Thematische Bibliographien / Arctic clouds

Inhaltsverzeichnis

  1. Zeitschriftenartikel
  2. Dissertationen
  3. Bücher
  4. Buchteile
  5. Konferenzberichte
  6. Berichte der Organisationen

Auswahl der wissenschaftlichen Literatur zum Thema „Arctic clouds“

Autor: Grafiati
Veröffentlicht am 30. Juni 2021
Zuletzt aktualisiert am 12. Februar 2022

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Zeitschriftenartikel zum Thema "Arctic clouds"

1

Zamora, Lauren M., Ralph A. Kahn, Sabine Eckhardt, Allison McComiskey, Patricia Sawamura, Richard Moore und Andreas Stohl. „Aerosol indirect effects on the nighttime Arctic Ocean surface from thin, predominantly liquid clouds“. Atmospheric Chemistry and Physics 17, Nr. 12 (20.06.2017): 7311–32. http://dx.doi.org/10.5194/acp-17-7311-2017.

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Abstract. Aerosol indirect effects have potentially large impacts on the Arctic Ocean surface energy budget, but model estimates of regional-scale aerosol indirect effects are highly uncertain and poorly validated by observations. Here we demonstrate a new way to quantitatively estimate aerosol indirect effects on a regional scale from remote sensing observations. In this study, we focus on nighttime, optically thin, predominantly liquid clouds. The method is based on differences in cloud physical and microphysical characteristics in carefully selected clean, average, and aerosol-impacted conditions. The cloud subset of focus covers just ∼ 5 % of cloudy Arctic Ocean regions, warming the Arctic Ocean surface by ∼ 1–1.4 W m−2 regionally during polar night. However, within this cloud subset, aerosol and cloud conditions can be determined with high confidence using CALIPSO and CloudSat data and model output. This cloud subset is generally susceptible to aerosols, with a polar nighttime estimated maximum regionally integrated indirect cooling effect of ∼ −0.11 W m−2 at the Arctic sea ice surface (∼ 8 % of the clean background cloud effect), excluding cloud fraction changes. Aerosol presence is related to reduced precipitation, cloud thickness, and radar reflectivity, and in some cases, an increased likelihood of cloud presence in the liquid phase. These observations are inconsistent with a glaciation indirect effect and are consistent with either a deactivation effect or less-efficient secondary ice formation related to smaller liquid cloud droplets. However, this cloud subset shows large differences in surface and meteorological forcing in shallow and higher-altitude clouds and between sea ice and open-ocean regions. For example, optically thin, predominantly liquid clouds are much more likely to overlay another cloud over the open ocean, which may reduce aerosol indirect effects on the surface. Also, shallow clouds over open ocean do not appear to respond to aerosols as strongly as clouds over stratified sea ice environments, indicating a larger influence of meteorological forcing over aerosol microphysics in these types of clouds over the rapidly changing Arctic Ocean.
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2

Tjernström, Michael, Joseph Sedlar und Matthew D. Shupe. „How Well Do Regional Climate Models Reproduce Radiation and Clouds in the Arctic? An Evaluation of ARCMIP Simulations“. Journal of Applied Meteorology and Climatology 47, Nr. 9 (01.09.2008): 2405–22. http://dx.doi.org/10.1175/2008jamc1845.1.

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Abstract Downwelling radiation in six regional models from the Arctic Regional Climate Model Intercomparison (ARCMIP) project is systematically biased negative in comparison with observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment, although the correlations with observations are relatively good. In this paper, links between model errors and the representation of clouds in these models are investigated. Although some modeled cloud properties, such as the cloud water paths, are reasonable in a climatological sense, the temporal correlation of model cloud properties with observations is poor. The vertical distribution of cloud water is distinctly different among the different models; some common features also appear. Most models underestimate the presence of high clouds, and, although the observed preference for low clouds in the Arctic is present in most of the models, the modeled low clouds are too thin and are displaced downward. Practically all models show a preference to locate the lowest cloud base at the lowest model grid point. In some models this happens also to be where the observations show the highest occurrence of the lowest cloud base; it is not possible to determine if this result is just a coincidence. Different factors contribute to model surface radiation errors. For longwave radiation in summer, a negative bias is present both for cloudy and clear conditions, and intermodel differences are smaller when clouds are present. There is a clear relationship between errors in cloud-base temperature and radiation errors. In winter, in contrast, clear-sky cases are modeled reasonably well, but cloudy cases show a very large intermodel scatter with a significant bias in all models. This bias likely results from a complete failure in all of the models to retain liquid water in cold winter clouds. All models overestimate the cloud attenuation of summer solar radiation for thin and intermediate clouds, and some models maintain this behavior also for thick clouds.
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Sotiropoulou, G., J. Sedlar, M. Tjernström, M. D. Shupe, I. M. Brooks und P. O. G. Persson. „The thermodynamic structure of summer Arctic stratocumulus and the dynamic coupling to the surface“. Atmospheric Chemistry and Physics Discussions 14, Nr. 3 (11.02.2014): 3815–74. http://dx.doi.org/10.5194/acpd-14-3815-2014.

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Abstract. The vertical structure of Arctic low-level clouds and Arctic boundary layer is studied, using observations from ASCOS (Arctic Summer Cloud Ocean Study), in the central Arctic, in late summer 2008. Two general types of cloud structures are examined: the "neutrally-stratified" and "stably-stratified" clouds. Neutrally-stratified are mixed-phase clouds where radiative-cooling near cloud top produces turbulence that creates a cloud-driven mixed layer. When this layer mixes with the surface-generated turbulence, the cloud layer is coupled to the surface, whereas when such an interaction does not occur, it remains decoupled; the latter state is most frequently observed. The decoupled clouds are usually higher compared to the coupled; differences in thickness or cloud water properties between the two cases are however not found. The surface fluxes are also very similar for both states. The decoupled clouds exhibit a bimodal thermodynamic structure, depending on the depth of the sub-cloud mixed layer (SML): clouds with shallower SMLs are disconnected from the surface by weak inversions, whereas those that lay over a deeper SML are associated with stronger inversions at the decoupling height. Neutrally-stratified clouds generally precipitate; the evaporation/sublimation of precipitation often enhances the decoupling state. Finally, stably-stratified clouds are usually lower, geometrically and optically thinner, non-precipitating liquid-water clouds, not containing enough liquid to drive efficient mixing through cloud-top cooling.
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Sotiropoulou, G., J. Sedlar, M. Tjernström, M. D. Shupe, I. M. Brooks und P. O. G. Persson. „The thermodynamic structure of summer Arctic stratocumulus and the dynamic coupling to the surface“. Atmospheric Chemistry and Physics 14, Nr. 22 (28.11.2014): 12573–92. http://dx.doi.org/10.5194/acp-14-12573-2014.

