Abstract New particle formation in the upper free troposphere is a major global source of cloud condensation nuclei (CCN) 1–4 . However, the precursor vapours that drive the process are not well understood. With experiments performed under upper tropospheric conditions in the CERN CLOUD chamber, we show that nitric acid, sulfuric acid and ammonia form particles synergistically, at rates that are orders of magnitude faster than those from any two of the three components. The importance of this mechanism depends on the availability of ammonia, which was previously thought to be efficiently scavenged by cloud droplets during convection. However, surprisingly high concentrations of ammonia and ammonium nitrate have recently been observed in the upper troposphere over the Asian monsoon region 5,6 . Once particles have formed, co-condensation of ammonia and abundant nitric acid alone is sufficient to drive rapid growth to CCN sizes with only trace sulfate. Moreover, our measurements show that these CCN are also highly efficient ice nucleating particles—comparable to desert dust. Our model simulations confirm that ammonia is efficiently convected aloft during the Asian monsoon, driving rapid, multi-acid HNO 3 –H 2 SO 4 –NH 3 nucleation in the upper troposphere and producing ice nucleating particles that more »
spread across the mid-latitude Northern Hemisphere. « less
McFarquhar, Greg M.; Bretherton, Chris; Marchand, Roger; Protat, Alain; DeMott, Paul J.; Alexander, Simon P.; Roberts, Greg C.; Twohy, Cynthia H.; Toohey, Darin; Siems, Steve; et al(
, Bulletin of the American Meteorological Society)
null
(Ed.)
Abstract Weather and climate models are challenged by uncertainties and biases in simulating Southern Ocean (SO) radiative fluxes that trace to a poor understanding of cloud, aerosol, precipitation and radiative processes, and their interactions. Projects between 2016 and 2018 used in-situ probes, radar, lidar and other instruments to make comprehensive measurements of thermodynamics, surface radiation, cloud, precipitation, aerosol, cloud condensation nuclei (CCN) and ice nucleating particles over the SO cold waters, and in ubiquitous liquid and mixed-phase cloudsnucleating particles over the SO cold waters, and in ubiquitous liquid and mixed-phase clouds common to this pristine environment. Data including soundings were collected from the NSF/NCAR G-V aircraft flying north-south gradients south of Tasmania, at Macquarie Island, and on the RV Investigator and RSV Aurora Australis. Synergistically these data characterize boundary layer and free troposphere environmental properties, and represent the most comprehensive data of this type available south of the oceanic polar front, in the cold sector of SO cyclones, and across seasons. Results show a largely pristine environments with numerous small and few large aerosols above cloud, suggesting new particle formation and limited long-range transport from continents, high variability in CCN and cloud droplet concentrations, and ubiquitous supercooled water in thin,more »multi-layered clouds, often with small-scale generating cells near cloud top. These observations demonstrate how cloud properties depend on aerosols while highlighting the importance of confirmed low clouds were responsible for radiation biases. The combination of models and observations is examining how aerosols and meteorology couple to control SO water and energy budgets.« less
Intense new particle formation events are regularly observed under highly polluted conditions, despite the high loss rates of nucleated clusters. Higher than expected cluster survival probability implies either ineffective scavenging by pre-existing particles or missing growth mechanisms. Here we present experiments performed in the CLOUD chamber at CERN showing particle formation from a mixture of anthropogenic vapours, under condensation sinks typical of haze conditions, up to 0.1 s −1 . We find that new particle formation rates substantially decrease at higher concentrations of pre-existing particles, demonstrating experimentally for the first time that molecular clusters are efficiently scavenged by larger sized particles. Additionally, we demonstrate that in the presence of supersaturated gas-phase nitric acid (HNO 3 ) and ammonia (NH 3 ), freshly nucleated particles can grow extremely rapidly, maintaining a high particle number concentration, even in the presence of a high condensation sink. Such high growth rates may explain the high survival probability of freshly formed particles under haze conditions. We identify under what typical urban conditions HNO 3 and NH 3 can be expected to contribute to particle survival during haze.
