scholarly journals Biomass Burning Aerosol as a Modulator of Droplet Number in the Southeast Atlantic Region

2019 ◽  
Author(s):  
Mary Kacarab ◽  
K. Lee Thornhill ◽  
Amie Dobracki ◽  
Steven G. Howell ◽  
Joseph R. O'Brien ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Central Africa ◽  
Aerosol Size Distribution ◽  
Atlantic Region ◽  
Radiative Impact ◽  
Biomass Burning Aerosol ◽  
Aerosol Cloud Interactions ◽  
Southeastern Atlantic

Abstract. 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 vertical updraft velocity 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 mid-campaign to concentrations between 500–800 cm−3. By late August and early September, relatively clean MBL conditions were sampled (

scholarly journals Modeling the solar radiative impact of aerosols from biomass burning during the Southern African Regional Science Initiative (SAFARI-2000) experiment

2003 ◽  
Vol 108 (D13) ◽  
pp. n/a-n/a ◽  
Author(s):  
Gunnar Myhre ◽  
Terje K. Berntsen ◽  
James M. Haywood ◽  
Jostein K. Sundet ◽  
Brent N. Holben ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Regional Science ◽  
Radiative Impact ◽  
Science Initiative

scholarly journals Microphysical properties and radiative impact of an intense biomass burning aerosol event measured over Ny-Ålesund, Spitsbergen in July 2015

Tellus B ◽  
2018 ◽  
Vol 70 (1) ◽  
pp. 1-23 ◽  
Author(s):  
C. Ritter ◽  
M. Angeles Burgos ◽  
C. Böckmann ◽  
D. Mateos ◽  
J. Lisok ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Microphysical Properties ◽  
Radiative Impact ◽  
Biomass Burning Aerosol

scholarly journals Deriving brown carbon from multiwavelength absorption measurements: method and application to AERONET and Aethalometer observations

2016 ◽  
Vol 16 (19) ◽  
pp. 12733-12752 ◽  
Author(s):  
Xuan Wang ◽  
Colette L. Heald ◽  
Arthur J. Sedlacek ◽  
Suzane S. de Sá ◽  
Scot T. Martin ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Cape Cod ◽  
Ambient Atmosphere ◽  
Brown Carbon ◽  
Aerosol Absorption ◽  
Multiple Wavelength ◽  
Radiative Impact ◽  
Wavelength Absorption ◽  
Photochemical Aging ◽  
Absorption Measurements

Abstract. The radiative impact of organic aerosols (OA) is a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. This radiative impact includes not only light scattering but also light absorption from a subclass of OA referred to as brown carbon (BrC). However, the absorption properties of BrC are poorly understood, leading to large uncertainties in modeling studies. To obtain observational constraints from measurements, a simple absorption Ångström exponent (AAE) method is often used to separate the contribution of BrC absorption from that of black carbon (BC). However, this attribution method is based on assumptions regarding the spectral dependence of BC that are often violated in the ambient atmosphere. Here we develop a new AAE method which improves upon previous approaches by using the information from the wavelength-dependent measurements themselves and by allowing for an atmospherically relevant range of BC properties, rather than fixing these at a single assumed value. We note that constraints on BC optical properties and mixing state would help further improve this method. We apply this method to multiwavelength absorption aerosol optical depth (AAOD) measurements at AERONET sites worldwide and surface aerosol absorption measurements at multiple ambient sites. We estimate that BrC globally contributes up to 40 % of the seasonally averaged absorption at 440 nm. We find that the mass absorption coefficient of OA (OA-MAC) is positively correlated with the BC ∕ OA mass ratio. Based on the variability in BC properties and BC ∕ OA emission ratio, we estimate a range of 0.05–1.5 m2 g−1 for OA-MAC at 440 nm. Using the combination of AERONET and OMI UV absorption observations we estimate that the AAE388∕440 nm for BrC is generally  ∼ 4 worldwide, with a smaller value in Europe (< 2). Our analyses of observations at two surface sites (Cape Cod, to the southeast of Boston, and the GoAmazon2014/5 T3 site, to the west of Manaus, Brazil) reveal no significant relationship between BrC absorptivity and photochemical aging in urban-influenced conditions. However, the absorption of BrC measured during the biomass burning season near Manaus is found to decrease with photochemical aging with a lifetime of  ∼ 1 day. This lifetime is comparable to previous observations within a biomass burning plume but much slower than estimated from laboratory studies. Given the large uncertainties associated with AERONET retrievals of AAOD, the most challenging aspect of our analysis is that an accurate, globally distributed, multiple-wavelength aerosol absorption measurement dataset is unavailable at present. Thus, achieving a better understanding of the properties, evolution, and impacts of global BrC will rely on the future deployment of accurate multiple-wavelength absorption measurements to which AAE methods, such as the approach developed here, can be applied.

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