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Abstract. The vertical structure of Arctic low-level clouds and Arctic boundary layer is studied, using observations from ASCOS (Arctic Summer Cloud Ocean Study), in the central Arctic, in late summer 2008. Two general types of cloud structures are examined: the "neutrally stratified" and "stably stratified" clouds. Neutrally stratified are mixed-phase clouds where radiative-cooling near cloud top produces turbulence that generates a cloud-driven mixed layer. When this layer mixes with the surface-generated turbulence, the cloud layer is coupled to the surface, whereas when such an interaction does not occur, it remains decoupled; the latter state is most frequently observed. The decoupled clouds are usually higher compared to the coupled; differences in thickness or cloud water properties between the two cases are however not found. The surface fluxes are also very similar for both states. The decoupled clouds exhibit a bimodal thermodynamic structure, depending on the depth of the sub-cloud mixed layer (SCML): clouds with shallower SCMLs are disconnected from the surface by weak inversions, whereas those that lay over a deeper SCML are associated with stronger inversions at the decoupling height. Neutrally stratified clouds generally precipitate; the evaporation/sublimation of precipitation often enhances the decoupling state. Finally, stably stratified clouds are usually lower, geometrically and optically thinner, non-precipitating liquid-water clouds, not containing enough liquid to drive efficient mixing through cloud-top cooling.
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5

Baek, Eun-Hyuk, Joo-Hong Kim, Sungsu Park, Baek-Min Kim und Jee-Hoon Jeong. „Impact of poleward heat and moisture transports on Arctic clouds and climate simulation“. Atmospheric Chemistry and Physics 20, Nr. 5 (12.03.2020): 2953–66. http://dx.doi.org/10.5194/acp-20-2953-2020.

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Abstract. Many general circulation models (GCMs) have difficulty simulating Arctic clouds and climate, causing substantial inter-model spread. To address this issue, two Atmospheric Model Intercomparison Project (AMIP) simulations from the Community Atmosphere Model version 5 (CAM5) and Seoul National University (SNU) Atmosphere Model version 0 (SAM0) with a unified convection scheme (UNICON) are employed to identify an effective mechanism for improving Arctic cloud and climate simulations. Over the Arctic, SAM0 produced a larger cloud fraction and cloud liquid mass than CAM5, reducing the negative Arctic cloud biases in CAM5. The analysis of cloud water condensation rates indicates that this improvement is associated with an enhanced net condensation rate of water vapor into the liquid condensate of Arctic low-level clouds, which in turn is driven by enhanced poleward transports of heat and moisture by the mean meridional circulation and transient eddies. The reduced Arctic cloud biases lead to improved simulations of surface radiation fluxes and near-surface air temperature over the Arctic throughout the year. The association between the enhanced poleward transports of heat and moisture and increase in liquid clouds over the Arctic is also evident not only in both models, but also in the multi-model analysis. Our study demonstrates that enhanced poleward heat and moisture transport in a model can improve simulations of Arctic clouds and climate.
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Loewe, Katharina, Annica M. L. Ekman, Marco Paukert, Joseph Sedlar, Michael Tjernström und Corinna Hoose. „Modelling micro- and macrophysical contributors to the dissipation of an Arctic mixed-phase cloud during the Arctic Summer Cloud Ocean Study (ASCOS)“. Atmospheric Chemistry and Physics 17, Nr. 11 (08.06.2017): 6693–704. http://dx.doi.org/10.5194/acp-17-6693-2017.

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Abstract. The Arctic climate is changing; temperature changes in the Arctic are greater than at midlatitudes, and changing atmospheric conditions influence Arctic mixed-phase clouds, which are important for the Arctic surface energy budget. These low-level clouds are frequently observed across the Arctic. They impact the turbulent and radiative heating of the open water, snow, and sea-ice-covered surfaces and influence the boundary layer structure. Therefore the processes that affect mixed-phase cloud life cycles are extremely important, yet relatively poorly understood. In this study, we present sensitivity studies using semi-idealized large eddy simulations (LESs) to identify processes contributing to the dissipation of Arctic mixed-phase clouds. We found that one potential main contributor to the dissipation of an observed Arctic mixed-phase cloud, during the Arctic Summer Cloud Ocean Study (ASCOS) field campaign, was a low cloud droplet number concentration (CDNC) of about 2 cm−3. Introducing a high ice crystal concentration of 10 L−1 also resulted in cloud dissipation, but such high ice crystal concentrations were deemed unlikely for the present case. Sensitivity studies simulating the advection of dry air above the boundary layer inversion, as well as a modest increase in ice crystal concentration of 1 L−1, did not lead to cloud dissipation. As a requirement for small droplet numbers, pristine aerosol conditions in the Arctic environment are therefore considered an important factor determining the lifetime of Arctic mixed-phase clouds.
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Xie, Shaocheng, Xiaohong Liu, Chuanfeng Zhao und Yuying Zhang. „Sensitivity of CAM5-Simulated Arctic Clouds and Radiation to Ice Nucleation Parameterization“. Journal of Climate 26, Nr. 16 (06.08.2013): 5981–99. http://dx.doi.org/10.1175/jcli-d-12-00517.1.

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Abstract Sensitivity of Arctic clouds and radiation in the Community Atmospheric Model, version 5, to the ice nucleation process is examined by testing a new physically based ice nucleation scheme that links the variation of ice nuclei (IN) number concentration to aerosol properties. The default scheme parameterizes the IN concentration simply as a function of ice supersaturation. The new scheme leads to a significant reduction in simulated IN concentration at all latitudes while changes in cloud amounts and properties are mainly seen at high- and midlatitude storm tracks. In the Arctic, there is a considerable increase in midlevel clouds and a decrease in low-level clouds, which result from the complex interaction among the cloud macrophysics, microphysics, and large-scale environment. The smaller IN concentrations result in an increase in liquid water path and a decrease in ice water path caused by the slowdown of the Bergeron–Findeisen process in mixed-phase clouds. Overall, there is an increase in the optical depth of Arctic clouds, which leads to a stronger cloud radiative forcing (net cooling) at the top of the atmosphere. The comparison with satellite data shows that the new scheme slightly improves low-level cloud simulations over most of the Arctic but produces too many midlevel clouds. Considerable improvements are seen in the simulated low-level clouds and their properties when compared with Arctic ground-based measurements. Issues with the observations and the model–observation comparison in the Arctic region are discussed.
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Stapf, Johannes, André Ehrlich, Evelyn Jäkel, Christof Lüpkes und Manfred Wendisch. „Reassessment of shortwave surface cloud radiative forcing in the Arctic: consideration of surface-albedo–cloud interactions“. Atmospheric Chemistry and Physics 20, Nr. 16 (26.08.2020): 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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Eastman, Ryan, und Stephen G. Warren. „Interannual Variations of Arctic Cloud Types in Relation to Sea Ice“. Journal of Climate 23, Nr. 15 (01.08.2010): 4216–32. http://dx.doi.org/10.1175/2010jcli3492.1.

