Lagos (8 μg m−3), while the carbon monoxide (CO) mixing ratio increased by 90 ppb in Abidjan and Accra due to BB. Moreover, BB aerosols were found to contribute to a 70% increase of organic carbon (OC) below 1 km in the PBL, followed by black carbon (BC) with 24.5%. This work highlights the contribution of the long-range transport of BB pollutants to pollution levels in SWA and their effects on the climate. It focuses on a case study of 3 days (5–7 July 2016). However, more research on a longer time period is necessary to inform decision making properly.This study emphasizes the need to implement a long-term air quality monitoring system in SWA as a method of climate change mitigation and adaptation.
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Morcrette, Jean-Jacques. "The Role of Cloud-Radiative Interactions in the Sensitivity of the E.C.M.W.F. Model Climate to Variations in Sea Surface Temperature". En Climate Sensitivity to Radiative Perturbations, 157–69. Berlin, Heidelberg: Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-61053-0_12.
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Dong, Peiming, Wei Han, Wei Li y Shuanglong Jin. "Assessment of Radiative Effect of Hydrometeors in Rapid Radiative Transfer Model in Support of Satellite Cloud and Precipitation Microwave Data Assimilation". En Data Assimilation for Atmospheric, Oceanic and Hydrologic Applications (Vol. III), 337–60. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-43415-5_15.
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Liou, K. N. "Radiative Transfer In Clouds". En Radiation and Cloud Processes in the Atmosphere, 255–339. Oxford University PressNew York, NY, 1992. http://dx.doi.org/10.1093/oso/9780195049107.003.0005.
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Abstract Clouds reflect, absorb, and transmit solar radiation. The amount of solar flux reflected, absorbed, and transmitted by clouds is a function of the optical depth, the geometry governing the sun, and the direction of detection. Under the planeparallel assumption, a number of the radiative transfer methodologies that have been introduced in Chapter 3 can be used to determine the radiative properties of clouds. As shown in various sections in that chapter, the fundamental radiative transfer equation has been developed for an ensemble of molecules and/or particulates. In the case of clouds, the basic scattering and absorption properties of cloud particles are determined by particle size distribution. Clouds can also reflect and transmit the thermal infrared (ir) radiation emitted from the surface and the atmosphere and, at the same time, emit ir radiation according to the temperature structure within them. Although Chapter 2 provides a comprehensive discussion of the transfer of irradiation in clear atmospheres, the general effects of scattering by cloud particles on ir radiation transfer have not been addressed.
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Emanuel, Kerry A. "Stratocumulus And Trade-Cumulus Boundary Layers". En Atmospheric Convection, 421–62. Oxford University PressNew York, NY, 1994. http://dx.doi.org/10.1093/oso/9780195066302.003.0013.
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Abstract In Chapter 3 we explored the properties of dry convective boundary layers that form when there is a positive buoyancy flux from the surface. Under a variety of conditions, such boundary layers become deep and/or moist enough that clouds form within them. When this happens, the properties of the boundary layer are strongly altered by the latent heat released and absorbed when water changes phase and by the very strong effect of clouds on radiative transfer. In this chapter we explore the properties of boundary layers strongly influenced by clouds that are shallow enough that little precipitation is formed. Boundary layers with clouds may be classified into four groups, illustrated in Figure 13.1: foggy layers, cloud-topped mixed layers, trade cumulus layers, and elevated stratocumulus/mixed trade cumulus-stratocumulus layers. These are discussed in the following sections. Fog is defined as cloud in contact with the surface. For the present purposes, we exclude from this definition cloud in contact with hills or mountains. Over land, fog may form at night as a consequence of radiative cooling of the surface. Heat is lost from the air radiatively and diffused downward into the surface by wind-induced turbulence. If the air near the ground is cooled to its dew-point temperature, condensation occurs, first near the ground and later at higher altitudes. Initially, the fog is thickest near the surface, with the cloud-water content falling off rapidly with altitude. If it does not achieve a thickness greater than a few meters by sunrise, it will remain in this state until absorption of sunlight by the surface and by the cloud itself raises the temperature enough to evaporate the cloud. Thin fog of this kind is not convective, because the cooling occurs from below.
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Liou, K. N. y Y. Gu. "Radiative Transfer in Cirrus Clouds: Light Scatting and Spectral Information". En Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0017.
