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3. THE GREENLAND FLOW DISTORTION EXPERIMENT

Author

Renfrew, I. A., Moore, G. W. K., Kristjánsson, J. E., Ólafsson, H., Gray, S. L., Petersen, G. N., Bovis, K., Brown, P. R. A., Føre, I., Haine, T., Hay, C., Irvine, E. A., Lawrence, A., Ohigashi, T., Outten, S., Pickart, R. S., Shapiro, M., Sproson, D., Swinbank, R., Woolley, A., and Zhang, S.

Published
2008

5. Cirrus Cloud Seeding has Potential to Cool Climate

Author

Storelvmo, T, Kristjansson, J. E, Muri, H, Pfeffer, M, Barahona, D, and Nenes, A

Subjects
Meteorology And Climatology
Abstract

Cirrus clouds, thin ice clouds in the upper troposphere, have a net warming effect on Earth s climate. Consequently, a reduction in cirrus cloud amount or optical thickness would cool the climate. Recent research indicates that by seeding cirrus clouds with particles that promote ice nucleation, their lifetimes and coverage could be reduced. We have tested this hypothesis in a global climate model with a state-of-the-art representation of cirrus clouds and find that cirrus cloud seeding has the potential to cancel the entire warming caused by human activity from pre-industrial times to present day. However, the desired effect is only obtained for seeding particle concentrations that lie within an optimal range. With lower than optimal particle concentrations, a seeding exercise would have no effect. Moreover, a higher than optimal concentration results in an over-seeding that could have the deleterious effect of prolonging cirrus lifetime and contributing to global warming.

Published
2013

6. Episodes of Cross-Polar Transport in the Arctic Troposphere During July 2008 as Seen from Models, Satellite, and Aircraft Observations

Author

Sodemann, H, Pommier, M, Arnold, S. R, Monks, S. A, Stebel, K, Burkhart, J. F, Hair, J. W, Diskin, G. S, Clerbaux, C, Coheur, P.-F, Hurtmans, D, Schlager, H, Blechschmidt, A.-M, Kristjansson, J. E, and Stohl, A

Subjects
Geophysics
Abstract

During the POLARCAT summer campaign in 2008, two episodes (2 5 July and 7 10 July 2008) occurred where low-pressure systems traveled from Siberia across the Arctic Ocean towards the North Pole. The two cyclones had extensive smoke plumes from Siberian forest fires and anthropogenic sources in East Asia embedded in their associated air masses, creating an excellent opportunity to use satellite and aircraft observations to validate the performance of atmospheric transport models in the Arctic, which is a challenging model domain due to numerical and other complications. Here we compare transport simulations of carbon monoxide (CO) from the Lagrangian transport model FLEXPART and the Eulerian chemical transport model TOMCAT with retrievals of total column CO from the IASI passive infrared sensor onboard the MetOp-A satellite. The main aspect of the comparison is how realistic horizontal and vertical structures are represented in the model simulations. Analysis of CALIPSO lidar curtains and in situ aircraft measurements provide further independent reference points to assess how reliable the model simulations are and what the main limitations are. The horizontal structure of mid-latitude pollution plumes agrees well between the IASI total column CO and the model simulations. However, finer-scale structures are too quickly diffused in the Eulerian model. Applying the IASI averaging kernels to the model data is essential for a meaningful comparison. Using aircraft data as a reference suggests that the satellite data are biased high, while TOMCAT is biased low. FLEXPART fits the aircraft data rather well, but due to added background concentrations the simulation is not independent from observations. The multi-data, multi-model approach allows separating the influences of meteorological fields, model realisation, and grid type on the plume structure. In addition to the very good agreement between simulated and observed total column CO fields, the results also highlight the difficulty to identify a data set that most realistically represents the actual pollution state of the Arctic atmosphere.

Published
2011
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7. Model Intercomparison of Indirect Aerosol Effects

Author

Penner, J. E, Quaas, J, Storelvmo, T, Takemura, T, Boucher, O, Guo, H, Kirkevag, A, Kristjansson, J. E, and Seland, O

Subjects
Meteorology And Climatology
Abstract

Modeled differences in predicted effects are increasingly used to help quantify the uncertainty of these effects. Here, we examine modeled differences in the aerosol indirect effect in a series of experiments that help to quantify how and why model-predicted aerosol indirect forcing varies between models. The experiments start with an experiment in which aerosol concentrations, the parameterization of droplet concentrations and the autoconversion scheme are all specified and end with an experiment that examines the predicted aerosol indirect forcing when only aerosol sources are specified. Although there are large differences in the predicted liquid water path among the models, the predicted aerosol first indirect effect for the first experiment is rather similar, about -0.6 W/sq m to -0.7 W/sq m. Changes to the autoconversion scheme can lead to large changes in the liquid water path of the models and to the response of the liquid water path to changes in aerosols. Adding an autoconversion scheme that depends on the droplet concentration caused a larger (negative) change in net outgoing shortwave radiation compared to the 1st indirect effect, and the increase varied from only 22% to more than a factor of three. The change in net shortwave forcing in the models due to varying the autoconversion scheme depends on the liquid water content of the clouds as well as their predicted droplet concentrations, and both increases and decreases in the net shortwave forcing can occur when autoconversion schemes are changed. The parameterization of cloud fraction within models is not sensitive to the aerosol concentration, and, therefore, the response of the modeled cloud fraction within the present models appears to be smaller than that which would be associated with model "noise". The prediction of aerosol concentrations, given a fixed set of sources, leads to some of the largest differences in the predicted aerosol indirect radiative forcing among the models, with values of cloud forcing ranging from -0.3 W/sq m to -1.4W/sq m. Thus, this aspect of modeling requires significant improvement in order to improve the prediction of aerosol indirect effects.