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Abstract Sea ice extent and thickness may be affected by cloud changes, and sea ice changes may in turn impart changes to cloud cover. Different types of clouds have different effects on sea ice. Visual cloud reports from land and ocean regions of the Arctic are analyzed here for interannual variations of total cloud cover and nine cloud types, and their relation to sea ice. Over the high Arctic, cloud cover shows a distinct seasonal cycle dominated by low stratiform clouds, which are much more common in summer than winter. Interannual variations of cloud amounts over the Arctic Ocean show significant correlations with surface air temperature, total sea ice extent, and the Arctic Oscillation. Low ice extent in September is generally preceded by a summer with decreased middle and precipitating clouds. Following a low-ice September there is enhanced low cloud cover in autumn. Total cloud cover appears to be greater throughout the year during low-ice years. Multidecadal trends from surface observations over the Arctic Ocean show increasing cloud cover, which may promote ice loss by longwave radiative forcing. Trends are positive in all seasons, but are most significant during spring and autumn, when cloud cover is positively correlated with surface air temperature. The coverage of summertime precipitating clouds has been decreasing over the Arctic Ocean, which may promote ice loss.
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Sartori, Ernani. „The Arctic ice melting confirms the new theory“. Journal of Water and Climate Change 10, Nr. 2 (05.10.2018): 321–43. http://dx.doi.org/10.2166/wcc.2018.153.

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Abstract The new theory shows that the global and the Arctic atmospheres behave as an open atmosphere (few clouds) or as a ‘closed’ atmosphere (fully cloudy), which explains the Arctic ice melting. Within the closed atmosphere the solar radiation, wind and evaporation are reduced while the water and air temperatures and the humidity increase. Real data confirm these effects for the planet and for the Arctic. Many authors did not understand these apparent inconsistencies, but this paper solves many intriguing problems, and provides solutions that led the present author to discover the new hydrological cycle. Some human activities increase the formation of clouds and precipitation or of droughts. The sun is not the only heat source for the atmosphere. Several real data confirm that clouds have increased over decades globally and at the Arctic. These intensifications also confirm the operation of the new hydrological cycle and of the Sartori theory. Many real data show that while the Arctic ice has melted, the cloud cover has pushed the temperatures up above freezing and has raised them by 2–3 °C compared to cloudless skies as well as acting to warm the Arctic for most of the annual cycles.
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Dissertationen zum Thema "Arctic clouds"

1

Beesley, John Anthony. „The climatic effects and requirements of arctic clouds /“. Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/10056.

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Zygmuntowska, Marta, Thorsten Mauritsen, Johannes Quaas und Lars Kaleschke. „Arctic clouds and surface radiation“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-185357.

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Clouds regulate the Earth’s radiation budget, both by reflecting part of the incoming sunlight leading to cooling and by absorbing and emitting infrared radiation which tends to have a warming effect. Globally averaged, at the top of the atmosphere the cloud radiative effect is to cool the climate, while at the Arctic surface, clouds are thought to be warming. Here we compare a passive instrument, the AVHRR-based retrieval from CM-SAF, with recently launched active instruments onboard CloudSat and CALIPSO and the widely used ERA-Interim reanalysis. We find that in particular in winter months the three data sets differ significantly. While passive satellite instruments have serious difficulties, detecting only half the cloudiness of the modeled clouds in the reanalysis, the active instruments are in between. In summer, the two satellite products agree having monthly means of 70–80 percent, but the reanalysis are approximately ten percent higher. The monthly mean long- and shortwave components of the surface cloud radiative effect obtained from the ERAInterim reanalysis are about twice that calculated on the basis of CloudSat’s radar-only retrievals, while ground based measurements from SHEBA are in between. We discuss these differences in terms of instrument-, retrieval- and reanalysis characteristics, which differ substantially between the analyzed datasets.
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Garrett, Timothy J. „Radiative properties of arctic clouds /“. Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/10090.

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4

Lampert, Astrid. „Airborne lidar observations of tropospheric arctic clouds“. Phd thesis, Universität Potsdam, 2009. http://opus.kobv.de/ubp/volltexte/2010/4121/.

