111 results on '"Ferrachat, Sylvaine"'
Search Results
2. Evaluating the Wegener–Bergeron–Findeisen process in ICON in large-eddy mode with in situ observations from the CLOUDLAB project.
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Omanovic, Nadja, Ferrachat, Sylvaine, Fuchs, Christopher, Henneberger, Jan, Miller, Anna J., Ohneiser, Kevin, Ramelli, Fabiola, Seifert, Patric, Spirig, Robert, Zhang, Huiying, and Lohmann, Ulrike
- Subjects
RAIN-making ,ICE clouds ,ICE formation & growth ,CLOUD droplets ,CLOUD condensation nuclei ,ICE crystals - Abstract
The ice phase in clouds is essential for precipitation formation over continents. The underlying processes for ice growth are still poorly understood, leading to large uncertainties in precipitation forecasts and climate simulations. One crucial aspect is the Wegener–Bergeron–Findeisen (WBF) process, which describes the growth of ice crystals at the expense of cloud droplets, leading to a partial or full glaciation of the cloud. In the CLOUDLAB project, we employ glaciogenic cloud seeding to initiate the ice phase in supercooled low-level clouds in Switzerland using uncrewed aerial vehicles with the goal of investigating the WBF process. An extensive setup of ground-based remote-sensing and balloon-borne in situ instrumentation allows us to observe the formation and subsequent growth of ice crystals in great detail. In this study, we compare the seeding signals observed in the field to those simulated using a numerical weather model in large-eddy mode (ICON-LEM). We first demonstrate the capability of the model to accurately simulate and reproduce the seeding experiments across different environmental conditions. Second, we investigate the WBF process in the model by comparing the simulated cloud droplet and ice crystal number concentration changes to in situ measurements. In the field experiments, simultaneous reductions in cloud droplet number concentrations with increased ice crystal number concentrations were observed, with periods showing a full depletion of cloud droplets. The model can reproduce the observed ice crystal number concentrations most of the time; however, it cannot reproduce the observed fast reductions in cloud droplet number concentrations. Our detailed analysis shows that the WBF process appears to be less efficient in the model than in the field. In the model, exaggerated ice crystal number concentrations are required to produce comparable changes in cloud droplet number concentrations, highlighting the inefficiency of the WBF process in the numerical weather model ICON. [ABSTRACT FROM AUTHOR]
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- 2024
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- View/download PDF
3. Modeling Atmospheric Transport of Cosmogenic Radionuclide 10Be Using GEOS‐Chem 14.1.1 and ECHAM6.3‐HAM2.3: Implications for Solar and Geomagnetic Reconstructions
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Zheng, Minjie, primary, Adolphi, Florian, additional, Ferrachat, Sylvaine, additional, Mekhaldi, Florian, additional, Lu, Zhengyao, additional, Nilsson, Andreas, additional, and Lohmann, Ulrike, additional
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- 2024
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4. Evaluating the Wegener-Bergeron-Findeisen process in ICON in large-eddy mode with in situ observations from the CLOUDLAB project
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Omanovic, Nadja, primary, Ferrachat, Sylvaine, additional, Fuchs, Christopher, additional, Henneberger, Jan, additional, Miller, Anna J., additional, Ohneiser, Kevin, additional, Ramelli, Fabiola, additional, Seifert, Patric, additional, Spirig, Robert, additional, Zhang, Huiying, additional, and Lohmann, Ulrike, additional
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- 2024
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- View/download PDF
5. Developing a climatological simplification of aerosols to enter the cloud microphysics of a global climate model.
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Proske, Ulrike, Ferrachat, Sylvaine, and Lohmann, Ulrike
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CLIMATE change models ,CLOUD condensation nuclei ,AEROSOLS ,MICROPHYSICS ,CLOUD droplets ,ICE clouds ,ATMOSPHERIC nucleation - Abstract
Aerosol particles influence cloud formation and properties. Hence climate models that aim for a physical representation of the climate system include aerosol modules. In order to represent more and more processes and aerosol species, their representation has grown increasingly detailed. However, depending on one's modelling purpose, the increased model complexity may not be beneficial, for example because it hinders understanding of model behaviour. Hence we develop a simplification in the form of a climatology of aerosol concentrations. In one approach, the climatology prescribes properties important for cloud droplet and ice crystal formation, the gateways for aerosols to enter the model cloud microphysics scheme. Another approach prescribes aerosol mass and number concentrations in general. Both climatologies are derived from full ECHAM-HAM simulations and can serve to replace the HAM aerosol module and thus drastically simplify the aerosol treatment. The first simplification reduces computational model time by roughly 65 %. However, the naive mean climatological treatment needs improvement to give results that are satisfyingly close to the full model. We find that mean cloud condensation nuclei (CCN) concentrations yield an underestimation of cloud droplet number concentration (CDNC) in the Southern Ocean, which we can reduce by allowing only CCN at cloud base (which have experienced hygroscopic growth in these conditions) to enter the climatology. This highlights the value of the simplification approach in pointing to unexpected model behaviour and providing a new perspective for its study and model development. [ABSTRACT FROM AUTHOR]
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- 2024
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- View/download PDF
6. Simulating the seeder-feeder impacts on cloud ice and precipitation over the Alps
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Dedekind, Zane, primary, Proske, Ulrike, additional, Ferrachat, Sylvaine, additional, Lohmann, Ulrike, additional, and Neubauer, David, additional
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- 2023
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7. Supplementary material to "Simulating the seeder-feeder impacts on cloud ice and precipitation over the Alps"
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Dedekind, Zane, primary, Proske, Ulrike, additional, Ferrachat, Sylvaine, additional, Lohmann, Ulrike, additional, and Neubauer, David, additional
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- 2023
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8. Constraining the instantaneous aerosol influence on cloud albedo
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Gryspeerdt, Edward, Quaas, Johannes, Ferrachat, Sylvaine, Gettelman, Andrew, Ghan, Steven, Lohmann, Ulrike, Morrison, Hugh, Neubauer, David, Partridge, Daniel G., Stier, Philip, Takemura, Toshihiko, Wang, Hailong, Wang, Minghuai, and Zhang, Kai
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- 2017
9. Modeling Atmospheric Transport of Cosmogenic Radionuclide 10Be Using GEOS‐Chem 14.1.1 and ECHAM6.3‐HAM2.3: Implications for Solar and Geomagnetic Reconstructions.
