Operations Updates
ARM Climate Research Facility Operations Update - August 31, 2007
This bimonthly report provides a brief summary of significant accomplishments and activities in the operations area of the ARM Climate Research Facility (ACRF).
Records Set Again; New Process Enhances Reporting of User Facility Statistics
The 2006 year-end ACRF statistics included a spatial distribution of global (shown here; click map for larger image) and U.S. users, and whether they were funded by the ARM Program. Click for a larger version.
A second straight record high number of users (1092) and a new record for visitor days (2083) were reported by ACRF for the third quarter of fiscal year 2007. The statistics also indicated a notable increase in non-ARM funded users at the ARM Mobile Facility deployment site in Germany, as well as large increases in total visitor days there and at the ACRF Southern Great Plains (SGP) site. These numbers are in indication of the ACRF's success in attracting new and non-ARM funded researchers. To aid in reporting on this important component of the user facility, a high level of coordination between ACRF staff at the External Data Center (XDC) and the Data Archive in recent months has resulted in the ability to identify the distribution of users and their funding affiliations.
In recent months, ACRF staff at the XDC and the Archive worked closely together in establishing a process to determine the number of users by ACRF site and by category-site visitor or data user. The list of site visitors was determined using the ACRF Site Access Request System, which provides both advance notice of on-site visits to site managers in order to coordinate needed support, as well as a mechanism for requesting and managing access to site network and computer resources. The Archive user statistics then required a match-up in the ARM People Database before determining whether a user was funded through the ARM Program or an external source. The ARM People Database provides information about users' affiliations. Their membership in one of the variety of groupings maintained in the People Database indicated whether the user was funded by the ARM Program.
Established as a user facility in 2003, the ACRF provides research capability for the global scientific community. The recent reporting process has thus far been applied to both the 2006 and 2007 quarterly statistics. Quarterly facility statistics for the ACRF are regularly posted on the on the ARM website under Facility Statistics.
New Calibration Method May Purge Old Procedure
This photo shows a pyrgeometer entering the blackbody calibration chamber. A blackbody is an object that absorbs all electromagnetic radiation that falls onto it. This lack of both transmission and reflection properties make blackbodies ideal sources for calibrating instruments that measure radiation, like the pyrgeometer.
A pyrgeometer is a type of radiometer that measures energy in the spectral range from approximately 3.5 to 50 micrometers. The ACRF uses more than 100 pyrgeometers for longwave irradiance data supporting climate studies, so accuracy and consistency in their operations is critical for obtaining reliable data. A new method for calibrating these instruments was tested with seven pyrgeometers during an outdoor study at the ACRF Southern Great Plains site, and showed excellent agreement with two instruments traceable to the World Infrared Standards Group (WISG).
Presently, pyrgeometers deployed by ACRF are calibrated with traceability to the manufacturer's blackbody. Though this traceability method is adequate, it is not recognized by the international community. To achieve acceptance within the international community, ARM researchers conducted a test on a collection of seven pyrgeometers using a blackbody system to characterize their thermal properties. These instruments were then deployed outdoors along with two reference pyrgeometers that are traceable to the WISG. The blackbody coefficients of the test instruments were then adjusted so that the measured irradiance by the test pyrgeometers would equal the irradiance measured by the reference instruments.
The resulting analysis, presented at the 2007 ARM Science Team Meeting in March, showed that the seven pyrgeometers agreed to better than ± 1.5 W/m2 uncertainty with 95% confidence level with respect to the two reference pyrgeometers under all sky conditions and during daytime and nighttime. Their method, analysis, and recommendations are documented on their Science Team Meeting poster.