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Due to the unique environmental conditions and different feedback mechanisms, the Arctic region is especially sensitive to climate changes. The influence of clouds on the radiation budget is substantial, but difficult to quantify and parameterize in models. In the framework of the PhD, elastic backscatter and depolarization lidar observations of Arctic clouds were performed during the international Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) from Svalbard in March and April 2007. Clouds were probed above the inaccessible Arctic Ocean with a combination of airborne instruments: The Airborne Mobile Aerosol Lidar (AMALi) of the Alfred Wegener Institute for Polar and Marine Research provided information on the vertical and horizontal extent of clouds along the flight track, optical properties (backscatter coefficient), and cloud thermodynamic phase. From the data obtained by the spectral albedometer (University of Mainz), the cloud phase and cloud optical thickness was deduced. Furthermore, in situ observations with the Polar Nephelometer, Cloud Particle Imager and Forward Scattering Spectrometer Probe (Laboratoire de Météorologie Physique, France) provided information on the microphysical properties, cloud particle size and shape, concentration, extinction, liquid and ice water content. In the thesis, a data set of four flights is analyzed and interpreted. The lidar observations served to detect atmospheric structures of interest, which were then probed by in situ technique. With this method, an optically subvisible ice cloud was characterized by the ensemble of instruments (10 April 2007). Radiative transfer simulations based on the lidar, radiation and in situ measurements allowed the calculation of the cloud forcing, amounting to -0.4 W m-2. This slight surface cooling is negligible on a local scale. However, thin Arctic clouds have been reported more frequently in winter time, when the clouds' effect on longwave radiation (a surface warming of 2.8 W m-2) is not balanced by the reduced shortwave radiation (surface cooling). Boundary layer mixed-phase clouds were analyzed for two days (8 and 9 April 2007). The typical structure consisting of a predominantly liquid water layer on cloud top and ice crystals below were confirmed by all instruments. The lidar observations were compared to European Centre for Medium-Range Weather Forecasts (ECMWF) meteorological analyses. A change of air masses along the flight track was evidenced in the airborne data by a small completely glaciated cloud part within the mixed-phase cloud system. This indicates that the updraft necessary for the formation of new cloud droplets at cloud top is disturbed by the mixing processes. The measurements served to quantify the shortcomings of the ECMWF model to describe mixed-phase clouds. As the partitioning of cloud condensate into liquid and ice water is done by a diagnostic equation based on temperature, the cloud structures consisting of a liquid cloud top layer and ice below could not be reproduced correctly. A small amount of liquid water was calculated for the lowest (and warmest) part of the cloud only. Further, the liquid water content was underestimated by an order of magnitude compared to in situ observations. The airborne lidar observations of 9 April 2007 were compared to space borne lidar data on board of the satellite Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). The systems agreed about the increase of cloud top height along the same flight track. However, during the time delay of 1 h between the lidar measurements, advection and cloud processing took place, and a detailed comparison of small-scale cloud structures was not possible. A double layer cloud at an altitude of 4 km was observed with lidar at the West coast in the direct vicinity of Svalbard (14 April 2007). The cloud system consisted of two geometrically thin liquid cloud layers (each 150 m thick) with ice below each layer. While the upper one was possibly formed by orographic lifting under the influence of westerly winds, or by the vertical wind shear shown by ECMWF analyses, the lower one might be the result of evaporating precipitation out of the upper layer. The existence of ice precipitation between the two layers supports the hypothesis that humidity released from evaporating precipitation was cooled and consequently condensed as it experienced the radiative cooling from the upper layer. In summary, a unique data set characterizing tropospheric Arctic clouds was collected with lidar, in situ and radiation instruments. The joint evaluation with meteorological analyses allowed a detailed insight in cloud properties, cloud evolution processes and radiative effects.
Die Arktis mit ihren speziellen Umweltbedingungen ist besonders empfindlich gegenüber Klimaveränderungen. Dabei spielen Wolken eine große Rolle im Strahlungsgleichgewicht, die aber nur schwer genau bestimmt und in Klimamodellen dargestellt werden kann. Die Daten für die Promotionsarbeit wurden im Frühjahr 2007 bei Flugzeug-Messungen von Wolken über dem Arktischen Ozean von Spitzbergen aus erhoben. Das dafür verwendete Lidar (Licht-Radar) des Alfred-Wegener-Instituts lieferte ein höhenaufgelöstes Bild der Wolkenstrukturen und ihrer Streu-Eigenschaften, andere Messgeräte ergänzten optische sowie mikrophysikalische Eigenschaften der Wolkenteilchen (Extinktion, Größenverteilung, Form, Konzentration, Flüssigwasser- und Eisgehalt, Messgeräte vom Laboratoire de Météorologie Physique, France) und Strahlungsmessungen (Uni Mainz). Während der Messkampagne herrschte Nordwind vor. Die untersuchten Luftmassen mit Ursprung fern von menschlichen Verschmutzungsquellen war daher sehr sauber. Beim Überströmen der kalten Luft über den offenen warmen Arktischen Ozean bildeten sich in der Grenzschicht (ca. 0-1500 m Höhe) Mischphasenwolken, die aus unterkühlten Wassertröpfchen im oberen Bereich und Eis im unteren Bereich der Wolken bestehen. Mit den Flugzeug-Messungen und numerischen Simulationen des Strahlungstransports wurde der Effekt einer dünnen Eiswolke auf den Strahlungshaushalt bestimmt. Die Wolke hatte lokal eine geringe Abkühlung der Erdoberfläche zur Folge. Ähnliche Wolken würden jedoch im Winter, wenn keine Sonnenstrahlung die Arktis erreicht, durch den Treibhauseffekt eine nicht vernachlässigbare Erwärmung der Oberfläche verursachen. Die Messungen der Mischphasenwolken wurden mit einem Wettervorhersagemodell (ECMWF) verglichen. Für die ständig neue Bildung von flüssigen Wassertropfen im oberen Teil der Wolke ist das Aufsteigen von feuchten Luftpaketen nötig. Während einer Messung wurden entlang der Flugstrecke verschiedene Luftmassen durchflogen. An der Luftmassengrenze wurde eine reine Eiswolke inmitten eines Mischphasen-Systems beobachtet. Die Messungen zeigen, dass das Mischen von Luftmassen den Nachschub an feuchter Luft blockiert, was unmittelbare Auswirkungen auf die thermodynamische Phase des Wolkenwassers hat. Weiterhin wurde bestimmt, wie groß die Abweichungen der Modellrechnungen von den Messungen bezüglich Wassergehalt und der Verteilung von Flüssigwasser und Eis waren. Durch die vereinfachte Wolken-Parameterisierung wurde die typische vertikale Struktur von Mischphasenwolken im Modell nicht wiedergegeben. Die flugzeuggetragenen Lidar-Messungen vom 9. April 2007 wurden mit Lidar-Messungen an Bord des Satelliten CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) verglichen. Die Messungen zeigten beide eine ansteigende Wolkenobergrenze entlang desselben Flugwegs. Da die Messungen jedoch nicht genau gleichzeitig durchgeführt wurden, war wegen Advektion und Prozessen in den Wolken kein genauer Vergleich der kleinskaligen Wolkenstrukturen möglich. Außerdem wurde eine doppelte Wolkenschicht in der freien Troposphäre (4 km Höhe) analysiert. Die Wolke bestand aus zwei separaten dünnen Schichten aus flüssigem Wasser (je 150 m dick) mit jeweils Eis darunter. Die untere Schicht entstand wahrscheinlich aus verdunstetem Eis-Niederschlag. Diese feuchte Schicht wurde durch die Abstrahlung der oberen Wolkenschicht gekühlt, so dass sie wieder kondensierte. Solche Wolkenformationen sind in der Arktis bisher vor allem in der Grenzschicht bekannt. Ein einzigartiger Datensatz von arktischen Wolken wurde mit einer Kombination verschiedener Flugzeug-Messgeräte erhoben. Zusammen mit meteorologischen Analysen konnten für verschiedene Fallstudien Wolkeneigenschaften, Entwicklungsprozesse und Auswirkungen auf den Strahlungshaushalt bestimmt werden.
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5

Pleavin, Thomas Daniel. „Large eddy simulations of Arctic stratus clouds“. Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/4934/.

