Are measurements for clarity (secchi disk) or turbidity (nephelometer) made for water quality related in any way to measurements made for optical or aerosol optical depth in meteorology?
A secchi disk is basically a measurement of optical depth, and is very similar in principle to the measurements of AOD made in meteorology. Those measurements are quantified at a particular wavelength of light (or a few discrete wavelengths), related to the Beer-Lambert law of light extinction. Light extinction occurs due to scattering and absorption and the total attenuation is integrated. A nephelometer, in contrast, has it's own light source which is shining on the particles, and a detector measures the reflected light (absorption is not being measured). The nephelometer is calibrated to measure particle density by volume of a particular type of particle, based on the reflected light signature.