Published
2006

8. Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes

Author

Boy, M. (Michael), Thomson, E. S. (Erik S.), Acosta Navarro, J.-C. (Juan-C.), Arnalds, O. (Olafur), Batchvarova, E. (Ekaterina), Back, J. (Jaana), Berninger, F. (Frank), Bilde, M. (Merete), Brasseur, Z. (Zoe), Dagsson-Waldhauserova, P. (Pavla), Castarede, D. (Dimitri), Dalirian, M. (Maryam), de Leeuw, G. (Gerrit), Dragosics, M. (Monika), Duplissy, E.-M. (Ella-Maria), Duplissy, J. (Jonathan), Ekman, A. M. (Annica M. L.), Fang, K. (Keyan), Gallet, J.-C. (Jean-Charles), Glasius, M. (Marianne), Gryning, S.-E. (Sven-Erik), Grythe, H. (Henrik), Hansson, H.-C. (Hans-Christen), Hansson, M. (Margareta), Isaksson, E. (Elisabeth), Iversen, T. (Trond), Jonsdottir, I. (Ingibjorg), Kasurinen, V. (Ville), Kirkevag, A. (Alf), Korhola, A. (Atte), Krejci, R. (Radovan), Kristjansson, J. E. (Jon Egill), Lappalainen, H. K. (Hanna K.), Lauri, A. (Antti), Lepparanta, M. (Matti), Lihavainen, H. (Heikki), Makkonen, R. (Risto), Massling, A. (Andreas), Meinander, O. (Outi), Nilsson, E. D. (E. Douglas), Olafsson, H. (Haraldur), Pettersson, J. B. (Jan B. C.), Prisle, N. L. (Nonne L.), Riipinen, I. (Ilona), Roldin, P. (Pontus), Ruppel, M. (Meri), Salter, M. (Matthew), Sand, M. (Maria), Seland, O. (Oyvind), Seppa, H. (Heikki), Skov, H. (Henrik), Soares, J. (Joana), Stohl, A. (Andreas), Strom, J. (Johan), Svensson, J. (Jonas), Swietlicki, E. (Erik), Tabakova, K. (Ksenia), Thorsteinsson, T. (Throstur), Virkkula, A. (Aki), Weyhenmeyer, G. A. (Gesa A.), Wu, Y. (Yusheng), Zieger, P. (Paul), Kulmala, M. (Markku), Boy, M. (Michael), Thomson, E. S. (Erik S.), Acosta Navarro, J.-C. (Juan-C.), Arnalds, O. (Olafur), Batchvarova, E. (Ekaterina), Back, J. (Jaana), Berninger, F. (Frank), Bilde, M. (Merete), Brasseur, Z. (Zoe), Dagsson-Waldhauserova, P. (Pavla), Castarede, D. (Dimitri), Dalirian, M. (Maryam), de Leeuw, G. (Gerrit), Dragosics, M. (Monika), Duplissy, E.-M. (Ella-Maria), Duplissy, J. (Jonathan), Ekman, A. M. (Annica M. L.), Fang, K. (Keyan), Gallet, J.-C. (Jean-Charles), Glasius, M. (Marianne), Gryning, S.-E. (Sven-Erik), Grythe, H. (Henrik), Hansson, H.-C. (Hans-Christen), Hansson, M. (Margareta), Isaksson, E. (Elisabeth), Iversen, T. (Trond), Jonsdottir, I. (Ingibjorg), Kasurinen, V. (Ville), Kirkevag, A. (Alf), Korhola, A. (Atte), Krejci, R. (Radovan), Kristjansson, J. E. (Jon Egill), Lappalainen, H. K. (Hanna K.), Lauri, A. (Antti), Lepparanta, M. (Matti), Lihavainen, H. (Heikki), Makkonen, R. (Risto), Massling, A. (Andreas), Meinander, O. (Outi), Nilsson, E. D. (E. Douglas), Olafsson, H. (Haraldur), Pettersson, J. B. (Jan B. C.), Prisle, N. L. (Nonne L.), Riipinen, I. (Ilona), Roldin, P. (Pontus), Ruppel, M. (Meri), Salter, M. (Matthew), Sand, M. (Maria), Seland, O. (Oyvind), Seppa, H. (Heikki), Skov, H. (Henrik), Soares, J. (Joana), Stohl, A. (Andreas), Strom, J. (Johan), Svensson, J. (Jonas), Swietlicki, E. (Erik), Tabakova, K. (Ksenia), Thorsteinsson, T. (Throstur), Virkkula, A. (Aki), Weyhenmeyer, G. A. (Gesa A.), Wu, Y. (Yusheng), Zieger, P. (Paul), and Kulmala, M. (Markku)

Abstract

The Nordic Centre of Excellence CRAICC (Cryosphere–Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011–2016, is the largest joint Nordic research and innovation initiative to date, aiming to strengthen research and innovation regarding climate change issues in the Nordic region. CRAICC gathered more than 100 scientists from all Nordic countries in a virtual centre with the objectives of identifying and quantifying the major processes controlling Arctic warming and related feedback mechanisms, outlining strategies to mitigate Arctic warming, and developing Nordic Earth system modelling with a focus on short-lived climate forcers (SLCFs), including natural and anthropogenic aerosols. The outcome of CRAICC is reflected in more than 150 peer-reviewed scientific publications, most of which are in the CRAICC special issue of the journal Atmospheric Chemistry and Physics. This paper presents an overview of the main scientific topics investigated in the centre and provides the reader with a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Faced with a vast amount of scientific discovery, we do not claim to completely summarize the results from CRAICC within this paper, but rather concentrate here on the main results which are related to feedback loops in climate change–cryosphere interactions that affect Arctic amplification.

Published
2019

9. The European Transdisciplinary Assessment of Climate Engineering (EuTRACE): Removing Greenhouse Gases from the Atmosphere and Reflecting Sunlight away from Earth

Author

Aaheim, A., Adriazola, P., Betz, G., Boucher, O., Carius, A., Devine-Right, P., Gullberg, A. T., Haszeldine, S., Haywood, J., Houghton, K., Ibarrola, R., Irvine, P., Kristjansson, J.-E., Lenton, T., Link, J. A., Maas, A., Meyer, L., Muri, H., Oschlies, Andreas, Proelß, Alexander, Rayner, T., Rickels, Wilfried, Ruthner, L., Scheffran, J., Schmidt, H., Schulz, M., Scott, V., Shackley, S., Tänzler, D., Watson, M., Vaughan, N., Schäfer, Stefan, Lawrence, Mark, Stelzer, Harald, Born, Wanda, and Low, Sean

Abstract

The European Transdisciplinary Assessment of Climate Engineering (EuTRACE): Removing Greenhouse Gases from the Atmosphere and Reflecting Sunlight away from Earth

Published
2015

10. Cirrus cloud seeding has potential to cool climate

Author

Storelvmo, T., Kristjansson, J. E., Muri, H., Pfeffer, M., Barahona, D., and Nenes, Athanasios

Subjects
Optimization, Optical thickness, Global warming, Cloud seeding, Recent researches, cirrus, human activity, Seeding particles, Particle concentrations, Deleterious effects, Upper troposphere, troposphere, Clouds, hypothesis testing, Global climate model, Optimal concentration, climate modeling, global climate
Abstract

Cirrus clouds, thin ice clouds in the upper troposphere, have a net warming effect on Earth's climate. Consequently, a reduction in cirrus cloud amount or optical thickness would cool the climate. Recent research indicates that by seeding cirrus clouds with particles that promote ice nucleation, their lifetimes and coverage could be reduced. We have tested this hypothesis in a global climate model with a state-of-the-art representation of cirrus clouds and find that cirrus cloud seeding has the potential to cancel the entire warming caused by human activity from pre-industrial times to present day. However, the desired effect is only obtained for seeding particle concentrations that lie within an optimal range. With lower than optimal particle concentrations, a seeding exercise would have no effect. Moreover, a higher than optimal concentration results in an over-seeding that could have the deleterious effect of prolonging cirrus lifetime and contributing to global warming. © 2013. American Geophysical Union. All Rights Reserved.

Published
2013

11. The European Transdisciplinary Assessment of Climate Engineering (EuTRACE): Removing Greenhouse Gases from the Atmosphere and Reflecting Sunlight away from Earth

Author

Schäfer, Stefan, Lawrence, Mark, Stelzer, Harald, Born, Wanda, Low, Sean, Aaheim, A., Adriazola, P., Betz, G., Boucher, O., Carius, A., Devine-Right, P., Gullberg, A. T., Haszeldine, S., Haywood, J., Houghton, K., Ibarrola, R., Irvine, P., Kristjansson, J.-E., Lenton, T., Link, J. A., Maas, A., Meyer, L., Muri, H., Oschlies, Andreas, Proelß, Alexander, Rayner, T., Rickels, Wilfried, Ruthner, L., Scheffran, J., Schmidt, H., Schulz, M., Scott, V., Shackley, S., Tänzler, D., Watson, M., Vaughan, N., Schäfer, Stefan, Lawrence, Mark, Stelzer, Harald, Born, Wanda, Low, Sean, Aaheim, A., Adriazola, P., Betz, G., Boucher, O., Carius, A., Devine-Right, P., Gullberg, A. T., Haszeldine, S., Haywood, J., Houghton, K., Ibarrola, R., Irvine, P., Kristjansson, J.-E., Lenton, T., Link, J. A., Maas, A., Meyer, L., Muri, H., Oschlies, Andreas, Proelß, Alexander, Rayner, T., Rickels, Wilfried, Ruthner, L., Scheffran, J., Schmidt, H., Schulz, M., Scott, V., Shackley, S., Tänzler, D., Watson, M., and Vaughan, N.

Abstract

The European Transdisciplinary Assessment of Climate Engineering (EuTRACE): Removing Greenhouse Gases from the Atmosphere and Reflecting Sunlight away from Earth

Published
2015
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12. An AeroCom initial assessment–optical properties in aerosol component modules of global models

Author

Kinne, S., Schulz, M., Textor, C., Guibert, S., Balkanski, Y., Bauer, S.E., Berntsen, T., Berglen, T.F., Boucher, O., Chin, M., Collins, W., Dentener, F., Diehl, T., Easter, R., Feichter, J., Fillmore, D., Ghan, S., Ginoux, P., Gong, S., Grini, A., Hendricks, J., Herzog, M., Horowitz, L., Isaksen, I., Iversen, T., Kirkevåg, A., Kloster, S., Koch, D., Kristjansson, J. E., Krol, M., Lauer, A., Lamarque, J. F., Lesins, G., Liu, X., Lohmann, U., Montanaro, V., Myhre, G., Penner, J., Pitari, G ., Reddy, S., Seland, O., Stier, P., Takemura, T., and Tie, X.