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Mixed-phase Arctic stratocumulus clouds are ubiquitous to the region during the summer months. However, despite their prevalence, very little is known about the processes which maintain the cloud. Recent observations have shown that Arctic stratocumulus commonly extend into the temperature inversion which caps the Arctic boundary layer. This is atypical to sub-tropical stratocumulus where the cloud top is found in the vicinity of the inversion base, and unexpected as strong longwave radiative cooling would be expected to keep the cloud top and inversion base heights in equilibrium. Uniquely to the Arctic, inversions in speci�c humidity are also commonly observed coincident with temperature inversions, and this is thought to contribute to the clouds' subsistence in the strongly stable inversion layer. In this thesis, observations from the Arctic Summer Cloud Ocean Study (ASCOS) are used to characterize the lower Arctic atmosphere and provide the basis for simulations of stratocumulus cloud encroachment into the Arctic temperature inversion. Observations show that cloud extending into the inversion by more than 100 m was a common occurrence during ASCOS, which is consistent with measurements made during previous summer field campaigns. Simulations made with the Met Office Large Eddy Model (LEM) were used to model the encroachment, and results suggest that the depth of encroachment has a high correlation with the humidity inversion strength. A number of different cloud-inversion regimes were identi�ed from the model simulations. When specific humidity fell of inside the temperature inversion, the high relative humidity of the region just above the inversion base was found to allow encroachment of cloud up to 40 m into the inversion layer. While in the presence of a speci�c humidity inversion the encroachment was larger reaching a maximum of 200 m. The presence of specific humidity inversions and their relationship to the encroaching cloud was determined to be self-sustaining, and the cloud found to remain at a quasi-stable depth for as long as a moisture source is available to replenish the loss of water from ice precipitation. However, encroachment of cloud into the inversion was shown to cause a signi�cant reduction in the buoyant production of TKE at cloud top, which led to turbulence shutting off completely in the clouds with the largest encroachment depth. This caused a thermal adjustment of the inversion layer to the cloud which led a reduction in the encroachment depth. The overall impact of encroachment on boundary layer turbulence was found to be significant, with TKE reduced by up to 90% in the simulations with the largest encroachment depth.
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Kanngießer, Franz, André Ehrlich und Manfred Wendisch. „Observations of glories above arctic boundary layer clouds to identify cloud phase“. Universität Leipzig, 2017. https://ul.qucosa.de/id/qucosa%3A16743.

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The glory is an optical phenomenon observed above liquid water clouds and consists of coloured rings around the anti-solar point. Since the glory is caused by scattering on spherical particles it can be used as a proxy to identify liquid water at the cloud top. Images taken with a CANON digital camera equipped with a fish-eye lens on board the research aircraft Polar 5 during the measurement campaign Radiation-Aerosol-Cloud Experiment in the Arctic Circle (RACEPAC) were analysed for glories. To identify glories an algorithm consisting of five criteria was developed by using simulations of the scattering angle dependent radiance and a test data set of measurements. The algorithm was tested and proved to be able to distinguish between images showing a glory and images not showing any glory.
Die Glorie ist eine optische Erscheinung, die über Flüssigwasserwolken beobachtet werden kann und aus farbigen Ringen um den Gegensonnenpunkt besteht. Da die Glorie durch Streuung an sphärischen Partikeln entsteht, kann sie zur Identifikation von Flüssigwasser am Wolkenoberrand genutzt werden. Bilder, die mit einer CANON Digitalkamera, die mit einem Fischaugenobjektiv ausgestattet war, von Bord des Forschungsflugzeugs Polar 5 während der Messkampagne RACEPAC aufgenommen worden, wurden auf das Auftreten von Glorien untersucht. Zur Identifikation wurde ein Algorithmus mit fünf Kriterien entwickelt, die mit Hilfe von Simulationen der streuwinkelabhängigen Radianz und einem Testdatensatz der Messungen erstellt wurden. Der Algorithmus wurde getestet und ist in der Lage zwischen Bildern mit und ohne Glorie zu unterscheiden.
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Poole, Lamont Rozelle. „Airborne lidar studies of Arctic polar stratospheric clouds“. Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184277.

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Airborne lidar measurements of Arctic polar stratospheric clouds (PSCs) in January 1984 and January 1986 are reported. The locales and altitudes of the clouds coincided in both years with very cold ambient temperatures. During the 1984 experiment, PSCs were observed on three flights north of Thule, Greenland; peak backscatter occurred near 20 km (at temperatures below 193 K). A single PSC formation was seen between Iceland and Scotland during the 1986 experiment, with beak backscatter occurring near 22 km (at temperatures from 188-191 K). A sequence of observations in this same area by the SAM II satellite sensor depicts the history of cloud development and dissipation. Enhancements in aerosol backscattering in excess of a factor of 100 were measured during the 1984 experiment at latitudes near the Pole where 50-mb temperatures approached the frost point. Depolarization in the backscattered signal was estimated as 30-40%, similar to that measured in cirrus clouds. Farther south, with 50-mb temperatures several degrees warmer, backscatter enhancement factors ranged from 20-30, and little or no depolarization was observed. Results similar to the latter were found during the 1986 experiment--enhancement factors near 50 (at the 30-mb level, with temperatures 3-5 K above the frost point), and little depolarization. The contrast in observations suggested the existence of distinct cloud growth regimes delineated by temperatures, as proposed in recent articles addressing Antarctic ozone depletion. A theoretical model was developed which interposes a stage of nitric acid trihydrate deposition between the two stages of cloud formation and growth assumed in earlier models (aerosol droplet precursors and ice particles). The calculated temperature dependence of backscatter and extinction agreed well with experimentally observed values, except for small systematic errors at the 30-mb level which may be due to poor characterization of the temperature field there. A companion theoretical study of PSC formation at 70 mb in the Antarctic showed that about 80% and 30% of the nitric acid and water vapor supplies, respectively, may be sequestered in relatively large (4-μm radius) cloud particles at a temperature near 189 K. Such large particles would fall at a rate of about 2 km wk⁻¹, suggesting that PSCs may act as a sink for these stratospheric trace gases.
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Lampert, Astrid [Verfasser]. „Airborne lidar observations of tropospheric Arctic clouds / Astrid Lampert“. Bremerhaven : AWI, Alfred-Wegener-Institut für Polar- und Meeresforschung, 2010. http://d-nb.info/101019965X/34.

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Cremer, Roxana, Johannes Quaas und Johannes Mülmenstädt. „Interactions between clouds and sea ice in the Arctic“. Universität Leipzig, 2017. https://ul.qucosa.de/id/qucosa%3A16773.

