Data From Rotating Shadowband Spectroradiometer Now Available in Data Archive

 
Published: 15 June 2006

The Rotating Shadowband Spectroradiometer (RSS) is calibrated bi-weekly with external lamp calibrators for accuracy.

After refinements based on a series of successful field trials, the latest Rotating Shadowband Spectroradiometer (RSS) joins the collection of permanent ARM instruments at the ARM Southern Great Plains (SGP) site. The current RSS—known as the RSS105—is deployed at the SGP Central Facility and is the first commercially built RSS manufactured by Yankee Environmental Systems, Inc. Since its deployment in May 2003, the RSS has operated continuously with only a 2.5% down time in the first 1035 days of operation. Irradiance data from RSS105 is now collected routinely and distributed via the Data Archive.

Two prototypes (RSS102 and RSS103), designed and built at the Atmospheric Sciences Research Center (State University of New York), were tested in several prolonged deployments between 1997-2003 at both the SGP site and North Slope of Alaska locale. In addition, an ultraviolet-RSS prototype was deployed at the SGP for two field campaigns—Diffuse IOP 2001 and Aerosol IOP 2003—and provided measurements in the 295 nm-385 nm range. All beta data from the RSS102, RSS103, and RSS105 are formerly available from the IOP Archive at http://www.db.arm.gov/cgi-bin/PIP/viewPIP.pl?pipNo=15.

This graph illustrates the retrieval of aerosol optical depth from direct normal irradiance calibrated via Langley regression.

The RSS implements the same automated shadowbanding technique used by the multi-filter rotating shadowband radiometer (MFRSR). Like the MFRSR, it provides simultaneous spectrally-resolved, direct-normal, diffuse-horizontal, and total-horizontal irradiance measurements and can be calibrated in-situ using the Langley regression. Calibrated bi-weekly with external lamp calibrators traceable to the National Institute of Standards and Technology (NIST) radiometric scale, the accuracy of irradiance data produced by the RSS is expected to be better than ±5% at all pixels in 360nm-1050nm spectral range, including calibration and instrument stability errors. Higher accuracy can be obtained when the responsivity is tied to the solar extraterrestrial irradiance via Langley regression. This approach is recommended when high precision (±0.01) measurements of optical depth are required. The calibration constants from the Langley regressions are available from the IOP Archive.