Atmospheric aerosols significantly offset positive radiative forcing due to their contributions as cloud condensation nuclei (CCN) and ice nucleating particles (INPs). The cloud-aerosol-precipitation interactions in the atmosphere are determined by physical and chemical properties of aerosol particles, which can undergo many cycles of droplet activation and subsequent drying before dry or wet deposition from the atmosphere. Secondary organic aerosol (SOA) is an abundant class of aerosol and has been previously shown to contribute to aerosol formed from cloud processing. Isoprene-derived secondary organic aerosol SOA (iSOA) is a particularly important class of aerosol involved in cloud processing. iSOA has both soluble and insoluble components, but there has been a measurement gap in characterizing the insoluble components, as most analyses have focused on soluble components. These measurements are needed as previous research has suggested that insoluble components could be important with respect to CCN and INP formation. Herein, we analyze the insoluble components of SOA generated from the reactive uptake of IEPOX onto acidic seed particles (ammonium sulfate + sulfuric acid at different ratios for different pH conditions) in an atmospheric chamber. We characterize the size distributions and chemical composition, using NanoParticle Tracking Analysis (NTA), Raman microspectroscopy and atomic force microscopy infraredmore »(AFM-IR) spectroscopy as a function of sulfate aerosol seed pH. These insights may help understand aerosol properties after cloud cycling in the atmosphere.« less
The number concentration and properties of aerosol particles serving as cloud condensation nuclei (CCN) are important for understanding cloud properties, including in the tropical Atlantic marine boundary layer (MBL), where marine cumulus clouds reflect incoming solar radiation and obscure the low-albedo ocean surface. Studies linking aerosol source, composition, and water uptake properties in this region have been conducted primarily during the summertime dust transport season, despite the region receiving a variety of aerosol particle types throughout the year. In this study, we compare size-resolved aerosol chemical composition data to the hygrocopicity parameter κ derived from size-resolved CCN measurements made during the Elucidating the Role of Clouds-Circulation Coupling in Climate (EUREC4A) and Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC) campaigns from January to February 2020. We observed unexpected periods of wintertime long-range transport of African smoke and dust to Barbados. During these periods, the accumulation-mode aerosol particle and CCN Number concentrations as well as the proportions of dust and smoke particles increased, whereas average κ slightly decreased (κ = 0.46 +/- 0.10) from marine background conditions (κ = 0.52 +/- 0.09) when the particles were mostly composed of marine organics and sulfate. Size-resolved chemical analysis shows that smoke particles were
the major contributor to the accumulation mode during long-range transport events, indicating that smoke is mainly responsible for the observed increase in CCN number concentrations. Earlier studies conducted at Barbados have mostly focused on the role of dust in CCN, but our results show that aerosol hygroscopicity and CCN number concentrations during wintertime long-range transport events over the tropical North Atlantic are also affected by African smoke. Our findings highlight the importance of African smoke for atmospheric processes and cloud formation over the Caribbean.
Technical Information
In the file “Dust_Mass_Conc_Royer2022” dust mass concentrations in grams per meter^3 are provided for each day of sampling. These data were used to generate Figure 2a in the manuscript. The file “Particle_Type_#fract_Royer2022” contains data obtained through CCSEM/EDX analysis and used to generate the temporal chemistry plot (Figure 4) provided in the manuscript. The data contains particle numbers for each particle type identified on stage 3 of the sampler, total particle numbers analyzed for the entire stage 3 sample, as well as particle number fractions in % values. In the file “Size-resolved_chem_Royer2022” we provide particle # and number fraction (%) values used to generate size-resolved chemistry plots in the manuscript (Figures 5a and 5b). The file includes all particle numbers and number fractions for sea salt, aged sea salt, dust+sea salt, dust, dust+smoke, smoke, sulfate, and organic particles in each size bin from 0.1 through 8.058 um during cumulative clean marine periods and CAT Event 1 as described in the manuscript. The file “K_at_0.16S_Royer2022” contains κ values calculated at 0.16% supersaturation (S) throughout the entire sampling period. These data were specifically used to generate the plot in Figure 7a. The file “CCN#_at_0.16S_Royer2022” contains cloud condensation nuclei (CCN) values calculated at 0.16% supersaturation (S) throughout the entire sampling period. These data were used to create the CCN portion of the plot in Figure 7b. More>>
Wendisch, M.; Brückner, M.; Crewell, S.; Ehrlich, A.; Notholt, J.; Lüpkes, C.; Macke, A.; Burrows, J. P.; Rinke, A.; Quaas, J.; et al(
