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...
Review status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.
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 Gao1Jens Redemann et al.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
Received: 08 May 2020 – Accepted for review: 07 Jun 2020 – Discussion started: 16 Jun 2020
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.
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...