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The feedback between clouds and sea ice got more importance in the last years, because of the declining Arctic sea ice extent. Previous observations show the formation of low clouds over newly formed open water. These low clouds are very important for the Arctic Energy Budget, because they warm the surface. This leads to increasing temperatures and stronger sea ice loss. To assess the relationship between sea ice cover and cloudiness, satellite observations by DARDAR were compared with both global climate reanalyses ERA–Interim and MACC. The analysis focuses on 2007 – 2010 and the relationship between different parameters from the different datasets. It is found that the reanalyses only poorly approximate the cloud cover in the Arctic. Consequently no strong correlation was found for the time period 2007 – 2010.
Das Wolken–Albedo–Feedback in der Arktis gewann in den letzten Jahren immer mehr an Bedeutung aufgrund des Rückganges der Meereisfläche. Vorhergehende Arbeiten zeigten die Bildung von tiefer Bewölkung über kürzlich aufgebrochenen Meereisstellen. Diese tiefen Wolken sind sehr wichtig für das arktische Energiebudget, wegen des Erwärmens der Oberfläche. Daraus folgt ein Anstieg in der bodennahen Temperatur und ein verstärkter Rückgang des Meereises. Um den Einfluss der Meereiskonzentration auf die Wolkenbildung zu untersuchen, werden in dieser Arbeit Satellitendaten von DARDAR mit den beiden globalen Klimareanalysen Era–interim und MACC verglichen. Analysiert werden Daten aus den Jahren 2007 bis 2010 und für verschiedene Oberflächenbedingungen werden Korrelationen der einzelnen Datensätze erstellt. Es hat sich gezeigt, dass die Darstellung der Wolkenbedeckung in der Arktis durch die Reanalyse Daten nicht geeignet ist. Aus diesem Grund wurden keine signifikanten Korrelationen in der Zeitspanne von 2007 bis 2010 gefunden.
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Achtert, Peggy. „Lidar Measurements of Polar Stratospheric Clouds in the Arctic“. Doctoral thesis, Stockholms universitet, Meteorologiska institutionen (MISU), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-88054.

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Polar Stratospheric Clouds (PSCs) play a key role for ozone depletion in the polar stratosphere. Its magnitude depends on the type of PSC and its lifetime and extent. This thesis presents PSC observations conducted with the Esrange lidar and the space-borne CALIPSO lidar. PSCs are separated into three types according to their optical properties. The occurrence rate of the different types which are often observed simultaneously as well as their interaction and connection is not well understood. To better understand the processes that govern PSC formation, observations need to be combined with a detailed view of the atmospheric background in which PSCs develop, exist, and are transformed from one type to another. This thesis introduces a new channel of the Esrange lidar for temperature profiling at heights below 35 km. The design of this channel and first temperature measurements within PSCs and cirrus clouds are presented. This is an important step since the majority of PSC-related literature extracts temperatures within PSCs from reanalysis data. In contrast to ground–based measurements space–borne lidar does not rely on cloud–free conditions. Hence, it provides an unprecedented opportunity for studying the connection between PSCs and the underlying synoptic–scale conditions which manifest as tropospheric clouds. This thesis shows that most of the PSCs observed in the Arctic during winter 2007/08 occurred in connection with tropospheric clouds. A combined analysis of ground-based and space-borne lidar observation of PSCs in combination with microphysical modeling can improve our understanding of PSC formation. A first case study of this approach shows how a PSC that was formed by synoptic-scale processes is transformed into another type while passing the Scandinavian mountains. Today a variety of classification schemes provides inconsistent information on PSC properties and types. This thesis suggests a unified classification scheme for lidar measurements of PSCs.

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Submitted. 

 

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Bücher zum Thema "Arctic clouds"

1

Smith, William L. The analysis of polar clouds from AVHRR satellite data using pattern recognition techniques: Final report. Madison, Wis: Space Science and Engineering Center, University of Wisconsin-Madison, 1990.

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Freese, Dietmar. Solare und terrestrische Strahlungswechselwirkung zwischen arktischen Eisflächen und Wolken =: Solar and terrestrial radiation interaction between arctic sea ice and clouds. Bremerhaven: Alfred-Wegener-Institut für Polar- und Meeresforschung, 1999.

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Guest, Peter Staples. A numerical, analytical and observational study of the effect of clouds on surface wind and wind stress during the central Arctic winter. Monterey, Calif: Naval Postgraduate School, 1992.

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Barron, John P. An objective technique for Arctic cloud analysis using multispectral AVHRR satellite imagery. Monterey, California: Naval Postgraduate School, 1988.

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Salvato, Gregory. Comparison between Arctic and subtropic ship exaust [i.e. exhaust] effects on cloud properties. Monterey, Calif: Naval Postgraduate School, 1992.

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author, Kukla G., Serreze Mark C. author, Lamont-Doherty Geological Observatory und United States. Department of Energy, Hrsg. Arctic cloud cover during the summers of 1977-1979. 1985.

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Sheep Husbandry and Production of Wool, Garments and Cloths in Archaic Sumer. Agade, 2002.

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1953-, Willig Judith A., Aikens C. Melvin und Fagan John Lee, Hrsg. Early human occupation in far western North America: The Clovis-Archaic interface. Carson City, Nev: Nevada State Museum, 1988.

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Crawford, Michael, und Rohina C. Rubicz. Molecular Genetic Evidence from Contemporary Populations for the Origins of Native North Americans. Herausgegeben von Max Friesen und Owen Mason. Oxford University Press, 2016. http://dx.doi.org/10.1093/oxfordhb/9780199766956.013.4.

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An overview of the current molecular genetic evidence for the origins of North American populations is presented, including specific examples from the authors’ work with the Aleutian Island inhabitants. Shared mitochondrial DNA and Y-chromosome DNA markers among Siberians and Native Americans point to a Pleistocene migration from Siberia into the Americas via Beringia. There was likely a later migration from Siberia to Alaska, based on the analysis of whole-genome sequence data from a Greenland Paleoeskimo that clusters this individual with Siberian populations. Coalescence date estimates for Native American mitochondrial DNA and Y-chromosome DNA haplogroups indicate that there was a population expansion approximately 15,000–18,000 that was associated with a pre-Clovis settlement of the Americas and coastal migration, and then a later expansion of circum-Arctic populations. Settlement of the Aleutian Archipelago took place via east-to-west migration of Aleut kin groups, accompanied by a clinal loss in mitochondrial DNA haplotype diversity.
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Goodyear, Albert C., und Christopher R. Moore, Hrsg. Early Human Life on the Southeastern Coastal Plain. University Press of Florida, 2018. http://dx.doi.org/10.5744/florida/9781683400349.001.0001.

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This book is a collection of articles written by established researchers on the early prehistory of the Coastal Plain of the Southeastern U.S. The Coastal Plain is considered both geographically, as it extends from Virginia to Alabama, and chronologically, over potentially the last 50,000 years. Topics considered are the Pre-Clovis at Topper, Capps, and Vero Site; the potential for inundated early sites on the shelf; the mapping and petrography of Coastal Plain chert sources; the Paleoindians on the South Carolina Coastal Plain; the Younger Dryas and the Cosmic Impact Hypothesis; site burial and Coastal Plain sedimentary processes; the Early Archaic period with different scales of spatial analysis; the broader view of the Southeastern Atlantic Slope as it has been researched over the past forty years; and the long view of early human ecology and migrations from North America and the Old World.
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Buchteile zum Thema "Arctic clouds"

1

Herman, Gerald F. „Arctic Stratus Clouds“. In The Geophysics of Sea Ice, 465–88. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4899-5352-0_7.

