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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  16 Jun 2020

16 Jun 2020

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This preprint is currently under review for the journal ACP.

An overview of the ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) project: aerosol-cloud-radiation interactions in the Southeast Atlantic basin

Jens Redemann1, Robert Wood2, Paquita Zuidema3, Sarah J. Doherty2, Bernadette Luna4, Samuel E. LeBlanc5,4, Michael S. Diamond2, Yohei Shinozuka7, Ian Y. Chang1, Rei Ueyama4, Leonhard Pfister4, Ju-me Ryoo4,35, Amie N. Dobracki3, Arlindo M. da Silva6, Karla M. Longo6,7, Meloë S. Kacenelenbogen4, Connor J. Flynn1, Kristina Pistone5,4, Nichola M. Knox8, Stuart J. Piketh9, James M. Haywood10, Paola Formenti11, Marc Mallet12, Philip Stier13, Andrew S. Ackerman14, Susanne E. Bauer14, Ann M. Fridlind14, Gregory R. Carmichael15, Pablo E. Saide16, Gonzalo A. Ferrada15, Steven G. Howell17, Steffen Freitag17, Brian Cairns14, Brent N. Holben6, Kirk D. Knobelspiesse6, Simone Tanelli18, Tristan S. L'Ecuyer19, Andrew M. Dzambo19, Ousmane O. Sy20, Greg M. McFarquhar1, Michael R. Poellot20, Siddhant Gupta1, Joseph R. O'Brien20, Athanasios Nenes21,36,37, Mary E. Kacarab21, Jenny P. S. Wong22, Jennifer D. Small-Griswold23, Kenneth L. Thornhill24,33, David Noone25,34, James R. Podolske4, K. Sebastian Schmidt26, Peter Pilewskie26, Hong Chen26, Sabrina P. Cochrane26, Arthur J. Sedlacek27, Timothy J. Lang28, Eric Stith29, Michal Segal-Rozenhaimer4,5,30, Richard A. Ferrare24, Sharon P. Burton24, Chris A. Hostetler24, David J. Diner18, Steven E. Platnick6, Jeffrey S. Myers31, Kerry G. Meyer6, Douglas A. Spangenberg33, Hal Maring32, and Lan Gao1 Jens Redemann et al.
  • 1University of Oklahoma, Norman, OK, USA
  • 2University of Washington, Seattle, WA, USA
  • 3University of Miami, Miami, FL, USA
  • 4NASA Ames Research Center, Moffett Field, CA, USA
  • 5Bay Area Environmental Research Institute, Moffett Field, CA, USA
  • 6NASA Goddard Space Flight Center, Greenbelt, MD, USA
  • 7Universities Space Research Association, Columbia, MD, USA
  • 8Department of Geo-Spatial Sciences and Technology, Namibia University of Science and Technology, Windhoek, Namibia
  • 9North-West University, Unit for Environmental Science and Management, Potchefstroom, North-West, South Africa
  • 10College of Engineering, Maths and Physical Science, University of Exeter, UK
  • 11Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA, UMR 7583), Creteil, France
  • 12Centre National de Recherches Météorologiques, Météo-France-CNRS, Toulouse, France
  • 13Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, UK
  • 14NASA Goddard Institute for Space Studies, New York, NY, USA
  • 15Center for Global and Regional Environmental Research,University of Iowa, Iowa City, IA, USA
  • 16Department of Atmospheric and Oceanic Sciences, and Institute of the Environment and Sustainability, University of California, Los Angeles, CA, USA
  • 17Department of Oceanography, University of Hawaii at Manoa, Honolulu, HI, USA
  • 18Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  • 19Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Madison, WI, USA
  • 20University of North Dakota, Grand Forks, ND, USA
  • 21Georgia Institute of Technology, Atlanta, GA, USA
  • 22Department of Chemistry and Biochemistry, Mount Allison University, Sackville, Canada
  • 23Department of Atmospheric Sciences, University of Hawaii at Manoa, Honolulu, HI, USA
  • 24NASA Langley Research Center, Hampton, VA, USA
  • 25College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvalis, OR, USA
  • 26University of Colorado, Boulder, CO, USA
  • 27Brookhaven National Laboratory, Upton, NY, USA
  • 28NASA Marshall Space Flight Center, Huntsville, AL, USA
  • 29National Suborbital Research Center, Moffett Field, CA, USA
  • 30Department of Geophysics and Planetary Sciences, Porter School of the Environment and Earth Sciences, Tel Aviv University, Tel Aviv, Israel
  • 31UC Santa Cruz, Santa Cruz, CA, USA
  • 32NASA Headquarters, Washington, DC, USA
  • 33Science Systems & Applications, Inc., Hampton, VA, USA
  • 34Department of Physics, University of Auckland, Auckland, New Zealand
  • 35Science and Technology Corporation, Moffett Field, CA, USA
  • 36Ecole Polytechnique Federale de Lausanne, Switzerland
  • 37Foundation for Research and Technology Hellas, Greece

Abstract. Southern Africa produces almost a third of the Earth’s biomass burning (BB) aerosol particles, yet the fate of these particles and their influence on regional and global climate is poorly understood. ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) is a five-year NASA EVS-2 (Earth Venture Suborbital-2) investigation with three Intensive Observation Periods designed to study key atmospheric processes that determine the climate impacts of these aerosols. During the Southern Hemisphere winter and spring (June-October), aerosol particles reaching 3–5 km in altitude are transported westward over the South-East Atlantic, where they interact with one of the largest subtropical stratocumulus subtropical stratocumulus (Sc) cloud decks in the world. The representation of these interactions in climate models remains highly uncertain in part due to a scarcity of observational constraints on aerosol and cloud properties, and due to the parameterized treatment of physical processes. Three ORACLES deployments by the NASA P-3 aircraft in September 2016, August 2017 and October 2018 (totaling ~350 science flight hours), augmented by the deployment of the NASA ER-2 aircraft for remote sensing in September 2016 (totaling ~100 science flight hours), were intended to help fill this observational gap. ORACLES focuses on three fundamental science questions centered on the climate effects of African BB aerosols: (a) direct aerosol radiative effects; (b) effects of aerosol absorption on atmospheric circulation and clouds; (c) aerosol-cloud microphysical interactions. This paper summarizes the ORACLES science objectives, describes the project implementation, provides an overview of the flights and measurements in each deployment, and highlights the integrative modeling efforts from cloud to global scales to address science objectives. Significant new findings on the vertical structure of BB aerosol physical and chemical properties, chemical aging, cloud condensation nuclei, rain and precipitation statistics, and aerosol indirect effects are emphasized, but their detailed descriptions are the subject of separate publications. The main purpose of this paper is to familiarize the broader scientific community with the ORACLES project and the data set it produced.

Jens Redemann et al.

Interactive discussion

Status: final response (author comments only)
Status: final response (author comments only)
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  • RC1: 'Review', Armin Sorooshian, 30 Jun 2020 Printer-friendly Version
  • RC2: 'Review', Anonymous Referee #2, 13 Aug 2020 Printer-friendly Version

Jens Redemann et al.

Jens Redemann et al.


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Publications Copernicus
Short summary
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 five-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 data set it produced, and the most important initial findings.
Southern Africa produces significant biomass burning emissions whose impacts on regional and...