Measurement Needs and Challenges for Absorbing Aerosol

Black Carbon, Brown Carbon, Dust and Coatings

Dan Lack

Daniel.lack@noaa.gov

Cloud & Aerosol Process Group

CSD/ESRL/NOAA

Presented at:

NIST Aerosol Metrology for 

Climate Workshop

15th March, 2011
Deposition

Snow Darkens

and Warms

BC in Clouds

Layer Warms

Surface Dimming

TOA Forcing

Absorbing Aerosols and Climate
Forcing

(Ramanathan and Carmichael 2008)

1. BC mixing state.

2. BC vertical distributions.

3. Inventories. 

4. Indirect effect.

- Precipitation patterns. 

ΔaF↑= 1/2FTT2(1−AC)×[SSAβa(1−RS)2 −2(1 − SSA)RS]AOD

• SSA – Aerosol single scatter albedo

• βa – Aerosol upscatter fraction

• AOD – Aerosol optical depth

Forcing Uncertainties

• AC – Cloud Fraction

• RS – Surface Albedo
SSA Evolution

(Russell et al 2002)
Coating Evolution

Absorbing Core / Clear Coat

Coating Evolution

Absorbing Core / Absorbing Coat

Absorption Evolution

Absorbing Organic Particles

Density Evolution

BC Fractal Dimension

SSA

1

0.2

SSA Evolution
Fractal BC, Clear Coatings, Evolving BC shape, evolving BrC

Non-Fractal BC, BrC Coatings

Sub-Equatorial: Dust

Global Distributions of Variations in Absorbing Material/Effects (simplified look)

(NOAA.gov)
Remote Sensing and Models

Models until recently Most models now Satellite/radiometer

retrievals

In-Situ Measurements
In-Situ Measurements:

1. BC mixing state.

2. BC vertical distributions.

3. Inventories. 

4. Indirect effect.

• Most information comes from mass measurements. 

Optics is inferred from in-situ laboratory or field studies.

– Mass extinction, scattering, absorption efficiencies.

• Extinction (± 1 - 10%)

• Scattering (& backscatter) (± 3 - 10%)

• Absorption (± 5 - 50%)
Extinction

• Cavity Ring Down

• Extinction cells

• CAPS Extinction

Baynard et al 2007

Massoli et al 2010

Langridge et al 2011
Scattering

• Nephelometers

• Integrating spheres

TSI Inc.

Absorbing Aerosol Biases

Massoli et al 2009
Absorption

• Filter-Based

– Corrections:

• Scattering (size?, SSA?)

• Flow

• Filter spot size

• Particle morphology

• Particle phase?

Petzold & Schonlinner 2004

Tian et al, 2009

• Photo-Acoustic Spectroscopy (PAS)

Lack et al, 2011
Simple absorbing systems (filter vs

PAS): 

Absorbing Mono-Disperse Spheres

(Lack et al 2008)

(Lack et al 2009)
Coated Absorbing Systems

(Lack et al 2009)
Water Uptake and Absorption

(Lack et al 2009) (Zhang et al 2008)
Filter-Based Absorption: Organic Particles

(Subramanian et al. 2007)

Black Carbon Organic + Black Carbon

(Lack et al. 2008)
Filter Based Absorption: Particle Size

(Lack et al 2009) (Nakayama et al 2010)
Filter Based: Variability

• Filter-based measurement has a number of issues.

• Muller et al, Characterization and intercomparison of aerosol 

absorption photometers: result of two intercomparison workshops. 

Atmos. Meas. Tech. 2011, 4, (2), 245-268.

Photo Acoustics (or PTI)

• Expensive, compared to filter methods.

• Can have biases at elevated RH or large particle sizes.

• Has yet to be widely deployed.
Long Term Monitoring

• Cannot spend $100’s K on state of the art.

– Filter-based methods will continue to be used 

unless new inexpensive techniques are available.

• Require simple instruments to be:

– Inexpensive

– Robust

– Simple operations

– Well characterised
Characterisation Requires

• Simple Absorbing standard:

– Spherical.

– Monodisperse (known sizes)

– Known refractive index (extinction, scattering, 

absorption at multiple wavelengths)

• More realistic absorbing standard (BC, soot)?

• RH Effects.

• Shape / Size Effects.

• Effects of OA.

• Effects of pressure.
Vertical Profiles

• Aircraft platforms require fast sampling. 

• Alternative: instrument development for simpler 

platforms (balloons?).

• Require instruments to be:

– Sensitive (immune to ambient and platform noise)

– Probe relevant parameters

• λ’s, coatings, BrC, RH

– Well characterised

• Cavity Ring Down and PAS technologies have not yet 

common aircraft research tools. 
References

Ramanathan, V.; Carmichael, G., Global and regional climate changes due to black carbon. Nature Geosci. 2008, 1, 221-227.