- Author
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Zheng, Minjie, Adolphi, Florian, Ferrachat, Sylvaine, Mekhaldi, Florian, Lu, Zhengyao, Nilsson, Andreas, and Lohmann, Ulrike
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ATMOSPHERIC transport ,ATMOSPHERIC models ,GEOMAGNETIC variations ,RADIOISOTOPES ,GEOMAGNETISM ,ATMOSPHERIC deposition - Abstract
A prerequisite to applying 10Be in natural archives for solar and geomagnetic reconstructions is to know how 10Be deposition reflects atmospheric production changes. However, this relationship remains debated. To address this, we use two state‐of‐the‐art global models GEOS‐Chem and ECHAM6.3‐HAM2.3 with the latest beryllium production model. During solar modulation, both models suggest that 10Be deposition reacts proportionally to global production changes, with minor latitudinal deposition biases (<5%). During geomagnetic modulation, however, 10Be deposition changes are enhanced by ∼15% in the tropics and attenuated by 20%–35% in subtropical and polar regions compared to global production changes. Such changes are also hemispherically asymmetric, attributed to asymmetric production between hemispheres. For the solar proton event in 774/5 CE, 10Be shows a 15% higher deposition increase in polar regions than in tropics. This study highlights the importance of atmospheric mixing when comparing 10Be from different locations or to independent geomagnetic field records. Plain Language Summary: The cosmogenic radionuclide beryllium‐10 (10Be) deposition in natural archives can be used to reconstruct solar and geomagnetic changes in the past. Understanding how 10Be deposition reflects atmospheric production rate changes is crucial for these applications. However, this relationship remains debated. To address this issue, we use two state‐of‐the‐art global models, GEOS‐Chem 14.1.1 and ECHAM6.3‐HAM2.3, along with the latest beryllium production model (CRAC: Be). When responding to solar modulation, both models indicate that 10Be deposition corresponds proportionally to global production rate changes, with a minor latitudinal bias. However, during geomagnetic modulation, 10Be deposition changes significantly compared to global production rate changes. 10Be deposition also shows varying hemispheric responses to geomagnetic modulation, attributed to the asymmetric production between hemispheres. For the extreme solar proton event in 774/5 CE, 10Be shows a higher deposition flux increase in the polar regions compared to the tropics. These findings underscore the need to account for atmospheric mixing on 10Be deposition from different locations, especially for the changes due to the geomagnetic field variations. Key Points: We used two state‐of‐the‐art global models incorporating the latest beryllium production rates to study the sources of 10Be deposition10Be deposition shows strong regional bias compared to the global signal in response to geomagnetic modulation but not to solar modulation10Be deposition shows varying hemispheric responses to geomagnetic modulation, attributed to the asymmetric production between hemispheres [ABSTRACT FROM AUTHOR]
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- 2024
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10. Addressing Complexity in Global Aerosol Climate Model Cloud Microphysics
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Proske, Ulrike, primary, Ferrachat, Sylvaine, additional, Klampt, Sina, additional, Abeling, Melina, additional, and Lohmann, Ulrike, additional
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- 2023
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11. Selective simulated seeding on hailstorms – a summertime case study over Switzerland
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Papaevangelou, Nikolaos, primary, Lohmann, Ulrike, additional, and Ferrachat, Sylvaine, additional
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- 2023
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12. Challenges in constraining anthropogenic aerosol effects on cloud radiative forcing using present-day spatiotemporal variability
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Ghan, Steven, Wang, Minghuai, Zhang, Shipeng, Ferrachat, Sylvaine, Gettelman, Andrew, Griesfeller, Jan, Kipling, Zak, Lohmann, Ulrike, Morrison, Hugh, Neubauer, David, Partridge, Daniel G., Stier, Philip, Takemura, Toshihiko, Wang, Hailong, and Zhang, Kai
- Published
- 2016
13. Developing a climatological simplification of aerosols to enter the cloud microphysics of a global climate model.
- Author
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Proske, Ulrike, Ferrachat, Sylvaine, and Lohmann, Ulrike
- Abstract
Aerosol particles influence cloud formation and properties. Hence climate models that aim for a physical representation of the climate system include aerosol modules. In order to represent more and more processes and aerosol species, their representation has grown increasingly detailed. However, depending on one's modeling purpose, the increased model complexity may not be beneficial, for example because it hinders understanding of model behaviour. Hence we develop a simplification in the form of a climatology of aerosol concentrations. In one approach, the climatology prescribes properties important for cloud droplet and ice crystal formation, the gateways for aerosols to enter the model cloud microphysics scheme. Another approach prescribes aerosol mass and number concentrations in general. Both climatologies are derived from full ECHAMHAM simulations and can serve to replace the HAM aerosol module and thus drastically simplify the aerosol treatment. The first simplification reduces computational model time by roughly 65%. However, the naive mean climatological treatment needs improvement to give results that are satisfyingly close to the full model. We find that mean CCN concentrations yield an underestimation of CDNC in the Southern Ocean, which we can reduce by allowing only CCN at cloud base (which have experienced hygroscopic growth in these conditions) to enter the climatology. This highlights the value of the simplification approach in pointing to unexpected model behaviour and providing a new perspective for its study and model development. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
14. Simulating the seeder-feeder impacts on cloud ice and precipitation over the Alps.
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Dedekind, Zane, Proske, Ulrike, Ferrachat, Sylvaine, Lohmann, Ulrike, and Neubauer, David
- Abstract
The ice phase impacts many cloud properties as well as cloud lifetime. Ice particles that sediment into a lower cloud from an upper cloud (external seeder-feeder process) or into the mixed-phase region of a deep cloud from cirrus levels (internal seeder-feeder process) can influence the ice phase of the lower cloud, amplify cloud glaciation and enhance surface precipitation. Recently, numerical weather prediction modeling studies have aimed at representing the ice crystal number concentration in mixed-phase clouds more accurately by including secondary ice formation processes. The increase in the ice crystal number concentration can impact the number of ice particles that sediment into the lower cloud and alter its composition and precipitation formation. In the Swiss Alps, the orography permits the formation of orographic clouds, making it ideal for studying the occurrence of multi-layered clouds and the seeder-feeder process. We present results from a case study on May 18, 2016, showing the occurrence frequency of multi-layered clouds and the seeder-feeder process. About half of all observed clouds were categorized as multi-layered, and the external seeder-feeder process occurred in 10% of these clouds. In between cloud layers, ≈ 60% of the ice particle mass was lost due to sublimation or melting. The external seeder-feeder process was found to be more important than the internal seeder-feeder process with regard to the impact on precipitation. In the case where the external seeder-feeder process was inhibited, the average surface precipitation and riming rate over the domain were both reduced by 8.5% and 3.9%, respectively. When ice-graupel collisions were allowed, further large reductions were seen in the liquid water fraction and riming rate. Inhibiting the internal seeder-feeder process enhanced the liquid water fraction by 6% compared to a reduction of 5.8% in the cloud condensate and, therefore, pointing towards the deamplification in cloud glaciation and a reduction in surface precipitation. Adding to the observational evidence of frequent seeder-feeder situations at least over Switzerland Proske et al. (2021), our study highlights the extensive influence of sedimenting ice particles on the properties of feeder clouds as well as on precipitation formation. [ABSTRACT FROM AUTHOR]
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- 2023
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15. By how much can co-condensation of semi-volatile compounds alter clouds?
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Wang, Yu, primary, Neubauer, David, additional, Chen, Ying, additional, Liu, Pengfei, additional, Luo, Beiping, additional, Proske, Ulrike, additional, Ferrachat, Sylvaine, additional, Marcolli, Claudia, additional, and Lohmann, Ulrike, additional
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- 2023
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16. Simplifying cloud microphysical process representation to reduce climate model complexity
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Proske, Ulrike, primary, Ferrachat, Sylvaine, additional, and Lohmann, Ulrike, additional
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- 2023
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17. Assessing the potential for simplification in global climate model cloud microphysics
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Proske, Ulrike, primary, Ferrachat, Sylvaine, additional, Neubauer, David, additional, Staab, Martin, additional, and Lohmann, Ulrike, additional
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- 2022
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18. Which cloud microphysical processes are dispensable in a global aerosol climate model?
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Proske, Ulrike, primary, Ferrachat, Sylvaine, additional, and Lohmann, Ulrike, additional
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- 2022
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19. Sensitivity of precipitation formation to secondary ice production in winter orographic mixed-phase clouds
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Dedekind, Zane, primary, Lauber, Annika, additional, Ferrachat, Sylvaine, additional, and Lohmann, Ulrike, additional
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- 2021
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20. Assessing the potential for simplification in global climate model cloud microphysics
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Proske, Ulrike, primary, Ferrachat, Sylvaine, additional, Neubauer, David, additional, Staab, Martin, additional, and Lohmann, Ulrike, additional
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- 2021
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21. How detailed do cloud microphysics need to be in climate models?
