A four-stream radiometer is an instrument combination that contains two types of sensors, pyranometers, and pyrgeometers. Pyranometers are sensors that convert shortwave solar radiation into an electrical signal that is then measured. Pyrgeometers are sensors that measure longwave near-surface infrared radiation in the wavelength spectrum, from approximately 4.5 μm to 100 μm.

Number deployed on SOS Project: 2

Make/model used on SOS Project: Hukseflux NR01

Daniel Hogan, a graduate student at University of Washington and SOS Project researcher, describes the function of the four-stream radiometer at the Kettle Ponds study site in Gothic, Colorado.