Subjects
model intercomparison, atmospheric aerosols, Dynamik der Atmosphäre, respiratory system, aerosol optical properties, complex mixtures, global modelling
Abstract

The AeroCom exercise diagnoses multi-component aerosol modules in global modeling. In an initial assessment simulated global distributions for mass and mid-visible aerosol optical thickness (aot) were compared among 20 different modules. Model diversity was also explored in the context of previous comparisons. For the component combined aot general agreement has improved for the annual global mean. At 0.11 to 0.14, simulated aot values are at the lower end of global averages suggested by remote sensing from ground (AERONET ca. 0.135) and space (satellite composite ca. 0.15). More detailed comparisons, however, reveal that larger differences in regional distribution and significant differences in compositional mixture remain. Of particular concern are large model diversities for contributions by dust and carbonaceous aerosol, because they lead to significant uncertainty in aerosol absorption (aab). Since aot and aab, both, influence the aerosol impact on the radiative energy-balance, the aerosol (direct) forcing uncertainty in modeling is larger than differences in aot might suggest. New diagnostic approaches are proposed to trace model differences in terms of aerosol processing and transport: These include the prescription of common input (e.g. amount, size and injection of aerosol component emissions) and the use of observational capabilities from ground (e.g. measurements networks) or space (e.g. correlations between aerosol and clouds).

Published
2006

13. Aerosol-climate interactions in the Norwegian Earth System Model-NorESM1-M

Author

Kirkevag, A., Iversen, T., Seland, O., Hoose, C., Kristjansson, J. E., Struthers, Hamish, Ekman, Annica M. L., Ghan, S., Griesfeller, J., Nilsson, E. Douglas, Schulz, M., Kirkevag, A., Iversen, T., Seland, O., Hoose, C., Kristjansson, J. E., Struthers, Hamish, Ekman, Annica M. L., Ghan, S., Griesfeller, J., Nilsson, E. Douglas, and Schulz, M.

Abstract

The objective of this study is to document and evaluate recent changes and updates to the module for aerosols and aerosol-cloud-radiation interactions in the atmospheric module CAM4-Oslo of the core version of the Norwegian Earth System Model (NorESM), NorESM1-M. Particular attention is paid to the role of natural organics, sea salt, and mineral dust in determining the gross aerosol properties as well as the anthropogenic contribution to these properties and the associated direct and indirect radiative forcing. The aerosol module is extended from earlier versions that have been published, and includes life-cycling of sea salt, mineral dust, particulate sulphate, black carbon, and primary and secondary organics. The impacts of most of the numerous changes since previous versions are thoroughly explored by sensitivity experiments. The most important changes are: modified prognostic sea salt emissions; updated treatment of precipitation scavenging and gravitational settling; inclusion of biogenic primary organics and methane sulphonic acid (MSA) from oceans; almost doubled production of land-based biogenic secondary organic aerosols (SOA); and increased ratio of organic matter to organic carbon (OM/OC) for biomass burning aerosols from 1.4 to 2.6. Compared with in situ measurements and remotely sensed data, the new treatments of sea salt and dust aerosols give smaller biases in near-surface mass concentrations and aerosol optical depth than in the earlier model version. The model biases for mass concentrations are approximately unchanged for sulphate and BC. The enhanced levels of modeled OM yield improved overall statistics, even though OM is still underestimated in Europe and overestimated in North America. The global anthropogenic aerosol direct radiative forcing (DRF) at the top of the atmosphere has changed from a small positive value to -0.08 W m(-2) in CAM4-Oslo. The sensitivity tests suggest that this change can be attributed to the new treatment of biomass bur, AuthorCount:11

Published
2013
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14. General overview : European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) - integrating aerosol research from nano to global scales

