Black carbon aerosol over the Los Angeles Basin during CalNex

Metcalf, A. R.; Craven, J. S.; Ensberg, J. J.; Brioude, J.; Angevine, W. M.; Sorooshian, Armin; Duong, H. T.; Jonsson, H.; Flagan, R. C.; Seinfeld, John H.

doi:10.1029/2011jd017255

Cited by 92 publications

(134 citation statements)

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“…A continuous flow thermal gradient cloud condensation nuclei counter (CCNc, Droplet Measurement Technologies Inc.; Roberts and Nenes, 2005) was used to quantify the number of particles that activated at supersaturations ranging from 0.2 % to 0.8 %. Black carbon (BC) mass measurements were obtained using a single particle soot photometer instrument (SP2; Droplet Measurement Technologies) (Schwarz et al, 2006;Metcalf et al, 2012).…”

Section: Field Deployment and First Resultsmentioning

confidence: 99%

Characterisation and airborne deployment of a new counterflow virtual impactor inlet

et al. 2012

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Abstract.A new counterflow virtual impactor (CVI) inlet is introduced with details of its design, laboratory characterisation tests and deployment on an aircraft during the 2011 Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE). The CVI inlet addresses three key issues in previous designs; in particular, the inlet operates with: (i) negligible organic contamination; (ii) a significant sample flow rate to downstream instruments (∼15 l min −1 ) that reduces the need for dilution; and (iii) a high level of accessibility to the probe interior for cleaning. Wind tunnel experiments characterised the cut size of sampled droplets and the particle size-dependent transmission efficiency in various parts of the probe. For a range of counter-flow rates and air velocities, the measured cut size was between 8.7-13.1 µm. The mean percentage error between cut size measurements and predictions from aerodynamic drag theory is 1.7 %. The CVI was deployed on the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter for thirty flights during E-PEACE to study aerosol-cloud-radiation interactions off the central coast of California in July and August 2011. Results are reported to assess the performance of the inlet including comparisons of particle number concentration downstream of the CVI and cloud drop number concentration measured by two independent aircraft probes. Measurements downstream of the CVI are also examined from one representative case flight coordinated with shipboard-emitted smoke that was intercepted in cloud by the Twin Otter.

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Section: Field Deployment and First Resultsmentioning

confidence: 99%

Characterisation and airborne deployment of a new counterflow virtual impactor inlet

et al. 2012

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“…Using Mie theory and assuming a core-shell model, the thickness of the coating present on the rBC core was calculated based on the measured scattering signal in conjunction with the measured rBC mass. The refractive index used for the core is 2.26 − 1.26i (Moteki et al, 2010;Taylor et al, 2015) and the refractive index used for the coating material is 1.5 − 0.0i (Metcalf et al, 2012;Schwarz et al, 2008), since the calibrations of the scattering signal were done with polystyrene latex spheres (PSLs). It should be noted that the assumption of concentric core-shell morphology is a simplification for rBC particles in the atmosphere (e.g., Moffet et al, 2016).…”

Section: Rbc Coating Thicknessesmentioning

confidence: 99%

An evaluation of three methods for measuring black carbon in Alert, Canada

et al. 2017

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Abstract. Absorption of sunlight by black carbon (BC) warms the atmosphere, which may be important for Arctic climate. The measurement of BC is complicated by the lack of a simple definition of BC and the absence of techniques that are uniquely sensitive to BC (e.g., Petzold et al., 2013). At the Global Atmosphere Watch baseline observatory in Alert, Nunavut (82.5 • N), BC mass is estimated in three ways, none of which fully represent BC: conversion of light absorption measured with an Aethalometer to give equivalent black carbon (EBC), thermal desorption of elemental carbon (EC) from weekly integrated filter samples to give EC, and measurement of incandescence from the refractory black carbon (rBC) component of individual particles using a single particle soot photometer (SP2). Based on measurements between March 2011 and December 2013, EBC and EC are 2.7 and 3.1 times higher than rBC, respectively. The EBC and EC measurements are influenced by factors other than just BC, and higher estimates of BC are expected from these techniques. Some bias in the rBC measurement may result from calibration uncertainties that are difficult to estimate here. Considering a number of factors, our best estimate of BC mass in Alert, which may be useful for evaluation of chemical transport models, is an average of the rBC and EC measurements with a range bounded by the rBC and EC combined with the respective measurement uncertainties. Winter-, spring-, summer-, and fall-averaged (± atmospheric variability) estimates of BC mass in Alert for this study period are 49 ± 28, 30 ± 26, 22 ± 13, and 29 ± 9 ng m −3 , respectively. Average coating thicknesses estimated from the SP2 are 25 to 40 % of the 160-180 nm diameter rBC core sizes. For particles of approximately 200-400 nm optical diameter, the fraction containing rBC cores is estimated to be between 10 and 16 %, but the possibility of smaller undetectable rBC cores in some of the particles cannot be excluded. Mass absorption coefficients (MACs) ± uncertainty at 550 nm wavelength, calculated from light absorption measurements divided by the best estimates of the BC mass concentrations, are 8.0 ± 4.0, 8.0 ± 4.0, 5.0 ± 2.5 and 9.0 ± 4.5 m 2 g −1 , for winter, spring, summer, and fall, respectively. Adjusted to better estimate absorption by BC only, the winter and spring values of MACs are 7.6 ± 3.8 and 7.7 ± 3.8 m 2 g −1 . There is evidence that the MAC values increase with coating thickness.