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Devasthale, Abhay, Joseph Sedlar, Michael Tjernström und Alexander Kokhanovsky. „A Climatological Overview of Arctic Clouds“. In Physics and Chemistry of the Arctic Atmosphere, 331–60. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-33566-3_5.

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Cairo, Francesco, und Tiziana Colavitto. „Polar Stratospheric Clouds in the Arctic“. In Physics and Chemistry of the Arctic Atmosphere, 415–67. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-33566-3_7.

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Ehrlich, André, Michael Schäfer, Elena Ruiz-Donoso und Manfred Wendisch. „Airborne Remote Sensing of Arctic Clouds“. In Springer Series in Light Scattering, 39–66. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-38696-2_2.

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von Savigny, Christian, Gerd Baumgarten und Franz-Josef Lübken. „Noctilucent Clouds: General Properties and Remote Sensing“. In Physics and Chemistry of the Arctic Atmosphere, 469–503. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-33566-3_8.

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Key, Jeffrey R. „Classification of Arctic Cloud and Sea Ice Features in Multi-Spectral Satellite Data“. In The GeoJournal Library, 145–79. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1122-5_8.

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Gorodetskaya, Irina V., und L. Bruno Tremblay. „Arctic Cloud Properties and Radiative Forcing from Observations and their Role in Sea Ice Decline Predicted by the NCAR CCSM3 Model During the 21st Century“. In Arctic Sea Ice Decline: Observations, Projections, Mechanisms, and Implications, 47–62. Washington, D.C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/180gm05.

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„Arctic Cloud Systems“. In Clouds and Climate, 297–310. Cambridge University Press, 2020. http://dx.doi.org/10.1017/9781107447738.011.

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Heintzenberg, J., H.-C. Hansson, J. A. Ogren, D. S. Covert und J.-P. Blanchet. „Physical and chemical properties of arctic aerosols and clouds“. In Arctic Air Pollution, 25–36. Cambridge University Press, 1987. http://dx.doi.org/10.1017/cbo9780511565496.005.

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Mioche, Guillaume, und Olivier Jourdan. „Spaceborne Remote Sensing and Airborne In Situ Observations of Arctic Mixed-Phase Clouds“. In Mixed-Phase Clouds, 121–50. Elsevier, 2018. http://dx.doi.org/10.1016/b978-0-12-810549-8.00006-4.

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Konferenzberichte zum Thema "Arctic clouds"

1

Shaw, Joseph A., Erik Edqvist, Hector E. Bravo, Kohei Mizutani und Brentha Thurairajah. „Measuring Arctic clouds with the infrared cloud imager“. In International Symposium on Optical Science and Technology, herausgegeben von Joseph A. Shaw. SPIE, 2002. http://dx.doi.org/10.1117/12.482315.

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Eloranta, Edwin W., Taneil Uttal und Matthew Shupe. „Cloud particle size measurements in Arctic clouds using lidar and radar data“. In 2007 IEEE International Geoscience and Remote Sensing Symposium. IEEE, 2007. http://dx.doi.org/10.1109/igarss.2007.4423292.

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Taylor, Patrick C. „Does a relationship between Arctic low clouds and sea ice matter?“ In RADIATION PROCESSES IN THE ATMOSPHERE AND OCEAN (IRS2016): Proceedings of the International Radiation Symposium (IRC/IAMAS). Author(s), 2017. http://dx.doi.org/10.1063/1.4975530.

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Sikand, M., J. Koskulics, K. Stamnes, B. Hamre, J. J. Stamnes und R. P. Lawson. „Mixed phase boundary layer clouds observed from a tethered balloon platform in the Arctic“. In RADIATION PROCESSES IN THE ATMOSPHERE AND OCEAN (IRS2012): Proceedings of the International Radiation Symposium (IRC/IAMAS). AIP, 2013. http://dx.doi.org/10.1063/1.4804826.

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Xie, Shaocheng, Xiaohong Liu, Chuanfeng Zhao und Yuying Zhang. „Impact of ice nucleation parameterizations on CAM5 simulated arctic clouds and radiation: A sensitivity study“. In NUCLEATION AND ATMOSPHERIC AEROSOLS: 19th International Conference. AIP, 2013. http://dx.doi.org/10.1063/1.4803378.

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Hoyle, C. R., I. Engel, B. P. Luo, M. C. Pitts, L. R. Poole, J. U. Grooß und T. Peter. „Heterogeneous formation of polar stratospheric clouds-nucleation of nitric acid trihydrate (NAT) in the arctic stratosphere“. In NUCLEATION AND ATMOSPHERIC AEROSOLS: 19th International Conference. AIP, 2013. http://dx.doi.org/10.1063/1.4803438.

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Hatledal, Lars I., Filippo Sanfilippo, Yingguang Chu und Houxiang Zhang. „A Voxel-Based Numerical Method for Computing and Visualising the Workspace of Offshore Cranes“. In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-41634.

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Workspace computation and visualisation is one of the most important criteria in offshore crane design in terms of geometry dimensioning, installation feasibility and operational performance evaluation. This paper presents a numerical method for the computation and visualisation of the workspace of offshore cranes. The Working Load Limit (WLL) and the Safe Working Load (SWL) can be automatically determined. A three-dimensional (3D) rectangular grid of voxels is used to describe the properties of the workspace. Firstly, a number of joint configurations are generated by using the Monte Carlo method, which are then mapped from joint to Cartesian space using forward kinematics (FK). The bounding box of the workspace is then derived from these points, and the voxels are distributed on planes inside the box. The method distinguishes voxels by whether they are reachable and if they are on the workspace boundary. The output of the method is an approximation of the workspace volume and point clouds depicting both the reachable space and the boundary of the workspace. Using a third-party software that can work with point clouds, such like MeshLab, a 3D mesh of the workspace can be obtained. A more in-depth description and the pseudo-code of the presented method are presented. As a case study, the workspace of a common type of offshore crane, with three rotational joints, is computed with the proposed method.
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Ramos, Marilia A., Enrique L. Droguett, Marcelo R. Martins und Henrique P. Souza. „Quantitative Risk Analysis and Comparison for Onshore and Offshore LNG Terminals: The Port of Suape - Brazil Case“. In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-50268.