Author

Kulmala, M., Asmi, A., Lappalainen, H. K., Baltensperger, U., Brenguier, J. -L, Facchini, M. C., Hansson, H. -C, Hov, O., O'Dowd, C. D., Poeschl, U., Wiedensohler, A., Boers, R., Boucher, O., de Leeuw, G., van der Gon, H. A. C. Denier, Feichter, J., Krejci, R., Laj, P., Lihavainen, H., Lohmann, U., McFiggans, G., Mentel, T., Pilinis, C., Riipinen, I., Schulz, M., Stohl, A., Swietlicki, E., Vignati, E., Alves, C., Amann, M., Ammann, M., Arabas, S., Artaxo, P., Baars, H., Beddows, D. C. S., Bergström, Robert, Beukes, J. P., Bilde, M., Burkhart, J. F., Canonaco, F., Clegg, S. L., Coe, H., Crumeyrolle, S., D'Anna, B., Decesari, S., Gilardoni, S., Fischer, M., Fjaeraa, A. M., Fountoukis, C., George, C., Gomes, L., Halloran, P., Hamburger, T., Harrison, R. M., Herrmann, H., Hoffmann, T., Hoose, C., Hu, M., Hyvarinen, A., Horrak, U., Iinuma, Y., Iversen, T., Josipovic, M., Kanakidou, M., Kiendler-Scharr, A., Kirkevag, A., Kiss, G., Klimont, Z., Kolmonen, P., Komppula, M., Kristjansson, J. -E, Laakso, L., Laaksonen, A., Labonnote, L., Lanz, V. A., Lehtinen, K. E. J., Rizzo, L. V., Makkonen, R., Manninen, H. E., McMeeking, G., Merikanto, J., Minikin, A., Mirme, S., Morgan, W. T., Nemitz, E., O'Donnell, D., Panwar, T. S., Pawlowska, H., Petzold, A., Pienaar, J. J., Pio, C., Plass-Duelmer, C., Prevot, A. S. H., Pryor, S., Reddington, C. L., Roberts, G., Rosenfeld, D., Schwarz, J., Seland, O., Sellegri, K., Shen, X. J., Shiraiwa, M., Siebert, H., Sierau, B., Simpson, D., Sun, J. Y., Topping, D., Tunved, P., Vaattovaara, P., Vakkari, V., Veefkind, J. P., Visschedijk, A., Vuollekoski, H., Vuolo, R., Wehner, B., Wildt, J., Woodward, S., Worsnop, D. R., van Zadelhoff, G. -J, Zardini, A. A., Zhang, K., van Zyl, P. G., Kerminen, V. -M, Carslaw, K. S., Pandis, S. N., Kulmala, M., Asmi, A., Lappalainen, H. K., Baltensperger, U., Brenguier, J. -L, Facchini, M. C., Hansson, H. -C, Hov, O., O'Dowd, C. D., Poeschl, U., Wiedensohler, A., Boers, R., Boucher, O., de Leeuw, G., van der Gon, H. A. C. Denier, Feichter, J., Krejci, R., Laj, P., Lihavainen, H., Lohmann, U., McFiggans, G., Mentel, T., Pilinis, C., Riipinen, I., Schulz, M., Stohl, A., Swietlicki, E., Vignati, E., Alves, C., Amann, M., Ammann, M., Arabas, S., Artaxo, P., Baars, H., Beddows, D. C. S., Bergström, Robert, Beukes, J. P., Bilde, M., Burkhart, J. F., Canonaco, F., Clegg, S. L., Coe, H., Crumeyrolle, S., D'Anna, B., Decesari, S., Gilardoni, S., Fischer, M., Fjaeraa, A. M., Fountoukis, C., George, C., Gomes, L., Halloran, P., Hamburger, T., Harrison, R. M., Herrmann, H., Hoffmann, T., Hoose, C., Hu, M., Hyvarinen, A., Horrak, U., Iinuma, Y., Iversen, T., Josipovic, M., Kanakidou, M., Kiendler-Scharr, A., Kirkevag, A., Kiss, G., Klimont, Z., Kolmonen, P., Komppula, M., Kristjansson, J. -E, Laakso, L., Laaksonen, A., Labonnote, L., Lanz, V. A., Lehtinen, K. E. J., Rizzo, L. V., Makkonen, R., Manninen, H. E., McMeeking, G., Merikanto, J., Minikin, A., Mirme, S., Morgan, W. T., Nemitz, E., O'Donnell, D., Panwar, T. S., Pawlowska, H., Petzold, A., Pienaar, J. J., Pio, C., Plass-Duelmer, C., Prevot, A. S. H., Pryor, S., Reddington, C. L., Roberts, G., Rosenfeld, D., Schwarz, J., Seland, O., Sellegri, K., Shen, X. J., Shiraiwa, M., Siebert, H., Sierau, B., Simpson, D., Sun, J. Y., Topping, D., Tunved, P., Vaattovaara, P., Vakkari, V., Veefkind, J. P., Visschedijk, A., Vuollekoski, H., Vuolo, R., Wehner, B., Wildt, J., Woodward, S., Worsnop, D. R., van Zadelhoff, G. -J, Zardini, A. A., Zhang, K., van Zyl, P. G., Kerminen, V. -M, Carslaw, K. S., and Pandis, S. N.

Published
2011
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15. The Greenland Flow Distortion Experiment

Author

Renfrew, Ian A., Petersen, Guðrún N., Outten, S., Sproson, D., Moore, G. W. K., Hay, C., Ohigashi, T., Zhang, S., Kristjansson, J. E., Fore, I., Olafsson, H., Gray, S. L., Irvine, E. A., Bovis, K., Brown, P. R. A., Swinbank, R., Haine, Thomas W. N., Lawrence, A., Pickart, Robert S., Shapiro, M., Woolley, A., Renfrew, Ian A., Petersen, Guðrún N., Outten, S., Sproson, D., Moore, G. W. K., Hay, C., Ohigashi, T., Zhang, S., Kristjansson, J. E., Fore, I., Olafsson, H., Gray, S. L., Irvine, E. A., Bovis, K., Brown, P. R. A., Swinbank, R., Haine, Thomas W. N., Lawrence, A., Pickart, Robert S., Shapiro, M., and Woolley, A.

Abstract

Author Posting. ©American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 89 (2008): 1307-1324, doi:10.1175/2008BAMS2508.1., Greenland has a major influence on the atmospheric circulation of the North Atlantic–western European region, dictating the location and strength of mesoscale weather systems around the coastal seas of Greenland and directly influencing synoptic-scale weather systems both locally and downstream over Europe. High winds associated with the local weather systems can induce large air–sea fluxes of heat, moisture, and momentum in a region that is critical to the overturning of the thermohaline circulation, and thus play a key role in controlling the coupled atmosphere–ocean climate system. The Greenland Flow Distortion Experiment (GFDex) is investigating the role of Greenland in defining the structure and predictability of both local and downstream weather systems through a program of aircraft-based observation and numerical modeling. The GFDex observational program is centered upon an aircraft-based field campaign in February and March 2007, at the dawn of the International Polar Year. Twelve missions were flown with the Facility for Airborne Atmospheric Measurements' BAe-146, based out of the Keflavik, Iceland. These included the first aircraft-based observations of a reverse tip jet event, the first aircraft-based observations of barrier winds off of southeast Greenland, two polar mesoscale cyclones, a dramatic case of lee cyclogenesis, and several targeted observation missions into areas where additional observations were predicted to improve forecasts. In this overview of GFDex the background, aims and objectives, and facilities and logistics are described. A summary of the campaign is provided, along with some of the highlights of the experiment., The GFDex would not have been possible without the dedication and flexibility shown by all at the FAAM, DirectFlight, and Avalon. GFDex was funded by the Natural Environmental Research Council (NE/C003365/1), the Canadian Foundation for Climate and Atmospheric Sciences (GR-641), and the European Union Fleet for Airborne Research (EUFAR) and European Union Coordinated Observing System (EUCOS) schemes.

