Operations Updates
ARM Climate Research Facility Operations Update - June 15, 2008
This bimonthly report provides a brief summary of significant accomplishments and activities in the operations area of the ARM Climate Research Facility (ACRF).
Mobile Facility Anchors Multi-site Aerosol Study in China
The AMF installation in Shouxian includes the primary shelters and operations area, an adjacent instrument field, and several more instruments located on the roof of a nearby building.
In its most complex ARM Mobile Facility (AMF) deployment to date, the ACRF is coordinating operations and data collection at four different sites for the Aerosol Indirect Effects Study in China. Anchored by the AMF in Shouxian, the campaign also includes a supplemental facility at Lake Taihu and an ancillary facility that will operate in series at two sites to the north. Needless to say, the campaign logistics kept the AMF operations team on their toes, culminating with opening ceremonies last month at the Shouxian and Lake Taihu sites. Attended by several Chinese dignitaries, media, and science team representatives, the ceremonies marked the official start of data collection by the AMF in Shouxian on May 16.
In preparation for this deployment, the AMF operations team worked to reduce the facility's footprint. They redesigned the Aerosol Observing System tower to lighten it and reduce install time. Similarly, the 10-meter meteorological tower was redesigned to accommodate instruments previously operated on tri-pods, and to match international height standards for ground radiation and wind measurements. Meanwhile, operations staff at the ACRF Southern Great Plains site scrambled to calibrate extra instruments to support the supplementary and ancillary facilities. These instruments included a sunphotometer, ceilometer, microwave radiometer profiler, and narrow field of view radiometer. In addition, the AMF operations team coordinated the deployment of a guest instrument called the Sun and Aureole Measurement system. This instrument is operating with the AMF and ancillary facility to obtain data for a related study about the optical depth of thin clouds in East Asia.
The various study sites underwent a "staggered start" to operations, beginning in April with data collection at the ancillary facility located at Zhangye. Operated by collaborators from the Lanzhou University, this facility has a limited suite of instruments and will be moved to Xianghe in July. Following the start of AMF data collection at Shouxian on May 16, the supplementary facility at Lake Taihu came online a few days later. This facility is located at the permanent observatory maintained by the Chinese Academy of Sciences and was enhanced with additional instruments and staff from the Nanjing University of Information Science and Technology and the University of Maryland. AMF operations staff assisted with the installation and calibration of several instruments at the Taihu site and provided training for local support staff. Data collection and data processing among the sites is being coordinated by the ACRF data system team. Extensive measurements of cloud, aerosol, radiation, and precipitation at the sites will provide comparative measurements to study regional aerosol effects.
Staying in Synch
Accurate time stamps on data collected at the ACRF sites are very important for confidence in using the measurements for research. At the dispersed facilities across the ACRF Southern Great Plains site, making sure all the instruments and their associated data logging systems are on the same clock is no easy task. Due to their remote locations, many of these field facilities still rely on dialup Internet connections and are susceptible to frequent power outages. After uncovering a minor but pervasive offset in time records, SGP site operations staff quickly diagnosed the problem and set about implementing a solution. New synchronization software installed throughout the site will ensure that future automatic clock resets account for any "drift" between the instrument hardware and data collection systems, keeping SGP site data in synch.
GPS receivers are installed at all the extended facilities throughout the SGP domain.
In February, SGP site operations staff discovered the flaw in the time-synch process used at the extended and intermediate facilities. During system startups or reboots, the method used for data transport—an Ethernet-based serial port—was causing clock instability. In addition, the startup process did not include access to the highly precise global positioning system (GPS) time signal available from the GPS receivers at each facility. In cooperation with various ARM instrument mentors, SGP site operations staff identified a commercial synchronization product from the same vendor that manufactures the GPS time servers at the ACRF ground sites. The new time synchronization software runs independent of offsite network connections, minimizing the risk of incorrect time settings, particularly where offsite communications are less reliable. Testing of the synchronization software in March proved very consistent, leading to its current installation at all SGP extended and intermediate facilities.