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The importance of cirrus clouds in climate has been recognized in the light of a number of intensive composite field observations: the First ISCCP Regional Experiment (FIRE) I in October-November 1986; FIRE II in November-December 1991; the European experiment on cirrus (ICE/EUCREX) in 1989; Subsonic Aircraft: Contrail and Cloud Effect Special Study (SUCCESS) in April 1996. Based on observations from the ground-based lidar and radar, airborne instrumentation, and satellites, cirrus clouds are typically located in the upper troposphere and lower stratosphere (Liou 1986). The formation, maintenance, and dissipation of cirrus clouds are directly associated with synoptic and mesoscale disturbances as well as related to deep cumulus outflows. Increases of high cloud cover have been reported at a number of urban airports in the United States based on surface observations spanning 40 years (Liou et al. 1990; Frankel et al. 1997). These increases have been attributed to the contrails and water vapor produced by jet airplane traffic. Satellite observations from NOAA polar-orbiting High-Resolution Infrared Radiation Sounder (HIRS) using the CO2 slicing method (Wylie et al. 1994) also show that cirrus cloud cover substantially increased between 60° S and 60° N during a 4-year period from June 1989 to September 1993. Understanding the role of cirrus clouds in climate must begin with reliable modeling of their radiative properties for incorporation in climate models as well as determination of the global variability of their composition, structure, and optical properties. Development of the remote sensing methodologies for the detection and retrieval of the ubiquitous visible and subvisual cirrus clouds requires the basic scattering, absorption, and polarization data for ice crystals in conjunction with appropriate radiative transfer models. We present the fundamentals involving radiative transfer in cirrus clouds and review pertinent research. In section 13.1, an overview of the subject of light scattering by ice crystals is presented in which we discuss a unification of the geometric optics approach for large ice particles and the finite-difference time domain numerical solution for small ice particles, referred to as the unified theory. Section 13.2 presents radiative transfer in cirrus clouds involving two unique properties: orientation of nonspherical ice crystals and cloud inhomogeneity.
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Heymsfield, Andrew J. y Greg M. McFarquhar. "Mid-latitude and Tropical Cirrus: Microphysical Properties". En Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0008.
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Cirrus, a principal cloud type that forms at low temperatures in the upper troposphere, is composed almost always of ice crystals (Heymsfield and Miloshevich 1989) and on average cover about 20% of the earth's surface (Hartmann et al. 1992). The purpose of this chapter is to characterize the microphysical properties of cirrus clouds. The Glossary of Meteorology (Huschke 1970) defines cirrus clouds as detached clouds in the form of white, delicate filaments, or white or mostly white patches, which are composed of ice crystals. This cloud type forms primarily in the upper troposphere, above about 8km (25,000 feet), where temperatures are generally below -30° C. There are a number of types of cirrus clouds, with the most frequent ones occurring in layers or sheets with horizontal dimensions of hundreds or even thousands of kilometers. Because horizontal dimensions are much greater than vertical extent, this particular type of cirrus cloud is called cirrostratus. Cirrus can also form in a patchy or tufted shape, when the ice crystals are large enough to acquire an appreciable fall velocity (the rate at which ice crystals fall in the vertical) so that trails of considerable vertical extent may form. These trails curve irregularly or slant, sometimes with a commalike shape, as a result of changes in the horizontal wind velocity with height and variations in the fall velocity of the ice crystals. A wispy, layered cloud that forms at the top of a cumulonimbus cloud, termed an “anvil” because of its shape, is a cirrus that consists essentially of ice debris which spreads outward from the convective parts of the storm. Anvils do not include the white, dense portions of thunderstorms or the active convective column. Anvils can spread to form large, widespread cloud layers. Tropical cirrus clouds are thought to arise primarily from cumulonimbus clouds. Unlike the thin, wispy cirrus typifying mid-latitudes, the high altitudes and extensive lateral and vertical development that often characterize tropical cirrus impose substantial large-scale radiative effects in the atmosphere and at the earth's surface (Hartmann et al. 1992; Collins et al. 1996). The cirrus-like low-level ice clouds and ice fogs of the Arctic are not considered cirrus.
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Stephens, Graeme. "Cirrus, Climate, and Global Change". En Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0024.
