Carbon aerosol visibility vs particle size distribution

Area of Science:

• Atmospheric Science
• Optical Physics
• Aerosol Science

Background:

• Aerosols significantly impact Earth's radiative balance and air quality.
• Understanding aerosol optical properties is crucial for climate modeling and visibility assessments.
• Carbon particles are a major component of atmospheric aerosols with strong optical effects.

Purpose of the Study:

• To determine the optical properties of carbon aerosols based on Mie theory.
• To calculate visibility reduction as a function of aerosol mass concentration and particle size distribution.
• To identify the specific particle diameters that maximize scattering, absorption, and extinction.

Main Methods:

• Mie theory calculations were employed to model aerosol optical properties.
• Log-normal particle size distributions were used to represent carbon aerosols.
• Optical cross sections were normalized by particle mass to identify key size regimes.

Main Results:

• The optical extinction coefficient was calculated to determine visibility.
• Scattering, absorption, and extinction efficiencies were analyzed across various particle sizes.
• For highly absorbing carbon particles, maximum optical effects occur at diameters between 0.15-0.5 micrometers (λ).

Conclusions:

• Particle size is a critical factor in determining the optical impact of aerosols.
• The identified size range (0.15-0.5 µm) is particularly important for highly absorbing carbon aerosols.
• These findings contribute to better modeling of aerosol effects on climate and visibility.