Published
2010

17. The effect of harmonized emissions on aerosol properties in global models – an AeroCom experiment

Author

Textor, C., Schulz, M., Guibert, S., Kinne, S., Balkanski, Y., Bauer, S., Berntsen, T., Berglen, T., Boucher, O., Chin, M., Dentener, F., Diehl, T., Feichter, J., Fillmore, D., Ginoux, P., Gong, S., Grini, A., Hendricks, J., Horowitz, L., Huang, P., Isaksen, I. S. A., Iversen, T., Kloster, S., Koch, D., Kirkevåg, A., Kristjansson, J. E., Krol, M., Lauer, A., Lamarque, J. F., Liu, X., Montanaro, V., Myhre, G., Penner, J. E., Pitari, G., Reddy, M. S., Seland, Ø., Stier, P., Takemura, T., Tie, X., Textor, C., Schulz, M., Guibert, S., Kinne, S., Balkanski, Y., Bauer, S., Berntsen, T., Berglen, T., Boucher, O., Chin, M., Dentener, F., Diehl, T., Feichter, J., Fillmore, D., Ginoux, P., Gong, S., Grini, A., Hendricks, J., Horowitz, L., Huang, P., Isaksen, I. S. A., Iversen, T., Kloster, S., Koch, D., Kirkevåg, A., Kristjansson, J. E., Krol, M., Lauer, A., Lamarque, J. F., Liu, X., Montanaro, V., Myhre, G., Penner, J. E., Pitari, G., Reddy, M. S., Seland, Ø., Stier, P., Takemura, T., and Tie, X.

Abstract

The effects of unified aerosol sources on global aerosol fields simulated by different models are examined in this paper. We compare results from two AeroCom experiments, one with different (ExpA) and one with unified emissions, injection heights, and particle sizes at the source (ExpB). Surprisingly, harmonization of aerosol sources has only a small impact on the simulated inter-model diversity of the global aerosol burden, and consequently global optical properties, as the results are largely controlled by model-specific transport, removal, chemistry (leading to the formation of secondary aerosols) and parameterizations of aerosol microphysics (e.g., the split between deposition pathways) and to a lesser extent by the spatial and temporal distributions of the (precursor) emissions. The burdens of black carbon and especially sea salt become more coherent in ExpB only, because the large ExpA diversities for these two species were caused by a few outliers. The experiment also showed that despite prescribing emission fluxes and size distributions, ambiguities in the implementation in individual models can lead to substantial differences. These results indicate the need for a better understanding of aerosol life cycles at process level (including spatial dispersal and interaction with meteorological parameters) in order to obtain more reliable results from global aerosol simulations. This is particularly important as such model results are used to assess the consequences of specific air pollution abatement strategies.

Published
2007

18. An AeroCom initial assessment – optical properties in aerosol component modules of global models

Author

Kinne, S., Schulz, M., Textor, C., Guibert, S., Balkanski, Y., Bauer, S. E., Berntsen, T., Berglen, T. F., Boucher, O., Chin, M., Collins, W., Dentener, F., Diehl, T., Easter, R., Feichter, J., Fillmore, D., Ghan, S., Ginoux, P., Gong, S., Grini, A., Hendricks, J., Herzog, M., Horowitz, L., Isaksen, I., Iversen, T., Kirkevåg, A., Kloster, S., Koch, D., Kristjansson, J. E., Krol, M., Lauer, A., Lamarque, J. F., Lesins, G., Liu, X., Lohmann, U., Montanaro, V., Myhre, G., Penner, J., Pitari, G., Reddy, S., Seland, O., Stier, P., Takemura, T., Tie, X., Kinne, S., Schulz, M., Textor, C., Guibert, S., Balkanski, Y., Bauer, S. E., Berntsen, T., Berglen, T. F., Boucher, O., Chin, M., Collins, W., Dentener, F., Diehl, T., Easter, R., Feichter, J., Fillmore, D., Ghan, S., Ginoux, P., Gong, S., Grini, A., Hendricks, J., Herzog, M., Horowitz, L., Isaksen, I., Iversen, T., Kirkevåg, A., Kloster, S., Koch, D., Kristjansson, J. E., Krol, M., Lauer, A., Lamarque, J. F., Lesins, G., Liu, X., Lohmann, U., Montanaro, V., Myhre, G., Penner, J., Pitari, G., Reddy, S., Seland, O., Stier, P., Takemura, T., and Tie, X.

Abstract

The AeroCom exercise diagnoses multi-component aerosol modules in global modeling. In an initial assessment simulated global distributions for mass and mid-visible aerosol optical thickness (aot) were compared among 20 different modules. Model diversity was also explored in the context of previous comparisons. For the component combined aot general agreement has improved for the annual global mean. At 0.11 to 0.14, simulated aot values are at the lower end of global averages suggested by remote sensing from ground (AERONET ca. 0.135) and space (satellite composite ca. 0.15). More detailed comparisons, however, reveal that larger differences in regional distribution and significant differences in compositional mixture remain. Of particular concern are large model diversities for contributions by dust and carbonaceous aerosol, because they lead to significant uncertainty in aerosol absorption (aab). Since aot and aab, both, influence the aerosol impact on the radiative energy-balance, the aerosol (direct) forcing uncertainty in modeling is larger than differences in aot might suggest. New diagnostic approaches are proposed to trace model differences in terms of aerosol processing and transport: These include the prescription of common input (e.g. amount, size and injection of aerosol component emissions) and the use of observational capabilities from ground (e.g. measurements networks) or space (e.g. correlations between aerosol and clouds).