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Understanding the climate of Earth and the way climate varies in time requires a quantitative understanding of the way water cycles back and forth between the atmosphere and at the Earth's surface. The exchanges of water between the surface and atmosphere establish the hydrological cycle, and it is the influence of this cycle on the energy budget of Earth that is central not only to understanding present climate but also to the prediction of climate change. Processes relating to the smallest of the reservoirs of water—namely, the atmospheric branch of the hydrological cycle—play an especially critical role in climate change. Water in vapor phase is the critical greenhouse gas (e.g., Chahine 1992) providing much studied feedbacks on climate forcing (Lindzen 1990; Rind et al. 1991; Stephens and Greenwald 1991; Inamdar and Ramanathan 1998; Hall and Manabe 1999). Water in the form of condensed, precipitation-sized particles is an important source of energy fueling circulation systems and is the fundamental supply of fresh water to life on Earth. Liquid water cloud droplets significantly modulate the radiative budget of the planet (e.g., Wielicki et al. 1995). Water that exists as ice particles suspended in the atmosphere is perhaps the smallest of the water reservoirs of the atmosphere, yet these ice crystals when distributed as part of large-scale cirrus clouds exert a disproportionate influence on the energy and water budgets of the planet. This chapter briefly speculates on the important ways cirrus clouds affect the Earth's climate. The topics discussed are central to what is referred to as the cloud-climate problem, which might be schematically represented in terms of the coupled processes represented in figure 20.1. The two most critical scientific questions associated with the cloud-climate problem are also stated in figure 20.1. Answers to these questions require a clearer understanding of how the large-scale circulation of the atmosphere governs cloud formation and evolution, how these clouds heat and moisten the atmosphere, and how this heating and moistening effect in turn feeds back to influence the dynamical and thermodynamical properties of the atmosphere.
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Del Genio, Anthony D. "GCM Simulations of Cirrus for Climate Studies". En Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0019.
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One of the great challenges in predicting the rate and geographical pattern of climate change is to faithfully represent the feedback effects of various cloud types that arise via different mechanisms in different parts of the atmosphere. Cirrus clouds are a particularly uncertain component of general circulation model (GCM) simulations of long-term climate change for a variety of reasons, as detailed below. First, cirrus encompass a wide range of optical thicknesses and altitudes. At one extreme are the thin tropopause cirrus that barely affect the short-wave albedo while radiating to space at very cold temperatures, producing a net positive effect on the planetary radiation balance and causing local upper troposphere warming, thus stabilizing the lapse rate. At the other extreme are thick cumulus anvil cirrus whose bases descend to the freezing level; these clouds produce significant but opposing short-wave and long-wave effects on the planetary energy balance while cooling the surface via their reflection of sunlight. In fact, satellite climatologies show a continuum of optical thicknesses between these two extremes (Rossow and Schiffer 1991). In a climate change, the net effect of cirrus might either be a positive or a negative feedback, depending on the sign and magnitude of the cloud cover change in each cloud-type category and the direction and extent of changes in their optical properties (see Stephens et al. 1990). Second, the dynamic processes that create cirrus are poorly resolved and different in different parts of the globe. In the tropics, small-scale convective transport of water from the planetary boundary layer to the upper troposphere is the immediate source of a significant fraction of the condensate in mesoscale cirrus anvils (see Gamache and Houze 1983), and ultimately the source of much of the water vapor that condenses out in large-scale uplift to form thinner cirrus. However, many observed thin cirrus cannot directly be identified with a convective source, suggesting that in situ upper troposphere dynamics and regeneration processes within cirrus (see Starr and Cox 1985) are important. In mid-latitudes, although summertime continental convection is a source of cirrus, in general cirrus is associated with mesoscale frontal circulations in synoptic-scale baroclinic waves and jet streaks (see Starr and Wylie 1990; Mace et al. 1995).
Actas de conferencias sobre el tema "Surface cloud radiative effect"
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Ou, S. C. y K. N. Liou. "Remote Sounding of Surface Radiative Fluxes in Cirrus Cloudy Conditions". En Optical Remote Sensing of the Atmosphere. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/orsa.1995.wb3.
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It has been long recognized that radiation and radiation perturbations play a critical role in the climate system (Liou 1992). Surface radiative fluxes are useful parameters for monitoring global change, for understanding of the effects of clouds on the radiation field, and for improving parameterization of surface sensible and latent heat fluxes. Monitoring of the radiation budget at the top of the atmosphere has been one of the prime satellite programs for the last 30 years. However, monitoring radiative fluxes at the surface over the globe from space cannot be performed in a direct way at the present time. In particular, since clouds are the prime regulators of the radiative fluxes, uncertainties in the retrieved cloud parameters, which are inputs to radiative transfer models, can introduce significant errors in the computed radiative fluxes. Thus, remote sounding of surface radiative fluxes in cloudy conditions requires the development of both satellite cloud retrieval scheme and radiation models.
