The effect of molecular anisotropy on backscattered UV (BUV) radiances
is computed by accounting for it in both Rayleigh optical thickness a
nd the scattering-phase matrix. If the effect of molecular anisotropy
is included only in the optical thickness and not in the phase matrix,
then for high sun (theta(0) similar to 0 degrees), the nadir radiance
(I-0) leaving the top of the atmosphere is approximately 1.8% higher
than the radiance (I-op) computed with the effect included in the phas
e matrix. For very low sun (theta(0) > 80 degrees), I-0 is approximate
ly 2.3% lower than I-op. For off-nadir radiances the relative increase
(decrease) depends on both the local zenith angle as well as the azim
uth angle. Also, an increase in the surface reflectivity decreases the
effect of molecular anisotropy on the upwelling radiances. Exclusion
of the anisotropy factor in the Rayleigh-phase matrix has very little
effect (<1%) on ozone retrieval from the BUV-type instruments. This is
because of the ratio technique used in the retrieval algorithm, which
practically cancels out the anisotropy effect. (C) 1995 Optical Socie
ty of America