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Proske, Ulrike, primary, Ferrachat, Sylvaine, additional, Neubauer, David, additional, and Lohmann, Ulrike, additional
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- 2021
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22. SALSA2.0: The sectional aerosol module of the aerosol–chemistry–climate model ECHAM6.3.0-HAM2.3-MOZ1.0
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Massachusetts Institute of Technology. Department of Civil and Environmental Engineering, Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences, Kokkola, Harri, Kühn, Thomas, Laakso, Anton, Bergman, Tommi, Lehtinen, Kari E. J., Mielonen, Tero, Arola, Antti, Stadtler, Scarlet, Korhonen, Hannele, Ferrachat, Sylvaine, Lohmann, Ulrike, Neubauer, David, Tegen, Ina, Siegenthaler-Le Drian, Colombe, Schultz, Martin G., Bey, Isabelle, Stier, Philip, Daskalakis, Nikos, Heald, Colette L., Romakkaniemi, Sami, Massachusetts Institute of Technology. Department of Civil and Environmental Engineering, Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences, Kokkola, Harri, Kühn, Thomas, Laakso, Anton, Bergman, Tommi, Lehtinen, Kari E. J., Mielonen, Tero, Arola, Antti, Stadtler, Scarlet, Korhonen, Hannele, Ferrachat, Sylvaine, Lohmann, Ulrike, Neubauer, David, Tegen, Ina, Siegenthaler-Le Drian, Colombe, Schultz, Martin G., Bey, Isabelle, Stier, Philip, Daskalakis, Nikos, Heald, Colette L., and Romakkaniemi, Sami
- Abstract
In this paper, we present the implementation and evaluation of the aerosol microphysics module SALSA2.0 in the framework of the aerosol-chemistry-climate model ECHAM-HAMMOZ. It is an alternative microphysics module to the default modal microphysics scheme M7 in ECHAM-HAMMOZ. The SALSA2.0 implementation within ECHAM-HAMMOZ is evaluated against observations of aerosol optical properties, aerosol mass, and size distributions, comparing also to the skill of the M7 implementation. The largest differences between the implementation of SALSA2.0 and M7 are in the methods used for calculating microphysical processes, i.e., nucleation, condensation, coagulation, and hydration. These differences in the microphysics are reflected in the results so that the largest differences between SALSA2.0 and M7 are evident over regions where the aerosol size distribution is heavily modified by the microphysical processing of aerosol particles. Such regions are, for example, highly polluted regions and regions strongly affected by biomass burning. In addition, in a simulation of the 1991 Mt. Pinatubo eruption in which a stratospheric sulfate plume was formed, the global burden and the effective radii of the stratospheric aerosol are very different in SALSA2.0 and M7. While SALSA2.0 was able to reproduce the observed time evolution of the global burden of sulfate and the effective radii of stratospheric aerosol, M7 strongly overestimates the removal of coarse stratospheric particles and thus underestimates the effective radius of stratospheric aerosol. As the mode widths of M7 have been optimized for the troposphere and were not designed to represent stratospheric aerosol, the ability of M7 to simulate the volcano plume was improved by modifying the mode widths, decreasing the standard deviations of the accumulation and coarse modes from 1.59 and 2.0, respectively, to 1.2 similar to what was observed after the Mt. Pinatubo eruption. Overall, SALSA2.0 shows promise in improving the aerosol de, NOAA (Grant NA17RJ1231), National Science Foundation (Grant ATM-0002035, ATM-0002698 and ATM04-01611)
- Published
- 2020
23. Supplementary material to "Sensitivity of precipitation formation to secondary ice production in winter orographic mixed-phase clouds"
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Dedekind, Zane, primary, Lauber, Annika, additional, Ferrachat, Sylvaine, additional, and Lohmann, Ulrike, additional
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- 2021
- Full Text
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24. The global aerosol-climate model echam6.3-ham2.3: Part 1: Aerosol evaluation
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Tegen, Ina, Neubauer, David, Ferrachat, Sylvaine, Siegenthaler-Le Drian, Colombe, Bey, Isabelle, Schutgens, Nick, Stier, Philip, Watson-Parris, Duncan, Stanelle, Tanja, Schmidt, Hauke, Rast, Sebastian, Kokkola, Harri, Schultz, Martin, Schroeder, Sabine, Daskalakis, Nikos, Barthel, Stefan, Heinold, Bernd, Lohmann, Ulrike, and Earth and Climate
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SDG 14 - Life Below Water ,respiratory system ,complex mixtures - Abstract
We introduce and evaluate aerosol simulations with the global aerosol–climate model ECHAM6.3–HAM2.3, which is the aerosol component of the fully coupled aerosol–chemistry–climate model ECHAM–HAMMOZ. Both the host atmospheric climate model ECHAM6.3 and the aerosol model HAM2.3 were updated from previous versions. The updated version of the HAM aerosol model contains improved parameterizations of aerosol processes such as cloud activation, as well as updated emission fields for anthropogenic aerosol species and modifications in the online computation of sea salt and mineral dust aerosol emissions. Aerosol results from nudged and free-running simulations for the 10-year period 2003 to 2012 are compared to various measurements of aerosol properties. While there are regional deviations between the model and observations, the model performs well overall in terms of aerosol optical thickness, but may underestimate coarse-mode aerosol concentrations to some extent so that the modeled particles are smaller than indicated by the observations. Sulfate aerosol measurements in the US and Europe are reproduced well by the model, while carbonaceous aerosol species are biased low. Both mineral dust and sea salt aerosol concentrations are improved compared to previous versions of ECHAM–HAM. The evaluation of the simulated aerosol distributions serves as a basis for the suitability of the model for simulating aerosol–climate interactions in a changing climate., Geoscientific Model Development, 12 (4), ISSN:1991-9603, ISSN:1991-959X
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- 2019
25. Data workflow: from raw data to archiving
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Ferrachat Sylvaine
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licensing ,ComputingMilieux_COMPUTERSANDEDUCATION ,data workflow ,data repositories ,FAIR "data management" "data workflow" "data repositories" "licensing" ,data management ,climate sciences ,FAIR - Abstract
Presentation about data workflow and FAIR principles given at theC2SM data management workshop (March 7th, 2019). Target audience:students. Context / domain science: atmospheric and climate sciences 
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- 2019
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26. Assessing the potential for simplification in global climate model cloud microphysics.