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Wacker, Stefan, Julian Gröbner y Laurent Vuilleumier. "Trends in surface radiation and cloud radiative effect over Switzerland in the past 15 years". En RADIATION PROCESSES IN THE ATMOSPHERE AND OCEAN (IRS2012): Proceedings of the International Radiation Symposium (IRC/IAMAS). AIP, 2013. http://dx.doi.org/10.1063/1.4804859.
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Nagaraja Rao, C. R. y Nian Zhang. "Mt. Pinatubo volcanic aerosol effects on the remote sensing of sea surface temperature". En OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1992. http://dx.doi.org/10.1364/oam.1992.fmm5.
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The stratospheric volcanic dust cloud resulting from the eruption of Mt. Pinatubo in June 1991 has adversely affected the retrieval of sea surface temperature from the upwelling infrared radiances (≈3.7,10.8, and 11.9 µm) measured by the Advanced Very High Resolution Radiometer onboard the NOAA polar orbiting satellites. Correction algorithms to restore the capability of sea surface temperature retrieval during such volcanic dust episodes have been developed by combining model simulations of the radiative effects of volcanic aerosols with shipboard and buoy measurements of sea surface temperature and the NOAA operational aerosol product. The operational implementation of the correction algorithms will be discussed, accompanied by examples of the restored sea surface temperature fields.
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Davies, R. "Comparison of longwave and shortwave cloud effects on equilibrium surface temperature using a radiative-convective model and 12 years of MISR observations". En RADIATION PROCESSES IN THE ATMOSPHERE AND OCEAN (IRS2012): Proceedings of the International Radiation Symposium (IRC/IAMAS). AIP, 2013. http://dx.doi.org/10.1063/1.4804871.
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Bisson, Scott E. y J. E. M. Goldsmith. "Measurements of Daytime and Upper Tropospheric Water Vapor Profiles by Raman Lidar". En Optical Remote Sensing of the Atmosphere. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/orsa.1995.thb1.
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One of the most important atmospheric constituents needed for climate and meteorological studies is water vapor. It plays an important role in driving atmospheric circulations through latent heat release and in determining the earth’s radiation budget, both through its radiative effects (water vapor is the major greenhouse gas) and through cloud formation. The vertical distribution of water vapor is particularly important because in addition to determining convective stability, radiative effects are also strongly altitude dependent. In fact, several one-dimensional radiative convective models1 have shown that although upper tropospheric (8-12 km) water vapor concentrations are 2-3 orders of magnitude less than those near the surface, upper tropospheric water vapor exerts an important influence on climate. What these models show is that for a given absolute increase in water vapor in the upper troposphere, the response or change in surface temperature is extremely disproportionate to the amount of water vapor. At present, considerable controversy exists over the nature of the vertical redistribution of water vapor in a changing climate, and particularly the distribution of water vapor in the upper troposphere. Understanding upper tropospheric moistening processes such as deep convection are therefore of prime importance in addressing the water vapor feedback question. Accurate measurements of the vertical and temporal variations of water vapor are essential for understanding atmospheric processes and hence model refinement.
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Eck, Thomas y Dennis Dye. "A Simple Method of Estimating Photosynthetically Active Radiation at the Earth's Surface from Satellite". En Optical Remote Sensing of the Atmosphere. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/orsa.1990.md11.
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A physically based method of estimating the photosynthetically active radiation (PAR) incident at the earth's surface is described. Ultraviolet reflectivity, inferred from the Total Ozone Monitoring Spectrometer (TOMS) onboard the polar orbiting Nimbus-7 satellite, is used to account for the effect of cloud albedo on the attenuation of PAR incident at the surface. The clear sky incident radiation for the PAR wavelengths (400-700 nm) is computed from the spectral model of Goldberg and Klein (1980). Monthly averages of incident PAR at the surface estimated from the satellite method differed from estimates of PAR from ground pyranometers by less than 6%. This method of PAR estimation can be applied globally over snow and ice free areas.
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Dev, Soumyabrata, Shilpa Manandhar, Feng Yuan, Yee Hui Lee y Stefan Winkler. "Cloud radiative effect study using sky camera". En 2017 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium). IEEE, 2017. http://dx.doi.org/10.1109/usnc-ursi.2017.8074899.
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Gao, Z. X., J. Yi, J. Sun, Y. L. Wang y Y. L. Zhang. "Method For Evaluating Three-dimensional Total Dose Effects Based On Structure Surface Cloud Picture". En 2018 International Conference on Radiation Effects of Electronic Devices (ICREED). IEEE, 2018. http://dx.doi.org/10.1109/icreed.2018.8905049.