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“…The BC core size which may reflect the features of primary sources, was systematically larger in winter than in late spring, maybe due to the significant contribution of residential emission sector. However the BC core size during hot season over the NCP was still significantly larger than in Europe (McMeeking et al, 2010;Liu et al, 2014) or North America (Schwarz et al, 2008;Metcalf et al, 2012) where the 25 transportation emission sector dominates in hot season. This indicates the complex combined sources even in hot season in China, in line with the emission inventory that the industrial and residential sectors still dominated over the transportation sector in hot season.…”

Section: Resultsmentioning

confidence: 99%

Aircraft measurements of black carbon in the boundary layer over the North China Plain

Zhao

Huang

Liu

et al. 2018

Preprint

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Black carbon aerosol (BC) is the principle absorber to modify the shortwave radiative balance between the lower atmosphere and the surface in polluted environment, which was in-situ characterized by aircraft measurements using a single particle soot photometer (DMT inc., SP2) throughout the boundary layer up to 3km over the North China Plain around Beijing megacity. The flights were conducted in both hot season (late 5 spring, Apr. -Jun. 2012, surface temperature >20°C, 10 flights) and cold season (winter, Dec. 2016, surface temperature <5°C, 6 flights). The BC mass in the daytime well-developed planetary boundary layer (BCPBL) was found to be largely influenced by meteorology which modulated the local emission and regional transport. The BCPBL in hot season showed no apparent vertical gradient or correlation with the PBL height (PBLH); whereas in winter the BCPBL decreased at higher altitude and accumulated towards the surface due 10 to reduced horizontal wind speed at low level, and was anti-correlated with the PBLH. The more homogenous vertical mixing of BCPBL in hot season may result from the stronger convective mixing due to higher surface temperature, in addition the predominant southerly wind may have advected the largely polluted air mass, offsetting its dilution effect; whereas in winter the predominant cleaner air mass from the north had important dilution effect on local emissions. The overall averages showed lower BC mass loading 15 in the surface layer during hot season but similar loadings (3.5-4 µg m -3 ) in the PBL for both seasons. The highly turbulent air conditions, as frequently observed in the early afternoon during hot season, largely diluted the BC mass down to the background level (~0.5 µg m -3 ); whereas in winter the BCPBL was significantly elevated under dynamic air condition due to efficient transport of polluted air mass from the south. 20The BCPBL in winter showed systematically larger core size (mass median diameter, MMD=217±4nm) than in late spring (209±7nm), which may be due to a higher contribution from the residential emission sector in cold season. The high BC mass loadings were mostly associated with a high fraction of thick coatings (Fcoating), and the higher air moisture enhanced the coating content of BCPBL. These suggest the primary sources with a range of co-emitted species significantly contributed to the coatings of BC, and the secondary 25 formation which could be enhanced by elevated RH also played important role. The BC after significant removal showed much lower Fcoating (~0.06) and smaller core size (MMD ~193nm), implying that the coated and larger BC particle was preferentially removed. The scavenging efficiency of BC in the entrainment zone (EZ) showed positive correlation with the change of coatings between PBL and EZ for both seasons (Fcoating,PBL > Fcoating,EZ), however showed seasonally different behaviors in terms of core size 30 (MMDPBL>MMDEZ in late spring, but the opposite in winter). These results provide the basis to evaluate the BC direct radi...

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Black carbon aerosol over the Los Angeles Basin during CalNex

Cited by 92 publications

References 200 publications

Characterisation and airborne deployment of a new counterflow virtual impactor inlet

Characterisation and airborne deployment of a new counterflow virtual impactor inlet

An evaluation of three methods for measuring black carbon in Alert, Canada

Aircraft measurements of black carbon in the boundary layer over the North China Plain

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