Guest Instruments to Collect Aerosol Data During Coastal Field Campaign

 
Published: 15 June 2005

The counter-flow virtual impactor (inset), which can characterize aerosol particles in cloud droplets, joins a number of other guest instruments at the ARM Mobile Facility deployment site at Point Reyes National Seashore in California.

The ARM Mobile Facility’s (AMF’s) inaugural field campaign, the Marine Stratus Radiation Aerosol and Drizzle (MASRAD) Intensive Operational Period, is well underway at Point Reyes National Seashore on the northern coast of California. As the title implies, the goal of MASRAD is to study the characteristics of marine stratus clouds, particularly the influence of aerosol particles on marine stratus drizzle properties. Taking advantage of the location and infrastructure established to support the campaign, a number of guest instruments are joining the AMF deployment to aid in the collection of data on aerosol properties.

The Cadenza cavity ring down instrument, provided by the National Aeronautics and Space Administration’s Ames Research Center, is being deployed from June through August to measure aerosol optical properties. “Cavity ring down” refers to the method of bouncing a pulse of light back and forth inside an enclosed cavity to measure the rate of extinction-or “ring down”-of the particles over time. The Cadenza technique uses this method plus independent measurements of light scattering on the same sample to obtain light absorption and albedo values. Measurements taken by the Cadenza will be compared with measurements taken by a Particle Soot/Absorption Photometer and other photoacoustic instruments included in the AMF baseline instrument collection. These measurements will provide a better understanding of aerosol properties during cloud-free conditions.

To aid in observation of cloud-aerosol interaction, a counter-flow virtual impactor (CVI) will be implemented in July to sample cloud drops. The CVI, sponsored by researchers from the DOE Atmospheric Science Program, uses its counter-flow capability to draw large cloud drops into a system that evaporates the moisture, isolating the aerosols that form cloud condensation nuclei.

These guest instruments are just a few that have been added to or will soon join the AMF on location at Point Reyes. The MASRAD field campaign began in mid-March and will last until September. To learn more about this campaign, see the October-December 2004 News Archive.