Coastal Clouds Field Campaign Takes Off in July

Published: 30 June 2005

The 2-channel NFOV gets careful attention as it joins the suite of instruments collecting data for the ARM Mobile Facility field campaign at Point Reyes National Seashore.

Since March 2005, the ARM Mobile Facility (AMF) has been at Point Reyes National Seashore in northern California for the Marine Stratus Radiation, Aerosol, and Drizzle Intensive Operational Period. The goals of this 6-month field campaign are to collect data from cloud/aerosol interactions and to improve understanding of cloud organization that is often associated with patches of drizzle. In June, two additional instruments were installed at the deployment site in preparation for the heart of the experiment in July, when two research aircraft join the campaign. ARM also hosted a media day on June 30, to give area reporters and guests the opportunity to tour the AMF instrumentation and shelters and to ask the science team questions about the campaign.

A 2-channel zenith-pointing narrow field of view radiometer (2NFOV) was installed atop one of the AMF operations shelters. The 1-second time resolution of radiances measured by the 2NFOV can follow the rapid changes in 3-dimensional cloud structures. Data collected by the 2NFOV during this field campaign will allow scientist to conduct extensive comparisons against other methods used to retrieve cloud property information. Because of its demonstrated ability for obtaining cloud optical depth measurements, an expanded version of the NFOV (one with 6 channels rather than 2) is being considered as a permanent addition to the baseline AMF instrument collection.

ARM operations staff also installed a “present weather detector” to aid in the interpretation of aerosol properties data collected by the aerosol observing system (AOS) already in place at the site. The present weather detector collects visibility, present weather, and precipitation data at 1 minute intervals. Visibility measurements from the detector allow sudden changes in aerosol properties to be associated with the onset or dissipation of fog. (The presence of fog is of primary concern to the AOS system measurements, because aerosols are effectively scavenged by fog.) Though sponsored by the National Oceanic and Atmospheric Administration as part of the AOS for this field campaign, the present weather detector will also become a permanent instrument in the AMF baseline collection. It will be mounted to the surface meteorology system for future deployments.

Throughout the month of July, two aircraft will fly over the deployment site to collect data from above, within, and below the clouds. Daytime-only flights by a Twin Otter, funded by the U.S. Office of Naval Research, and the Atmospheric Science Program’s G1 research aircraft will allow researchers to combine vertical atmospheric profile measurements with AMF surface measurements, resulting in a more complete characterization of cloud and aerosol properties.