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Christensen MW, Gettelman A, Cermak J, Dagan G, Diamond M, Douglas A, Feingold G, Glassmeier F, Goren T, Grosvenor DP, Gryspeerdt E, Kahn R, Li Z, Ma PL, Malavelle F, McCoy IL, McCoy DT, McFarquhar G, Mülmenstädt J, Pal S, Possner A, Povey A, Quaas J, Rosenfeld D, Schmidt A, Schrödner R, Sorooshian A, Stier P, Toll V, Watson-Parris D, Wood R, Yang M, Yuan T. Opportunistic experiments to constrain aerosol effective radiative forcing. ATMOSPHERIC CHEMISTRY AND PHYSICS 2022; 22:641-674. [PMID: 35136405 PMCID: PMC8819675 DOI: 10.5194/acp-22-641-2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Aerosol-cloud interactions (ACIs) are considered to be the most uncertain driver of present-day radiative forcing due to human activities. The nonlinearity of cloud-state changes to aerosol perturbations make it challenging to attribute causality in observed relationships of aerosol radiative forcing. Using correlations to infer causality can be challenging when meteorological variability also drives both aerosol and cloud changes independently. Natural and anthropogenic aerosol perturbations from well-defined sources provide "opportunistic experiments" (also known as natural experiments) to investigate ACI in cases where causality may be more confidently inferred. These perturbations cover a wide range of locations and spatiotemporal scales, including point sources such as volcanic eruptions or industrial sources, plumes from biomass burning or forest fires, and tracks from individual ships or shipping corridors. We review the different experimental conditions and conduct a synthesis of the available satellite datasets and field campaigns to place these opportunistic experiments on a common footing, facilitating new insights and a clearer understanding of key uncertainties in aerosol radiative forcing. Cloud albedo perturbations are strongly sensitive to background meteorological conditions. Strong liquid water path increases due to aerosol perturbations are largely ruled out by averaging across experiments. Opportunistic experiments have significantly improved process-level understanding of ACI, but it remains unclear how reliably the relationships found can be scaled to the global level, thus demonstrating a need for deeper investigation in order to improve assessments of aerosol radiative forcing and climate change.
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Affiliation(s)
- Matthew W. Christensen
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, OX1 3PU, UK
- Atmospheric Science & Global Change Division, Pacific Northwest National Laboratory, Richland, WA 99354, Washington, USA
| | | | - Jan Cermak
- Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research, Karlsruhe, Germany
- Karlsruhe Institute of Technology (KIT), Institute of Photogrammetry and Remote Sensing, Karlsruhe, Germany
| | - Guy Dagan
- Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Michael Diamond
- Department of Atmospheric Sciences, University of Washington, Seattle, USA
- NOAA Chemical Sciences Laboratory (CSL), Boulder, Colorado, USA
- Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, Colorado, USA
| | - Alyson Douglas
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, OX1 3PU, UK
| | - Graham Feingold
- NOAA Chemical Sciences Laboratory (CSL), Boulder, Colorado, USA
| | - Franziska Glassmeier
- Department Geoscience and Remote Sensing, Delft University of Technology, P.O. Box 5048, 2600GA Delft, the Netherlands
| | - Tom Goren
- Institute for Meteorology, Universität Leipzig, Leipzig, Germany
| | - Daniel P. Grosvenor
- National Centre for Atmospheric Sciences, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
| | - Edward Gryspeerdt
- Space and Atmospheric Physics Group, Imperial College London, London, UK
| | - Ralph Kahn
- Earth Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - Zhanqing Li
- Department of Atmospheric and Oceanic Science, University of Maryland, College Park, USA
| | - Po-Lun Ma
- Atmospheric Science & Global Change Division, Pacific Northwest National Laboratory, Richland, WA 99354, Washington, USA
| | - Florent Malavelle
- Met Office, Atmospheric Dispersion and Air Quality, Fitzroy Rd, Exeter, EX1 3PB, UK
| | - Isabel L. McCoy
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA
- Cooperative Programs for the Advancement of Earth System Science (CPAESS), University Corporation for Atmospheric Research, Boulder, CO, USA
| | - Daniel T. McCoy
- Department of Atmospheric Sciences, University of Wyoming, Laramie, USA
| | - Greg McFarquhar
- Cooperative Institute for Severe and High Impact Weather Research and Operations (CIWRO) and School of Meteorology, University of Oklahoma, Norman, OK, USA
- School of Meteorology, University of Oklahoma, Norman, OK, USA
| | - Johannes Mülmenstädt
- Atmospheric Science & Global Change Division, Pacific Northwest National Laboratory, Richland, WA 99354, Washington, USA
| | - Sandip Pal
- Department of Geosciences, Texas Tech University, Lubbock, TX, USA
| | - Anna Possner
- Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Adam Povey
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, OX1 3PU, UK
- National Centre for Earth Observation, University of Oxford, Oxford, OX1 3PU, UK
| | - Johannes Quaas
- Institute for Meteorology, Universität Leipzig, Leipzig, Germany
| | - Daniel Rosenfeld
- Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Anja Schmidt
- Department of Geography, University of Cambridge, Cambridge, UK
- Department of Chemistry, University of Cambridge, Cambridge, UK
| | | | - Armin Sorooshian
- Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, USA
- Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, USA
| | - Philip Stier
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, OX1 3PU, UK
| | - Velle Toll
- Institute of Physics, University of Tartu, Tartu, Estonia
| | - Duncan Watson-Parris
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, OX1 3PU, UK
| | - Robert Wood
- Department of Atmospheric Sciences, University of Washington, Seattle, USA
| | - Mingxi Yang
- Plymouth Marine Laboratory, Prospect Place, Plymouth, PL1 3DH, UK
| | - Tianle Yuan
- Joint Center for Earth Systems Technologies, University of Maryland, Baltimore County, Baltimore, MD, USA
- Earth Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA
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Schulze BC, Charan SM, Kenseth CM, Kong W, Bates KH, Williams W, Metcalf AR, Jonsson HH, Woods R, Sorooshian A, Flagan RC, Seinfeld JH. Characterization of Aerosol Hygroscopicity Over the Northeast Pacific Ocean: Impacts on Prediction of CCN and Stratocumulus Cloud Droplet Number Concentrations. EARTH AND SPACE SCIENCE (HOBOKEN, N.J.) 2020; 7:e2020EA001098. [PMID: 33225018 PMCID: PMC7676499 DOI: 10.1029/2020ea001098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 05/23/2020] [Indexed: 06/11/2023]
Abstract
During the Marine Aerosol Cloud and Wildfire Study (MACAWS) in June and July of 2018, aerosol composition and cloud condensation nuclei (CCN) properties were measured over the N.E. Pacific to characterize the influence of aerosol hygroscopicity on predictions of ambient CCN and stratocumulus cloud droplet number concentrations (CDNC). Three vertical regions were characterized, corresponding to the marine boundary layer (MBL), an above-cloud organic aerosol layer (AC-OAL), and the free troposphere (FT) above the AC-OAL. The aerosol hygroscopicity parameter (κ) was calculated from CCN measurements (κ CCN) and bulk aerosol mass spectrometer (AMS) measurements (κ AMS). Within the MBL, measured hygroscopicities varied between values typical of both continental environments (~0.2) and remote marine locations (~0.7). For most flights, CCN closure was achieved within 20% in the MBL. For five of the seven flights, assuming a constant aerosol size distribution produced similar or better CCN closure than assuming a constant "marine" hygroscopicity (κ = 0.72). An aerosol-cloud parcel model was used to characterize the sensitivity of predicted stratocumulus CDNC to aerosol hygroscopicity, size distribution properties, and updraft velocity. Average CDNC sensitivity to accumulation mode aerosol hygroscopicity is 39% as large as the sensitivity to the geometric median diameter in this environment. Simulations suggest CDNC sensitivity to hygroscopicity is largest in marine stratocumulus with low updraft velocities (<0.2 m s-1), where accumulation mode particles are most relevant to CDNC, and in marine stratocumulus or cumulus with large updraft velocities (>0.6 m s-1), where hygroscopic properties of the Aitken mode dominate hygroscopicity sensitivity.
