Sunphotometer Re-installed at North Slope of Alaska

Published: 15 May 2004

The CIMEL sunphotometer takes sky radiance measurements during daylight hours, when the sun is above horizon.

In early May, a CIMEL sunphotometer owned by the National Aeronautics and Space Administration (NASA) was re-installed at Barrow, Alaska, one of two research sites that make up the ARM Climate Research Facility’s North Slope of Alaska (NSA) locale. The CIMEL is a multi-channel, automatic sun-and-sky scanning radiometer that takes daytime measurements of direct solar radiance and sky radiance at the Earth’s surface. Measurements are taken at discrete wavelengths in visible and near-infrared regions of the solar spectrum.

Four CIMEL instruments are routinely calibrated and rotated for use at the ARM Climate Research Facility’s Southern Great Plains locale in Oklahoma (since 1998), and Tropical Western Pacific’s Nauru site (since 1999), providing continual data on atmospheric transmission and scattering properties in mid-latitudes and the tropics, respectively. Because this instrument is weather-proof and requires little maintenance during periods of adverse weather conditions, it is an excellent addition to the instrument suite at Barrow. The CIMEL had been removed for service at NASA prior to the onset of polar night in Alaska, when darkness rules the sky from September through March.

Data from the CIMEL in Barrow are transmitted to a satellite, sent to the NASA Goddard Space Fight Center for processing, and then distributed to the ARM Climate Research Facility External Data Center where they become part of the ARM Data Archive. Though installed at Barrow as part of NASA’s AErosol RObotic NETwork, the newly installed CIMEL may be used to support ARM arctic experiments, and may further interest collaborators at NASA to conduct satellite validation activities at the NSA.