, Bulletin of the American Meteorological Society)
Abstract Mechanisms behind the phenomenon of Arctic amplification are widely discussed. To contribute to this debate, the (AC) 3 project was established in 2016 ( www.ac3-tr.de/ ). It comprises modeling and data analysis efforts as well as observational elements. The project has assembled a wealth of ground-based, airborne, shipborne, and satellite data of physical, chemical, and meteorological properties of the Arctic atmosphere, cryosphere, and upper ocean that are available for the Arctic climate research community. Short-term changes and indications of long-term trends in Arctic climate parameters have been detected using existing and new data. For example, a distinct atmospheric moistening, an increase of regional storm activities, an amplified winter warming in the Svalbard and North Pole regions, and a decrease of sea ice thickness in the Fram Strait and of snow depth on sea ice have been identified. A positive trend of tropospheric bromine monoxide (BrO) column densities during polar spring was verified. Local marine/biogenic sources for cloud condensation nuclei and ice nucleating particles were found. Atmospheric–ocean and radiative transfer models were advanced by applying new parameterizations of surface albedo, cloud droplet activation, convective plumes and related processes over leads, and turbulent transfer coefficients for stable surface layers. Four modesmore »of the surface radiative energy budget were explored and reproduced by simulations. To advance the future synthesis of the results, cross-cutting activities are being developed aiming to answer key questions in four focus areas: lapse rate feedback, surface processes, Arctic mixed-phase clouds, and airmass transport and transformation.« less
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@article{osti_10326856,
place = {Country unknown/Code not available},
title = {Synergistic HNO3–H2SO4–NH3 upper tropospheric particle formation},
url = {https://par.nsf.gov/biblio/10326856},
DOI = {10.1038/s41586-022-04605-4},
abstractNote = {Abstract New particle formation in the upper free troposphere is a major global source of cloud condensation nuclei (CCN) 1–4 . However, the precursor vapours that drive the process are not well understood. With experiments performed under upper tropospheric conditions in the CERN CLOUD chamber, we show that nitric acid, sulfuric acid and ammonia form particles synergistically, at rates that are orders of magnitude faster than those from any two of the three components. The importance of this mechanism depends on the availability of ammonia, which was previously thought to be efficiently scavenged by cloud droplets during convection. However, surprisingly high concentrations of ammonia and ammonium nitrate have recently been observed in the upper troposphere over the Asian monsoon region 5,6 . Once particles have formed, co-condensation of ammonia and abundant nitric acid alone is sufficient to drive rapid growth to CCN sizes with only trace sulfate. Moreover, our measurements show that these CCN are also highly efficient ice nucleating particles—comparable to desert dust. Our model simulations confirm that ammonia is efficiently convected aloft during the Asian monsoon, driving rapid, multi-acid HNO 3 –H 2 SO 4 –NH 3 nucleation in the upper troposphere and producing ice nucleating particles that spread across the mid-latitude Northern Hemisphere.},
journal = {Nature},
volume = {605},
number = {7910},
author = {Wang, Mingyi and Xiao, Mao and Bertozzi, Barbara and Marie, Guillaume and Rörup, Birte and Schulze, Benjamin and Bardakov, Roman and He, Xu-Cheng and Shen, Jiali and Scholz, Wiebke and Marten, Ruby and Dada, Lubna and Baalbaki, Rima and Lopez, Brandon and Lamkaddam, Houssni and Manninen, Hanna E. and Amorim, António and Ataei, Farnoush and Bogert, Pia and Brasseur, Zoé and Caudillo, Lucía and De Menezes, Louis-Philippe and Duplissy, Jonathan and Ekman, Annica M. and Finkenzeller, Henning and Carracedo, Loïc Gonzalez and Granzin, Manuel and Guida, Roberto and Heinritzi, Martin and Hofbauer, Victoria and Höhler, Kristina and Korhonen, Kimmo and Krechmer, Jordan E. and Kürten, Andreas and Lehtipalo, Katrianne and Mahfouz, Naser G. and Makhmutov, Vladimir and Massabò, Dario and Mathot, Serge and Mauldin, Roy L. and Mentler, Bernhard and Müller, Tatjana and Onnela, Antti and Petäjä, Tuukka and Philippov, Maxim and Piedehierro, Ana A. and Pozzer, Andrea and Ranjithkumar, Ananth and Schervish, Meredith and Schobesberger, Siegfried and Simon, Mario and Stozhkov, Yuri and Tomé, António and Umo, Nsikanabasi Silas and Vogel, Franziska and Wagner, Robert and Wang, Dongyu S. and Weber, Stefan K. and Welti, André and Wu, Yusheng and Zauner-Wieczorek, Marcel and Sipilä, Mikko and Winkler, Paul M. and Hansel, Armin and Baltensperger, Urs and Kulmala, Markku and Flagan, Richard C. and Curtius, Joachim and Riipinen, Ilona and Gordon, Hamish and Lelieveld, Jos and El-Haddad, Imad and Volkamer, Rainer and Worsnop, Douglas R. and Christoudias, Theodoros and Kirkby, Jasper and Möhler, Ottmar and Donahue, Neil M.},
}