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Proske, Ulrike, Ferrachat, Sylvaine, Neubauer, David, Staab, Martin, and Lohmann, Ulrike
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Cloud properties and their evolution influence Earth's radiative balance. The cloud microphysical (CMP) processes that shape these properties are therefore important to be represented in global climate models. Historically, parameterizations in these models have grown more detailed and complex. However, a simpler formulation of CMP processes may leave the model results mostly unchanged while enabling an easier interpretation of model results and helping to increase process understanding. This study employs sensitivity analysis on an emulated perturbed parameter ensemble of the global aerosol-climate model ECHAM-HAM to illuminate the impact of selected CMP cloud ice processes on model output. The response to the phasing of a process thereby serves as a proxy for the effect of a simplification. Aggregation of ice crystals is found to be the dominant CMP process in influencing key variables such as the ice water path or cloud radiative effects, while riming of cloud droplets on snow influences mostly the liquid phase. Accretion of ice and snow and self-collection of ice crystals have a negligible influence on model output and are therefore identified as suitable candidates for future simplifications. In turn, the dominating role of aggregation suggests that this process has the greatest need to be represented correctly. A seasonal and spatially resolved analysis employing a spherical harmonics expansion of the data corroborates the results. This study introduces a new framework to evaluate a processes' impact in a complex numerical model, and paves the way for simplifications of CMP processes leading to more interpretable climate models. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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27. The global aerosol-climate model ECHAM6.3-HAM2.3 – Part 2: Cloud evaluation, aerosol radiative forcing and climate sensitivity
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Neubauer, David, primary, Ferrachat, Sylvaine, additional, Siegenthaler-Le Drian, Colombe, additional, Stier, Philip, additional, Partridge, Daniel G., additional, Tegen, Ina, additional, Bey, Isabelle, additional, Stanelle, Tanja, additional, Kokkola, Harri, additional, and Lohmann, Ulrike, additional
- Published
- 2019
- Full Text
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28. Supplementary material to "The global aerosol-climate model ECHAM6.3-HAM2.3 – Part 2: Cloud evaluation, aerosol radiative forcing and climate sensitivity"
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Neubauer, David, primary, Ferrachat, Sylvaine, additional, Siegenthaler-Le Drian, Colombe, additional, Stier, Philip, additional, Partridge, Daniel G., additional, Tegen, Ina, additional, Bey, Isabelle, additional, Stanelle, Tanja, additional, Kokkola, Harri, additional, and Lohmann, Ulrike, additional
- Published
- 2019
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29. The chemistry–climate model ECHAM6.3-HAM2.3-MOZ1.0
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Schultz, Martin G., Stadtler, Scarlet, Schröder, Sabine, Taraborrelli, Domenico, Franco, Bruno, Krefting, Jonathan, Henrot, Alexandra, Ferrachat, Sylvaine, Lohmann, Ulrike, Neubauer, David, Siegenthaler-Le Drian, Colombe, Wahl, Sebastian, Kokkola, Harri, Kühn, Thomas, Rast, Sebastian, Schmidt, Hauke, Stier, Philip, Kinnison, Doug, Tyndall, Geoffrey S., Orlando, John J., Wespes, Catherine, Schultz, Martin G., Stadtler, Scarlet, Schröder, Sabine, Taraborrelli, Domenico, Franco, Bruno, Krefting, Jonathan, Henrot, Alexandra, Ferrachat, Sylvaine, Lohmann, Ulrike, Neubauer, David, Siegenthaler-Le Drian, Colombe, Wahl, Sebastian, Kokkola, Harri, Kühn, Thomas, Rast, Sebastian, Schmidt, Hauke, Stier, Philip, Kinnison, Doug, Tyndall, Geoffrey S., Orlando, John J., and Wespes, Catherine
- Abstract
The chemistry–climate model ECHAM-HAMMOZ contains a detailed representation of tropospheric and stratospheric reactive chemistry and state-of-the-art parameterizations of aerosols using either a modal scheme (M7) or a bin scheme (SALSA). This article describes and evaluates the model version ECHAM6.3-HAM2.3-MOZ1.0 with a focus on the tropospheric gas-phase chemistry. A 10-year model simulation was performed to test the stability of the model and provide data for its evaluation. The comparison to observations concentrates on the year 2008 and includes total column observations of ozone and CO from IASI and OMI, Aura MLS observations of temperature, HNO3, ClO, and O3 for the evaluation of polar stratospheric processes, an ozonesonde climatology, surface ozone observations from the TOAR database, and surface CO data from the Global Atmosphere Watch network. Global budgets of ozone, OH, NOx, aerosols, clouds, and radiation are analyzed and compared to the literature. ECHAM-HAMMOZ performs well in many aspects. However, in the base simulation, lightning NOx emissions are very low, and the impact of the heterogeneous reaction of HNO3 on dust and sea salt aerosol is too strong. Sensitivity simulations with increased lightning NOx or modified heterogeneous chemistry deteriorate the comparison with observations and yield excessively large ozone budget terms and too much OH. We hypothesize that this is an impact of potential issues with tropical convection in the ECHAM model.
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- 2018
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30. The aerosol-climate model ECHAM6.3-HAM2.3: Aerosol evaluation
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Tegen, Ina, primary, Neubauer, David, additional, Ferrachat, Sylvaine, additional, Siegenthaler-Le Drian, Colombe, additional, Bey, Isabelle, additional, Schutgens, Nick, additional, Stier, Philip, additional, Watson-Parris, Duncan, additional, Stanelle, Tanja, additional, Schmidt, Hauke, additional, Rast, Sebastian, additional, Kokkola, Harri, additional, Schultz, Martin, additional, Schroeder, Sabine, additional, Daskalakis, Nikos, additional, Barthel, Stefan, additional, Heinold, Bernd, additional, and Lohmann, Ulrike, additional
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- 2018
- Full Text
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31. SALSA2.0: The sectional aerosol module of the aerosol–chemistry–climate model ECHAM6.3.0-HAM2.3-MOZ1.0
- Author
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Kokkola, Harri, primary, Kühn, Thomas, additional, Laakso, Anton, additional, Bergman, Tommi, additional, Lehtinen, Kari E. J., additional, Mielonen, Tero, additional, Arola, Antti, additional, Stadtler, Scarlet, additional, Korhonen, Hannele, additional, Ferrachat, Sylvaine, additional, Lohmann, Ulrike, additional, Neubauer, David, additional, Tegen, Ina, additional, Siegenthaler-Le Drian, Colombe, additional, Schultz, Martin G., additional, Bey, Isabelle, additional, Stier, Philip, additional, Daskalakis, Nikos, additional, Heald, Colette L., additional, and Romakkaniemi, Sami, additional
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- 2018
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32. The CLAW DSL
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Clement, Valentin, primary, Ferrachat, Sylvaine, additional, Fuhrer, Oliver, additional, Lapillonne, Xavier, additional, Osuna, Carlos E., additional, Pincus, Robert, additional, Rood, Jon, additional, and Sawyer, William, additional
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- 2018
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33. The chemistry–climate model ECHAM6.3-HAM2.3-MOZ1.0
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Schultz, Martin G., primary, Stadtler, Scarlet, additional, Schröder, Sabine, additional, Taraborrelli, Domenico, additional, Franco, Bruno, additional, Krefting, Jonathan, additional, Henrot, Alexandra, additional, Ferrachat, Sylvaine, additional, Lohmann, Ulrike, additional, Neubauer, David, additional, Siegenthaler-Le Drian, Colombe, additional, Wahl, Sebastian, additional, Kokkola, Harri, additional, Kühn, Thomas, additional, Rast, Sebastian, additional, Schmidt, Hauke, additional, Stier, Philip, additional, Kinnison, Doug, additional, Tyndall, Geoffrey S., additional, Orlando, John J., additional, and Wespes, Catherine, additional
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- 2018
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34. The global aerosol-climate model ECHAM-HAM, version 2: sensitivity to improvements in process representations
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Zhang, K., O'Donnell, Declan, Kazil, Jan, Stier, Philip, Kinne, Stefan, Lohmann, Ulrike, Ferrachat, Sylvaine, Croft, Betty, Quaas, Johannes, Wan, H., Rast, Sebastian, Feichter, Johann, Max-Planck-Institut für Meteorologie, University of Colorado, University of Oxford, Eidgenössische Technische Hochschule Zürich, Dalhousie University, Pacific Northwest National Laboratory, and NOAA Earth System Research Laboratory (ESRL)
- Subjects
lcsh:Chemistry ,lcsh:QD1-999 ,Klima, Atmosphäre, Wolken, Aerosol ,ddc:551 ,complex mixtures ,lcsh:Physics ,lcsh:QC1-999 ,Physics::Atmospheric and Oceanic Physics ,climate, atmosphere, clouds, aerosol - Abstract
