气候变化领域集成服务门户(CCPortal): Biomass burning aerosol as a modulator of the droplet number in the southeast Atlantic region

CCPortal

DOI	10.5194/acp-20-3029-2020
	Biomass burning aerosol as a modulator of the droplet number in the southeast Atlantic region
	Kacarab M.; Lee Thornhill K.; Dobracki A.; Howell S.G.; O'Brien J.R.; Freitag S.; Poellot M.R.; Wood R.; Zuidema P.; Redemann J.; Nenes A.
发表日期	2020
ISSN	1680-7316
起始页码	3029
结束页码	3040
卷号	20 期号:5
英文摘要	The southeastern Atlantic (SEA) and its associated cloud deck, off the west coast of central Africa, is an area where aerosol-cloud interactions can have a strong radiative impact. Seasonally, extensive biomass burning (BB) aerosol plumes from southern Africa reach this area. The NASA ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) study focused on quantitatively understanding these interactions and their importance. Here we present measurements of cloud condensation nuclei (CCN) concentration, aerosol size distribution, and characteristic vertical updraft velocity (w) in and around the marine boundary layer (MBL) collected by the NASA P-3B aircraft during the August 2017 ORACLES deployment. BB aerosol levels vary considerably but systematically with time; high aerosol concentrations were observed in the MBL (800-1000 cm-3) early on, decreasing midcampaign to concentrations between 500 and 800 cm-3. By late August and early September, relatively clean MBL conditions were sampled (< 500 cm-3). These data then drive a state-of-the-art droplet formation parameterization from which the predicted cloud droplet number and its sensitivity to aerosol and dynamical parameters are derived. Droplet closure was achieved to within 20 %. Droplet formation sensitivity to aerosol concentration, w, and the hygroscopicity parameter, k, vary and contribute to the total droplet response in the MBL clouds. When aerosol concentrations exceed ~ 900 cm-3 and maximum supersaturation approaches 0.1 %, droplet formation in the MBL enters a velocity-limited droplet activation regime, where the cloud droplet number responds weakly to CCN concentration increases. Below ~ 500 cm-3, in a clean MBL, droplet formation is much more sensitive to changes in aerosol concentration than to changes in vertical updraft. In the competitive regime, where the MBL has intermediate pollution (500-800 cm-3), droplet formation becomes much more sensitive to hygroscopicity (k) variations than it does in clean and polluted conditions. Higher concentrations increase the sensitivity to vertical velocity by more than 10-fold. We also find that characteristic vertical velocity plays a very important role in driving droplet formation in a more polluted MBL regime, in which even a small shift in wmay make a significant difference in droplet concentrations. Identifying regimes where droplet number variability is driven primarily by updraft velocity and not by aerosol concentration is key for interpreting aerosol indirect effects, especially with remote sensing. The droplet number responds proportionally to changes in characteristic velocity, offering the possibility of remote sensing of wunder velocity-limited conditions. © Author(s) 2020.
语种	英语
scopus关键词	aerosol; biomass burning; cloud condensation nucleus; concentration (composition); radiative transfer; volcanic cloud; Atlantic Ocean; Atlantic Ocean (Southeast)
来源期刊	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/141483
作者单位	School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, United States; NASA Langley Research Center, Hampton, VA 23666, United States; Department of Oceanography, University of Hawaii at Manoa, Honolulu, HI 96822, United States; Department of Atmospheric Sciences, University of North Dakota, Grand Forks, ND 58202, United States; Department of Atmospheric Sciences, University of Washington, Seattle, WA 98195, United States; Department of Atmospheric Sciences, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149, United States; School of Meteorology, University of Oklahoma, Norman, OK 73072, United States; Institute for Chemical Engineering Sciences, Foundation for Research and Technology-Hellas, Patras, 26504, Greece; Laboratory of Atmospheric Processes and Their Impacts, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Federale de Lausanne, Lausanne, 1015, Switzerland
推荐引用方式 GB/T 7714	Kacarab M.,Lee Thornhill K.,Dobracki A.,et al. Biomass burning aerosol as a modulator of the droplet number in the southeast Atlantic region[J],2020,20(5).
APA	Kacarab M..,Lee Thornhill K..,Dobracki A..,Howell S.G..,O'Brien J.R..,...&Nenes A..(2020).Biomass burning aerosol as a modulator of the droplet number in the southeast Atlantic region.Atmospheric Chemistry and Physics,20(5).
MLA	Kacarab M.,et al."Biomass burning aerosol as a modulator of the droplet number in the southeast Atlantic region".Atmospheric Chemistry and Physics 20.5(2020).