Operations Updates
ARM Climate Research Facility Operations Update - November 15, 2007
This bimonthly report provides a brief summary of significant accomplishments and activities in the operations area of the ARM Climate Research Facility (ACRF).
Commercial Infrared Sky Imagers Compared
Three of the four instruments used in the sky imager intercomparison are visible in this photo taken on the Guest Instrument Facility platform at the SGP site. They are the Solmirus All Sky Infrared Visible Analyzer (foreground); Heitronics Nubiscope (top right); and Atmos Cloud Infrared Radiometer-4 (far left). Click for a larger image.
Four infrared imaging instruments were installed and operated at the ACRF Southern Great Plains (SGP) site for the Infrared Sky Imager Intercomparison Study, which took place from August 28 to October 5. The principle objective of this campaign was to compare measurements of cloud fraction from different types of commercially available infrared sky imagers and to compare the daytime values with the Total Sky Imager (TSI) at the SGP site. Most of the data from the participating instruments have been processed, and preliminary results were presented at the ARM Cloud Properties Working Group Meeting in mid-November. These results will be supplemented with the remaining data and shared in a poster at the American Geophysical Union Meeting in San Francisco in December.
In 2004, the ARM Radiative Processes Working Group requested the addition of an infrared sky imaging system to the ACRF measurement suite to provide nighttime cloud data. For this purpose, an All-Sky Thermal Infrared Camera from Blue Sky Imaging Ltd. (BSI) was purchased and deployed at the SGP Guest Instrument Facility in October 2005. When compared to TSI images from the site, daytime images from the BSI instrument compared favorably, but derived cloud amounts significantly underestimated the TSI values when the sky was more than 50% cloudy. Due to poor cloud fraction data, alternatives to the BSI instrument were investigated and led to this study.
For the intercomparison with the BSI, alternative instruments included a Heitronics Nubiscope from Germany, an Atmos Cloud Infrared Radiometer-4 (CIR-4) from France, and a Solmirus All Sky Infrared Visible Analyzer from the United States. To accommodate these instruments, ACRF operations staff added three additional computers to the SGP network and completed the required remote access requests for the participants. Thus far, data have processed from the Heitronics, Atmos, and BSI instruments; data transfer from the Solmirus instrument was delayed and is still being processed.
