Articles | Volume 16, issue 11
https://doi.org/10.5194/acp-16-7239-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/acp-16-7239-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Research article
| 
10 Jun 2016
Research article |
| 10 Jun 2016
Exploring an approximation for the homogeneous freezing temperature of water droplets
Kuan-Ting O
CORRESPONDING AUTHOR
University of Washington, Department of Atmospheric Sciences, Seattle, WA, USA
Robert Wood
University of Washington, Department of Atmospheric Sciences, Seattle, WA, USA
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Chris J. Wright, Joel A. Thornton, Lyatt Jaeglé, Yang Cao, Yannian Zhu, Jihu Liu, Randall Jones II, Robert H. Holzworth, Daniel Rosenfeld, Robert Wood, Peter Blossey, and Daehyun Kim
EGUsphere, https://doi.org/10.48550/arXiv.2408.07207, https://doi.org/10.48550/arXiv.2408.07207, 2024
This preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).
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Aerosol particles influence clouds, which exert a large forcing on solar radiation and fresh water. To better understand the mechanisms by which aerosol influences thunderstorms, we look at the two busiest shipping lanes in the world, where recent regulations have reduced sulfur emissions by nearly an order of magnitude. We find that the reduction in emissions has been accompanied by a dramatic decrease in both lightning and the number of droplets in clouds over the shipping lanes.
Philip J. Rasch, Haruki Hirasawa, Mingxuan Wu, Sarah J. Doherty, Robert Wood, Hailong Wang, Andy Jones, James Haywood, and Hansi Singh
Geosci. Model Dev., 17, 7963–7994, https://doi.org/10.5194/gmd-17-7963-2024, https://doi.org/10.5194/gmd-17-7963-2024, 2024
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We introduce a protocol to compare computer climate simulations to better understand a proposed strategy intended to counter warming and climate impacts from greenhouse gas increases. This slightly changes clouds in six ocean regions to reflect more sunlight and cool the Earth. Example changes in clouds and climate are shown for three climate models. Cloud changes differ between the models, but precipitation and surface temperature changes are similar when their cooling effects are made similar.
Lucas A. McMichael, Michael J. Schmidt, Robert Wood, Peter N. Blossey, and Lekha Patel
Geosci. Model Dev., 17, 7867–7888, https://doi.org/10.5194/gmd-17-7867-2024, https://doi.org/10.5194/gmd-17-7867-2024, 2024
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Marine cloud brightening (MCB) is a climate intervention technique to potentially cool the climate. Climate models used to gauge regional climate impacts associated with MCB often assume large areas of the ocean are uniformly perturbed. However, a more realistic representation of MCB application would require information about how an injected particle plume spreads. This work aims to develop such a plume-spreading model.
Ehsan Erfani, Robert Wood, Peter Blossey, Sarah J. Doherty, and Ryan Eastman
EGUsphere, https://doi.org/10.5194/egusphere-2024-3232, https://doi.org/10.5194/egusphere-2024-3232, 2024
This preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).
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In this study, we explore how marine clouds interact with aerosols. We introduce a novel approach to identify a reduced number of representative cases from a wide array of observed environmental conditions prevalent in the Northeast Pacific. We created over 2200 trajectories from observations and used cloud-resolving simulations to investigate how marine low clouds evolve in two different cases. It is shown that aerosols can delay cloud breakup, but their impact depends on precipitation.
Je-Yun Chun, Robert Wood, Peter N. Blossey, and Sarah J. Doherty
EGUsphere, https://doi.org/10.5194/egusphere-2024-2439, https://doi.org/10.5194/egusphere-2024-2439, 2024
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This study explores how aerosols affect clouds transitioning from stratocumulus to cumulus along trade winds under varying atmospheric conditions. We found that aerosols typically reduce precipitation and raise cloud height, but their impact changes when subsidence changes by aerosol enhancement are considered. Our findings indicate that the cooling effect of aerosols might be overestimated if these atmospheric changes are not accounted for.
Ryan Eastman, Isabel L. McCoy, Hauke Schulz, and Robert Wood
Atmos. Chem. Phys., 24, 6613–6634, https://doi.org/10.5194/acp-24-6613-2024, https://doi.org/10.5194/acp-24-6613-2024, 2024
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Cloud types are determined using machine learning image classifiers applied to satellite imagery for 1 year in the North Atlantic. This survey of these cloud types shows that the climate impact of a cloud scene is, in part, a function of cloud type. Each type displays a different mix of thick and thin cloud cover, with the fraction of thin cloud cover having the strongest impact on the clouds' radiative effect. Future studies must account for differing properties and processes among cloud types.
Calvin Howes, Pablo E. Saide, Hugh Coe, Amie Dobracki, Steffen Freitag, Jim M. Haywood, Steven G. Howell, Siddhant Gupta, Janek Uin, Mary Kacarab, Chongai Kuang, L. Ruby Leung, Athanasios Nenes, Greg M. McFarquhar, James Podolske, Jens Redemann, Arthur J. Sedlacek, Kenneth L. Thornhill, Jenny P. S. Wong, Robert Wood, Huihui Wu, Yang Zhang, Jianhao Zhang, and Paquita Zuidema
Atmos. Chem. Phys., 23, 13911–13940, https://doi.org/10.5194/acp-23-13911-2023, https://doi.org/10.5194/acp-23-13911-2023, 2023
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To better understand smoke properties and its interactions with clouds, we compare the WRF-CAM5 model with observations from ORACLES, CLARIFY, and LASIC field campaigns in the southeastern Atlantic in August 2017. The model transports and mixes smoke well but does not fully capture some important processes. These include smoke chemical and physical aging over 4–12 days, smoke removal by rain, sulfate particle formation, aerosol activation into cloud droplets, and boundary layer turbulence.
Amie Dobracki, Paquita Zuidema, Steven G. Howell, Pablo Saide, Steffen Freitag, Allison C. Aiken, Sharon P. Burton, Arthur J. Sedlacek III, Jens Redemann, and Robert Wood
Atmos. Chem. Phys., 23, 4775–4799, https://doi.org/10.5194/acp-23-4775-2023, https://doi.org/10.5194/acp-23-4775-2023, 2023
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Southern Africa produces approximately one-third of the world’s carbon from fires. The thick smoke layer can flow westward, interacting with the southeastern Atlantic cloud deck. The net radiative impact can alter regional circulation patterns, impacting rainfall over Africa. We find that the smoke is highly absorbing of sunlight, mostly because it contains more black carbon than smoke over the Northern Hemisphere.
Ian Chang, Lan Gao, Connor J. Flynn, Yohei Shinozuka, Sarah J. Doherty, Michael S. Diamond, Karla M. Longo, Gonzalo A. Ferrada, Gregory R. Carmichael, Patricia Castellanos, Arlindo M. da Silva, Pablo E. Saide, Calvin Howes, Zhixin Xue, Marc Mallet, Ravi Govindaraju, Qiaoqiao Wang, Yafang Cheng, Yan Feng, Sharon P. Burton, Richard A. Ferrare, Samuel E. LeBlanc, Meloë S. Kacenelenbogen, Kristina Pistone, Michal Segal-Rozenhaimer, Kerry G. Meyer, Ju-Mee Ryoo, Leonhard Pfister, Adeyemi A. Adebiyi, Robert Wood, Paquita Zuidema, Sundar A. Christopher, and Jens Redemann
Atmos. Chem. Phys., 23, 4283–4309, https://doi.org/10.5194/acp-23-4283-2023, https://doi.org/10.5194/acp-23-4283-2023, 2023
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Abundant aerosols are present above low-level liquid clouds over the southeastern Atlantic during late austral spring. The model simulation differences in the proportion of aerosol residing in the planetary boundary layer and in the free troposphere can greatly affect the regional aerosol radiative effects. This study examines the aerosol loading and fractional aerosol loading in the free troposphere among various models and evaluates them against measurements from the NASA ORACLES campaign.
Francesca Gallo, Janek Uin, Kevin J. Sanchez, Richard H. Moore, Jian Wang, Robert Wood, Fan Mei, Connor Flynn, Stephen Springston, Eduardo B. Azevedo, Chongai Kuang, and Allison C. Aiken
Atmos. Chem. Phys., 23, 4221–4246, https://doi.org/10.5194/acp-23-4221-2023, https://doi.org/10.5194/acp-23-4221-2023, 2023
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This study provides a summary statistic of multiday aerosol plume transport event influences on aerosol physical properties and the cloud condensation nuclei budget at the U.S. Department of Energy Atmospheric Radiation Measurement Facility in the eastern North Atlantic (ENA). An algorithm that integrates aerosol properties is developed and applied to identify multiday aerosol transport events. The influence of the aerosol plumes on aerosol populations at the ENA is successively assessed.
Zhenquan Wang, Jian Yuan, Robert Wood, Yifan Chen, and Tiancheng Tong
Atmos. Chem. Phys., 23, 3247–3266, https://doi.org/10.5194/acp-23-3247-2023, https://doi.org/10.5194/acp-23-3247-2023, 2023
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This study develops a novel profile-based algorithm based on the ERA5 to estimate the inversion strength in the planetary boundary layer better than the previous inversion index, which is a key low-cloud-controlling factor. This improved measure is more effective at representing the meteorological influence on low-cloud variations. It can better constrain the meteorological influence on low clouds to better isolate cloud responses to aerosols or to estimate low cloud feedbacks in climate models.
Je-Yun Chun, Robert Wood, Peter Blossey, and Sarah J. Doherty
Atmos. Chem. Phys., 23, 1345–1368, https://doi.org/10.5194/acp-23-1345-2023, https://doi.org/10.5194/acp-23-1345-2023, 2023
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We investigate the impact of injected aerosol on subtropical low marine clouds under a variety of meteorological conditions using high-resolution model simulations. This study illustrates processes perturbed by aerosol injections and their impact on cloud properties (e.g., cloud number concentration, thickness, and cover). We show that those responses are highly sensitive to background meteorological conditions, such as precipitation, and background cloud properties.
