New Radiometer Tested for Measuring Thin Clouds

Published: 15 March 2008

The TCRSR is shown here on the roof of the Radiometer Calibration Facility at the SGP site. Two shadowbands rotate around the radiometer's sensor, located just inside the smaller shadowband. They reflect light away from the sensor at multiple angles so that it simultaneously records signals of scattered light. — The TCRSR is shown here on the roof of the Radiometer Calibration Facility at the SGP site. Two shadowbands rotate around the radiometer’s sensor, located just inside the smaller shadowband. They reflect light away from the sensor at multiple angles so that it simultaneously records signals of scattered light.

A Thin-Cloud Rotating Shadowband Radiometer (TCRSR) has completed a month of testing at the ARM Southern Great Plains (SGP) site to assess its ability to simultaneously retrieve measurements of the size and density of cloud droplets in “thin” clouds, i.e., clouds with water content less than 100 grams per square meter. Both of these properties are essential to understanding cloud-climate interaction, but current measurement techniques are not as accurate as desired.

The TCRSR measures the angular distribution, or spread, of light from the sun scattered toward the instrument in six narrow spectral bands. Each of these bands is approximately 10 nanometers wide and centered at 415, 500, 610, 660, 870, and 940 nm. The prototype instrument was designed and tested in the summer and fall of 2007. Based on promising results, it was deployed at SGP in early January 2008. Results from the TCRSR observations will be compared to those made by other ARM instruments. If the technique is successful, the TCRSR may be considered for routine deployment at all ARM sites.

# # #

The ARM Climate Research Facility is a DOE Office of Science user facility. The ARM Facility is operated by nine DOE national laboratories, including .