This paper introduces and evaluates the second version of the global aerosol-climate model ECHAM-HAM. Major changes have been brought into the model, including new parameterizations for aerosol nucleation and water uptake, an explicit treatment of secondary organic aerosols, modified emission calculations for sea salt and mineral dust, the coupling of aerosol microphysics to a two-moment stratiform cloud microphysics scheme, and alternative wet scavenging parameterizations. These revisions extend the model's capability to represent details of the aerosol lifecycle and its interaction with climate. Nudged simulations of the year 2000 are carried out to compare the aerosol properties and global distribution in HAM1 and HAM2, and to evaluate them against various observations. Sensitivity experiments are performed to help identify the impact of each individual update in model formulation. Results indicate that from HAM1 to HAM2 there is a marked weakening of aerosol water uptake in the lower troposphere, reducing the total aerosol water burden from 75 Tg to 51 Tg. The main reason is the newly introduced κ-Köhler-theory-based water uptake scheme uses a lower value for the maximum relative humidity cutoff. Particulate organic matter loading in HAM2 is considerably higher in the upper troposphere, because the explicit treatment of secondary organic aerosols allows highly volatile oxidation products of the precursors to be vertically transported to regions of very low temperature and to form aerosols there. Sulfate, black carbon, particulate organic matter and mineral dust in HAM2 have longer lifetimes than in HAM1 because of weaker in-cloud scavenging, which is in turn related to lower autoconversion efficiency in the newly introduced two-moment cloud microphysics scheme. Modification in the sea salt emission scheme causes a significant increase in the ratio (from 1.6 to 7.7) between accumulation mode and coarse mode emission fluxes of aerosol number concentration. This leads to a general increase in the number concentration of smaller particles over the oceans in HAM2, as reflected by the higher Ångström parameters. Evaluation against observation reveals that in terms of model performance, main improvements in HAM2 include a marked decrease of the systematic negative bias in the absorption aerosol optical depth, as well as smaller biases over the oceans in Ångström parameter and in the accumulation mode number concentration. The simulated geographical distribution of aerosol optical depth (AOD) is better correlated with the MODIS data, while the surface aerosol mass concentrations are very similar to those in the old version. The total aerosol water content in HAM2 is considerably closer to the multi-model average from Phase I of the AeroCom intercomparison project. Model deficiencies that require further efforts in the future include (i) positive biases in AOD over the ocean, (ii) negative biases in AOD and aerosol mass concentration in high-latitude regions, and (iii) negative biases in particle number concentration, especially that of the Aitken mode, in the lower troposphere in heavily polluted regions., Atmospheric Chemistry and Physics, 12 (19), ISSN:1680-7375, ISSN:1680-7367
- Published
- 2016
35. The Chemistry Climate Model ECHAM6.3-HAM2.3-MOZ1.0
- Author
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Schultz, Martin G., primary, Stadtler, Scarlet, additional, Schröder, Sabine, additional, Taraborrelli, Domenico, additional, Franco, Bruno, additional, Krefting, Jonathan, additional, Henrot, Alexandra, additional, Ferrachat, Sylvaine, additional, Lohmann, Ulrike, additional, Neubauer, David, additional, Siegenthaler-Le Drian, Colombe, additional, Wahl, Sebastian, additional, Kokkola, Harri, additional, Kühn, Thomas, additional, Rast, Sebastian, additional, Schmidt, Hauke, additional, Stier, Philip, additional, Kinnison, Doug, additional, Tyndall, Geoffrey S., additional, Orlando, John J., additional, and Wespes, Catherine, additional
- Published
- 2017
- Full Text
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36. Effect of anthropogenic aerosol emissions on precipitation in warm conveyor belts in the western North Pacific in winter – a model study with ECHAM6-HAM
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Joos, Hanna, primary, Madonna, Erica, additional, Witlox, Kasja, additional, Ferrachat, Sylvaine, additional, Wernli, Heini, additional, and Lohmann, Ulrike, additional
- Published
- 2017
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37. The global aerosol–climate model ECHAM6.3–HAM2.3 – Part 2: Cloud evaluation, aerosol radiative forcing, and climate sensitivity.
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Neubauer, David, Ferrachat, Sylvaine, Siegenthaler-Le Drian, Colombe, Stier, Philip, Partridge, Daniel G., Tegen, Ina, Bey, Isabelle, Stanelle, Tanja, Kokkola, Harri, and Lohmann, Ulrike
- Subjects
- *
CLIMATE sensitivity , *RADIATIVE forcing , *STRATOCUMULUS clouds , *CLOUD droplets , *ICING (Meteorology) , *CLOUDINESS , *SNOWFLAKES - Abstract
The global aerosol–climate model ECHAM6.3–HAM2.3 (E63H23) as well as the previous model versions ECHAM5.5–HAM2.0 (E55H20) and ECHAM6.1–HAM2.2 (E61H22) are evaluated using global observational datasets for clouds and precipitation. In E63H23, the amount of low clouds, the liquid and ice water path, and cloud radiative effects are more realistic than in previous model versions. E63H23 has a more physically based aerosol activation scheme, improvements in the cloud cover scheme, changes in the detrainment of convective clouds, changes in the sticking efficiency for the accretion of ice crystals by snow, consistent ice crystal shapes throughout the model, and changes in mixed-phase freezing; an inconsistency in ice crystal number concentration (ICNC) in cirrus clouds was also removed. Common biases in ECHAM and in E63H23 (and in previous ECHAM–HAM versions) are a cloud amount in stratocumulus regions that is too low and deep convective clouds over the Atlantic and Pacific oceans that form too close to the continents (while tropical land precipitation is underestimated). There are indications that ICNCs are overestimated in E63H23. Since clouds are important for effective radiative forcing due to aerosol–radiation and aerosol–cloud interactions (ERF ari+aci) and equilibrium climate sensitivity (ECS), differences in ERF ari+aci and ECS between the model versions were also analyzed. ERF ari+aci is weaker in E63H23 (-1.0 W m -2) than in E61H22 (-1.2 W m -2) (or E55H20; -1.1 W m -2). This is caused by the weaker shortwave ERF ari+aci (a new aerosol activation scheme and sea salt emission parameterization in E63H23, more realistic simulation of cloud water) overcompensating for the weaker longwave ERF ari+aci (removal of an inconsistency in ICNC in cirrus clouds in E61H22). The decrease in ECS in E63H23 (2.5 K) compared to E61H22 (2.8 K) is due to changes in the entrainment rate for shallow convection (affecting the cloud amount feedback) and a stronger cloud phase feedback. Experiments with minimum cloud droplet number concentrations (CDNCmin) of 40 cm -3 or 10 cm -3 show that a higher value of CDNCmin reduces ERF ari+aci as well as ECS in E63H23. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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- View/download PDF
38. On the characteristics of aerosol indirect effect based on dynamic regimes in global climate models
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Zhang, Shipeng, Wang, Minghuai, Ghan, Steven J., Ding, Aijun, Wang, Hailong, Zhang, Kai, Neubauer, David, Lohmann, Ulrike, Ferrachat, Sylvaine, Takeamura, Toshihiko, Gettelman, Andrew, Morrison, Hugh, Lee, Yunha, Shindell, Drew T., Partridge, Daniel G., Stier, Philip, Kipling, Zak, Fu, Congbin, Zhang, Shipeng, Wang, Minghuai, Ghan, Steven J., Ding, Aijun, Wang, Hailong, Zhang, Kai, Neubauer, David, Lohmann, Ulrike, Ferrachat, Sylvaine, Takeamura, Toshihiko, Gettelman, Andrew, Morrison, Hugh, Lee, Yunha, Shindell, Drew T., Partridge, Daniel G., Stier, Philip, Kipling, Zak, and Fu, Congbin
- Abstract
Aerosol-cloud interactions continue to constitute a major source of uncertainty for the estimate of climate radiative forcing. The variation of aerosol indirect effects (AIE) in climate models is investigated across different dynamical regimes, determined by monthly mean 500 hPa vertical pressure velocity (omega(500)), lower-tropospheric stability (LTS) and large-scale surface precipitation rate derived from several global climate models (GCMs), with a focus on liquid water path (LWP) response to cloud condensation nuclei (CCN) concentrations. The LWP sensitivity to aerosol perturbation within dynamic regimes is found to exhibit a large spread among these GCMs. It is in regimes of strong large-scale ascent (omega(500)aEuro-aEuro parts per thousand < aEuro-a'25 hPa day(-1)) and low clouds (stratocumulus and trade wind cumulus) where the models differ most. Shortwave aerosol indirect forcing is also found to differ significantly among different regimes. Shortwave aerosol indirect forcing in ascending regimes is close to that in subsidence regimes, which indicates that regimes with strong large-scale ascent are as important as stratocumulus regimes in studying AIE. It is further shown that shortwave aerosol indirect forcing over regions with high monthly large-scale surface precipitation rate (> 0.1 mm day(-1)) contributes the most to the total aerosol indirect forcing (from 64 to nearly 100 %). Results show that the uncertainty in AIE is even larger within specific dynamical regimes compared to the uncertainty in its global mean values, pointing to the need to reduce the uncertainty in AIE in different dynamical regimes.
