Daylight visible/NIR whole-sky imagers for cloud and radiance monitoring in support of UV research programs

Janet E. Shields; Richard W. Johnson; Monette E. Karr; Art R. Burden; Justin G. Baker

doi:10.1117/12.509062

4 November 2003 Daylight visible/NIR whole-sky imagers for cloud and radiance monitoring in support of UV research programs

Janet E. Shields, Richard W. Johnson, Monette E. Karr, Art R. Burden, Justin G. Baker

Author Affiliations +

Proceedings Volume 5156, Ultraviolet Ground- and Space-based Measurements, Models, and Effects III; (2003) https://doi.org/10.1117/12.509062
Event: Optical Science and Technology, SPIE's 48th Annual Meeting, 2003, San Diego, California, United States

Abstract

Measurements of UV radiation at the earth’s surface may be highly impacted by the presence of clouds. In order to provide support for UV research, a Daylight Visible/NIR Whole Sky Imager was developed to provide cloud fraction assessment over the whole sky, as well as measurements of the radiance distribution over the full sky in several spectral bands. Radiances are determined in approximately 700,000 directions simultaneously with a given optical filter. Data may be acquired in seven spectral bands that may be selected for the application. The current instrument uses filters near 450 and 650 nm, open-hole, filters in the blue-green broadband and NIR long-pass, and two polarizers. Opaque and thin cloud fraction is determined from images acquired in the blue and red wavelengths. A more sophisticated version of the algorithm to detect thinner clouds and enable aerosol assessment is in development, and will be based on use of the NIR data in conjunction with the blue and red data. This paper will provide an overview of the instrument design and calibration, and sample sky radiance results. The cloud algorithms for determination of cloud fraction will be discussed, and the cloud imager results will also be presented.

Citation Download Citation

Janet E. Shields, Richard W. