Volume scattering function measurement error: effect of angular resolution of the nephelometer.
The finite angular resolution of nephelometers causes systematic measurement error of the volume scattering function. For scattering angles <90 degrees this error depends mainly on the angular resolution of the nephelometer. For scattering angles >90 degrees the error also depends on the attenuation of light in seawater and the instrument size. For nephelometers with angular resolution of ~2 degrees , in clean ocean waters the error may assume a negative value of the order of -20% at scattering angles smaller than ~5 degrees , i.e., the scattering function may be underestimated. The error may then increase to as much as +15% at ~10 degrees , i.e., the scattering function may be overestimated. For greater scattering angles the error decreases to a few percent until, in turbid coastal waters, it may reach a negative peak of the order of -3% at ~170 degrees , followed by an increase to about +15% for scattering angles in the vicinity of 175 degrees .
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