- Published
- 2016
- Full Text
- View/download PDF
39. Effect of anthropogenic aerosol emissions on precipitation in warm conveyor belts in the western North Pacific in winter – a model study with ECHAM6-HAM
- Author
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Joos, Hanna, primary, Madonna, Erica, additional, Witlox, Kasja, additional, Ferrachat, Sylvaine, additional, Wernli, Heini, additional, and Lohmann, Ulrike, additional
- Published
- 2016
- Full Text
- View/download PDF
40. On the characteristics of aerosol indirect effect based on dynamic regimes in global climate models
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Zhang, Shipeng, primary, Wang, Minghuai, additional, Ghan, Steven J., additional, Ding, Aijun, additional, Wang, Hailong, additional, Zhang, Kai, additional, Neubauer, David, additional, Lohmann, Ulrike, additional, Ferrachat, Sylvaine, additional, Takeamura, Toshihiko, additional, Gettelman, Andrew, additional, Morrison, Hugh, additional, Lee, Yunha, additional, Shindell, Drew T., additional, Partridge, Daniel G., additional, Stier, Philip, additional, Kipling, Zak, additional, and Fu, Congbin, additional
- Published
- 2016
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- View/download PDF
41. Aerosol nucleation and its role for clouds and Earth’s radiative forcing in the aerosol-climate model ECHAM5-HAM
- Author
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Max-Planck-Institut für Meteorologie, University of Oxford, Eidgenössische Technische Hochschule Zürich, Kazil, Jan, Stier, Philip, Zhang, Kai, Quaas, Johannes, Kinne, Stefan, O''Donnell, D., Rast, Sebastian, Esch, Monika, Ferrachat, Sylvaine, Lohmann, Ulrike, Feichter, Johann, Max-Planck-Institut für Meteorologie, University of Oxford, Eidgenössische Technische Hochschule Zürich, Kazil, Jan, Stier, Philip, Zhang, Kai, Quaas, Johannes, Kinne, Stefan, O''Donnell, D., Rast, Sebastian, Esch, Monika, Ferrachat, Sylvaine, Lohmann, Ulrike, and Feichter, Johann
- Abstract
Nucleation from the gas phase is an important source of aerosol particles in the Earth’s atmosphere, contributing to the number of cloud condensation nuclei, which form cloud droplets. We have implemented in the aerosolclimate model ECHAM5-HAM a new scheme for neutral and charged nucleation of sulfuric acid and water based on laboratory data, and nucleation of an organic compound and sulfuric acid using a parametrization of cluster activation based on field measurements. We give details of the implementation, compare results with observations, and investigate the role of the individual aerosol nucleation mechanisms for clouds and the Earth’s radiative forcing. The results of our simulations are most consistent with observations when neutral and charged nucleation of sulfuric acid proceed throughout the troposphere and nucleation due to cluster activation is limited to the forested boundary layer. The globally averaged annual mean contributions of the individual nucleation processes to total absorbed solar short-wave radiation via the direct, semi-direct, indirect cloud-albedo and cloud-lifetime effects in our simulations are −1.15 W/m2 for charged H2SO4/H2O nucleation, −0.235 W/m2 for cluster activation, and −0.05 W/m2 for neutral H2SO4/H2O nucleation. The overall effect of nucleation is −2.55 W/m2, which exceeds the sum of the individual terms due to feedbacks and interactions in the model. Aerosol nucleation contributes over the oceans with −2.18 W/m2 to total absorbed solar short-wave radiation, compared to −0.37 W/m2 over land. We explain the higher effect of aerosol nucleation on Earth’s radiative forcing over the oceans with the larger area covered by ocean clouds, due to the larger contrast in albedo between clouds and the ocean surface compared to continents, and the larger susceptibility of pristine clouds owing to the saturation of effects. The large effect of charged nucleation in our simulations is not in contradiction with small effects seen in local me
- Published
- 2015
42. The global aerosol-climate model ECHAM-HAM, version 2: sensitivity to improvements in process representations
- Author
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Max-Planck-Institut für Meteorologie, University of Colorado, University of Oxford, Eidgenössische Technische Hochschule Zürich, Dalhousie University, Pacific Northwest National Laboratory, NOAA Earth System Research Laboratory (ESRL), Zhang, Kai, O''Donnell, Declan, Kazil, Jan, Stier, Philip, Kinne, Stefan, Lohmann, Ulrike, Ferrachat, Sylvaine, Croft, Betty, Quaas, Johannes, Wan, Hui, Rast, Sebastian, Feichter, Johann, Max-Planck-Institut für Meteorologie, University of Colorado, University of Oxford, Eidgenössische Technische Hochschule Zürich, Dalhousie University, Pacific Northwest National Laboratory, NOAA Earth System Research Laboratory (ESRL), Zhang, Kai, O''Donnell, Declan, Kazil, Jan, Stier, Philip, Kinne, Stefan, Lohmann, Ulrike, Ferrachat, Sylvaine, Croft, Betty, Quaas, Johannes, Wan, Hui, Rast, Sebastian, and Feichter, Johann
- Abstract
This paper introduces and evaluates the second version of the global aerosol-climate model ECHAM-HAM. Major changes have been brought into the model, including new parameterizations for aerosol nucleation and water uptake, an explicit treatment of secondary organic aerosols, modified emission calculations for sea salt and mineral dust, the coupling of aerosol microphysics to a two-moment stratiform cloud microphysics scheme, and alternative wet scavenging parameterizations. These revisions extend the model’s capability to represent details of the aerosol lifecycle and its interaction with climate. Nudged simulations of the year 2000 are carried out to compare the aerosol properties and global distribution in HAM1 and HAM2, and to evaluate them against various observations. Sensitivity experiments are performed to help identify the impact of each individual update in model formulation. Results indicate that from HAM1 to HAM2 there is a marked weakening of aerosol water uptake in the lower troposphere, reducing the total aerosol water burden from 75 Tg to 51 Tg. The main reason is the newly introduced k-Köhler-theory-based water uptake scheme uses a lower value for the maximum relative humidity cutoff. Particulate organic matter loading in HAM2 is considerably higher in the upper troposphere, because the explicit treatment of secondary organic aerosols allows highly volatile oxidation products of the precursors to be vertically transported to regions of very low temperature and to form aerosols there. Sulfate, black carbon, particulate organic matter and mineral dust in HAM2 have longer lifetimes than in HAM1 because of weaker incloud scavenging, which is in turn related to lower autoconversion efficiency in the newly introduced two-moment cloud microphysics scheme. Modification in the sea salt emission scheme causes a significant increase in the ratio (from 1.6 to 7.7) between accumulation mode and coarse mode emission fluxes of aerosol number concentration. This lea
- Published
- 2015
43. Soot microphysical effects on liquid clouds, a multi-model investigation
- Author
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Columbia University, Laboratoire des Sciences du Climat et de l’Environnement, NASA GISS, Pacific Northwest National Laboratory, Eidgenössische Technische Hochschule Zürich, Karlsruher Institut für Technologie, Norwegian Meteorological Institute, Max-Planck-Institut für Meteorologie, University of Oslo, Kyushu University, Koch, Dorothy, Balkanski, Yves, Bauer, Susanne E., Easter, Richard C., Ferrachat, Sylvaine, Ghan, Steven J., Hoose, Corinna, Iversen, Trond, Kirkevåg, Alf, Kristjansson, Jon Egill, Liu, Xiaohong, Lohmann, Ulrike, Menon, Surabi, Quaas, Johannes, Schulz, Michael, Seland, Øyvind, Takemura, Toshihiko, Yan, N., Columbia University, Laboratoire des Sciences du Climat et de l’Environnement, NASA GISS, Pacific Northwest National Laboratory, Eidgenössische Technische Hochschule Zürich, Karlsruher Institut für Technologie, Norwegian Meteorological Institute, Max-Planck-Institut für Meteorologie, University of Oslo, Kyushu University, Koch, Dorothy, Balkanski, Yves, Bauer, Susanne E., Easter, Richard C., Ferrachat, Sylvaine, Ghan, Steven J., Hoose, Corinna, Iversen, Trond, Kirkevåg, Alf, Kristjansson, Jon Egill, Liu, Xiaohong, Lohmann, Ulrike, Menon, Surabi, Quaas, Johannes, Schulz, Michael, Seland, Øyvind, Takemura, Toshihiko, and Yan, N.