Published
2005

21. Soot microphysical effects on liquid clouds, a multi-model investigation

Author

Koch, D., primary, Balkanski, Y., additional, Bauer, S. E., additional, Easter, R. C., additional, Ferrachat, S., additional, Ghan, S. J., additional, Hoose, C., additional, Iversen, T., additional, Kirkevåg, A., additional, Kristjansson, J. E., additional, Liu, X., additional, Lohmann, U., additional, Menon, S., additional, Quaas, J., additional, Schulz, M., additional, Seland, Ø., additional, Takemura, T., additional, and Yan, N., additional

Published
2011
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22. Soot microphysical effects on liquid clouds, a multi-model investigation

Author

Koch, D., primary, Balkanski, Y., additional, Bauer, S. E., additional, Easter, R. C., additional, Ferrachat, S., additional, Ghan, S. J., additional, Hoose, C., additional, Iversen, T., additional, Kirkevåg, A., additional, Kristjansson, J. E., additional, Liu, X., additional, Lohmann, U., additional, Menon, S., additional, Quaas, J., additional, Schulz, M., additional, Seland, Ø., additional, Takemura, T., additional, and Yan, N., additional

Published
2010
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23. The effect of harmonized emissions on aerosol properties in global models – an AeroCom experiment

Author

Textor, C., primary, Schulz, M., additional, Guibert, S., additional, Kinne, S., additional, Balkanski, Y., additional, Bauer, S., additional, Berntsen, T., additional, Berglen, T., additional, Boucher, O., additional, Chin, M., additional, Dentener, F., additional, Diehl, T., additional, Feichter, J., additional, Fillmore, D., additional, Ginoux, P., additional, Gong, S., additional, Grini, A., additional, Hendricks, J., additional, Horowitz, L., additional, Huang, P., additional, Isaksen, I. S. A., additional, Iversen, T., additional, Kloster, S., additional, Koch, D., additional, Kirkevåg, A., additional, Kristjansson, J. E., additional, Krol, M., additional, Lauer, A., additional, Lamarque, J. F., additional, Liu, X., additional, Montanaro, V., additional, Myhre, G., additional, Penner, J. E., additional, Pitari, G., additional, Reddy, M. S., additional, Seland, Ø., additional, Stier, P., additional, Takemura, T., additional, and Tie, X., additional

Published
2007
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26. An AeroCom initial assessment – optical properties in aerosol component modules of global models

Author

Kinne, S., primary, Schulz, M., additional, Textor, C., additional, Guibert, S., additional, Balkanski, Y., additional, Bauer, S. E., additional, Berntsen, T., additional, Berglen, T. F., additional, Boucher, O., additional, Chin, M., additional, Collins, W., additional, Dentener, F., additional, Diehl, T., additional, Easter, R., additional, Feichter, J., additional, Fillmore, D., additional, Ghan, S., additional, Ginoux, P., additional, Gong, S., additional, Grini, A., additional, Hendricks, J., additional, Herzog, M., additional, Horowitz, L., additional, Isaksen, I., additional, Iversen, T., additional, Kirkevåg, A., additional, Kloster, S., additional, Koch, D., additional, Kristjansson, J. E., additional, Krol, M., additional, Lauer, A., additional, Lamarque, J. F., additional, Lesins, G., additional, Liu, X., additional, Lohmann, U., additional, Montanaro, V., additional, Myhre, G., additional, Penner, J., additional, Pitari, G., additional, Reddy, S., additional, Seland, O., additional, Stier, P., additional, Takemura, T., additional, and Tie, X., additional

Published
2006
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27. Analysis and quantification of the diversities of aerosol life cycles within AeroCom

Author

Textor, C., primary, Schulz, M., additional, Guibert, S., additional, Kinne, S., additional, Balkanski, Y., additional, Bauer, S., additional, Berntsen, T., additional, Berglen, T., additional, Boucher, O., additional, Chin, M., additional, Dentener, F., additional, Diehl, T., additional, Easter, R., additional, Feichter, H., additional, Fillmore, D., additional, Ghan, S., additional, Ginoux, P., additional, Gong, S., additional, Grini, A., additional, Hendricks, J., additional, Horowitz, L., additional, Huang, P., additional, Isaksen, I., additional, Iversen, I., additional, Kloster, S., additional, Koch, D., additional, Kirkevåg, A., additional, Kristjansson, J. E., additional, Krol, M., additional, Lauer, A., additional, Lamarque, J. F., additional, Liu, X., additional, Montanaro, V., additional, Myhre, G., additional, Penner, J., additional, Pitari, G., additional, Reddy, S., additional, Seland, Ø., additional, Stier, P., additional, Takemura, T., additional, and Tie, X., additional

Published
2006
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29. Analysis and quantification of the diversities of aerosol life cycles within AeroCom

Author

Textor, C., primary, Schulz, M., additional, Guibert, S., additional, Kinne, S., additional, Balkanski, Y., additional, Bauer, S., additional, Berntsen, T., additional, Berglen, T., additional, Boucher, O., additional, Chin, M., additional, Dentener, F., additional, Diehl, T., additional, Easter, R., additional, Feichter, H., additional, Fillmore, D., additional, Ghan, S., additional, Ginoux, P., additional, Gong, S., additional, Grini, A., additional, Hendricks, J., additional, Horowitz, L., additional, Huang, P., additional, Isaksen, I., additional, Iversen, T., additional, Kloster, S., additional, Koch, D., additional, Kirkevåg, A., additional, Kristjansson, J. E., additional, Krol, M., additional, Lauer, A., additional, Lamarque, J. F., additional, Liu, X., additional, Montanaro, V., additional, Myhre, G., additional, Penner, J., additional, Pitari, G., additional, Reddy, S., additional, Seland, Ø., additional, Stier, P., additional, Takemura, T., additional, and Tie, X., additional

Published
2005
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30. An AeroCom initial assessment – optical properties in aerosol component modules of global models