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Affiliation(s)
- B. C. Schulze
- Department of Environmental Science and Engineering, California Institute of Technology, Pasadena, CA, USA
| | - S. M. Charan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
| | - C. M. Kenseth
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
| | - W. Kong
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
| | - K. H. Bates
- Center for the Environment, Harvard University, Cambridge, MA, USA
| | - W. Williams
- Department of Environmental Engineering and Earth Sciences, Clemson University, Anderson, SC, USA
| | - A. R. Metcalf
- Department of Environmental Engineering and Earth Sciences, Clemson University, Anderson, SC, USA
| | | | - R. Woods
- Naval Postgraduate School, Monterey, CA, USA
| | - A. Sorooshian
- Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, USA
- Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, USA
| | - R. C. Flagan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
- Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA
| | - J. H. Seinfeld
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
- Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA
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Bellouin N, Quaas J, Gryspeerdt E, Kinne S, Stier P, Watson‐Parris D, Boucher O, Carslaw KS, Christensen M, Daniau A, Dufresne J, Feingold G, Fiedler S, Forster P, Gettelman A, Haywood JM, Lohmann U, Malavelle F, Mauritsen T, McCoy DT, Myhre G, Mülmenstädt J, Neubauer D, Possner A, Rugenstein M, Sato Y, Schulz M, Schwartz SE, Sourdeval O, Storelvmo T, Toll V, Winker D, Stevens B. Bounding Global Aerosol Radiative Forcing of Climate Change. REVIEWS OF GEOPHYSICS (WASHINGTON, D.C. : 1985) 2020; 58:e2019RG000660. [PMID: 32734279 PMCID: PMC7384191 DOI: 10.1029/2019rg000660] [Citation(s) in RCA: 91] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 09/30/2019] [Accepted: 10/03/2019] [Indexed: 05/04/2023]
Abstract
Aerosols interact with radiation and clouds. Substantial progress made over the past 40 years in observing, understanding, and modeling these processes helped quantify the imbalance in the Earth's radiation budget caused by anthropogenic aerosols, called aerosol radiative forcing, but uncertainties remain large. This review provides a new range of aerosol radiative forcing over the industrial era based on multiple, traceable, and arguable lines of evidence, including modeling approaches, theoretical considerations, and observations. Improved understanding of aerosol absorption and the causes of trends in surface radiative fluxes constrain the forcing from aerosol-radiation interactions. A robust theoretical foundation and convincing evidence constrain the forcing caused by aerosol-driven increases in liquid cloud droplet number concentration. However, the influence of anthropogenic aerosols on cloud liquid water content and cloud fraction is less clear, and the influence on mixed-phase and ice clouds remains poorly constrained. Observed changes in surface temperature and radiative fluxes provide additional constraints. These multiple lines of evidence lead to a 68% confidence interval for the total aerosol effective radiative forcing of -1.6 to -0.6 W m-2, or -2.0 to -0.4 W m-2 with a 90% likelihood. Those intervals are of similar width to the last Intergovernmental Panel on Climate Change assessment but shifted toward more negative values. The uncertainty will narrow in the future by continuing to critically combine multiple lines of evidence, especially those addressing industrial-era changes in aerosol sources and aerosol effects on liquid cloud amount and on ice clouds.
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Affiliation(s)
- N. Bellouin
- Department of MeteorologyUniversity of ReadingReadingUK
| | - J. Quaas
- Institute for MeteorologyUniversität LeipzigLeipzigGermany
| | - E. Gryspeerdt
- Space and Atmospheric Physics GroupImperial College LondonLondonUK
| | - S. Kinne
- Max Planck Institute for MeteorologyHamburgGermany
| | - P. Stier
- Atmospheric, Oceanic and Planetary Physics, Department of PhysicsUniversity of OxfordOxfordUK
| | - D. Watson‐Parris
- Atmospheric, Oceanic and Planetary Physics, Department of PhysicsUniversity of OxfordOxfordUK
| | - O. Boucher
- Institut Pierre‐Simon Laplace, Sorbonne Université/CNRSParisFrance
| | - K. S. Carslaw
- School of Earth and EnvironmentUniversity of LeedsLeedsUK
| | - M. Christensen
- Atmospheric, Oceanic and Planetary Physics, Department of PhysicsUniversity of OxfordOxfordUK
| | - A.‐L. Daniau
- EPOC, UMR 5805, CNRS‐Université de BordeauxPessacFrance
| | - J.‐L. Dufresne