- Abstract
We use global models to explore the microphysical effects of carbonaceous aerosols on liquid clouds. Although absorption of solar radiation by soot warms the atmosphere, soot may cause climate cooling due to its contribution to cloud condensation nuclei (CCN) and therefore cloud brightness. Six global models conducted three soot experiments; four of the models had detailed aerosol microphysical schemes. The average cloud radiative response to biofuel soot (black and organic carbon), including both indirect and semi-direct effects, is −0.11Wm−2, comparable in size but opposite in sign to the respective direct effect. In a more idealized fossil fuel black carbon experiment, some models calculated a positive cloud response because soot provides a deposition sink for sulfuric and nitric acids and secondary organics, decreasing nucleation and evolution of viable CCN. Biofuel soot particles were also typically assumed to be larger and more hygroscopic than for fossil fuel soot and therefore caused more negative forcing, as also found in previous studies. Diesel soot (black and organic carbon) experiments had relatively smaller cloud impacts with five of the models <±0.06Wm−2 from clouds. The results are subject to the caveats that variability among models, and regional and interrannual variability for each model, are large. This comparison together with previously published results stresses the need to further constrain aerosol microphysical schemes. The non-linearities resulting from the competition of opposing effects on the CCN population make it difficult to extrapolate from idealized experiments to likely impacts of realistic potential emission changes.
- Published
- 2015
44. The aerosol-climate model ECHAM6.3-HAM2.3: Aerosol evaluation.
- Author
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Tegen, Ina, Neubauer, David, Ferrachat, Sylvaine, Drian, Colombe Siegenthaler-Le, Bey, Isabelle, Schutgens, Nick, Stier, Philip, Watson-Parris, Duncan, Stanelle, Tanja, Schmidt, Hauke, Rast, Sebastian, Kokkola, Harri, Schultz, Martin, Schroeder, Sabine, Daskalakis, Nikos, Barthel, Stefan, Heinold, Bernd, and Lohmann, Ulrike
- Subjects
ATMOSPHERIC aerosols ,ATMOSPHERIC models - Abstract
We introduce and evaluate the aerosol simulations with the global aerosol-climate model ECHAM6.3-HAM2.3, which is the aerosol component of the fully coupled aerosol-chemistry-climate model ECHAM-HAMMOZ. Both the host atmospheric climate model ECHAM6.3 and the aerosol model HAM2.3 were updated from previous versions. The updated version of the HAM aerosol model contains improved parameterizations of aerosol processes such as cloud activation, as well as updated emission fields for anthropogenic aerosol species and modifications in the online computation of sea salt and mineral dust aerosol emissions. Aerosol results from nudged and free running simulations for the 10-year period 2003 to 2012 are compared to various measurements of aerosol properties. While there are regional deviations between model and observations, the model performs well overall in terms of aerosol optical thickness, but may underestimate coarse mode aerosol concentrations to some extent, so that the modeled particles are smaller than indicated by the observations. Sulfate aerosol measurements in the US and Europe are reproduced well by the model, while carbonaceous aerosol species are biased low. Both mineral dust and sea salt aerosol concentrations are improved compared to previous versions of ECHAM-HAM. The evaluation of the simulated aerosol distributions serves as a basis for the suitability of the model for simulating aerosol-climate interactions in a changing climate. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
45. Soot microphysical effects on liquid clouds, a multi-model investigation
- Author
-
Koch, Dorothy, Balkanski, Yves, Bauer, Susanne E., Easter, R.C., Ferrachat, Sylvaine, Ghan, Steven J., Hoose, C., Iversen, Trond, Kirkevåg, Alf, Kristjansson, Jon E., Liu, X., Lohmann, Ulrike, Menon, S., Quaas, Johannes, Schulz, Michael, Seland, Øyvind, Takemura, Toshihiko, and Yan, N.
- Abstract
We use global models to explore the microphysical effects of carbonaceous aerosolson clouds. Although absorption of solar radiation by soot warms the atmosphere, sootmay cause climate cooling due to its contribution to cloud condensation nuclei (CCN)and therefore cloud brightness. Six global models conducted three soot experiments; four of the models had detailed aerosol microphysical schemes. The average cloudradiative response to biofuel soot (black and organic carbon), including both indirectand semi-direct effects, is−0.11 Wm−2, comparable in size but opposite in sign tothe respective direct effect. In a more idealized fossil fuel black carbon experiment,some models calculated a positive cloud response because soot provides a deposition sink for sulfuric and nitric acids and secondary organics, decreasing nucleation andevolution of viable CCN. Biofuel soot particles were also typically assumed to be largerand more hygroscopic than for fossil fuel soot and therefore caused more negativeforcing, as also found in previous studies. Diesel soot (black and organic carbon)experiments had relatively smaller cloud impacts with five of the models
- Published
- 2010
46. The influence of absorbed solar radiation by Saharan dust on hurricane genesis
- Author
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Bretl, Sebastian, primary, Reutter, Philipp, additional, Raible, Christoph C., additional, Ferrachat, Sylvaine, additional, Poberaj, Christina Schnadt, additional, Revell, Laura E., additional, and Lohmann, Ulrike, additional
- Published
- 2015
- Full Text
- View/download PDF
47. Impact of parametric uncertainties on the present-day climate and on the anthropogenic aerosol effect
- Author
-
Lohmann, Ulrike and Ferrachat, Sylvaine
- Abstract
Clouds constitute a large uncertainty in global climate modeling and climate changeprojections as many clouds are smaller than the size of a model grid box. Some pro-cesses, such as the rates of rain and snow formation that have a large impact onclimate, cannot be observed. These processes are thus used as tuning parameters in order to achieve radiation balance. Here we systematically investigate the impactof various tunable parameters within the convective and stratiform cloud schemes andof the ice cloud optical properties on the present-day climate in terms of clouds, radi-ation and precipitation. The total anthropogenic aerosol effect between pre-industrialand present-day times amounts to−1.00 Wm−2obtained as an average over all simulations as compared to−1.02 Wm−2from those simulations where the global annualmean top-of-the atmosphere radiation balance is within±1 Wm−2. The parametric un-certainty when taking all simulations into account has an uncertainty range of 25%between the minimum and maximum value. It is reduced to 11% when only the simu-lations with a balanced top-of-the atmosphere radiation are considered., Atmospheric Chemistry and Physics Discussions, 10 (8), ISSN:1680-7375, ISSN:1680-7367
