Physical, Chemical and Optical Properties of Aerosol: Airborne Observations for MIRAGE, INTEX-B, IMPEX

Hawaii Group for Environmental Aerosol ResearchSchool of Ocean and Earth Science and TechnologyUniversity of HawaiiA. Clarke, J. Zhou, Y. Shinozuka, V. Kapustin, C. McNaughton, S. Howell, M. Pinkerton

In concert with Langley Aerosol Research Group – B. Anderson et al.

Somewhere North of Veracruz, March 2006 Photo A. Clarke

Preliminary observationsPotential Collaborators:B. AndersonE. BrowellJ. JimenezP. DeCarloG. KokR. WeberJ. DibbM.AveryG. Sachseand others

Measurements

• Size distributions - DMA**(0.01-.15um); OPC** (0.15-1.5um); APS>1um and FMPS (courtesy of TSI)

DMA and OPC include volatility @ 150, 300C• Light scattering & backscattering (Total and Submicron at 450,

550, 700nm)

• Light absorption (est. Black Carbon at 450, 550, 700nm)

• f(RH) or Gamma (humidity dependence of light scattering) {DC-8}

Interests

• Size Distributions and Volatility as a measure of size-resolved composition, mixing state and evolution

• Spectral dependence of optical properties linked to sources• Process studies and gas to particle conversion and mixing• Improving physiochemical links to model and satellite products.

Photo courtesy Cam McNaughton

E-W GradientDust

MC Pollution

16:01 – 20:03

20:38 – 23:01

23:11 – 23:20

Dust Pollution

Wavelength dependence of light scattering (angstrom Exponent) provides continuous indication of coarse dust and fine pollution aerosol.

Examples of thermal analysis of size distributionsAmbient (green), 150C (red), 300C (black)

CCNproxy

CCNproxy

Can we link Satellite measurable optical properties to CCN for certain air mass types -- Indirect Effect? Use DMA number between 80-200nm as CCNproxy.

PollutionDust

A “Rainbow” suggests a relation may exist when stratifed by airmass type

VOLATILE TANDEM DMA STUDIES REVEAL INTERNAL MIXING QUANTIFIES AMOUNT OF VOLATILE COMPONETS MIXED WITH A REFRACTORY COMPONENT OR CORE

VolatilityTDMA measurements aboard C-130 (left column) and DC-8 (right column) during MILAGRO. Selected sizes (rows) of 70, 100 and 140nm are heated to 300C to identify the volatile and refractory fractions (black lines). Variability in refractory residual sizes for a given selected size are highlighted as the smallest and the largest residual sizes.

Large variability is related both to sources and evolution of the aerosol. Note that the MIRAGE data collected closer to Mexico City has median Volatile Fractions that are less than INTEX-B -- probably because the latter are generally more aged.

70nm

100nm

140nm

The wavelength dependence of absorption and its link to AMS organic mass fraction

Relative scattering increase [f(RH) 40:85] agrees with expected values and revels presence of dust and organics with low values

Dust &Organics

Aerosol optical properties are a function of their size and composition.

To quantify this effect we measured f(RH), the ratio of scattering at 85%RH to the “dry” scattering at 45%RH.

These values also span our observed RH range from low humidity near Mexico City to high humidity often in aged aerosol transported out over the Gulf of Mexico.

The single scatter albedo (ratio of scattering to sum of absorption and scattering) is important for climate studies.

Measured SSA vs. absorption per unit submicron mass for the last two DC-8 flights over Mexico.

Absorption per mass carried in models and resulting optics can be tested against the dependency evident here.

The red symbols are for dry (45%RH) as experienced near MC and the blue are for the same aerosol at 85%RH as may be experienced over the Gulf of Mexico.

The “wet” SSA is much higher than the measured dry SSA values and are more tightly clustered about a line. This reveals the coupling between the chemistry (ions), absorption and optical properties.

The role of humidity in modifying optical properties such as SSA when transported from dry to humid environment (eg. Mexico City to the Gulf of Mexico)

}Expected change in SSA for MC aerosol transported to marine boundary layer

Boundary Layer Rolls and Vertical Mixing Non-Precipitating clouds and air-mass exchange

Circled area indicates plume of fresh pollution measured near Tampico – see McNaughton et al., poster on regional profiles etc..

NOTE: CO2 still needs a few sec. time shift to left

1. RH and light scattering correlated for upward moving boundary layer pollution.

2. CO2 and Ozone anti-correlated reflecting more ozone aloft and more CO2 below

3. RH and ozone also anti-correlated

Organized vertical mixing of boundary layer pollution and clean free troposphere aerosol

More smaller volatile CN and CCN mixing downward from FT

More refractory combustion particles moving up from MBL into free troposphere

Organized vertical mixing of boundary layer pollution and clean free troposphere aerosol

A. Clarke, V. Kapustin, S. Howell, J. Zhou, C. McNaughton, Y. Shinozuka University of Hawaii

(INTEX-B flights 11-13, DIAL Lidar, E.V. Browell, NASA, LaRC and aerosol vertical profiles), indicate the removal pathway for dust and pollution via subsidence into the marine boundary layer.

Regional Variability in the wavelength dependence of absorption

Dust or Biomass Burning

Pollution

Regional Variability in Single Scatter Albedo

SP2 Incandescent Mass fraction vs. OPC refractory Volume Fraction

DUST DOMINATED

SUMMARY

• Volatility and state of mixing linked to both SP2 and AMS data.

• f(RH) is an essential tool to assess ambient optical properties.

• Small scale boundary layer rolls and clouds provide effective and structured mixing for boundary layer and free troposphere air

• Large scale regional subsidence and entrainment provide a major pathway from the free troposphere into the boundary layer where removal can be effective.

• Some hope for satellite retrieval of optical properties linked to CCN if stratified by air-mass type.

• Large Scale regional characteristics evident in the wavelength dependence of scattering, absorption and single scatter albedo.

• Optical properties and closure studies – see other presentations.