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Giroux, Jean, André Villemaire y Roger W. Saunders. "A New Airborne Fourier Transform Spectrometer for Meteorological Applications". En Fourier Transform Spectroscopy. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/fts.1995.ffd4.
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Bomem is currently integrating ARIES (Airborne Radiometer Interferometer Evaluation System), a Fourier transform (FT) interferometer to be installed in a pod of the UK Meteorological Office Hercules C-130 aircraft. This new infrared (IR) instrument has numerous science goals. First it will provide invaluable data to help refine IR radiative transfer models such as FASCODE. It will also help characterize the emissivity and the surface temperature of sea and ground under various conditions (snow, ice, etc.). The IR spectral signature holds a wealth of information so that other physical properties of the atmosphere such as clouds and aerosol effect can also be studied. Retrieval of total column amount of some of the atmosphere minor constituents will be possible as well. Data from the ARIES instrument is also foreseen to be used to support the development of advanced atmospheric sounders such as IASI (IR Atmospheric Sounding Interferometer, a Franco-Italian project) and AIRS (Advanced IR Sounder, a NASA project).
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Costa, M. J., V. Salgueiro, D. Santos, D. Bortoli, A. M. Silva y R. Salgado. "Surface cloud radiative forcing in the South of Portugal". En RADIATION PROCESSES IN THE ATMOSPHERE AND OCEAN (IRS2012): Proceedings of the International Radiation Symposium (IRC/IAMAS). AIP, 2013. http://dx.doi.org/10.1063/1.4804862.
Texto completoInformes sobre el tema "Surface cloud radiative effect"
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Potter, G. L. The effect of horizontal resolution on cloud radiative forcing in the ECMWF model. PCMDI report No. 22. Office of Scientific and Technical Information (OSTI), mayo de 1995. http://dx.doi.org/10.2172/114640.
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Shomer, Ilan, Louise Wicker, Uzi Merin y William L. Kerr. Interactions of Cloud Proteins, Pectins and Pectinesterases in Flocculation of Citrus Cloud. United States Department of Agriculture, febrero de 2002. http://dx.doi.org/10.32747/2002.7580669.bard.
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The overall objective was to understand the cloud flocculation of citrus juice by characterization of the interactions between proteins and pectins, and to determine the role of PE isozymes in catalyzing this phenomenon. Specific objectives were to: 1. identify/characterize cloud-proteins in relation to their coagulable properties and affinity to pectins; 2. to determine structural changes of PME and other proteins induced by cation/pectin interactions; 3. localize cloud proteins, PME and bound protein/pectates in unheated and pasteurized juices; 4. to create "sensitized" pectins and determine their effect on clarification. The original objectives were not changed but the methods and approach were modified due to specific research requirements. Two i postulates were: 1. there is a specific interaction of cloud proteins with de-esterified regions of ! pectin and this contributes to cloud loss; 2. isozymes of pectin-methyl-esterase (PME) vary in efficiency to create sensitized pectins. The appearance of citrus fruit juice is an important quality factor and is determined by the color and turbidity that .are conferred by the suspended particles, i.e., by the cloud and its homogeneity. Under some circumstances the cloud tend to flocculate and the juice clarifies. The accepted approach to explain the clarification is based on pectin demethoxylation by PME that promotes formation of Ca-pectate. Therefore, the juice includes immediate heat-inactivation upon ~ squeezing. Protein coagulation also promotes cloud instability of citrus fruit extracts. However, the clarification mechanism is not fully understood. Information accumulated from several laboratories indicates that clarification is a more complex process than can be explained by a single mechanism. The increasing trend to consume natural-fresh juice emphasizing the importance of the knowledge to assure homogeneity of fresh juice. The research included complementary directions: Conditions that induce cloud-instability of natural- juice [IL]. Evaluate purification schemes of protein [USA]. Identifications of proteins, pectin and neutral sugars ([IL]; Structure of the cloud components using light and electron microscopy and immuno-labeling of PME, high-methoxyl-pectin (HMP) and low-methoxyl-pectin (LMP); Molecular weight of calcium sensitized pectins [US]; Evaluation of the products of PME activity [US]. Fractions and size distribution and cloud components [IL-US]. The optimal pH activity of PME is 7 and the flocculation pH of the cloud is 3-4. Thus, the c roles of PME, proteins and pectins in the cloud instability, were studied in pH ranges of 2- 7. The experiments led to establish firstly repeatable simulate conditions for cloud instability [IL]. Thermostable PME (TS-PE) known to induce cloud instability, but also thermolabile forms of PME (TL-PE) caused clarification, most likely due to the formation and dissolution of inactive :. PE-pectin complexes and displacement of a protective colloid from the cloud surface [US]. Furthermore, elimination of non-PME protein increases TS-PE activity, indicating that non-PME proteins moderate PME activity [US]. Other experiments Concomitantly with the study of the PME activity but promotes the association of cloud-proteins to pectin. Adjusting of the juice pH to f 7 retains the cloud stability and re-adjusting of the pH to 40% DE reacts to immuno-labeling in the cloud fragments, whereas
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Wilkowski. L51487 Predict the Interaction of Fracture Toughness and Constraint Effects for Surface Cracked Pipe. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), abril de 1985. http://dx.doi.org/10.55274/r0010596.