- Published
- 2010
- Full Text
- View/download PDF
48. Constraining the instantaneous aerosol influence on cloud albedo.
- Author
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Quaas, Johannes, Gryspeerdt, Edward, Toshihiko Takemura, Ferrachat, Sylvaine, Lohmann, Ulrike, Neubauer, David, Gettelman, Andrew, Morrison, Hugh, Ghan, Steven, Hailong Wang, Kai Zhang, Minghuai Wang, Partridge, Daniel G., and Stier, Philip
- Subjects
ATMOSPHERIC aerosols ,CLOUDS ,RADIATIVE forcing ,EFFECT of human beings on weather ,INFRARED albedo - Abstract
Much of the uncertainty in estimates of the anthropogenic forcing of climate change comes from uncertainties in the instantaneous effect of aerosols on cloud albedo, known as the Twomey effect or the radiative forcing from aerosol–cloud interactions (RFaci), a component of the total or effective radiative forcing. Because aerosols serving as cloud condensation nuclei can have a strong influence on the cloud droplet number concentration (N
d ), previous studies have used the sensitivity of the Nd to aerosol properties as a constraint on the strength of the RFaci. However, recent studies have suggested that relationships between aerosol and cloud properties in the present-day climate may not be suitable for determining the sensitivity of the Nd to anthropogenic aerosol perturbations. Using an ensemble of global aerosol–climate models, this study demonstrates how joint histograms between Nd and aerosol properties can account for many of the issues raised by previous studies. It shows that if the anthropogenic contribution to the aerosol is known, the RFaci can be diagnosed to within 20% of its actual value. The accuracy of different aerosol proxies for diagnosing the RFaci is investigated, confirming that using the aerosol optical depth significantly underestimates the strength of the aerosol–cloud interactions in satellite data. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
49. Mélange par convection et survivance des hétérogénéités géochimiques dans le manteau
- Author
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Ferrachat, Sylvaine, École normale supérieure de Lyon (ENS de Lyon), Université Joseph-Fourier - Grenoble I, and Yannick Ricard
- Subjects
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics ,géochimie ,[SDE.MCG]Environmental Sciences/Global Changes ,hétérogénéité ,Mélange ,chaos lagrangien ,convection ,dynamique du manteau terrestre - Abstract
Mantle dynamics is implicitely contained in the geochemical signature of ridge basalts and hotspots basalts. On the one hand, the shallow mantle, sampled in ridge basalts, is shown to be relatively homogeneous. On the other hand, the deep mantle, sampled in hotspots basalts, appears to be very heterogeneous. It seems to be in contradiction with many geophysical constraints : mantle convection is vigorous and is likely to induce large fluxes of material between upper and lower parts. How is it possible to isolate areas with distinct geochemical features ? In this work, we study the mixing properties of simple flows mimicking mantle convection. This way, we try to understand the geochemical signature of basalts. We first show that the boundary conditions imposed by plate motions are of crucial importance for the mixing properties of the flow. With relatively realistic 3D boundary conditions, we can maintain some heterogeneous areas in a globally homogeneized system. Second, we demonstrate that the viscous layering of the mantle does not induce significant differences in the mixing properties between shallower and deeper parts. However, we also show that oceanic crust segregation in the D" layer seems to be a good way to explain the geochemical data. The last part of the thesis consists in comparing the results of convective simulations and box models about mantle dynamics. It is shown that the latter should use about 15 boxes to keep raisonnable values of particule dispersion. It is far greater than what is generaly assumed.; La signature géochimique des basaltes de rides ou de points chauds nous renseigne sur la dynamique du manteau terrestre. Le manteau superficiel, échantillonné dans les basaltes de rides, nous apparaît essentiellement homogène. A l'opposè, le manteau profond, échantillonné dans les basaltes de points chauds, se révèle trés hètérogène. Ceci semble contredire la plupart des observations et contraintes issues de la géophysique : la convection du manteau est très efficace, et elle génère vraisemblablement des flux de matière importants entre parties supérieure et inférieure. Comment, dans ces conditions, préserver des zones géochimiquement très différentes ? Dans cette thèse, nous étudions les propriétés de mélange d'écoulements simples simulant la convection du manteau pour tenter de donner un sens à la signature géochimique des basaltes. Nous montrons tout d'abord que la géométrie et la vitesse des plaques lithosphériques sont cruciales pour l'efficacité du mélange de l'écoulement mantellique. Avec des conditions aux limites tridimensionnelles relativement réalistes, on peut préserver des zones hétérogènes dans un système globalement homogène. Ensuite, nous mettons en évidence le fait que la stratification visqueuse du manteau ne peut être invoquée pour expliquer les différences géochimiques entre parties superficielle et profonde. Nous montrons par contre qu'envisager l'existence d'un réservoir de croûte océanique ancienne dans la couche D" peut permettre d'expliquer la signature des basaltes. Enfin, nous présentons une étude comparative des résultats de simulations de convection et de modèles de boîtes géochimiques concernant la dynamique du manteau. Il apparaît que les seconds devraient utiliser environ 15 boîtes pour que le taux dispersion implicite des éléments reste réaliste. Ce chiffre est très supérieur à ceux des modèles de boîtes publiés dans la littérature.
- Published
- 2000
50. Convective mixing and survival of geochemical heterogeneities
- Author
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Ferrachat, Sylvaine and Talour, Pascale
- Subjects
[SDE.MCG] Environmental Sciences/Global Changes ,géochimie ,[SDU.STU.TE] Sciences of the Universe [physics]/Earth Sciences/Tectonics ,hétérogénéité ,Mélange ,chaos lagrangien ,convection ,dynamique du manteau terrestre - Abstract
Mantle dynamics is implicitely contained in the geochemical signature of ridge basalts and hotspots basalts. On the one hand, the shallow mantle, sampled in ridge basalts, is shown to be relatively homogeneous. On the other hand, the deep mantle, sampled in hotspots basalts, appears to be very heterogeneous. It seems to be in contradiction with many geophysical constraints : mantle convection is vigorous and is likely to induce large fluxes of material between upper and lower parts. How is it possible to isolate areas with distinct geochemical features ? In this work, we study the mixing properties of simple flows mimicking mantle convection. This way, we try to understand the geochemical signature of basalts. We first show that the boundary conditions imposed by plate motions are of crucial importance for the mixing properties of the flow. With relatively realistic 3D boundary conditions, we can maintain some heterogeneous areas in a globally homogeneized system. Second, we demonstrate that the viscous layering of the mantle does not induce significant differences in the mixing properties between shallower and deeper parts. However, we also show that oceanic crust segregation in the D" layer seems to be a good way to explain the geochemical data. The last part of the thesis consists in comparing the results of convective simulations and box models about mantle dynamics. It is shown that the latter should use about 15 boxes to keep raisonnable values of particule dispersion. It is far greater than what is generaly assumed., La signature géochimique des basaltes de rides ou de points chauds nous renseigne sur la dynamique du manteau terrestre. Le manteau superficiel, échantillonné dans les basaltes de rides, nous apparaît essentiellement homogène. A l'opposè, le manteau profond, échantillonné dans les basaltes de points chauds, se révèle trés hètérogène. Ceci semble contredire la plupart des observations et contraintes issues de la géophysique : la convection du manteau est très efficace, et elle génère vraisemblablement des flux de matière importants entre parties supérieure et inférieure. Comment, dans ces conditions, préserver des zones géochimiquement très différentes ? Dans cette thèse, nous étudions les propriétés de mélange d'écoulements simples simulant la convection du manteau pour tenter de donner un sens à la signature géochimique des basaltes. Nous montrons tout d'abord que la géométrie et la vitesse des plaques lithosphériques sont cruciales pour l'efficacité du mélange de l'écoulement mantellique. Avec des conditions aux limites tridimensionnelles relativement réalistes, on peut préserver des zones hétérogènes dans un système globalement homogène. Ensuite, nous mettons en évidence le fait que la stratification visqueuse du manteau ne peut être invoquée pour expliquer les différences géochimiques entre parties superficielle et profonde. Nous montrons par contre qu'envisager l'existence d'un réservoir de croûte océanique ancienne dans la couche D" peut permettre d'expliquer la signature des basaltes. Enfin, nous présentons une étude comparative des résultats de simulations de convection et de modèles de boîtes géochimiques concernant la dynamique du manteau. Il apparaît que les seconds devraient utiliser environ 15 boîtes pour que le taux dispersion implicite des éléments reste réaliste. Ce chiffre est très supérieur à ceux des modèles de boîtes publiés dans la littérature.
- Published
- 2000
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