UHSAS

Marine ARM GPCI Investigation of Clouds (MAGIC): Ultra-High Sensitivity Aerosol Spectrometer (UHSAS)

1 October 2012 - 30 September 2013

Lead Scientist: Ernie Lewis

Observatory: AMF, MAG

The ability of aerosol particles to serve as cloud condensation nuclei and form cloud drops depends primarily on their size and additionally on their composition. Thus measurements of the size distribution and concentration of aerosol particles is crucial for understanding and parameterizing cloud formation processes and aerosol-cloud interactions. The Ultra-High Sensitivity Aerosol Spectrometer (UHSAS) was deployed with the AMF2 during the MAGIC deployment aboard the Horizon Lines cargo ship Spirit making regular transects between Los Angeles, CA and Honolulu, HI between October, 2012 and September, 2013. The UHSAS uses a high intensity infrared laser to count and size individual aerosol particles with optical diameters between 0.06 and 1 mm, thus providing size distributions and concentrations of aerosol particles in this size range. This size range is important as it contains the majority of particles that function as cloud condensation nuclei. Size distributions were provided by AMF2 using the HTDMA for only part of the time. The measurement with the UHSAS provided more detailed information on temporal variability of the quantity and allowed intercomparison with the HTDMA. As the UHSAS provided optical diameter, it was a good complement to the HTDMA which measured mobility diameter.