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This report summarizes a program designed to quantify the disagreement between the standard t x 2t bend specimen and surface-cracked pipe data. The effect of untracked ligament length on upper-shelf toughness was also investigated. Ultimately, the findings will have application to pipeline girth welds. But in this first step, unwelded line-pipe steel specimens were used throughout this investigation. Obviously, weld metal specimen data would be more directly applicable to welded pipe. However, weld metal test data exhibit more scatter than base metal data (largely due to material non-homogeneity). This scatter could cloud the general data trends under investigation. Consequently, base metal specimens were used to more clearly establish these trends. This will form a basis for further investigations on weld metals.
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Wicker, Louise, Ilan Shomer y Uzi Merin. Membrane Processing of Citrus Extracts: Effects on Pectinesterase Activity and Cloud Stability. United States Department of Agriculture, octubre de 1993. http://dx.doi.org/10.32747/1993.7568754.bard.
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The U.S. team studied the role of cations and pH on thermolabile (TL-PE) and thermostable (TS-PE), permeation in ultrafiltration (UF) membranes, affinity to ion exchange membranes, mechanism of cation and pH activation, and effect on PE stability. An optimum pH and cation concentration exists for activity and UF permeation, which is specific for each cation type. Incomplete release of PE from a pectin complex resulted in low PE binding to cationic and anionic membranes. Incubation of PE at low pH increases the surface hydrophobicity, especially TL-PE, but the secondary structure of TL-PE is not greatly affected. The Israeli team showed that stable cloud colloidal constituents flocculate following the conversion of soluble to insoluble biopolymers. First, formation of pectic acid by pectinesterase activity is followed by the formation of calcium pectate gel. This process initiates a myriad of poorly defined reactions that result in juice clarification. Second, protein coagulation by heat resulted in flocculation of proteinacous bound cloud constituents, particularly after enzymatic pectin degradation. Pectinesterase activity is proposed to be an indirect cause for clarification; whereas binding of cloud constituents is the primary event in clarification by pectate gel and coagulated proteins. Understanding the mechanism of interaction of protein and pectic polymers is key to understanding cloud instability. Based on the above, it was hypothesized that the structure of pectin-protein coagulates plays a key role in cloud instability.
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Wehr, Tobias, ed. EarthCARE Mission Requirements Document. European Space Agency, noviembre de 2006. http://dx.doi.org/10.5270/esa.earthcare-mrd.2006.
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ESA's EarthCARE (Cloud, Aerosol and Radiation Explorer) mission - scheduled to be launched in 2024 - is the largest and most complex Earth Explorer to date and will advance our understanding of the role that clouds and aerosols play in reflecting incident solar radiation back into space and trapping infrared radiation emitted from Earth's surface. The mission is being implemented in cooperation with JAXA (Japan Aerospace Exploration Agency). It carries four scientific instruments. The Atmospheric Lidar (ATLID), operating at 355 nm wavelength and equipped with a high-spectral resolution and depolarisation receiver, measures profiles of aerosols and thin clouds. The Cloud Profiling Radar (CPR, contribution of JAXA), operates at 94 GHz to measure clouds and precipitation, as well as vertical motion through its Doppler functionality. The Multi-Spectral Imager provides across-track information of clouds and aerosols. The Broad-Band Radiometer (BBR) measures the outgoing reflected solar and emitted thermal radiation in order to derive broad-band radiative fluxes at the top of atmosphere. The Mission Requirement Document defines the scientific mission objectives and observational requirements of EarthCARE. The document has been written by the ESA-JAXA Joint Mission Advisory Group for EarthCARE.