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Aerosol Asymmetry Factor

Other Names

Scattering Asymmetry


It is a measure of the preferred scattering direction ( forward or backward ) for the light encountering the aerosol particles.
In radiative transfer studies, asymmetry factor 'g' is equal to the mean value of μ (the cosine of the scattering angle), weighted by the angular scattering phase function P(μ). Phase function is defined as the energy scattered per unit solid angle in a given direction to the average energy in all directions.

The asymmetry factor approaches +1 for scattering strongly peaked in the forward direction and -1 for scattering strongly peaked in the backward direction.

In general, g=0 indicates scattering directions evenly distributed between forward and backward directions, i.e isotropic scattering (e.g scattering from small particles)

g<0 scattering in the backward direction (i.e scattering angle > 90 deg., often backscattering is referred to scattering at 180 deg.

g>0 scattering in the forward direction (i.e scattering angle < 90, often forward-scattering is referred to scattering at 0 deg. For larger size or Mie particles, g is close to +1.


(1) Computation of Scattering Phase function (3) Radiative Transfer Model
(2) Characterization of Aerosol Particles (4) Earth Radiation Budget Study

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Last updated: Sep 09, 2009 02:27 PM ET