The nephelometer measures the total scattering and hemispheric backscattering of aerosol. Nephelometers are deployed in pairs, with one measuring the ambient conditions and the other measuring the scattering as a function of slowly increasing or decreasing relative humidity (RH). The combination can then be used to derive the hygroscopic growth factor as a function of RH: f(RH).
The nephelometer is part of the aerosol observing system (AOS).