Ju-Mee Ryoo, Leonhard Pfister, Rei Ueyama, Paquita Zuidema, Robert Wood, Ian Chang, and Jens Redemann
Atmos. Chem. Phys., 22, 14209–14241, https://doi.org/10.5194/acp-22-14209-2022, https://doi.org/10.5194/acp-22-14209-2022, 2022
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The variability in the meteorological fields during each deployment is highly modulated at a daily to synoptic timescale. This paper, along with part 1, the climatological overview paper, provides a meteorological context for interpreting the airborne measurements gathered during the three ORACLES deployments. This study supports related studies focusing on the detailed investigation of the processes controlling stratocumulus decks, aerosol lifting, transport, and their interactions.
Paul A. Barrett, Steven J. Abel, Hugh Coe, Ian Crawford, Amie Dobracki, James Haywood, Steve Howell, Anthony Jones, Justin Langridge, Greg M. McFarquhar, Graeme J. Nott, Hannah Price, Jens Redemann, Yohei Shinozuka, Kate Szpek, Jonathan W. Taylor, Robert Wood, Huihui Wu, Paquita Zuidema, Stéphane Bauguitte, Ryan Bennett, Keith Bower, Hong Chen, Sabrina Cochrane, Michael Cotterell, Nicholas Davies, David Delene, Connor Flynn, Andrew Freedman, Steffen Freitag, Siddhant Gupta, David Noone, Timothy B. Onasch, James Podolske, Michael R. Poellot, Sebastian Schmidt, Stephen Springston, Arthur J. Sedlacek III, Jamie Trembath, Alan Vance, Maria A. Zawadowicz, and Jianhao Zhang
Atmos. Meas. Tech., 15, 6329–6371, https://doi.org/10.5194/amt-15-6329-2022, https://doi.org/10.5194/amt-15-6329-2022, 2022
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To better understand weather and climate, it is vital to go into the field and collect observations. Often measurements take place in isolation, but here we compared data from two aircraft and one ground-based site. This was done in order to understand how well measurements made on one platform compared to those made on another. Whilst this is easy to do in a controlled laboratory setting, it is more challenging in the real world, and so these comparisons are as valuable as they are rare.
Michael S. Diamond, Pablo E. Saide, Paquita Zuidema, Andrew S. Ackerman, Sarah J. Doherty, Ann M. Fridlind, Hamish Gordon, Calvin Howes, Jan Kazil, Takanobu Yamaguchi, Jianhao Zhang, Graham Feingold, and Robert Wood
Atmos. Chem. Phys., 22, 12113–12151, https://doi.org/10.5194/acp-22-12113-2022, https://doi.org/10.5194/acp-22-12113-2022, 2022
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Smoke from southern Africa blankets the southeast Atlantic from June-October, overlying a major transition region between overcast and scattered clouds. The smoke affects Earth's radiation budget by absorbing sunlight and changing cloud properties. We investigate these effects in regional climate and large eddy simulation models based on international field campaigns. We find that large-scale circulation changes more strongly affect cloud transitions than smoke microphysical effects in our case.
Jessica Danker, Odran Sourdeval, Isabel L. McCoy, Robert Wood, and Anna Possner
Atmos. Chem. Phys., 22, 10247–10265, https://doi.org/10.5194/acp-22-10247-2022, https://doi.org/10.5194/acp-22-10247-2022, 2022
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Using spaceborne lidar-radar retrievals, we show that seasonal changes in cloud phase outweigh changes in cloud-phase statistics across cloud morphologies at given cloud-top temperatures. These results show that cloud morphology does not seem to pose a primary constraint on cloud-phase statistics in the Southern Ocean. Meanwhile, larger changes in in-cloud albedo across cloud morphologies are observed in supercooled liquid rather than mixed-phase stratocumuli.
Matthew W. Christensen, Andrew Gettelman, Jan Cermak, Guy Dagan, Michael Diamond, Alyson Douglas, Graham Feingold, Franziska Glassmeier, Tom Goren, Daniel P. Grosvenor, Edward Gryspeerdt, Ralph Kahn, Zhanqing Li, Po-Lun Ma, Florent Malavelle, Isabel L. McCoy, Daniel T. McCoy, Greg McFarquhar, Johannes Mülmenstädt, Sandip Pal, Anna Possner, Adam Povey, Johannes Quaas, Daniel Rosenfeld, Anja Schmidt, Roland Schrödner, Armin Sorooshian, Philip Stier, Velle Toll, Duncan Watson-Parris, Robert Wood, Mingxi Yang, and Tianle Yuan
Atmos. Chem. Phys., 22, 641–674, https://doi.org/10.5194/acp-22-641-2022, https://doi.org/10.5194/acp-22-641-2022, 2022
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Trace gases and aerosols (tiny airborne particles) are released from a variety of point sources around the globe. Examples include volcanoes, industrial chimneys, forest fires, and ship stacks. These sources provide opportunistic experiments with which to quantify the role of aerosols in modifying cloud properties. We review the current state of understanding on the influence of aerosol on climate built from the wide range of natural and anthropogenic laboratories investigated in recent decades.
Sarah J. Doherty, Pablo E. Saide, Paquita Zuidema, Yohei Shinozuka, Gonzalo A. Ferrada, Hamish Gordon, Marc Mallet, Kerry Meyer, David Painemal, Steven G. Howell, Steffen Freitag, Amie Dobracki, James R. Podolske, Sharon P. Burton, Richard A. Ferrare, Calvin Howes, Pierre Nabat, Gregory R. Carmichael, Arlindo da Silva, Kristina Pistone, Ian Chang, Lan Gao, Robert Wood, and Jens Redemann
Atmos. Chem. Phys., 22, 1–46, https://doi.org/10.5194/acp-22-1-2022, https://doi.org/10.5194/acp-22-1-2022, 2022
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Between July and October, biomass burning smoke is advected over the southeastern Atlantic Ocean, leading to climate forcing. Model calculations of forcing by this plume vary significantly in both magnitude and sign. This paper compares aerosol and cloud properties observed during three NASA ORACLES field campaigns to the same in four models. It quantifies modeled biases in properties key to aerosol direct radiative forcing and evaluates how these biases propagate to biases in forcing.
Amie Dobracki, Paquita Zuidema, Steve Howell, Pablo Saide, Steffen Freitag, Allison C. Aiken, Sharon P. Burton, Arthur J. Sedlacek III, Jens Redemann, and Robert Wood
Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2021-1081, https://doi.org/10.5194/acp-2021-1081, 2022
Preprint withdrawn
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The global maximum of shortwave-absorbing aerosol above cloud occurs above the southeast Atlantic, where the biomass-burning aerosol provides a distinct aerosol radiative warming of regional climate. The smoke aerosols are unusually highly absorbing of sunlight. This study seeks to understand the cause. We conclude the aerosol is already strongly absorbing at the fire emission source, but that chemical aging, through encouraging a net loss of organic aerosol, also contributes.
Ju-Mee Ryoo, Leonhard Pfister, Rei Ueyama, Paquita Zuidema, Robert Wood, Ian Chang, and Jens Redemann
Atmos. Chem. Phys., 21, 16689–16707, https://doi.org/10.5194/acp-21-16689-2021, https://doi.org/10.5194/acp-21-16689-2021, 2021
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Part 1 of the meteorological overview paper highlights the anomalous meteorological characteristics during the ORACLES deployment compared to the climatological mean at monthly timescales. The upper-level wave disturbance and the associated anomalous circulation explain the weakening of AEJ-S through the reduction of the strength of the heat low over the land during August 2017. This may also help explain the anomalously low aerosol optical depth observed in the August 2017 ORACLES deployment.
Rachel Atlas, Johannes Mohrmann, Joseph Finlon, Jeremy Lu, Ian Hsiao, Robert Wood, and Minghui Diao
Atmos. Meas. Tech., 14, 7079–7101, https://doi.org/10.5194/amt-14-7079-2021, https://doi.org/10.5194/amt-14-7079-2021, 2021
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Many clouds with temperatures between 0 °C and −40 °C contain both liquid and ice particles, and the ratio of liquid to ice particles influences how the clouds interact with radiation and moderate Earth's climate. We use a machine learning method called random forest to classify images of individual cloud particles as either liquid or ice. We apply our algorithm to images captured by aircraft within clouds overlying the Southern Ocean, and we find that it outperforms two existing algorithms.
Robert Wood
Atmos. Chem. Phys., 21, 14507–14533, https://doi.org/10.5194/acp-21-14507-2021, https://doi.org/10.5194/acp-21-14507-2021, 2021
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A simple model is described to assess the potential for increasing solar reflection by augmenting the aerosol population below marine low clouds, which increases the concentration of cloud droplets. The model is used to predict global cooling from marine cloud brightening climate intervention as a function of the quantity, size, and lifetime of salt particles injected per sprayer, the number of sprayers deployed, the cloud updraft speed, and unperturbed aerosol size distribution.
Yang Wang, Guangjie Zheng, Michael P. Jensen, Daniel A. Knopf, Alexander Laskin, Alyssa A. Matthews, David Mechem, Fan Mei, Ryan Moffet, Arthur J. Sedlacek, John E. Shilling, Stephen Springston, Amy Sullivan, Jason Tomlinson, Daniel Veghte, Rodney Weber, Robert Wood, Maria A. Zawadowicz, and Jian Wang
Atmos. Chem. Phys., 21, 11079–11098, https://doi.org/10.5194/acp-21-11079-2021, https://doi.org/10.5194/acp-21-11079-2021, 2021
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This paper reports the vertical profiles of trace gas and aerosol properties over the eastern North Atlantic, a region of persistent but diverse subtropical marine boundary layer (MBL) clouds. We examined the key processes that drive the cloud condensation nuclei (CCN) population and how it varies with season and synoptic conditions. This study helps improve the model representation of the aerosol processes in the remote MBL, reducing the simulated aerosol indirect effects.
