First Results from the Groundbased Fog and Aerosol Spectrometer

DARREL BAUMGARDNER, Dagen Hughes, Paul Zieger, Mike Carrabus, Almuth Neuberger, Droplet Measurement Technologies

     Abstract Number: 577
     Working Group: Instrumentation and Methods

Abstract
Droplet Measurement Technologies LLC (Droplet) has recently developed a single particle optical spectrometer that is a ground-based version of Droplet’s airborne Cloud and Aerosol Spectrometer with Polarization (Baumgardner et al., 2001,2014). The Ground-based Fog and Aerosol Spectrometer (GFAS) measures directly, or derives: 1) Equivalent optical diameter (EOD) of particles 0.5 – 60 µm, 2) Number and volume concentrations > 3000 cm-3, 3) Shape factor using polarization detection, 4) complex refractive index (CRI). The shape factor is used to differentiate liquid droplets from ice crystals, dust particles or ash from biomass burning. The complex refractive index determines if fog droplets are mixed with either dissolved or insoluble material.

The GFAS was recently deployed for three months in the PO Valley where it measured a broad variety of events where fog was mixed with fog and the CRI was clearly linked to air mass origin, i.e. whether the air was coming from cleaner or more polluted sources.

This presentation will highlight the many unique features of the GFAS, illustrated with field observations.