Russell, P. B.; Redemann, J.; Schmid, B.; Bergstrom, R. W.; Livingston, J. M.; McIntosh, D. M.; Ramirez, S. A.; Hartley, S.; Hobbs, P. V.; Quinn, P. K.; 

Carrico, C. M.; Rood, M. J.; Ostrom, E.; Noone, K. J.; von Hoyningen-Huene, W.; Remer, L., Comparison of aerosol single scattering albedos derived by 

diverse techniques in two North Atlantic experiments. Journal of the Atmospheric Sciences 2002, 59, (3), 609.

Baynard, T.; Pettersson, A.; Lovejoy, E.; Brown, S.; Lack, D.; Massoli, P.; Osthoff, H.; Ciciora, S.; Dube, B.; Ravishankara, A. R., Design and Application of a 

Pulsed Cavity Ring-Down Aerosol Extinction Spectrometer for Field Measurements. Aerosol Sci. Tech. 2007, 41, (4), 447 - 462.

Massoli, P.; Murphy, D. M.; Lack, D. A.; Baynard, T.; Brock, C. A.; Lovejoy, E. R., Uncertainty in Light Scattering Measurements by TSI Nephelometer: 

Results from Laboratory Studies and Implications for Ambient Measurements. Aerosol Science And Technology 2009, 42, (11), 1064-1074.

Petzold, A.; Schˆnlinner, M., Multi-angle absorption photometry--a new method for the measurement of aerosol light absorption and atmospheric 

black carbon. Journal of Aerosol Science 2004, 35, (4), 421-441.

Tian, G.; Moosm√oller, H.; Arnott, W. P., Simultaneous Photoacoustic Spectroscopy of Aerosol and Oxygen A-Band Absorption for the Calibration of 

Aerosol Light Absorption Measurements. Aerosol Science and Technology 2009, 43, (11), 1084 - 1090.

Lack, D. A.; Corbett, J.; Lerner, B.; Massoli, P.; Quinn, P. K.; Coffman, D.; Bates, T. S.; Covert, D. S.; Sierau, B.; Herndon, S.; Onasch, T.; Baynard, T.; 

Lovejoy, E. R.; Ravishankara, A. R.; Williams, E., Particulate Emissions from Commercial Shipping. Chemical, Physical and Optical Properties. Journal of 

Geophysical Research 2009, 114, (D00F04), doi:10.1029/2008JD011300.

Lack, D. A.; Cappa, C. D.; Covert, D. S.; Baynard, T.; Massoli, P.; Sierau, B.; Bates, T. S.; Quinn, P. K.; Lovejoy, E. R.; Ravishankara, A. R., Bias in Filter 

Based Aerosol Light Absorption Measurements Due to Organic Aerosol Loading: Evidence from Ambient Measurements. Aerosol Science and 

Technology 2008, 42, (12), 1033-1041.

Lack, D. A.; Cappa, C. D.; Cross, E. S.; Massoli, P.; Ahern, A. T.; Davidovits, P.; Onasch, T. B., Absorption Enhancement of Coated Absorbing Aerosols: 

Validation of the Photo-Acoustic Technique for Measuring the Enhancement Aerosol Science and Technology 2009, 43, (10), 1006-1012.

Subramanian, R.; Roden, C. A.; Boparai, P.; Bond, T. C., Yellow Beads and Missing Particles: Trouble Ahead for Filter-Based Absorption Measurements. 

Aerosol Science and Technology 2007, 41, (6), 630-637.

Nakayama, T.; Kondo, Y.; Moteki, N.; Sahu, L. K.; Kinase, T.; Kita, K.; Matsumi, Y., Size-dependent correction factors for absorption measurements using 

filter-based photometers: PSAP and COSMOS. J. Aerosol. Sci. 2010, 41, (4), 333-343.

Lack, D. A.; Covert, D. C.; Baynard, T.; Massoli, P.; Sieru, B.; Lovejoy, E. R.; Ravishankara, A. R., The Relative Humidity Dependence of the Absorption of 

Mineral Dust Aerosol after Long-Range Atmospheric Transport from the Sahara. Geophysical Research Letters 2009, 36, (L24805), 

doi:10.1029/2009GL041002.

Lack, D,A. et al. Aircraft Instrument for Comprehensive Characterization of Aerosol Optical Properties, Part 2: Black and Brown Carbon Absorption and 

Absorption Enhancement Measured with Photo Acoustic Spectroscopy, submitted to AS&T, 2011.

Langridge, J. et al Aircraft instrument for comprehensive characterisation of aerosol optical properties, part 1: wavelength dependent optical extinction 

and its relative humidity dependence measured using cavity ringdown spectroscopy, submitted to AS&T, 2011

Zhang, R.; Khalizov, A. F.; Pagels, J.; Zhang, D.; Xue, H.; McMurry, P. H., Variability in Morphology, Hygroscopicity, and Optical Properties of Soot 

Aerosols During Atmospheric Processing. Proceedings of the National Academy of Sciences 2008, 105, (30), 10291-10296.