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In recent decades, natural gas has been gaining importance in world energy scene and established itself as an important source of energy. One of the biggest obstacles to increase the usage of natural gas is its transportation, mostly done in its liquid form, LNG – Liquefied Natural Gas, and storage. It involves the liquefaction of natural gas, transport by ship, its storage and subsequent regasification, in order to get natural gas in its original form and send it to the final destination through natural gas pipeline system. Nowadays, most terminals for receiving, storing and regasificating LNG, as well as sending-out natural gas are built onshore. These terminals, however, are normally built close to populated areas, where consuming centers can be found, creating safety risks to the population nearby. Apart from possible damages caused by its cryogenic temperatures, LNG spills are associated with hazards such as pool fires and ignition of drifting vapor clouds. Alternatively to onshore terminals, there are currently several offshore terminals projects in the world and some are already running. Today, Brazil owns two FSRU (Floating Storage and Regasification Unit) type offshore terminals, one in Guanabara Bay, Rio de Janeiro and the other in Pece´m, Ceara´, both contracted to PETROBRAS. The identification of the operation risks sources of LNG terminals onshore and offshore and its quantification through mathematical models can identify the most suitable terminal type for a particular location. In order to identify and compare the risks suggested by onshore and offshore LNG terminals, we have taken the example of the Suape Port and its Industrial Complex, located in Pernambuco, Brazil, which is a promising location for the installation of a LNG terminal. The present work has focused on calculating the distance to the LNG vapor cloud with the lower flammability limits (LFL), as well as thermal radiation emitted by pool fire, in case of a LNG spill from an onshore and from an offshore terminal. The calculation was made for both day and night periods, and for three types of events: operational accident, non-operational accident and worst case event, corresponding to a hole size of 0,75m, 1,5m e 5m, respectively. Even though the accidents that happen at an onshore terminal generate smaller vulnerability distances, according to the results it would not be desirable for the Suape Port, due to the location high density of industries and people working. Therefore, an offshore terminal would be more desirable, since it presents less risk to the surrounding populations, as well as for workers in this location.
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Wemmenhove, Rik, Erwin Loots und Arthur E. P. Veldman. „Hydrodynamic Wave Loading on Offshore Structures Simulated by a Two-Phase Flow Model“. In 25th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/omae2006-92253.

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The numerical simulation of hydrodynamic wave loading on different types of offshore structures is important to predict forces on and water motion around these structures. This paper presents a numerical study of two-phase flow over a sloping bottom with the presence of breaking waves. The details of the numerical model, an improved Volume Of Fluid (iVOF) method, are presented in the paper. The program has been developed initially to study the sloshing of liquid fuel in satellites. This micro-gravity environment requires a very accurate and robust description of the free surface. Later, the numerical model has been used for calculations of green water loading and the analysis of anti-roll and sloshing tanks, including the coupling with ship motions. The model has been extended recently to take two-phase flow effects into account. Two-phase flow effects are particularly important near the free surface, where loads on offshore structures strongly depend on the interaction between different phases like air and water. Entrapment of air pockets and entrainment of bubble clouds have a cushioning effect on breaking wave impacts. The velocity field around the interface of air and water, being continuous across the free surface, requires special attention. By using a newly-developed gravity-consistent discretisation, spurious velocities at the free surface are prevented. Thus far, the second air phase has been treated as incompressible. Taking compressibility effects into account requires a pressure-density relation for grid cells containing air. The expansion and compression of air pockets is considered as an adiabatic process. The numerical model is validated on several test cases. In this paper special attention will be paid to the impact of a breaking wave over a sloping bottom.
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Frühling, Christian. „Basic Design Considerations for Arctic Submarine Concepts“. In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-41288.

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The paper discusses basic design considerations for civil submarines which are supposed to be applied in ice covered waters. The vessels taken into consideration are in the range of 4000 t displacement with lengths of approx. 60–100 m. Main mission scenarios relate to installation, maintenance and repair of subsea equipment, sub-ice oil spill response, and sub-ice seismic. Topics covered in this paper are related to geographic boundary conditions, the basic hull layout, hydrodynamics in shallow ice covered waters, hydrodynamics under surfaced conditions, and cargo transportation. The paper closes with a conceptual design example for a multi-purpose submarine.
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Berichte der Organisationen zum Thema "Arctic clouds"

1

Shaw, J. A. Arctic Clouds Infrared Imaging Field Campaign Report. Office of Scientific and Technical Information (OSTI), März 2016. http://dx.doi.org/10.2172/1248496.

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Turner, David D. Microphysical Properties of Single and Mixed-Phase Arctic Clouds Derived from AERI Observations. Office of Scientific and Technical Information (OSTI), Juni 2003. http://dx.doi.org/10.2172/1000181.

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Stephen J. Vavrus. Final Technical Report for Project "Improving the Simulation of Arctic Clouds in CCSM3". Office of Scientific and Technical Information (OSTI), November 2008. http://dx.doi.org/10.2172/940966.

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4

Hobbs, Peter V. The Spectral Radiative Properties of Stratus Clouds and Ice Surfaces in the Arctic. Fort Belvoir, VA: Defense Technical Information Center, September 1997. http://dx.doi.org/10.21236/ada627637.

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5

Korolev, A., A. Shashkov und H. Barker. Parameterization of the Extinction Coefficient in Ice and Mixed-Phase Arctic Clouds during the ISDAC Field Campaign. Office of Scientific and Technical Information (OSTI), März 2012. http://dx.doi.org/10.2172/1035864.

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6

Verlinde, Johannes. Arctic Cloud Microphysical Processes. Final report. Office of Scientific and Technical Information (OSTI), Dezember 2019. http://dx.doi.org/10.2172/1578280.

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7

Kenneth Sassen. Improved Arctic Cloud and Aerosol Research and Model Parameterizations. Office of Scientific and Technical Information (OSTI), März 2007. http://dx.doi.org/10.2172/900752.

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8

Hobbs, Peter V. Airborne Studies of Ocean-Particle-Cloud-Interactions in the Arctic. Fort Belvoir, VA: Defense Technical Information Center, September 1993. http://dx.doi.org/10.21236/ada270752.

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9

Xie, S., J. Boyle, S. Klein, X. Liu und S. Ghan. Evaluation of Mixed-Phase Cloud Parameterizations in Short-Range Weather Forecasts with CAM3 and AM2 for Mixed-Phase Arctic Cloud Experiment. Office of Scientific and Technical Information (OSTI), Juni 2007. http://dx.doi.org/10.2172/1021003.

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10

Kogan, Yefim L. Study of Midlatitude and Arctic Aerosol-cloud-radiation Feedbacks Based on LES Model with Explicit Ice and Liquid Phase Microphysics. Fort Belvoir, VA: Defense Technical Information Center, September 1997. http://dx.doi.org/10.21236/ada634900.

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