Kristina Pistone, Paquita Zuidema, Robert Wood, Michael Diamond, Arlindo M. da Silva, Gonzalo Ferrada, Pablo E. Saide, Rei Ueyama, Ju-Mee Ryoo, Leonhard Pfister, James Podolske, David Noone, Ryan Bennett, Eric Stith, Gregory Carmichael, Jens Redemann, Connor Flynn, Samuel LeBlanc, Michal Segal-Rozenhaimer, and Yohei Shinozuka
Atmos. Chem. Phys., 21, 9643–9668, https://doi.org/10.5194/acp-21-9643-2021, https://doi.org/10.5194/acp-21-9643-2021, 2021
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Using aircraft-based measurements off the Atlantic coast of Africa, we found the springtime smoke plume was strongly correlated with the amount of water vapor in the atmosphere (more smoke indicated more humidity). We see the same general feature in satellite-assimilated and free-running models. Our analysis suggests this relationship is not caused by the burning but originates due to coincident continental meteorology plus fires. This air is transported over the ocean without further mixing.
Johannes Mohrmann, Robert Wood, Tianle Yuan, Hua Song, Ryan Eastman, and Lazaros Oreopoulos
Atmos. Chem. Phys., 21, 9629–9642, https://doi.org/10.5194/acp-21-9629-2021, https://doi.org/10.5194/acp-21-9629-2021, 2021
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Observations of marine-boundary-layer conditions are composited by cloud type, based on a new classification dataset. It is found that two cloud types, representing regions of clustered and suppressed low-level clouds, occur in very similar large-scale conditions but are distinguished from each other by considering low-level circulation and surface wind fields, validating prior results from modeling.
Maria A. Zawadowicz, Kaitlyn Suski, Jiumeng Liu, Mikhail Pekour, Jerome Fast, Fan Mei, Arthur J. Sedlacek, Stephen Springston, Yang Wang, Rahul A. Zaveri, Robert Wood, Jian Wang, and John E. Shilling
Atmos. Chem. Phys., 21, 7983–8002, https://doi.org/10.5194/acp-21-7983-2021, https://doi.org/10.5194/acp-21-7983-2021, 2021
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This paper describes the results of a recent field campaign in the eastern North Atlantic, where two mass spectrometers were deployed aboard a research aircraft to measure the chemistry of aerosols and trace gases. Very clean conditions were found, dominated by local sulfate-rich acidic aerosol and very aged organics. Evidence of
long-range transport of aerosols from the continents was also identified.
Jens Redemann, Robert Wood, Paquita Zuidema, Sarah J. Doherty, Bernadette Luna, Samuel E. LeBlanc, Michael S. Diamond, Yohei Shinozuka, Ian Y. Chang, Rei Ueyama, Leonhard Pfister, Ju-Mee Ryoo, Amie N. Dobracki, Arlindo M. da Silva, Karla M. Longo, Meloë S. Kacenelenbogen, Connor J. Flynn, Kristina Pistone, Nichola M. Knox, Stuart J. Piketh, James M. Haywood, Paola Formenti, Marc Mallet, Philip Stier, Andrew S. Ackerman, Susanne E. Bauer, Ann M. Fridlind, Gregory R. Carmichael, Pablo E. Saide, Gonzalo A. Ferrada, Steven G. Howell, Steffen Freitag, Brian Cairns, Brent N. Holben, Kirk D. Knobelspiesse, Simone Tanelli, Tristan S. L'Ecuyer, Andrew M. Dzambo, Ousmane O. Sy, Greg M. McFarquhar, Michael R. Poellot, Siddhant Gupta, Joseph R. O'Brien, Athanasios Nenes, Mary Kacarab, Jenny P. S. Wong, Jennifer D. Small-Griswold, Kenneth L. Thornhill, David Noone, James R. Podolske, K. Sebastian Schmidt, Peter Pilewskie, Hong Chen, Sabrina P. Cochrane, Arthur J. Sedlacek, Timothy J. Lang, Eric Stith, Michal Segal-Rozenhaimer, Richard A. Ferrare, Sharon P. Burton, Chris A. Hostetler, David J. Diner, Felix C. Seidel, Steven E. Platnick, Jeffrey S. Myers, Kerry G. Meyer, Douglas A. Spangenberg, Hal Maring, and Lan Gao
Atmos. Chem. Phys., 21, 1507–1563, https://doi.org/10.5194/acp-21-1507-2021, https://doi.org/10.5194/acp-21-1507-2021, 2021
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Southern Africa produces significant biomass burning emissions whose impacts on regional and global climate are poorly understood. ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) is a 5-year NASA investigation designed to study the key processes that determine these climate impacts. The main purpose of this paper is to familiarize the broader scientific community with the ORACLES project, the dataset it produced, and the most important initial findings.
Jim M. Haywood, Steven J. Abel, Paul A. Barrett, Nicolas Bellouin, Alan Blyth, Keith N. Bower, Melissa Brooks, Ken Carslaw, Haochi Che, Hugh Coe, Michael I. Cotterell, Ian Crawford, Zhiqiang Cui, Nicholas Davies, Beth Dingley, Paul Field, Paola Formenti, Hamish Gordon, Martin de Graaf, Ross Herbert, Ben Johnson, Anthony C. Jones, Justin M. Langridge, Florent Malavelle, Daniel G. Partridge, Fanny Peers, Jens Redemann, Philip Stier, Kate Szpek, Jonathan W. Taylor, Duncan Watson-Parris, Robert Wood, Huihui Wu, and Paquita Zuidema
Atmos. Chem. Phys., 21, 1049–1084, https://doi.org/10.5194/acp-21-1049-2021, https://doi.org/10.5194/acp-21-1049-2021, 2021
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Every year, the seasonal cycle of biomass burning from agricultural practices in Africa creates a huge plume of smoke that travels many thousands of kilometres over the Atlantic Ocean. This study provides an overview of a measurement campaign called the cloud–aerosol–radiation interaction and forcing for year 2017 (CLARIFY-2017) and documents the rationale, deployment strategy, observations, and key results from the campaign which utilized the heavily equipped FAAM atmospheric research aircraft.
Tianle Yuan, Hua Song, Robert Wood, Johannes Mohrmann, Kerry Meyer, Lazaros Oreopoulos, and Steven Platnick
Atmos. Meas. Tech., 13, 6989–6997, https://doi.org/10.5194/amt-13-6989-2020, https://doi.org/10.5194/amt-13-6989-2020, 2020
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We use deep transfer learning techniques to classify satellite cloud images into different morphology types. It achieves the state-of-the-art results and can automatically process a large amount of satellite data. The algorithm will help low-cloud researchers to better understand their mesoscale organizations.
Yohei Shinozuka, Pablo E. Saide, Gonzalo A. Ferrada, Sharon P. Burton, Richard Ferrare, Sarah J. Doherty, Hamish Gordon, Karla Longo, Marc Mallet, Yan Feng, Qiaoqiao Wang, Yafang Cheng, Amie Dobracki, Steffen Freitag, Steven G. Howell, Samuel LeBlanc, Connor Flynn, Michal Segal-Rosenhaimer, Kristina Pistone, James R. Podolske, Eric J. Stith, Joseph Ryan Bennett, Gregory R. Carmichael, Arlindo da Silva, Ravi Govindaraju, Ruby Leung, Yang Zhang, Leonhard Pfister, Ju-Mee Ryoo, Jens Redemann, Robert Wood, and Paquita Zuidema
Atmos. Chem. Phys., 20, 11491–11526, https://doi.org/10.5194/acp-20-11491-2020, https://doi.org/10.5194/acp-20-11491-2020, 2020
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In the southeast Atlantic, well-defined smoke plumes from Africa advect over marine boundary layer cloud decks; both are most extensive around September, when most of the smoke resides in the free troposphere. A framework is put forth for evaluating the performance of a range of global and regional atmospheric composition models against observations made during the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) airborne mission in September 2016.
Francesca Gallo, Janek Uin, Stephen Springston, Jian Wang, Guangjie Zheng, Chongai Kuang, Robert Wood, Eduardo B. Azevedo, Allison McComiskey, Fan Mei, Adam Theisen, Jenni Kyrouac, and Allison C. Aiken
Atmos. Chem. Phys., 20, 7553–7573, https://doi.org/10.5194/acp-20-7553-2020, https://doi.org/10.5194/acp-20-7553-2020, 2020
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Continuous high-time-resolution ambient data can include periods when aerosol properties do not represent regional aerosol processes due to high-concentration local events. We develop a novel aerosol mask at the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) facility in the eastern North Atlantic (ENA). We use two ground sites to validate the mask, include a comparison with aircraft overflights, and provide guidance to increase data quality at ENA and other locations.
Mary Kacarab, K. Lee Thornhill, Amie Dobracki, Steven G. Howell, Joseph R. O'Brien, Steffen Freitag, Michael R. Poellot, Robert Wood, Paquita Zuidema, Jens Redemann, and Athanasios Nenes
Atmos. Chem. Phys., 20, 3029–3040, https://doi.org/10.5194/acp-20-3029-2020, https://doi.org/10.5194/acp-20-3029-2020, 2020
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We find that extensive biomass burning aerosol plumes from southern Africa can profoundly influence clouds in the southeastern Atlantic. Concurrent variations in vertical velocity, however, are found to magnify the relationship between boundary layer aerosol and the cloud droplet number. Neglecting these covariances may strongly bias the sign and magnitude of aerosol impacts on the cloud droplet number.
Sam Pennypacker, Michael Diamond, and Robert Wood
Atmos. Chem. Phys., 20, 2341–2351, https://doi.org/10.5194/acp-20-2341-2020, https://doi.org/10.5194/acp-20-2341-2020, 2020
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Using observations from instruments deployed to a small island in the southeast Atlantic, we study days when the atmospheric concentrations of particles near the surface are exceptionally low. Interestingly, these ultra-clean boundary layers occur in the same months as the smokiest boundary layers associated with biomass burning in Africa. We find evidence that enhancements in drizzle scavenging, on top of a seasonal maximum in cloudiness and precipitation, likely drive these conditions.
Samuel E. LeBlanc, Jens Redemann, Connor Flynn, Kristina Pistone, Meloë Kacenelenbogen, Michal Segal-Rosenheimer, Yohei Shinozuka, Stephen Dunagan, Robert P. Dahlgren, Kerry Meyer, James Podolske, Steven G. Howell, Steffen Freitag, Jennifer Small-Griswold, Brent Holben, Michael Diamond, Robert Wood, Paola Formenti, Stuart Piketh, Gillian Maggs-Kölling, Monja Gerber, and Andreas Namwoonde
Atmos. Chem. Phys., 20, 1565–1590, https://doi.org/10.5194/acp-20-1565-2020, https://doi.org/10.5194/acp-20-1565-2020, 2020
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The southeast Atlantic during August–October experiences layers of smoke from biomass burning over marine stratocumulus clouds. Here we present the light attenuation of the smoke and its dependence in the spatial, vertical, and spectral domain through direct measurements from an airborne platform during September 2016. From our observations of this climatically important smoke, we found an average aerosol optical depth of 0.32 at 500 nm, slightly lower than comparative satellite measurements.
Marc Mallet, Pierre Nabat, Paquita Zuidema, Jens Redemann, Andrew Mark Sayer, Martin Stengel, Sebastian Schmidt, Sabrina Cochrane, Sharon Burton, Richard Ferrare, Kerry Meyer, Pablo Saide, Hiren Jethva, Omar Torres, Robert Wood, David Saint Martin, Romain Roehrig, Christina Hsu, and Paola Formenti
Atmos. Chem. Phys., 19, 4963–4990, https://doi.org/10.5194/acp-19-4963-2019, https://doi.org/10.5194/acp-19-4963-2019, 2019
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The model is able to represent LWP but not the LCF. AOD is consistent over the continent but also over ocean (ACAOD). Differences are observed in SSA due to the absence of internal mixing in ALADIN-Climate. A significant regional gradient of the forcing at TOA is observed. An intense positive forcing is simulated over Gabon. Results highlight the significant effect of enhanced moisture on BBA extinction. The surface dimming modifies the energy budget.
Guangjie Zheng, Yang Wang, Allison C. Aiken, Francesca Gallo, Michael P. Jensen, Pavlos Kollias, Chongai Kuang, Edward Luke, Stephen Springston, Janek Uin, Robert Wood, and Jian Wang
Atmos. Chem. Phys., 18, 17615–17635, https://doi.org/10.5194/acp-18-17615-2018, https://doi.org/10.5194/acp-18-17615-2018, 2018
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Here, we elucidate the key processes that drive marine boundary layer (MBL) aerosol size distribution in the eastern North Atlantic (ENA) using long-term measurements. The governing equations of particle concentration are established for different modes. Particles entrained from the free troposphere represent the major source of MBL cloud condensation nuclei (CCN), contributing both directly to CCN population and indirectly by supplying Aitken-mode particles that grow to CCN in the MBL.
Anna Possner, Hailong Wang, Robert Wood, Ken Caldeira, and Thomas P. Ackerman
Atmos. Chem. Phys., 18, 17475–17488, https://doi.org/10.5194/acp-18-17475-2018, https://doi.org/10.5194/acp-18-17475-2018, 2018
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We quantify aerosol–cloud radiative interactions in a regime of deep open-cell stratocumuli (boundary layer depth 1.5 km), a regime which remains largely unexplored within this context and yet is more dominant than cases of shallow stratocumuli previously studied. We simulate substantial increases in albedo in a regime where ship tracks are not found and argue that such changes may escape detection and attribution through remote sensing due to the large natural variability in the system.
Michael S. Diamond, Amie Dobracki, Steffen Freitag, Jennifer D. Small Griswold, Ashley Heikkila, Steven G. Howell, Mary E. Kacarab, James R. Podolske, Pablo E. Saide, and Robert Wood
Atmos. Chem. Phys., 18, 14623–14636, https://doi.org/10.5194/acp-18-14623-2018, https://doi.org/10.5194/acp-18-14623-2018, 2018
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Smoke from Africa can mix into clouds over the southeast Atlantic and create new droplets, which brightens the clouds, reflects more sunlight, and thus cools the region. Using aircraft data from a NASA field campaign, we find that cloud properties are correlated with smoke as expected when the smoke is below the clouds but not when smoke is above the clouds because it takes several days for clouds to mix smoke downward. We recommend methods that can track clouds as they move for future studies.
Daniel P. Grosvenor, Odran Sourdeval, and Robert Wood
Atmos. Meas. Tech., 11, 4273–4289, https://doi.org/10.5194/amt-11-4273-2018, https://doi.org/10.5194/amt-11-4273-2018, 2018
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We provide a parameterized correction to the retrieval of cloud effective radius from satellite instruments to account for the assumption that the retrieved value is representative of that at cloud top, whereas in reality it is representative of that lower down. The error leads to errors (which we quantify) in the retrieved cloud droplet concentrations of up to 38 % for stratocumulus regions and also to liquid water path errors, both of which can be corrected using our parameterizations.
Daniel T. McCoy, Frida A.-M. Bender, Daniel P. Grosvenor, Johannes K. Mohrmann, Dennis L. Hartmann, Robert Wood, and Paul R. Field
Atmos. Chem. Phys., 18, 2035–2047, https://doi.org/10.5194/acp-18-2035-2018, https://doi.org/10.5194/acp-18-2035-2018, 2018
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The interaction between clouds and aerosols represents the largest source of uncertainty in the anthropogenic radiative forcing. Cloud droplet number concentration (CDNC) is the state variable that moderates the interaction between aerosol and clouds. Here we show that CDNC decreases off the coasts of East Asia and North America due to controls on emissions. We support this analysis through an examination of volcanism in Hawaii and Vanuatu.
Xiaoli Zhou, Andrew S. Ackerman, Ann M. Fridlind, Robert Wood, and Pavlos Kollias
Atmos. Chem. Phys., 17, 12725–12742, https://doi.org/10.5194/acp-17-12725-2017, https://doi.org/10.5194/acp-17-12725-2017, 2017
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Shallow maritime clouds make a well-known transition from stratocumulus to trade cumulus with flow from the subtropics equatorward. Three-day large-eddy simulations that investigate the potential influence of overlying African biomass burning plumes during that transition indicate that cloud-related impacts are likely substantially cooling to negligible at the top of the atmosphere, with magnitude sensitive to background and perturbation aerosol and cloud properties.
C. R. Terai, C. S. Bretherton, R. Wood, and G. Painter
Atmos. Chem. Phys., 14, 8071–8088, https://doi.org/10.5194/acp-14-8071-2014, https://doi.org/10.5194/acp-14-8071-2014, 2014
D. P. Grosvenor and R. Wood
Atmos. Chem. Phys., 14, 7291–7321, https://doi.org/10.5194/acp-14-7291-2014, https://doi.org/10.5194/acp-14-7291-2014, 2014
A. Muhlbauer, I. L. McCoy, and R. Wood
Atmos. Chem. Phys., 14, 6695–6716, https://doi.org/10.5194/acp-14-6695-2014, https://doi.org/10.5194/acp-14-6695-2014, 2014
A. H. Berner, C. S. Bretherton, R. Wood, and A. Muhlbauer
Atmos. Chem. Phys., 13, 12549–12572, https://doi.org/10.5194/acp-13-12549-2013, https://doi.org/10.5194/acp-13-12549-2013, 2013
C. R. Terai and R. Wood
Atmos. Chem. Phys., 13, 9899–9914, https://doi.org/10.5194/acp-13-9899-2013, https://doi.org/10.5194/acp-13-9899-2013, 2013
A. Gettelman, H. Morrison, C. R. Terai, and R. Wood
Atmos. Chem. Phys., 13, 9855–9867, https://doi.org/10.5194/acp-13-9855-2013, https://doi.org/10.5194/acp-13-9855-2013, 2013
R. C. George, R. Wood, C. S. Bretherton, and G. Painter
Atmos. Chem. Phys., 13, 6305–6328, https://doi.org/10.5194/acp-13-6305-2013, https://doi.org/10.5194/acp-13-6305-2013, 2013
C. H. Twohy, J. R. Anderson, D. W. Toohey, M. Andrejczuk, A. Adams, M. Lytle, R. C. George, R. Wood, P. Saide, S. Spak, P. Zuidema, and D. Leon
Atmos. Chem. Phys., 13, 2541–2562, https://doi.org/10.5194/acp-13-2541-2013, https://doi.org/10.5194/acp-13-2541-2013, 2013
Related subject area
Subject: Clouds and Precipitation | Research Activity: Laboratory Studies | Altitude Range: Troposphere | Science Focus: Physics (physical properties and processes)
Stable and unstable fall motions of plate-like ice crystal analogues
Secondary ice production – no evidence of efficient rime-splintering mechanism
Fragmentation of ice particles: laboratory experiments on graupel–graupel and graupel–snowflake collisions
Molecular simulations reveal that heterogeneous ice nucleation occurs at higher temperatures in water under capillary tension
Measurement of the collision rate coefficients between atmospheric ions and multiply charged aerosol particles in the CERN CLOUD chamber
Re-evaluating cloud chamber constraints on depositional ice growth in cirrus clouds – Part 1: Model description and sensitivity tests
Ice nucleation by smectites: the role of the edges
A single-parameter hygroscopicity model for functionalized insoluble aerosol surfaces
Mexican agricultural soil dust as a source of ice nucleating particles
The impact of (bio-)organic substances on the ice nucleation activity of the K-feldspar microcline in aqueous solutions
Secondary ice production during the break-up of freezing water drops on impact with ice particles
High homogeneous freezing onsets of sulfuric acid aerosol at cirrus temperatures
Laboratory and field studies of ice-nucleating particles from open-lot livestock facilities in Texas
Comment on “Review of experimental studies of secondary ice production” by Korolev and Leisner (2020)
Effect of chemically induced fracturing on the ice nucleation activity of alkali feldspar
Ice nucleation ability of ammonium sulfate aerosol particles internally mixed with secondary organics
Ice-nucleating particles in precipitation samples from the Texas Panhandle
Comparative study on immersion freezing utilizing single-droplet levitation methods
Exploratory experiments on pre-activated freezing nucleation on mercuric iodide
Application of holography and automated image processing for laboratory experiments on mass and fall speed of small cloud ice crystals
Review of experimental studies of secondary ice production
The role of contact angle and pore width on pore condensation and freezing
Technical note: Equilibrium droplet size distributions in a turbulent cloud chamber with uniform supersaturation
Protein aggregates nucleate ice: the example of apoferritin
No anomalous supersaturation in ultracold cirrus laboratory experiments
Lateral facet growth of ice and snow – Part 1: Observations and applications to secondary habits
The ice-nucleating ability of quartz immersed in water and its atmospheric importance compared to K-feldspar
Ice nucleation properties of K-feldspar polymorphs and plagioclase feldspars
Enhanced ice nucleation activity of coal fly ash aerosol particles initiated by ice-filled pores
A comprehensive characterization of ice nucleation by three different types of cellulose particles immersed in water
Activation of intact bacteria and bacterial fragments mixed with agar as cloud droplets and ice crystals in cloud chamber experiments
Anomalous holiday precipitation over southern China
Coal fly ash: linking immersion freezing behavior and physicochemical particle properties
Surface roughness during depositional growth and sublimation of ice crystals
Ice nucleation abilities of soot particles determined with the Horizontal Ice Nucleation Chamber
The efficiency of secondary organic aerosol particles acting as ice-nucleating particles under mixed-phase cloud conditions
Uncertainty in counting ice nucleating particles with continuous flow diffusion chambers
Experimental evidence of the rear capture of aerosol particles by raindrops
Refreeze experiments with water droplets containing different types of ice nuclei interpreted by classical nucleation theory
Pre-activation of aerosol particles by ice preserved in pores
Heterogeneous ice nucleation on dust particles sourced from nine deserts worldwide – Part 1: Immersion freezing
A comparative study of K-rich and Na/Ca-rich feldspar ice-nucleating particles in a nanoliter droplet freezing assay
Ice nucleation efficiency of AgI: review and new insights
The adsorption of fungal ice-nucleating proteins on mineral dusts: a terrestrial reservoir of atmospheric ice-nucleating particles
Cloud chamber experiments on the origin of ice crystal complexity in cirrus clouds
Phase transition observations and discrimination of small cloud particles by light polarization in expansion chamber experiments
Analysis of isothermal and cooling-rate-dependent immersion freezing by a unifying stochastic ice nucleation model
Pre-activation of ice-nucleating particles by the pore condensation and freezing mechanism
Influence of the ambient humidity on the concentration of natural deposition-mode ice-nucleating particles
Comparison of measured and calculated collision efficiencies at low temperatures
Jennifer R. Stout, Christopher D. Westbrook, Thorwald H. M. Stein, and Mark W. McCorquodale
Atmos. Chem. Phys., 24, 11133–11155, https://doi.org/10.5194/acp-24-11133-2024, https://doi.org/10.5194/acp-24-11133-2024, 2024
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This study uses 3D-printed ice crystal analogues falling in a water–glycerine mix and observed with multi-view cameras, simulating atmospheric conditions. Four types of motion are observed: stable, zigzag, transitional, and spiralling. Particle shape strongly influences motion; complex shapes have a wider range of conditions where they fall steadily compared to simple plates. The most common orientation of unstable particles is non-horizontal, contrary to prior assumptions of always horizontal.
Johanna S. Seidel, Alexei A. Kiselev, Alice Keinert, Frank Stratmann, Thomas Leisner, and Susan Hartmann
Atmos. Chem. Phys., 24, 5247–5263, https://doi.org/10.5194/acp-24-5247-2024, https://doi.org/10.5194/acp-24-5247-2024, 2024
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Clouds often contain several thousand times more ice crystals than aerosol particles catalyzing ice formation. This phenomenon, commonly known as ice multiplication, is often explained by secondary ice formation due to the collisions between falling ice particles and droplets. In this study, we mimic this riming process. Contrary to earlier experiments, we found no efficient ice multiplication, which fundamentally questions the importance of the rime-splintering mechanism.
Pierre Grzegorczyk, Sudha Yadav, Florian Zanger, Alexander Theis, Subir K. Mitra, Stephan Borrmann, and Miklós Szakáll
Atmos. Chem. Phys., 23, 13505–13521, https://doi.org/10.5194/acp-23-13505-2023, https://doi.org/10.5194/acp-23-13505-2023, 2023
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Secondary ice production generates high concentrations of ice crystals in clouds. These processes have been poorly understood. We conducted experiments at the wind tunnel laboratory of the Johannes Gutenberg University, Mainz, on graupel–graupel and graupel–snowflake collisions. From these experiments fragment number, size, cross-sectional area, and aspect ratio were determined.
Elise Rosky, Will Cantrell, Tianshu Li, Issei Nakamura, and Raymond A. Shaw
Atmos. Chem. Phys., 23, 10625–10642, https://doi.org/10.5194/acp-23-10625-2023, https://doi.org/10.5194/acp-23-10625-2023, 2023
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Using computer simulations of water, we find that water under tension freezes more easily than under normal conditions. A linear equation describes how freezing temperature increases with tension. Accordingly, simulations show that naturally occurring tension in water capillary bridges leads to higher freezing temperatures. This work is an early step in determining if atmospheric cloud droplets freeze due to naturally occurring tension, for example, during processes such as droplet collisions.
Joschka Pfeifer, Naser G. A. Mahfouz, Benjamin C. Schulze, Serge Mathot, Dominik Stolzenburg, Rima Baalbaki, Zoé Brasseur, Lucia Caudillo, Lubna Dada, Manuel Granzin, Xu-Cheng He, Houssni Lamkaddam, Brandon Lopez, Vladimir Makhmutov, Ruby Marten, Bernhard Mentler, Tatjana Müller, Antti Onnela, Maxim Philippov, Ana A. Piedehierro, Birte Rörup, Meredith Schervish, Ping Tian, Nsikanabasi S. Umo, Dongyu S. Wang, Mingyi Wang, Stefan K. Weber, André Welti, Yusheng Wu, Marcel Zauner-Wieczorek, Antonio Amorim, Imad El Haddad, Markku Kulmala, Katrianne Lehtipalo, Tuukka Petäjä, António Tomé, Sander Mirme, Hanna E. Manninen, Neil M. Donahue, Richard C. Flagan, Andreas Kürten, Joachim Curtius, and Jasper Kirkby
Atmos. Chem. Phys., 23, 6703–6718, https://doi.org/10.5194/acp-23-6703-2023, https://doi.org/10.5194/acp-23-6703-2023, 2023
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Attachment rate coefficients between ions and charged aerosol particles determine their lifetimes and may also influence cloud dynamics and aerosol processing. Here we present novel experiments that measure ion–aerosol attachment rate coefficients for multiply charged aerosol particles under atmospheric conditions in the CERN CLOUD chamber. Our results provide experimental discrimination between various theoretical models.
Kara D. Lamb, Jerry Y. Harrington, Benjamin W. Clouser, Elisabeth J. Moyer, Laszlo Sarkozy, Volker Ebert, Ottmar Möhler, and Harald Saathoff
Atmos. Chem. Phys., 23, 6043–6064, https://doi.org/10.5194/acp-23-6043-2023, https://doi.org/10.5194/acp-23-6043-2023, 2023
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This study investigates how ice grows directly from vapor in cirrus clouds by comparing observations of populations of ice crystals growing in a cloud chamber against models developed in the context of single-crystal laboratory studies. We demonstrate that previous discrepancies between different experimental measurements do not necessarily point to different physical interpretations but are rather due to assumptions that were made in terms of how experiments were modeled in previous studies.
Anand Kumar, Kristian Klumpp, Chen Barak, Giora Rytwo, Michael Plötze, Thomas Peter, and Claudia Marcolli
Atmos. Chem. Phys., 23, 4881–4902, https://doi.org/10.5194/acp-23-4881-2023, https://doi.org/10.5194/acp-23-4881-2023, 2023
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Smectites are a major class of clay minerals that are ice nucleation (IN) active. They form platelets that swell or even delaminate in water by intercalation of water between their layers. We hypothesize that at least three smectite layers need to be stacked together to host a critical ice embryo on clay mineral edges and that the larger the surface edge area is, the higher the freezing temperature. Edge sites on such clay particles play a crucial role in imparting IN ability to such particles.
Chun-Ning Mao, Kanishk Gohil, and Akua A. Asa-Awuku
Atmos. Chem. Phys., 22, 13219–13228, https://doi.org/10.5194/acp-22-13219-2022, https://doi.org/10.5194/acp-22-13219-2022, 2022
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The impact of molecular-level surface chemistry for aerosol water uptake and droplet growth is not well understood. In this work we show changes in water uptake due to molecular-level surface chemistry can be measured and quantified. In addition, we develop a single-parameter model, representing changes in aerosol chemistry that can be used in global climate models to reduce the uncertainty in aerosol-cloud predictions.
Diana L. Pereira, Irma Gavilán, Consuelo Letechipía, Graciela B. Raga, Teresa Pi Puig, Violeta Mugica-Álvarez, Harry Alvarez-Ospina, Irma Rosas, Leticia Martinez, Eva Salinas, Erika T. Quintana, Daniel Rosas, and Luis A. Ladino
Atmos. Chem. Phys., 22, 6435–6447, https://doi.org/10.5194/acp-22-6435-2022, https://doi.org/10.5194/acp-22-6435-2022, 2022
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Airborne particles were i) collected in an agricultural fields and ii) generated in the laboratory from agricultural soil samples to analyze their ice nucleating abilities. It was found that the size and chemical composition of the Mexican agricultural dust particles influence their ice nucleating behavior, where the organic components are likely responsible for their efficiency as INPs. The INP concentrations from the present study are comparable to those from higher latitudes.
Kristian Klumpp, Claudia Marcolli, and Thomas Peter
Atmos. Chem. Phys., 22, 3655–3673, https://doi.org/10.5194/acp-22-3655-2022, https://doi.org/10.5194/acp-22-3655-2022, 2022
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Surface interactions with solutes can significantly alter the ice nucleation activity of mineral dust. Past studies revealed the sensitivity of microcline, one of the most ice-active types of dust in the atmosphere, to inorganic solutes. This study focuses on the interaction of microcline with bio-organic substances and the resulting effects on its ice nucleation activity. We observe strongly hampered ice nucleation activity due to the presence of carboxylic and amino acids but not for polyols.
Rachel L. James, Vaughan T. J. Phillips, and Paul J. Connolly
Atmos. Chem. Phys., 21, 18519–18530, https://doi.org/10.5194/acp-21-18519-2021, https://doi.org/10.5194/acp-21-18519-2021, 2021
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Secondary ice production (SIP) plays an important role in ice formation within mixed-phase clouds. We present a laboratory investigation of a potentially new SIP mechanism involving the collisions of supercooled water drops with ice particles. At impact, the supercooled water drop fragments form smaller secondary drops. Approximately 30 % of the secondary drops formed during the retraction phase of the supercooled water drop impact freeze over a temperature range of −4 °C to −12 °C.
Julia Schneider, Kristina Höhler, Robert Wagner, Harald Saathoff, Martin Schnaiter, Tobias Schorr, Isabelle Steinke, Stefan Benz, Manuel Baumgartner, Christian Rolf, Martina Krämer, Thomas Leisner, and Ottmar Möhler
Atmos. Chem. Phys., 21, 14403–14425, https://doi.org/10.5194/acp-21-14403-2021, https://doi.org/10.5194/acp-21-14403-2021, 2021
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Homogeneous freezing is a relevant mechanism for the formation of cirrus clouds in the upper troposphere. Based on an extensive set of homogeneous freezing experiments at the AIDA chamber with aqueous sulfuric acid aerosol, we provide a new fit line for homogeneous freezing onset conditions of sulfuric acid aerosol focusing on cirrus temperatures. In the atmosphere, homogeneous freezing thresholds have important implications on the cirrus cloud occurrence and related cloud radiative effects.
Naruki Hiranuma, Brent W. Auvermann, Franco Belosi, Jack Bush, Kimberly M. Cory, Dimitrios G. Georgakopoulos, Kristina Höhler, Yidi Hou, Larissa Lacher, Harald Saathoff, Gianni Santachiara, Xiaoli Shen, Isabelle Steinke, Romy Ullrich, Nsikanabasi S. Umo, Hemanth S. K. Vepuri, Franziska Vogel, and Ottmar Möhler
Atmos. Chem. Phys., 21, 14215–14234, https://doi.org/10.5194/acp-21-14215-2021, https://doi.org/10.5194/acp-21-14215-2021, 2021
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We present laboratory and field studies showing that an open-lot livestock facility is a substantial source of atmospheric ice-nucleating particles (INPs). The ambient concentration of INPs from livestock facilities in Texas is very high. It is up to several thousand INPs per liter below –20 °C and may impact regional aerosol–cloud interactions. About 50% of feedlot INPs were supermicron in diameter. No notable amount of known ice-nucleating microorganisms was found in our feedlot samples.
Vaughan T. J. Phillips, Jun-Ichi Yano, Akash Deshmukh, and Deepak Waman
Atmos. Chem. Phys., 21, 11941–11953, https://doi.org/10.5194/acp-21-11941-2021, https://doi.org/10.5194/acp-21-11941-2021, 2021
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For decades, high concentrations of ice observed in precipitating mixed-phase clouds have created an enigma. Such concentrations are higher than can be explained by the action of aerosols or by the spontaneous freezing of most cloud droplets. The controversy has partly persisted due to the lack of laboratory experimentation in ice microphysics, especially regarding fragmentation of ice, a topic reviewed by a recent paper. Our comment attempts to clarify some issues with regards to that review.
Alexei A. Kiselev, Alice Keinert, Tilia Gaedeke, Thomas Leisner, Christoph Sutter, Elena Petrishcheva, and Rainer Abart
Atmos. Chem. Phys., 21, 11801–11814, https://doi.org/10.5194/acp-21-11801-2021, https://doi.org/10.5194/acp-21-11801-2021, 2021
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Alkali feldspar is the most abundant mineral in the Earth's crust and is often present in mineral dust aerosols that are responsible for the formation of rain and snow in clouds. However, the cloud droplets containing pure potassium-rich feldspar would not freeze unless cooled down to a very low temperature. Here we show that partly replacing potassium with sodium would induce fracturing of feldspar, exposing a crystalline surface that could initiate freezing at higher temperature.
Barbara Bertozzi, Robert Wagner, Junwei Song, Kristina Höhler, Joschka Pfeifer, Harald Saathoff, Thomas Leisner, and Ottmar Möhler
Atmos. Chem. Phys., 21, 10779–10798, https://doi.org/10.5194/acp-21-10779-2021, https://doi.org/10.5194/acp-21-10779-2021, 2021
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Internally mixed particles composed of sulfate and organics are among the most abundant aerosol types. Their ice nucleation (IN) ability influences the formation of cirrus and, thus, the climate. We show that the presence of a thin organic coating suppresses the heterogeneous IN ability of crystalline ammonium sulfate particles. However, the IN ability of the same particle can substantially change if subjected to atmospheric processing, mainly due to differences in the resulting morphology.
Hemanth S. K. Vepuri, Cheyanne A. Rodriguez, Dimitrios G. Georgakopoulos, Dustin Hume, James Webb, Gregory D. Mayer, and Naruki Hiranuma
Atmos. Chem. Phys., 21, 4503–4520, https://doi.org/10.5194/acp-21-4503-2021, https://doi.org/10.5194/acp-21-4503-2021, 2021
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Due to a high frequency of storm events, West Texas is an ideal location to study ice-nucleating particles (INPs) in severe precipitation. Our results present that cumulative INP concentration in our precipitation samples below −20 °C could be high in the samples collected while observing > 10 mm h−1 precipitation with notably large hydrometeor sizes and an implication of cattle feedyard bacteria inclusion. Marine bacteria were found in a subset of our precipitation and cattle feedyard samples.
Miklós Szakáll, Michael Debertshäuser, Christian Philipp Lackner, Amelie Mayer, Oliver Eppers, Karoline Diehl, Alexander Theis, Subir Kumar Mitra, and Stephan Borrmann
Atmos. Chem. Phys., 21, 3289–3316, https://doi.org/10.5194/acp-21-3289-2021, https://doi.org/10.5194/acp-21-3289-2021, 2021
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The freezing of cloud drops is promoted by ice-nucleating particles immersed in the drops. This process is essential to understand ice and subsequent precipitation formation in clouds. We investigated the efficiency of several particle types to trigger immersion freezing with two single-drop levitation techniques: a wind tunnel and an acoustic levitator. The evaluation accounted for different conditions during our two series of experiments, which is also applicable to future comparison studies.
Gabor Vali
Atmos. Chem. Phys., 21, 2551–2568, https://doi.org/10.5194/acp-21-2551-2021, https://doi.org/10.5194/acp-21-2551-2021, 2021
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The freezing of water drops in clouds is a prime example for the role of ice-nucleating particles (INPs). Mercuric iodide particles and a few other substances can be conditioned to become very effective INPs after previous ice formation and moderate heating to melt temperatures, opening a new pathway to ice formation in the atmosphere and in other systems like tissue preservation, artificial snow making, and more.
Maximilian Weitzel, Subir K. Mitra, Miklós Szakáll, Jacob P. Fugal, and Stephan Borrmann
Atmos. Chem. Phys., 20, 14889–14901, https://doi.org/10.5194/acp-20-14889-2020, https://doi.org/10.5194/acp-20-14889-2020, 2020
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The properties of ice crystals smaller than 150 µm in diameter were investigated in a cold-room laboratory using digital holography and microscopy. Automated image processing has been used to determine the track of falling ice crystals, and collected crystals were melted and scanned under a microscope to infer particle mass. A parameterization relating particle size and mass was determined which describes ice crystals in this size range more accurately than existing relationships.
Alexei Korolev and Thomas Leisner
Atmos. Chem. Phys., 20, 11767–11797, https://doi.org/10.5194/acp-20-11767-2020, https://doi.org/10.5194/acp-20-11767-2020, 2020
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Secondary ice production (SIP) plays a key role in the formation of ice particles in tropospheric clouds. This work presents a critical review of the laboratory studies related to secondary ice production. It aims to identify gaps in our knowledge of SIP as well as to stimulate further laboratory studies focused on obtaining a quantitative description of efficiencies for each SIP mechanism.
Robert O. David, Jonas Fahrni, Claudia Marcolli, Fabian Mahrt, Dominik Brühwiler, and Zamin A. Kanji
Atmos. Chem. Phys., 20, 9419–9440, https://doi.org/10.5194/acp-20-9419-2020, https://doi.org/10.5194/acp-20-9419-2020, 2020
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Ice crystal formation plays an important role in controlling the Earth's climate. However, the mechanisms responsible for ice formation in the atmosphere are still uncertain. Here we use surrogates for atmospherically relevant porous particles to determine the role of pore diameter and wettability on the ability of porous particles to nucleate ice in the atmosphere. Our results are consistent with the pore condensation and freeing mechanism.
Steven K. Krueger
Atmos. Chem. Phys., 20, 7895–7909, https://doi.org/10.5194/acp-20-7895-2020, https://doi.org/10.5194/acp-20-7895-2020, 2020
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When CCN are injected into a turbulent cloud chamber at a constant rate, and the rate of droplet activation is balanced by the rate of droplet fallout, a steady-state droplet size distribution (DSD) can be achieved. Analytic DSDs and PDFs of droplet radius were derived for such conditions when there is uniform supersaturation. Given the chamber height, the analytic PDF is determined by the supersaturation alone. This could allow one to infer the supersaturation that produced a measured PDF.
María Cascajo-Castresana, Robert O. David, Maiara A. Iriarte-Alonso, Alexander M. Bittner, and Claudia Marcolli
Atmos. Chem. Phys., 20, 3291–3315, https://doi.org/10.5194/acp-20-3291-2020, https://doi.org/10.5194/acp-20-3291-2020, 2020
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Atmospheric ice-nucleating particles are rare but relevant for cloud glaciation. A source of particles that nucleate ice above −15 °C is biological material including some proteins. Here we show that proteins of very diverse functions and structures can nucleate ice. Among these, the iron storage protein apoferritin stands out, with activity up to −4 °C. We show that its activity does not stem from correctly assembled proteins but from misfolded protein monomers or oligomers and aggregates.
Benjamin W. Clouser, Kara D. Lamb, Laszlo C. Sarkozy, Jan Habig, Volker Ebert, Harald Saathoff, Ottmar Möhler, and Elisabeth J. Moyer
Atmos. Chem. Phys., 20, 1089–1103, https://doi.org/10.5194/acp-20-1089-2020, https://doi.org/10.5194/acp-20-1089-2020, 2020
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Previous measurements of water vapor in the upper troposphere and lower stratosphere (UT/LS) have shown unexpectedly high concentrations of water vapor in ice clouds, which may be due to an incomplete understanding of the structure of ice and the behavior of ice growth in this part of the atmosphere. Water vapor measurements during the 2013 IsoCloud campaign at the AIDA cloud chamber show no evidence of this
anomalous supersaturationin conditions similar to the real atmosphere.
Jon Nelson and Brian D. Swanson
Atmos. Chem. Phys., 19, 15285–15320, https://doi.org/10.5194/acp-19-15285-2019, https://doi.org/10.5194/acp-19-15285-2019, 2019
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Ice crystals in clouds have a wide variety. But many crystal forms are inexplicable using the common approach of modeling the growth rates normal to the crystal faces. Instead of using only this normal-growth approach, we suggest including lateral facet growth processes. Using such lateral processes, backed up by new experiments, we give explanations for some of these puzzling forms. The forms include the center droxtal in stellar crystals, scrolls, capped columns, sheath bundles, and trigonals.
Alexander D. Harrison, Katherine Lever, Alberto Sanchez-Marroquin, Mark A. Holden, Thomas F. Whale, Mark D. Tarn, James B. McQuaid, and Benjamin J. Murray
Atmos. Chem. Phys., 19, 11343–11361, https://doi.org/10.5194/acp-19-11343-2019, https://doi.org/10.5194/acp-19-11343-2019, 2019
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Mineral dusts are a source of ice-nucleating particles (INPs) in the atmosphere. Here we present a comprehensive survey of the ice-nucleating ability of naturally occurring quartz. We show the ice-nucleating variability of quartz and its sensitivity to time spent in water and air. We propose four new parameterizations for the minerals quartz, K feldspar, albite and plagioclase to predict INP concentrations in the atmosphere and show that K-feldspar is the dominant INP type in mineral dusts.
André Welti, Ulrike Lohmann, and Zamin A. Kanji
Atmos. Chem. Phys., 19, 10901–10918, https://doi.org/10.5194/acp-19-10901-2019, https://doi.org/10.5194/acp-19-10901-2019, 2019
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The ice nucleation ability of singly immersed feldspar particles in suspended water droplets relevant for ice crystal formation under mixed-phase cloud conditions is presented. The effects of particle size, crystal structure, trace metal and mineralogical composition are discussed by testing up to five different diameters in the submicron range and nine different feldspar samples at conditions relevant for ice nucleation in mixed-phase clouds.
Nsikanabasi Silas Umo, Robert Wagner, Romy Ullrich, Alexei Kiselev, Harald Saathoff, Peter G. Weidler, Daniel J. Cziczo, Thomas Leisner, and Ottmar Möhler
Atmos. Chem. Phys., 19, 8783–8800, https://doi.org/10.5194/acp-19-8783-2019, https://doi.org/10.5194/acp-19-8783-2019, 2019
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Annually, over 600 Tg of coal fly ash (CFA) is produced; a significant proportion of this amount is injected into the atmosphere, which could significantly contribute to heterogeneous ice formation in clouds. This study presents an improved understanding of CFA particles' behaviour in forming ice in clouds, especially when exposed to lower temperatures before being re-circulated in the upper troposphere or entrained into the lower troposphere.
Naruki Hiranuma, Kouji Adachi, David M. Bell, Franco Belosi, Hassan Beydoun, Bhaskar Bhaduri, Heinz Bingemer, Carsten Budke, Hans-Christian Clemen, Franz Conen, Kimberly M. Cory, Joachim Curtius, Paul J. DeMott, Oliver Eppers, Sarah Grawe, Susan Hartmann, Nadine Hoffmann, Kristina Höhler, Evelyn Jantsch, Alexei Kiselev, Thomas Koop, Gourihar Kulkarni, Amelie Mayer, Masataka Murakami, Benjamin J. Murray, Alessia Nicosia, Markus D. Petters, Matteo Piazza, Michael Polen, Naama Reicher, Yinon Rudich, Atsushi Saito, Gianni Santachiara, Thea Schiebel, Gregg P. Schill, Johannes Schneider, Lior Segev, Emiliano Stopelli, Ryan C. Sullivan, Kaitlyn Suski, Miklós Szakáll, Takuya Tajiri, Hans Taylor, Yutaka Tobo, Romy Ullrich, Daniel Weber, Heike Wex, Thomas F. Whale, Craig L. Whiteside, Katsuya Yamashita, Alla Zelenyuk, and Ottmar Möhler
Atmos. Chem. Phys., 19, 4823–4849, https://doi.org/10.5194/acp-19-4823-2019, https://doi.org/10.5194/acp-19-4823-2019, 2019
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A total of 20 ice nucleation measurement techniques contributed to investigate the immersion freezing behavior of cellulose particles – natural polymers. Our data showed several types of cellulose are able to nucleate ice as efficiently as some mineral dust samples and cellulose has the potential to be an important atmospheric ice-nucleating particle. Continued investigation/collaboration is necessary to obtain further insight into consistency or diversity of ice nucleation measurements.
Kaitlyn J. Suski, David M. Bell, Naruki Hiranuma, Ottmar Möhler, Dan Imre, and Alla Zelenyuk
Atmos. Chem. Phys., 18, 17497–17513, https://doi.org/10.5194/acp-18-17497-2018, https://doi.org/10.5194/acp-18-17497-2018, 2018
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This work investigates the cloud condensation nuclei and ice nucleation activity of bacteria using cloud chamber data and a single particle mass spectrometer. The size and chemical composition of the cloud residuals show that bacterial fragments mixed with agar growth media activate preferentially over intact bacteria cells as cloud condensation nuclei. Intact bacteria cells do not make it into cloud droplets; they thus cannot serve as immersion-mode ice nucleating particles.
Jiahui Zhang, Dao-Yi Gong, Rui Mao, Jing Yang, Ziyin Zhang, and Yun Qian
Atmos. Chem. Phys., 18, 16775–16791, https://doi.org/10.5194/acp-18-16775-2018, https://doi.org/10.5194/acp-18-16775-2018, 2018
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The Chinese Spring Festival (also known as the Chinese New Year or Lunar New Year) is the most important festival in China. This paper reports that during the Chinese Spring Festival, the precipitation over southern China has been significantly reduced. The precipitation reduction is due to anomalous northerly winds. We suppose that anomalous atmospheric circulation is likely related to the human activity during holidays. It is an interesting phenomenon.
Sarah Grawe, Stefanie Augustin-Bauditz, Hans-Christian Clemen, Martin Ebert, Stine Eriksen Hammer, Jasmin Lubitz, Naama Reicher, Yinon Rudich, Johannes Schneider, Robert Staacke, Frank Stratmann, André Welti, and Heike Wex
Atmos. Chem. Phys., 18, 13903–13923, https://doi.org/10.5194/acp-18-13903-2018, https://doi.org/10.5194/acp-18-13903-2018, 2018
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In this study, coal fly ash particles immersed in supercooled cloud droplets were analyzed concerning their freezing behavior. Additionally, physico-chemical particle properties (morphology, chemical composition, crystallography) were investigated. In combining both aspects, components that potentially contribute to the observed freezing behavior of the ash could be identified. Interactions at the particle-water interface, that depend on suspension time and influence freezing, are discussed.
Jens Voigtländer, Cedric Chou, Henner Bieligk, Tina Clauss, Susan Hartmann, Paul Herenz, Dennis Niedermeier, Georg Ritter, Frank Stratmann, and Zbigniew Ulanowski
Atmos. Chem. Phys., 18, 13687–13702, https://doi.org/10.5194/acp-18-13687-2018, https://doi.org/10.5194/acp-18-13687-2018, 2018
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Surface roughness of ice crystals has recently been acknowledged to strongly influence the radiative properties of cold clouds such as cirrus, but it is unclear how this roughness arises. The study investigates the origins of ice surface roughness under a variety of atmospherically relevant conditions, using a novel method to measure roughness quantitatively. It is found that faster growth leads to stronger roughness. Roughness also increases following repeated growth–sublimation cycles.
Fabian Mahrt, Claudia Marcolli, Robert O. David, Philippe Grönquist, Eszter J. Barthazy Meier, Ulrike Lohmann, and Zamin A. Kanji
Atmos. Chem. Phys., 18, 13363–13392, https://doi.org/10.5194/acp-18-13363-2018, https://doi.org/10.5194/acp-18-13363-2018, 2018
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The ice nucleation ability of different soot particles in the cirrus and mixed-phase cloud temperature regime is presented. The impact of aerosol particle size, particle morphology, organic matter and hydrophilicity on ice nucleation is examined. We propose ice nucleation proceeds via a pore condensation freezing mechanism for soot particles with the necessary physicochemical properties that nucleated ice well below water saturation.
Wiebke Frey, Dawei Hu, James Dorsey, M. Rami Alfarra, Aki Pajunoja, Annele Virtanen, Paul Connolly, and Gordon McFiggans
Atmos. Chem. Phys., 18, 9393–9409, https://doi.org/10.5194/acp-18-9393-2018, https://doi.org/10.5194/acp-18-9393-2018, 2018
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The coupled system of the Manchester Aerosol Chamber and Manchester Ice Cloud Chamber was used to study the ice-forming abilities of secondary
organic aerosol particles under mixed-phase cloud conditions. Given the vast abundance of secondary organic particles in the atmosphere, they
might present an important contribution to ice-nucleating particles. However, we find that in the studied temperature range (20 to 28 °C)
the secondary organic particles do not nucleate ice particles.
Sarvesh Garimella, Daniel A. Rothenberg, Martin J. Wolf, Robert O. David, Zamin A. Kanji, Chien Wang, Michael Rösch, and Daniel J. Cziczo
Atmos. Chem. Phys., 17, 10855–10864, https://doi.org/10.5194/acp-17-10855-2017, https://doi.org/10.5194/acp-17-10855-2017, 2017
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This study investigates systematic and variable low bias in the measurement of ice nucleating particle concentration using continuous flow diffusion chambers. We find that non-ideal instrument behavior exposes particles to different humidities and/or temperatures than predicted from theory. We use a machine learning approach to quantify and minimize the uncertainty associated with this measurement bias.
Pascal Lemaitre, Arnaud Querel, Marie Monier, Thibault Menard, Emmanuel Porcheron, and Andrea I. Flossmann
Atmos. Chem. Phys., 17, 4159–4176, https://doi.org/10.5194/acp-17-4159-2017, https://doi.org/10.5194/acp-17-4159-2017, 2017
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We present new measurements of the efficiency with which aerosol particles are collected by raindrops. These measurements provide the link to reconcile the scavenging coefficients obtained from theoretical approaches with those from experimental studies. We provide proof of the rear capture that is a fundamental effect on submicroscopic particles. Finally, we propose an expression to take into account this mechanism to calculate the collection efficiency for drops within the rain size range.
Lukas Kaufmann, Claudia Marcolli, Beiping Luo, and Thomas Peter
Atmos. Chem. Phys., 17, 3525–3552, https://doi.org/10.5194/acp-17-3525-2017, https://doi.org/10.5194/acp-17-3525-2017, 2017
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To improve the understanding of heterogeneous ice nucleation, we have subjected different ice nuclei to repeated freezing cycles and evaluated the freezing temperatures with different parameterizations of classical nucleation theory. It was found that two fit parameters were necessary to describe the temperature dependence of the nucleation rate.
Claudia Marcolli
Atmos. Chem. Phys., 17, 1595–1622, https://doi.org/10.5194/acp-17-1595-2017, https://doi.org/10.5194/acp-17-1595-2017, 2017
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Laboratory studies from the last century have shown that some types of particles are susceptible to pre-activation, i.e. they are able to develop macroscopic ice at warmer temperatures or lower relative humidities after they had been involved in an ice nucleation event before. This review analyses these works under the presumption that pre-activation occurs by ice preserved in pores, and it discusses atmospheric scenarios for which pre-activation might be important.
Yvonne Boose, André Welti, James Atkinson, Fabiola Ramelli, Anja Danielczok, Heinz G. Bingemer, Michael Plötze, Berko Sierau, Zamin A. Kanji, and Ulrike Lohmann
Atmos. Chem. Phys., 16, 15075–15095, https://doi.org/10.5194/acp-16-15075-2016, https://doi.org/10.5194/acp-16-15075-2016, 2016
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We compare the immersion freezing behavior of four airborne to 11 surface-collected dust samples to investigate the role of different minerals for atmospheric ice nucleation on desert dust. We find that present K-feldspars dominate at T > 253 K, while quartz does at colder temperatures, and surface-collected dust samples are not necessarily representative for airborne dust. For improved ice cloud prediction, modeling of quartz and feldspar emission and transport are key.
Andreas Peckhaus, Alexei Kiselev, Thibault Hiron, Martin Ebert, and Thomas Leisner
Atmos. Chem. Phys., 16, 11477–11496, https://doi.org/10.5194/acp-16-11477-2016, https://doi.org/10.5194/acp-16-11477-2016, 2016
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The precipitation in midlatitude clouds proceeds predominantly via nucleation of ice in the supercooled droplets containing foreign inclusions, like feldspar mineral dust, that have been recently identified as one of the most active ice nucleating agents in the atmosphere. We have built an apparatus to observe the freezing of feldspar immersed in up to 1500 identical droplets simultaneously. With this setup we investigated four feldspar samples and show that it can induce freezing at −5 °C.
Claudia Marcolli, Baban Nagare, André Welti, and Ulrike Lohmann
Atmos. Chem. Phys., 16, 8915–8937, https://doi.org/10.5194/acp-16-8915-2016, https://doi.org/10.5194/acp-16-8915-2016, 2016
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Silver iodide is one of the best-investigated ice nuclei. It has relevance for the atmosphere since it is used for glaciogenic cloud seeding. Nevertheless, many open questions remain. This paper gives an overview of silver iodide as an ice nucleus and tries to identify the factors that influence the ice nucleation ability of silver iodide.
Daniel O'Sullivan, Benjamin J. Murray, James F. Ross, and Michael E. Webb
Atmos. Chem. Phys., 16, 7879–7887, https://doi.org/10.5194/acp-16-7879-2016, https://doi.org/10.5194/acp-16-7879-2016, 2016
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In the absence of particles which can trigger freezing, cloud droplets can exist in a supercooled liquid state well below the melting point. However, the sources of efficient ice-nucleating particles in the atmosphere are uncertain. Here we show that ice-nucleating proteins produced by soil fungi can bind to clay particles in soils. Hence, the subsequent dispersion of soil particles into the atmosphere acts as a route through which biological ice nucleators can influence clouds.
Martin Schnaiter, Emma Järvinen, Paul Vochezer, Ahmed Abdelmonem, Robert Wagner, Olivier Jourdan, Guillaume Mioche, Valery N. Shcherbakov, Carl G. Schmitt, Ugo Tricoli, Zbigniew Ulanowski, and Andrew J. Heymsfield
Atmos. Chem. Phys., 16, 5091–5110, https://doi.org/10.5194/acp-16-5091-2016, https://doi.org/10.5194/acp-16-5091-2016, 2016
Leonid Nichman, Claudia Fuchs, Emma Järvinen, Karoliina Ignatius, Niko Florian Höppel, Antonio Dias, Martin Heinritzi, Mario Simon, Jasmin Tröstl, Andrea Christine Wagner, Robert Wagner, Christina Williamson, Chao Yan, Paul James Connolly, James Robert Dorsey, Jonathan Duplissy, Sebastian Ehrhart, Carla Frege, Hamish Gordon, Christopher Robert Hoyle, Thomas Bjerring Kristensen, Gerhard Steiner, Neil McPherson Donahue, Richard Flagan, Martin William Gallagher, Jasper Kirkby, Ottmar Möhler, Harald Saathoff, Martin Schnaiter, Frank Stratmann, and António Tomé
Atmos. Chem. Phys., 16, 3651–3664, https://doi.org/10.5194/acp-16-3651-2016, https://doi.org/10.5194/acp-16-3651-2016, 2016
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Processes in the atmosphere are often governed by the physical and chemical properties of small cloud particles. Ice, water, and mixed clouds, as well as viscous aerosols, were formed under controlled conditions at the CLOUD-CERN facility. The experimental results show a link between cloud particle properties and their unique optical fingerprints. The classification map presented here allows easier discrimination between various particles such as viscous organic aerosol, salt, ice, and liquid.
Peter A. Alpert and Daniel A. Knopf
Atmos. Chem. Phys., 16, 2083–2107, https://doi.org/10.5194/acp-16-2083-2016, https://doi.org/10.5194/acp-16-2083-2016, 2016
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A stochastic immersion freezing model is introduced capable of reproducing laboratory data for a variety of experimental methods using a time and surface area dependent ice nucleation process. The assumption that droplets contain identical surface area is evaluated. A quantitative uncertainty analysis of the laboratory observed freezing process is presented. Our results imply that ice nuclei surface area assumptions are crucial for interpretation of experimental immersion freezing results.
Robert Wagner, Alexei Kiselev, Ottmar Möhler, Harald Saathoff, and Isabelle Steinke
Atmos. Chem. Phys., 16, 2025–2042, https://doi.org/10.5194/acp-16-2025-2016, https://doi.org/10.5194/acp-16-2025-2016, 2016
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We have investigated the enhancement of the ice nucleation ability of well-known and abundant ice nucleating particles like dust grains due to pre-activation. Temporary exposure to a low temperature (228 K) provokes that pores and surface cracks of the particles are filled with ice, which makes them better nuclei for the growth of macroscopic ice crystals at high temperatures (245–260 K).
M. L. López and E. E. Ávila
Atmos. Chem. Phys., 16, 927–932, https://doi.org/10.5194/acp-16-927-2016, https://doi.org/10.5194/acp-16-927-2016, 2016
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This work deals with the origin and nature of atmospheric ice-nucleating particles (INPs). An accurate determination of the atmospheric INP concentration is relevant since INPs induce freezing in clouds, thus initiating an efficient mechanism for cloud particles to reach a precipitating size.
The effect of relative humidity on the INP concentration at ground level was analyzed and discussed.
B. Nagare, C. Marcolli, O. Stetzer, and U. Lohmann
Atmos. Chem. Phys., 15, 13759–13776, https://doi.org/10.5194/acp-15-13759-2015, https://doi.org/10.5194/acp-15-13759-2015, 2015
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We determined collision efficiencies of cloud droplets with aerosol particles experimentally and found that they were around 1 order of magnitude higher than theoretical formulations that include Brownian diffusion, impaction, interception, thermophoretic, diffusiophoretic and electric forces. This is most probably due to uncertainties and inaccuracies in the theoretical formulations of thermophoretic and diffusiophoretic processes.
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Short summary
In this work, based on the well-known formulae of classical nucleation theory (CNT), the temperature at which the mean number of critical embryos inside a droplet is unity is derived from the Boltzmann distribution function and explored as a new simplified approximation for homogeneous freezing temperature. It thus appears that the simplicity of this approximation makes it potentially useful for predicting homogeneous freezing temperatures of water droplets in the atmosphere.
In this work, based on the well-known formulae of classical nucleation theory (CNT), the...
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