Articles | Volume 26, issue 10
https://doi.org/10.5194/acp-26-6593-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-26-6593-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
18 May 2026
Research article |
| 18 May 2026
| 18 May 2026
Evaluating Long-term seasonal variability of aerosol optical properties in Colorado
Erin K. Boedicker
NOAA Earth System Research Laboratory, Boulder, CO 80305, USA
Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA
Andre Bergeron
Graduate School of Geography, Clark University, Worcester, MA 01016, USA
Gerardo Carrillo-Cardenas
Department of Atmospheric Sciences, University of Utah, Salt Lake City, UT 84112, USA
Dominik Kulakowski
Graduate School of Geography, Clark University, Worcester, MA 01016, USA
John Rogan
Graduate School of Geography, Clark University, Worcester, MA 01016, USA
Elisabeth Andrews
NOAA Earth System Research Laboratory, Boulder, CO 80305, USA
Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA
Department of Atmospheric Sciences, University of Utah, Salt Lake City, UT 84112, USA
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Erin K. Boedicker, Elisabeth Andrews, Patrick J. Sheridan, and Patricia K. Quinn
Atmos. Chem. Phys., 23, 9525–9547, https://doi.org/10.5194/acp-23-9525-2023, https://doi.org/10.5194/acp-23-9525-2023, 2023
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We present 15 years of measurements from a marine site on the northern California coast and characterize the seasonal trends of aerosol ion composition and optical properties at the site. We investigate the relationship between the chemical and optical properties and show that they both support similar seasonal variations in aerosol sources at the site. Additionally, we show through comparisons to other marine aerosol observations that the site is representative of a clean marine environment.
Erin K. Boedicker, Holly M. DeBolt, Ryan Fulgam, Ethan W. Emerson, and Delphine K. Farmer
Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2022-431, https://doi.org/10.5194/acp-2022-431, 2022
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We present particle flux and size-resolved dry deposition measurements from a pine forest for all four major seasons. Dry deposition of particles was highest in the winter and was significantly elevated compared to the summer data. Several mechanisms were investigated to determine what effects were driving the enhanced deposition in the winter. We show that the wintertime changes are likely caused by changes in plant physiology and needle structure that increase the influence of interception.
Inés Zabala, Juan Andrés Casquero-Vera, Elisabeth Andrews, Andrea Casans, Gerardo Carrillo-Cardenas, Anna Gannet Hallar, and Gloria Titos
Atmos. Chem. Phys., 26, 3697–3722, https://doi.org/10.5194/acp-26-3697-2026, https://doi.org/10.5194/acp-26-3697-2026, 2026
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This study presents a comprehensive analysis of cloud condensation nuclei (CCN) phenomenology across nine observatories in diverse environments. We evaluate CCN prediction methods based on aerosol chemical composition and optical properties, including empirical and machine learning approaches. While simplified chemical schemes provide first-order estimates, incorporating optical data substantially improves CCN prediction accuracy in regions without direct measurements.
Ross James Herbert, Larissa Lacher, Alexander Böhmländer, Mark D. Tarn, Antione Canzi, Aidan Pantoya, Evelyn Freney, Kristina Höhler, Pia Bogert, Celine Planche, Ping Tian, Michael Adams, Sarah Barr, David Brus, Nicole Büttner, Martin Daily, Konstantinos Doulgeris, Konstantinos Eleftheridadis, Grant Forster, Romy Fösig, Dimitrios Georgakopoulos, Maria Gini, A. Gannett Hallar, Radovan Krejci, Elke Ludewig, Mauro Mazzola, Ian B. McCubbin, Tuukka Petäjä, Joseph Robinson, Franziska Vogel, Paul Zieger, Stephen R. Arnold, Kenneth S. Carslaw, Naruki Hiranuma, Ottmar Möhler, and Benjamin J. Murray
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2026-41, https://doi.org/10.5194/essd-2026-41, 2026
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Ice formation in sub-zero clouds is influenced by airborne particles called ice-nucleating particles (INPs), whose concentrations vary substantially over short time and spatial scales. To assess the role of INPs in our climate, a comprehensive and consistent global dataset is essential. Our GloPINE model-ready dataset is a major step in this direction, comprising 36,000 measurements made using a single instrument design (PINE) over 70,000 hours of operation at 20 northern hemisphere sites.