- Laboratoire de Météorologie Dynamique/IPSL, CNRS, Sorbonne Université, Ecole Normale Supérieure, PSL Research University, Ecole PolytechniqueParisFrance
| | - G. Feingold
- NOAA ESRL Chemical Sciences DivisionBoulderCOUSA
| | - S. Fiedler
- Max Planck Institute for MeteorologyHamburgGermany
- Now at Institut für Geophysik und MeteorologieUniversität zu KölnKölnGermany
| | - P. Forster
- Priestley International Centre for ClimateUniversity of LeedsLeedsUK
| | - A. Gettelman
- National Center for Atmospheric ResearchBoulderCOUSA
| | - J. M. Haywood
- CEMPSUniversity of ExeterExeterUK
- UK Met Office Hadley CentreExeterUK
| | - U. Lohmann
- Institute for Atmospheric and Climate ScienceETH ZürichZürichSwitzerland
| | | | - T. Mauritsen
- Department of MeteorologyStockholm UniversityStockholmSweden
| | - D. T. McCoy
- School of Earth and EnvironmentUniversity of LeedsLeedsUK
| | - G. Myhre
- Center for International Climate and Environmental Research‐Oslo (CICERO)OsloNorway
| | - J. Mülmenstädt
- Institute for MeteorologyUniversität LeipzigLeipzigGermany
| | - D. Neubauer
- Institute for Atmospheric and Climate ScienceETH ZürichZürichSwitzerland
| | - A. Possner
- Department of Global EcologyCarnegie Institution for ScienceStanfordCAUSA
- Now at Institute for Atmospheric and Environmental SciencesGoethe UniversityFrankfurtGermany
| | | | - Y. Sato
- Department of Applied Energy, Graduate School of Engineering, Nagoya UniversityNagoyaJapan
- Now at Faculty of Science, Department of Earth and Planetary SciencesHokkaido UniversitySapporoJapan
| | - M. Schulz
- Climate Modelling and Air Pollution Section, Research and Development DepartmentNorwegian Meteorological InstituteOsloNorway
| | - S. E. Schwartz
- Brookhaven National Laboratory Environmental and Climate Sciences DepartmentUptonNYUSA
| | - O. Sourdeval
- Institute for MeteorologyUniversität LeipzigLeipzigGermany
- Laboratoire d'Optique AtmosphériqueUniversité de LilleVilleneuve d'AscqFrance
| | - T. Storelvmo
- Department of GeosciencesUniversity of OsloOsloNorway
| | - V. Toll
- Department of MeteorologyUniversity of ReadingReadingUK
- Now at Institute of PhysicsUniversity of TartuTartuEstonia
| | - D. Winker
- NASA Langley Research CenterHamptonVAUSA
| | - B. Stevens
- Max Planck Institute for MeteorologyHamburgGermany
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Rosenfeld D, Zhu Y, Wang M, Zheng Y, Goren T, Yu S. Aerosol-driven droplet concentrations dominate coverage and water of oceanic low-level clouds. Science 2019; 363:science.aav0566. [PMID: 30655446 DOI: 10.1126/science.aav0566] [Citation(s) in RCA: 136] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 01/09/2019] [Indexed: 11/02/2022]
Abstract
A lack of reliable estimates of cloud condensation nuclei (CCN) aerosols over oceans has severely limited our ability to quantify their effects on cloud properties and extent of cooling by reflecting solar radiation-a key uncertainty in anthropogenic climate forcing. We introduce a methodology for ascribing cloud properties to CCN and isolating the aerosol effects from meteorological effects. Its application showed that for a given meteorology, CCN explains three-fourths of the variability in the radiative cooling effect of clouds, mainly through affecting shallow cloud cover and water path. This reveals a much greater sensitivity of cloud radiative forcing to CCN than previously reported, which means too much cooling if incorporated into present climate models. This suggests the existence of compensating aerosol warming effects yet to be discovered, possibly through deep clouds.
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Affiliation(s)
- Daniel Rosenfeld
- Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel. .,School of Atmospheric Sciences, Nanjing University, China
| | - Yannian Zhu
- Meteorological Institute of Shaanxi Province, Xi'an, China
| | - Minghuai Wang
- School of Atmospheric Sciences, Nanjing University, China. .,Joint International Research Laboratory of Atmospheric and Earth System Sciences and Institute for Climate and Global Change Research, Nanjing University, China
| | - Youtong Zheng
- Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA
| | - Tom Goren
- University of Leipzig, Leipzig, Germany
| | - Shaocai Yu
- Research Center for Air Pollution and Health; Key Laboratory of Environmental Remediation and Ecological Health, Ministry of Education, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, Zhejiang, P.R. China. .,Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91123, USA.,Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, Fujian 361021, P.R. China
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