New Narrow Field of View Radiometer Widens Range of Radiance Data

Published: 15 August 2004

Development of a new, two-channel narrow field of view (NFOV) radiometer for the ARM Climate Research Facility Southern Great Plains site is nearly complete. The two-channel NFOV replaces a similar single-channel instrument that was destroyed by lightning in June 2002, and adds a 673 nm (red) measurement to the measurement at 870 nm (near infrared). Repairs to the original NFOV were completed and calibrated first, so that it could be used to check the calibration of the 2-channel version. This comparison proved to be a very valuable step, as it revealed a subtle electronics problem in the new version that caused a drift in the readings. With the problem solved, completion of the new instrument is imminent, and deployment at SGP is anticipated in September.

Development of the two channel unit required construction of new instrument housing and incorporation of a new data logger. The new NFOV radiometer collects data using a CR10X measurement and control system (from Campbell Scientific). Instrument output consists of a time series of 1-second observations of zenith spectral radiance. These radiance data can be used to characterize the optical properties of clouds. The additional 673 nm radiance measurement is an important element in developing cloud optical depth algorithms and retrieval methods, particularly for broken cloud fields.