Alexander Garber, Zhaoxia Pu, and Anna Gannet Hallar
EGUsphere, https://doi.org/10.5194/egusphere-2025-6413, https://doi.org/10.5194/egusphere-2025-6413, 2026
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This study examines how Saharan dust aerosols influenced the evolution of Tropical Storm Hermine (2022) using WRF-Chem simulations and NASA CPEX-CV observations. Results show that dust radiative effects weakened and disrupted storm organization, while reanalysis data underestimated dust concentrations. The findings highlight the importance of accurately representing aerosols to improve tropical cyclone simulations and hazard prediction.
Christopher N. Rapp, Gerardo Carrillo-Cardenas, Sining Niu, Yue Zhang, Fred J. Brechtel, A. Gannet Hallar, and Daniel J. Cziczo
EGUsphere, https://doi.org/10.5194/egusphere-2025-4222, https://doi.org/10.5194/egusphere-2025-4222, 2025
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Particles within aerosol vary in both size and concentration and is termed a particle size distribution (PSD). Aerosol particles are rarely distributed such that only one similar group of particles (mode) exists. In reality, the PSD is often the sum of multiple individual modes. This work introduces an accessible tool used to decompose complex PSDs so each mode can be characterized and used to infer important properties relevant to health and climate such as formation processes and composition.
Tyler R. Elgiar, Loknath Dhar, Lynne Gratz, A. Gannet Hallar, Rainer Volkamer, and Seth N. Lyman
Atmos. Chem. Phys., 25, 16387–16399, https://doi.org/10.5194/acp-25-16387-2025, https://doi.org/10.5194/acp-25-16387-2025, 2025
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We compare verified atmospheric mercury measurements against output from the GEOS-Chem photochemical transport model. We show the model is unable to reproduce measured atmospheric oxidized mercury concentrations, even in several cases where oxidation rates in the model are enhanced.
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EGUsphere, https://doi.org/10.5194/egusphere-2025-4492, https://doi.org/10.5194/egusphere-2025-4492, 2025
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We observe a trend of increasing ice-nucleating particle (INP) concentration in spring in the Rocky Mountains, related to regional dust emissions that may intensify with climate change. Additionally, super-micrometer particles were found as the most important contributors to the INP population. This finding was partly enabled by a novel setup of the Portable Ice Nucleation Experiment (PINE), coupled with a pumped-counterflow virtual impactor allowing for direct analysis of INP properties.
Aidan D. Pantoya, Stephanie R. Simonsen, Elisabeth Andrews, Ross Burgener, Christopher J. Cox, Gijs de Boer, Bryan D. Thomas, and Naruki Hiranuma
Aerosol Research, 3, 253–270, https://doi.org/10.5194/ar-3-253-2025, https://doi.org/10.5194/ar-3-253-2025, 2025
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We present continuous ice-nucleating particle data that were measured in the Alaskan Arctic from October 2021 to December 2023. We found a greater efficiency in the arctic immersion freezing during fall compared to those found previously at two mid-latitude sites, together with profound freezing efficiencies in spring, presumably due to arctic haze events. Our study will be useful for improving atmospheric models to simulate cloud feedback and determine their impact on the global radiative energy budget.
Paul J. DeMott, Jessica A. Mirrielees, Sarah Suda Petters, Daniel J. Cziczo, Markus D. Petters, Heinz G. Bingemer, Thomas C. J. Hill, Karl Froyd, Sarvesh Garimella, A. Gannet Hallar, Ezra J. T. Levin, Ian B. McCubbin, Anne E. Perring, Christopher N. Rapp, Thea Schiebel, Jann Schrod, Kaitlyn J. Suski, Daniel Weber, Martin J. Wolf, Maria Zawadowicz, Jake Zenker, Ottmar Möhler, and Sarah D. Brooks
Atmos. Meas. Tech., 18, 639–672, https://doi.org/10.5194/amt-18-639-2025, https://doi.org/10.5194/amt-18-639-2025, 2025
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The Fifth International Ice Nucleation Workshop Phase 3 (FIN-03) compared the ambient atmospheric performance of ice-nucleating particle (INP) measuring systems and explored general methods for discerning atmospheric INP compositions. Mirroring laboratory results, INP concentrations agreed within 5–10 factors. Measurements of total aerosol properties and investigations of INP compositions supported a dominant role of soil and plant organic aerosol elements as INPs during the study.
Fernando Rejano, Andrea Casans, Marta Via, Juan Andrés Casquero-Vera, Sonia Castillo, Hassan Lyamani, Alberto Cazorla, Elisabeth Andrews, Daniel Pérez-Ramírez, Andrés Alastuey, Francisco Javier Gómez-Moreno, Lucas Alados-Arboledas, Francisco José Olmo, and Gloria Titos
Atmos. Chem. Phys., 24, 13865–13888, https://doi.org/10.5194/acp-24-13865-2024, https://doi.org/10.5194/acp-24-13865-2024, 2024
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Eleanor J. Derry, Tyler R. Elgiar, Taylor Y. Wilmot, Nicholas W. Hoch, Noah S. Hirshorn, Peter Weiss-Penzias, Christopher F. Lee, John C. Lin, A. Gannet Hallar, Rainer Volkamer, Seth N. Lyman, and Lynne E. Gratz
Atmos. Chem. Phys., 24, 9615–9643, https://doi.org/10.5194/acp-24-9615-2024, https://doi.org/10.5194/acp-24-9615-2024, 2024
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Surendra Shrestha, Christopher A. Williams, Brendan M. Rogers, John Rogan, and Dominik Kulakowski
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Alessandro Bigi, Giorgio Veratti, Elisabeth Andrews, Martine Collaud Coen, Lorenzo Guerrieri, Vera Bernardoni, Dario Massabò, Luca Ferrero, Sergio Teggi, and Grazia Ghermandi
Atmos. Chem. Phys., 23, 14841–14869, https://doi.org/10.5194/acp-23-14841-2023, https://doi.org/10.5194/acp-23-14841-2023, 2023
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Atmospheric particles include compounds that play a key role in the greenhouse effect and air toxicity. Concurrent observations of these compounds by multiple instruments are presented, following deployment within an urban environment in the Po Valley, one of Europe's pollution hotspots. The study compares these data, highlighting the impact of ground emissions, mainly vehicular traffic and biomass burning, on the absorption of sun radiation and, ultimately, on climate change and air quality.
Erin K. Boedicker, Elisabeth Andrews, Patrick J. Sheridan, and Patricia K. Quinn
Atmos. Chem. Phys., 23, 9525–9547, https://doi.org/10.5194/acp-23-9525-2023, https://doi.org/10.5194/acp-23-9525-2023, 2023
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We present 15 years of measurements from a marine site on the northern California coast and characterize the seasonal trends of aerosol ion composition and optical properties at the site. We investigate the relationship between the chemical and optical properties and show that they both support similar seasonal variations in aerosol sources at the site. Additionally, we show through comparisons to other marine aerosol observations that the site is representative of a clean marine environment.
Daniel A. Jaffe, Colleen Miller, Katie Thompson, Brandon Finley, Manna Nelson, James Ouimette, and Elisabeth Andrews
Atmos. Meas. Tech., 16, 1311–1322, https://doi.org/10.5194/amt-16-1311-2023, https://doi.org/10.5194/amt-16-1311-2023, 2023
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PurpleAir sensors (PASs) are low-cost tools to measure fine particulate matter (PM) concentrations. However, the raw PAS data have significant biases, so the sensors must be corrected. We analyzed data from numerous sites and found that the standard correction to the PAS Purple Air data is accurate in urban pollution events and smoke events but leads to a 6-fold underestimate in the PM2.5 concentrations in dust events. We propose a new correction algorithm to address this problem.
Noah S. Hirshorn, Lauren M. Zuromski, Christopher Rapp, Ian McCubbin, Gerardo Carrillo-Cardenas, Fangqun Yu, and A. Gannet Hallar
Atmos. Chem. Phys., 22, 15909–15924, https://doi.org/10.5194/acp-22-15909-2022, https://doi.org/10.5194/acp-22-15909-2022, 2022
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New particle formation (NPF) is a source of atmospheric aerosol number concentration that can impact climate by growing to larger sizes and under proper conditions form cloud condensation nuclei (CCN). Using novel methods, we find that at Storm Peak Laboratory, a remote, mountaintop site in Colorado, NPF is observed to enhance CCN concentrations in the spring by a factor of 1.54 and in the winter by a factor of 1.36 which can occur on a regional scale having important climate implications.
Erin K. Boedicker, Holly M. DeBolt, Ryan Fulgam, Ethan W. Emerson, and Delphine K. Farmer
Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2022-431, https://doi.org/10.5194/acp-2022-431, 2022
Preprint withdrawn
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We present particle flux and size-resolved dry deposition measurements from a pine forest for all four major seasons. Dry deposition of particles was highest in the winter and was significantly elevated compared to the summer data. Several mechanisms were investigated to determine what effects were driving the enhanced deposition in the winter. We show that the wintertime changes are likely caused by changes in plant physiology and needle structure that increase the influence of interception.
Anna L. Hodshire, Ezra J. T. Levin, A. Gannet Hallar, Christopher N. Rapp, Dan R. Gilchrist, Ian McCubbin, and Gavin R. McMeeking
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2022-216, https://doi.org/10.5194/amt-2022-216, 2022
Publication in AMT not foreseen
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The new Continuous Flow Diffusion Chamber-Ice Activation Spectrometer collected 4 months of ice nucleating particle (INP) measurements at a 5-minute resolution at the mountainside Storm Peak Laboratory. Most long-term INP measurements are at a time resolution of a day or longer: our instrument is a promising advance towards high-resolution long-term INP measurements. We observe higher peak INP concentrations than previous mountain studies, possibly due to the higher time resolution of our data.
Libby Koolik, Michael Roesch, Carmen Dameto de Espana, Christopher Nathan Rapp, Lesly J. Franco Deloya, Chuanyang Shen, A. Gannet Hallar, Ian B. McCubbin, and Daniel J. Cziczo
Atmos. Meas. Tech., 15, 3213–3222, https://doi.org/10.5194/amt-15-3213-2022, https://doi.org/10.5194/amt-15-3213-2022, 2022
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A new inlet for studying the small particles, droplets, and ice crystals that constitute mixed-phase clouds has been constructed and is described here. This new inlet was tested in the laboratory. We present the performance of the new inlet to demonstrate its capability of separating ice, droplets, and small particles.
Aki Virkkula, Henrik Grythe, John Backman, Tuukka Petäjä, Maurizio Busetto, Christian Lanconelli, Angelo Lupi, Silvia Becagli, Rita Traversi, Mirko Severi, Vito Vitale, Patrick Sheridan, and Elisabeth Andrews
Atmos. Chem. Phys., 22, 5033–5069, https://doi.org/10.5194/acp-22-5033-2022, https://doi.org/10.5194/acp-22-5033-2022, 2022
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Optical properties of surface aerosols at Dome C, Antarctica, in 2007–2013 and their potential source areas are presented. The equivalent black carbon (eBC) mass concentrations were compared with eBC measured at three other Antarctic sites: the South Pole (SPO) and two coastal sites, Neumayer and Syowa. Transport analysis suggests that South American BC emissions are the largest contributor to eBC at Dome C.
