Atmospheric Particles

Size range: 0.003 to 50 m, 0.003 m particle contains ~1000 molecules

Concentration ranges: 10-5 - 105 cm-3 = 10 - 1011 m-3

Sources: combustion, organic emissions, volcanoes, earths surface, gas to particle conversions,

Mass concentrations: 1 - 100 g m-3 (density of air 1 kg m-3) ppbm

Composition: sulfates, nitrates, ammonium, organics, carbon, crustal material, silicates, water,

Removal: sedimentation, cloud processes, evaporation.

Complete characterization of atmospheric aerosol requires time and space resolved measurements of aerosol:

numbersize (geometric, optical, aerodynamic)surface areavolumemasscompositionoptical properties (scattering + absorption = extinction)shape (droplets to chain aggregates)phasechargenucleating characteristics (nucleation of water, ice, nitric acid hydrates)

|( Nucleation Mode ---(||(Accumulation Mode(||(Coarse Mode ------

10-3 10-2 10-1 100 101 102 |______|______|_____|______|______|_____|______|______|_____|______|______|_____|______|______|_____|

Diameter ((m)

|( Filters -------------------------------------------------------------------------------

|( Diffusion --------------(|

|( Impaction/Interception, Centrifuge/Cyclone

|( Cascade Impactors ---------------(|

|( Thermal Precipitation ---------------------(|

|( Electrostatic Precipitation ----------(|

|(Transmission Electron Microscope (|

|( Scanning Electron Microscope ---------------(|

|( Optical Microscope -------------------

|(Diffusion Analysis(|

|( Electrostatic Analysis -------(|

|( Laser cavity (|

|(Optical Particle Counter (|

~|( Nephelometer/Backscattersonde -------

|( Condensation Nuclei, Ultrafine-----------------------------------------

|( Condensation Nuclei, Conventional--------------------------

~|( Cloud Condensation Nuclei -------------------

~|( Ice Nuclei ------------------------------------------

- |( Single particle composition ---------------------

10-21 10-18 10-15 10-12 10-9

|______|______|_____|______|______|_____|______|______|_____|______|______|_____|______|______|_____|

Mass (g, density = 1 g cm-3)

10-6 10-5 10-4 10-3 10-2 10-1 100 101

__________|__________________|__________|__________|___________|_______|__________|_______|_____

Terminal Velocity (km d-1)

10-3 10-2 10-1 100 101 102

|______|______|_____|______|______|_____|______|______|_____|______|______|_____|______|______|_____|

Diameter ((m)

PCASP -Passive Cavity Aerosol Spectrometer,r > 0.05 - 1.5 m

FSSP - Forward Scattering Spectrometer Probe, r > 0.2 - 15.0 m

MASP - Multi-angle Aerosol Scattering Probe, r > 0.2 - 10.0 m

Nephelometer - aerosol scattering, hemispheric backscatter

Aethalometer - aerosol absorption

Aerosol Composition Mass Spectrometer (ACMS)MagneticElectron50C

AerodyneAerosolMassSpectrometer

The FactsAtmospheric aerosol have a global impact on the atmosphere far exceeding their mass concentration. These impacts include pivotal roles in the hydrologic, radiative, and chemical balance of the atmosphere.Atmospheric aerosol are difficult to measure, and instrument selection depends heavily on measurement goals and ranges of interest.Measurement errors/variations are inherently large due to small sample sizes and large geophysical variations.Measurement quality depends heavily on frequent and careful instrument calibration and characterization.A complete characterization of atmospheric aerosol populations is only addressable with a suite of instruments.Atmospheric aerosol ranges:size: 1 - 10,000 nmconcentrations: 10-4 - 104 cm-3shape droplets to chain aggregatescompositions - large fraction of the periodic table

The ChallengesProvide a climatology of tropospheric aerosol which reduces uncertainties in our understanding of earths radiation budget, particularly over continents.Address questions related to the variation of single scatter albedo from hemisphere to hemisphere, maritime - continental, urban - ruralRefine our understanding of the processes of water, ice, and hydrate nucleation, and characterize the populations of cloud condensation nuclei, ice nuclei, and hydrate nuclei.Establish proper extrapolations: from surface aerosol measurements to atmospheric aerosol profiles from local to global measurementsfrom global satellite measurements to global geophysical parameters

http://www.iac.ethz.ch/staff/krieger/pdf/SpektroskopischeMethoden2.pdfAcknowledging some of the material sourcesTSI Inc web site

optimized to focus particles between 0.1 and 2 m transmission better than 90% at 40 70 mbar, decreases towards larger paricles transition time 30 ms, composition changes negligibleAerodynamic Lens - Focussing Principle