Breakout Summary Report
ARM/ASR User and PI Meeting
Shortwave-absorbing aerosols and their interactions with the large-scale environment
24 June 2020
2:00 PM - 4:00 PM
100
Paquita Zuidema, Allison Aiken, Art Sedlaceck, Yan Feng
24 June 2020
2:00 PM - 4:00 PM
100
Paquita Zuidema, Allison Aiken, Art Sedlaceck, Yan Feng
Breakout Description
Biomass-burning aerosols (BBA) represent complex mixtures of black and brown carbon that include organic aerosols, distinguishing them from the soot emitted by fossil fuels. The aerosol chemical composition, irrespective of source, will change with age, affecting the aerosol’s optical and cloud-nucleating properties in time-dependent ways. These affect the direct aerosol radiative effect, which also depends on the underlying albedo, either of the earth’s surface or clouds. Such aerosols are also effective cloud nucleators. Clouds, if present, adjust to the presence of smoke. Clouds can adjust both radiatively to the shortwave absorption, or indirectly through changes to their microphysics when clouds and aerosols mix. The dominant processes will vary with the aerosol-cloud vertical structure, which can vary seasonally, while the dominant cloud adjustments will also evolve as the clouds advect with the prevailing wind.Modeling efforts are necessary to help articulate the significant processes, with model-observational closure/validation studies necessary for promoting confidence in model-based analyses. The characterization of truly aged biomass-burning aerosol, its relationship to the prevalent marine cloud, and the processes by which the clouds interact with the smoke, motivated the LASIC (Layered Atlantic Smoke Interactions with Clouds) campaign held in the remote southeast Atlantic on Ascension Island. The motivating issues occur globally. Lab studies are encouraged. We invite all attendees with relevant material.
Participants: We are soliciting short presentations. If you would like to present, please send a title and a few sentences describing your contribution to the conveners (pzuidema@miami.edu, aikenac@lanl.gov, yfeng@anl.gov and sedlacek@bnl.gov) by early June.
Main Discussion
The session agenda is below; I recognize this is also available elsewhere but feel it is useful to show as it guided the main discussion. This primarily occurred via the Zoom Chat feature during the session, spilling over into email after the session, indicating the depth of enthusiasm. One item that invigorated discussion in particular was the aging process for the biomass-burning aerosol. A valuable aspect of this session is that two other field campaigns were held concurrently over the southeast Atlantic with LASIC: the aircraft UK CLARIFY campaign, also based on Ascension, and the NASA ORACLES campaign. An invigorating aspect of this session was the discussion linking the three campaigns together, as there is now some analysis available from all 3 campaigns with which to do this.Agenda:
Aerosol processes:
2:02 Art Sedlacek: on the mixing state lifecycle of biomass-burning black carbon, from BBOP to LASIC [10 minutes +2 Q/A]
2:14 Amie Dobracki: Rethinking the lifetime of biomass-burning-aerosol in the free troposphere [10 minutes + 2 Q/A]
2:26 Michal Segal-Rozenhaimer: Assessing the Link Between Aerosol Mixing State, Structure and Composition and their Optical Properties: Ascension Island as a Testbed for the South-East Atlantic Aerosol [10 minutes + 2 Q/A]
Aerosol-Cloud Interactions:
2:38 Allison Collow and Mark Miller: Radiative Heating Rate Profiles over the Southeast Atlantic
Ocean during the 2016 and 2017 Biomass Burning Seasons [10 minutes+ 2 Q/A]
2:50 Paul Barrett: On the collaboration between UK CLARIFY and LASIC [10 minutes+ 2 Q/A]
3:02 Jianhao Zhang: Amplification of the seasonal cycle in low clouds over the remote southeast Atlantic when biomass-burning aerosol is present [10 minutes + 2 Q/A]
3:14 Pablo Saide and Calvin Howes: Hygroscopicity parameter from LASIC observations and comparison to models [10 minutes + 2 Q/A]
The Modeling Frontier:
3:26 Yan Feng: Evolution of Biomass Burning Aerosol Properties: a Model Comparison to the LASIC and ORACLES Observations [ 10 minutes+ 2 Q/A]
3:38 Michael Diamond, Ann Fridlind/Andrew Ackerman, Jan Kazil: Stratocumulus-to-cumulus transitions in the presence of smoke [15 minutes+ 5 Q/A]
3:58 Where do we go from here? [2 minutes]
Key Findings
Most of this analysis is still ongoing, and other than the presentation by Allison Collow and Mark Miller, none of this has been published yet. I would argue that each presentation listed above contained a new key finding.Issues
Not really. We need to keep momentum to make sure the analyses represented in this session are finished and published.Needs
No real specific needs were identified. Primarily we need to maintain energy on the various collaborative inter-campaign projects.Decisions
Several modeling studies are examining the stratocumulus to cumulus transition, and several modeling groups are interested in comparing to the new LASIC datasets. One decision made is to improve coordination between these efforts. Another follow-up virtual meeting will be held to promote both of these inter-related activities, currently anticipated for October (2020).The conveners also felt that it would be valuable to hold this session again at the next annual meeting.
Future Plans
Another follow-up virtual meeting will be held to promote both of these inter-related activities, currently anticipated for October (2020).The conveners also felt that it would be valuable to hold this session again at the next annual meeting.