Julia Schmale, Sangeeta Sharma, Stefano Decesari, Jakob Pernov, Andreas Massling, Hans-Christen Hansson, Knut von Salzen, Henrik Skov, Elisabeth Andrews, Patricia K. Quinn, Lucia M. Upchurch, Konstantinos Eleftheriadis, Rita Traversi, Stefania Gilardoni, Mauro Mazzola, James Laing, and Philip Hopke
Atmos. Chem. Phys., 22, 3067–3096, https://doi.org/10.5194/acp-22-3067-2022, https://doi.org/10.5194/acp-22-3067-2022, 2022
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Long-term data sets of Arctic aerosol properties from 10 stations across the Arctic provide evidence that anthropogenic influence on the Arctic atmospheric chemical composition has declined in winter, a season which is typically dominated by mid-latitude emissions. The number of significant trends in summer is smaller than in winter, and overall the pattern is ambiguous with some significant positive and negative trends. This reflects the mixed influence of natural and anthropogenic emissions.
James R. Ouimette, William C. Malm, Bret A. Schichtel, Patrick J. Sheridan, Elisabeth Andrews, John A. Ogren, and W. Patrick Arnott
Atmos. Meas. Tech., 15, 655–676, https://doi.org/10.5194/amt-15-655-2022, https://doi.org/10.5194/amt-15-655-2022, 2022
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We show that the low-cost PurpleAir sensor can be characterized as a cell-reciprocal nephelometer. At two very different locations (Mauna Loa Observatory in Hawaii and the Table Mountain rural site in Colorado), the PurpleAir measurements are highly correlated with the submicrometer aerosol scattering coefficient measured by a research-grade integrating nephelometer. These results imply that, with care, PurpleAir data may be used to evaluate climate and air quality models.
Anna L. Hodshire, Ezra J. T. Levin, A. Gannet Hallar, Christopher N. Rapp, Dan R. Gilchrist, Ian McCubbin, and Gavin R. McMeeking
Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2022-29, https://doi.org/10.5194/acp-2022-29, 2022
Preprint withdrawn
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The new Continuous Flow Diffusion Chamber-Ice Activation Spectrometer collected 4 months of ice nucleating particle (INP) measurements at a 5-minute resolution at the mountainside Storm Peak Laboratory. Most long-term INP measurements are at a time resolution of a day or longer: our instrument is a promising advance towards high-resolution long-term INP measurements. We observe higher peak INP concentrations than previous mountain studies, possibly due to the higher time resolution of our data.
Clémence Rose, Martine Collaud Coen, Elisabeth Andrews, Yong Lin, Isaline Bossert, Cathrine Lund Myhre, Thomas Tuch, Alfred Wiedensohler, Markus Fiebig, Pasi Aalto, Andrés Alastuey, Elisabeth Alonso-Blanco, Marcos Andrade, Begoña Artíñano, Todor Arsov, Urs Baltensperger, Susanne Bastian, Olaf Bath, Johan Paul Beukes, Benjamin T. Brem, Nicolas Bukowiecki, Juan Andrés Casquero-Vera, Sébastien Conil, Konstantinos Eleftheriadis, Olivier Favez, Harald Flentje, Maria I. Gini, Francisco Javier Gómez-Moreno, Martin Gysel-Beer, Anna Gannet Hallar, Ivo Kalapov, Nikos Kalivitis, Anne Kasper-Giebl, Melita Keywood, Jeong Eun Kim, Sang-Woo Kim, Adam Kristensson, Markku Kulmala, Heikki Lihavainen, Neng-Huei Lin, Hassan Lyamani, Angela Marinoni, Sebastiao Martins Dos Santos, Olga L. Mayol-Bracero, Frank Meinhardt, Maik Merkel, Jean-Marc Metzger, Nikolaos Mihalopoulos, Jakub Ondracek, Marco Pandolfi, Noemi Pérez, Tuukka Petäjä, Jean-Eudes Petit, David Picard, Jean-Marc Pichon, Veronique Pont, Jean-Philippe Putaud, Fabienne Reisen, Karine Sellegri, Sangeeta Sharma, Gerhard Schauer, Patrick Sheridan, James Patrick Sherman, Andreas Schwerin, Ralf Sohmer, Mar Sorribas, Junying Sun, Pierre Tulet, Ville Vakkari, Pieter Gideon van Zyl, Fernando Velarde, Paolo Villani, Stergios Vratolis, Zdenek Wagner, Sheng-Hsiang Wang, Kay Weinhold, Rolf Weller, Margarita Yela, Vladimir Zdimal, and Paolo Laj
Atmos. Chem. Phys., 21, 17185–17223, https://doi.org/10.5194/acp-21-17185-2021, https://doi.org/10.5194/acp-21-17185-2021, 2021
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Aerosol particles are a complex component of the atmospheric system the effects of which are among the most uncertain in climate change projections. Using data collected at 62 stations, this study provides the most up-to-date picture of the spatial distribution of particle number concentration and size distribution worldwide, with the aim of contributing to better representation of aerosols and their interactions with clouds in models and, therefore, better evaluation of their impact on climate.
