The effect of forward scattered light on the extinction of aerosols in a White type optical cell

Photons are traced through a simplified White type cell to determine the adjustment to compensate for detected forward scattered light in measuring aerosol optical depth. Verification is performed by comparing the optical depth determined from optical extinction with that calculated from the measured concentration of monodisperse polystyrene latex (PSL) spheres. As the adjustments derived for representative urban and marine aerosols are similar to or larger than those required for the PSL spheres, forward scattered light needs to be considered for real world conditions with our instrument. Although the described adjustment is specific to this instrument, it is shown that it may be significant for other detection geometries.