Don Grainger PI,

1
Optical Properties of Volcanic Ash

• Don Grainger (PI),
• Ellie Highwood (Collaborator),
• Dan Peters (PDRA)
• Inform and consult others about our plans to use
  the MSF aerosol cell

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Outline

• Overview
• Don Grainger
• A Microphysical Model for Cell Generated Aerosols
• Sachchida Tripathi
• Optical Properties of Volcanic Ash Proposed
  experimental method
• Dan Peters

3

• Definition
• Aerosol Optical Properties Refractive index
  (real and imaginary components) over the
  wavelength range 350 nm to about 16 µm.
• Motivation
• These values are necessary for
• quantitative remote sensing of aerosol properties
• calculating the impact of aerosols on the
  atmospheric radiation balance and hence climate

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Inheritance

• Measurements of sulphuric acid particles
• Adam Heathfield
• Measurements of mimic polar stratospheric cloud
  particles
• Steve Bass
• Robert McPheat

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Issues

• Characterisation of what is being observed!
• Size distribution
• Measurement (SMPS, OPC)
• Modelling (microphysical model)
• Composition
• Measurement (mass spec)
• Modelling (IR band signatures)
• Multiple scattering
• Particle non-sphericity

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To Do!

• Yet to write up
• An adequate description of the method of
  determining refractive indices from extinction
  measurements
• (Reflects a certain lack of confidence in the
  absolute values because of nervousness about the
  aerosol size distribution)
• Associated cell work (Mie theory, multiple
  scattering, microphysical modelling)
• PSC work
• Applied our measurements to satellite
  observations or radiative calculations

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Optical Properties of Volcanic Ash will provide
the framework to address these issues and
accomplish outstanding tasks