Sho Ohata, Tatsuhiro Mori, Yutaka Kondo, Sangeeta Sharma, Antti Hyvärinen, Elisabeth Andrews, Peter Tunved, Eija Asmi, John Backman, Henri Servomaa, Daniel Veber, Konstantinos Eleftheriadis, Stergios Vratolis, Radovan Krejci, Paul Zieger, Makoto Koike, Yugo Kanaya, Atsushi Yoshida, Nobuhiro Moteki, Yongjing Zhao, Yutaka Tobo, Junji Matsushita, and Naga Oshima
Atmos. Meas. Tech., 14, 6723–6748, https://doi.org/10.5194/amt-14-6723-2021, https://doi.org/10.5194/amt-14-6723-2021, 2021
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Reliable values of mass absorption cross sections (MACs) of black carbon (BC) are required to determine mass concentrations of BC at Arctic sites using different types of filter-based absorption photometers. We successfully estimated MAC values for these instruments through comparison with independent measurements of BC by a continuous soot monitoring system called COSMOS. These MAC values are consistent with each other and applicable to study spatial and temporal variation in BC in the Arctic.
Gloria Titos, María A. Burgos, Paul Zieger, Lucas Alados-Arboledas, Urs Baltensperger, Anne Jefferson, James Sherman, Ernest Weingartner, Bas Henzing, Krista Luoma, Colin O'Dowd, Alfred Wiedensohler, and Elisabeth Andrews
Atmos. Chem. Phys., 21, 13031–13050, https://doi.org/10.5194/acp-21-13031-2021, https://doi.org/10.5194/acp-21-13031-2021, 2021
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This paper investigates the impact of water uptake on aerosol optical properties, in particular the aerosol light-scattering coefficient. Although in situ measurements are performed at low relative humidity (typically at
RH < 40 %), to address the climatic impact of aerosol particles it is necessary to take into account the effect that water uptake may have on the aerosol optical properties.
Amy Hrdina, Jennifer G. Murphy, Anna Gannet Hallar, John C. Lin, Alexander Moravek, Ryan Bares, Ross C. Petersen, Alessandro Franchin, Ann M. Middlebrook, Lexie Goldberger, Ben H. Lee, Munkh Baasandorj, and Steven S. Brown
Atmos. Chem. Phys., 21, 8111–8126, https://doi.org/10.5194/acp-21-8111-2021, https://doi.org/10.5194/acp-21-8111-2021, 2021
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Wintertime air pollution in the Salt Lake Valley is primarily composed of ammonium nitrate, which is formed when gas-phase ammonia and nitric acid react. The major point in this work is that the chemical composition of snow tells a very different story to what we measured in the atmosphere. With the dust–sea salt cations observed in PM2.5 and particle sizing data, we can estimate how much nitric acid may be lost to dust–sea salt that is not accounted for and how much more PM2.5 this could form.
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Short summary
We present analysis of long-term aerosol measurements from two sites in Colorado. In this work, we characterize seasonal trends of aerosol optical properties for both sites and perform trend analysis to investigate changes in sources over time. We show that there is a significant increase in the influence of extreme events like smoke and dust, and explore the relationship between optical properties to identify aerosol types and temporal patterns at the two sites.
We present analysis of long-term aerosol measurements from two sites in Colorado. In this work,...
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