Author

Kinne, S., primary, Schulz, M., additional, Textor, C., additional, Guibert, S., additional, Balkanski, Y., additional, Bauer, S. E., additional, Berntsen, T., additional, Berglen, T. F., additional, Boucher, O., additional, Chin, M., additional, Collins, W., additional, Dentener, F., additional, Diehl, T., additional, Easter, R., additional, Feichter, J., additional, Fillmore, D., additional, Ghan, S., additional, Ginoux, P., additional, Gong, S., additional, Grini, A., additional, Hendricks, J., additional, Herzog, M., additional, Horowitz, L., additional, Isaksen, I., additional, Iversen, T., additional, Kirkevåg, A., additional, Kloster, S., additional, Koch, D., additional, Kristjansson, J. E., additional, Krol, M., additional, Lauer, A., additional, Lamarque, J. F., additional, Lesins, G., additional, Liu, X., additional, Lohmann, U., additional, Montanaro, V., additional, Myhre, G., additional, Penner, J., additional, Pitari, G., additional, Reddy, S., additional, Seland, O., additional, Stier, P., additional, Takemura, T., additional, and Tie, X., additional

Published
2005
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31. Can a reduction of solar irradiance counteract CO2-induced climate change? - Results from four Earth system models.

Author

Schmidt, H., Alterskjær, K., Karam, D. Bou, Boucher, O., Jones, A., Kristjansson, J. E., Niemeier, U., Schulz, M., Aaheim, A., Benduhn, F., Lawrence, M., and Timmreck1, C.

Subjects
CLIMATE change, GLOBAL warming, ATMOSPHERIC temperature, ENVIRONMENTAL engineering, EVAPORATION (Meteorology)
Abstract

The article presents a study on the comparison of four Earth system models to climate engineering. The study compared the two couteracting forcings I G1 of the GeoMIP to the preindustrial climate. The result of the study shows that the reduction in evaporation compensated the reduction of the meridional temperature gradient in all models compared to the control simulation.

Published
2012
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32. Indirect radiative forcing of aerosols via water vapor above non-precipitating maritime cumulus clouds.

Author

Pfeffer, M. A., Kristjansson, J. E., Stordal, F., Berntsen, T., and Fast, J.

Abstract

Aerosol-cloud-water vapor interactions in clean maritime air have been described for different aerosol sources using the WRF-Chem atmospheric model. The simulations were made over the Lesser Antilles in the region of the RICO measurement campaign where the clouds are low, patchy, typical trade-wind cumuli. In this very clean air, sea salt and DMS are found to have greater effects than anthropogenic pollution on the cloud droplets' effective radii and longwave and shortwave outgoing top of atmosphere radiation. The changes in radiation due to each aerosol source are a function of how each source influences aerosol concentration, cloud droplet number concentration, cloud droplet sizes, and water vapor concentration. Changes in outgoing shortwave radiation are due predominantly to changes in the clouds, followed by the direct aerosol effect which is about 2/3 as important, followed by the effects of water vapor which is in turn about 2/3 as important as the direct effect. Changes in outgoing longwave radiation are due predominantly to changes in the clouds, with changes in water vapor being about 1/10 as important. The simulated changes in water vapor concentration are due to the competing effects of aerosol particles being able to both enhance condensation of available water vapor and enhance evaporation of smaller droplets. These changes are independent of precipitation effects as there is essentially no drizzle in the domain. It is expected that the indirect radiative forcing of aerosols via water vapor may be stronger in dirtier and more strongly convective conditions. [ABSTRACT FROM AUTHOR]

Published
2011
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33. Combined observational and modeling based study of the aerosol indirect effect.

Author

Storelvmo, T., Kristjansson, J. E., Myhre1, G., Johnsrud, M., and Stordal, F.

Abstract

The indirect effect of aerosols via liquid clouds is investigated by comparing aerosol and cloud characteristics from the Global Climate Model CAM-Oslo to those observed by the MODIS instrument onboard the TERRA and AQUA satellites (http://modis.gsfc.nasa.gov). The comparison is carried out for 15 selected regions ranging from remote and clean to densely populated and polluted. For each region, the regression coefficient and correlation coefficient for the following parameters are calculated: Aerosol Optical Depth vs. Liquid Cloud Optical Thickness, Aerosol Optical Depth vs. Liquid Cloud Droplet Effective Radius and Aerosol Optical Depth vs. Cloud Liquid Water Path. Modeled and observed correlation coefficients and regression coefficients are then compared for a 3-year period starting in January 2001. Additionally, global maps for a number of aerosol and cloud parameters crucial for the understanding of the aerosol indirect effect are compared for the same period of time. Significant differences are found between MODIS and CAM-Oslo both in the regional and global comparison. However, both the model and the observations show a positive correlation between Aerosol Optical Depth and Cloud Optical Depth in practically all regions and for all seasons, in agreement with the current understanding of aerosol-cloud interactions. The correlation between Aerosol Optical Depth and Liquid Cloud Droplet Effective Radius is variable both in the model and the observations. However, the model reports the expected negative correlation more often than the MODIS data. Aerosol Optical Depth is overall positively correlated to Cloud Liquid Water Path both in the model and the observations, with a few regional exceptions. [ABSTRACT FROM AUTHOR]

Published
2006
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34. Soot microphysical effects on liquid clouds, a multi-model investigation

Author

Koch, D., Balkanski, Y., Bauer, S. E., Easter, R. C., Ferrachat, S., Ghan, S. J., Hoose, C., Iversen, T., Kirkevåg, A., Kristjansson, J. E., Liu, X., Lohmann, U., Menon, S., Quaas, J., Schulz, M., Seland, Ø., Takemura, T., and Yan, N.

Subjects
13. Climate action, 7. Clean energy

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