Operations Updates
ARM Climate Research Facility Operations Update - August 31, 2006
This bimonthly report provides a brief summary of significant accomplishments and activities in the operations area of the ARM Climate Research Facility (ACRF).
Infrared Loss Study Underway at North Slope of Alaska
At ACRF's North Slope of Alaska site in Barrow, collocated sky radiometers are being evaluated to refine the methodology that accounts for infrared loss in polar conditions.
In the far northern reaches of Alaska, extended periods of both darkness and daylight occur throughout the year. Additionally, extremely cold weather conditions contribute to a harsh operating environment for research equipment. Therefore, broadband radiometers at the ACRF North Slope of Alaska (NSA) site are equipped with electric heaters inside the ventilators to keep frost and snow from causing interference with the measurements. Unfortunately, both of these issues - heating elements and the lack or surplus of sunlight at certain times of the year - appear to have an effect on correction methods used for known infrared loss problems in broadband shortwave measurements. In August, ARM researchers began a one-year field campaign to obtain the observational data needed for investigating and refining the infrared loss correction methodology for surface broadband measurements acquired at the NSA site.
Anomalous results were discovered during testing of the value added product, ARM Diffuse Correction, when recently applied to NSA data. The correction methodology uses nighttime offset data to establish a correction relationship applied during all hours. However, at NSA the majority of the "nighttime" data occurs during the winter months, while most of the daylight occurs during the summer months under far different ambient conditions. In addition, the existing infrared loss correction methodology was developed without the use of heaters in the ventilators, which were shown to have an effect on the instrument case and dome temperatures.
The Pyranometer Infrared Loss Study will result in comparative data with which to investigate and quantify these effects, both for correcting for infrared loss and effects the current ventilator heaters might be having on the basic measurements. Researchers will also investigate various permutations of the amount of ventilation and heating to perhaps optimize the broadband measurement strategy for NSA. The latter studies will evolve as early results are obtained. Overall, the IOP is targeted at improving both understanding, and the quality and accuracy, of radiative measurements in the polar regions.
New Lidars Installed at Tropical Western Pacific Site
A representative from Sigma Space Corporation trains ACRF operations staff in Darwin, Australia, on various components of the new micropulse lidar. The lidar, shown at left, will be placed in one of the outdoor instrument shelters, below a hole in the roof for the laser to pulse through.
As reported in May, all the ACRF sites are benefiting from new and upgraded micropulse lidars. This month, the new lidar was received in Darwin, Australia, with training provided by a representative of Sigma Space Corporation, the manufacturer of the instrument. The other two sites in ACRF's Tropical Western Pacific locale—Manus and Nauru Island—will receive their new lidars during a regularly scheduled maintenance visit to the remote islands later this year.
Training on the new lidar covers installation, which is fairly straightforward, and the more complex repairs. Because the lidar is a sophisticated laser instrument, it requires laser safety training, special laser goggles, and a baseline eye examination for all technicians authorized to replace the laser diode module. ACRF operations personnel are developing a video of the setup process to assist with the installation and training for new users.
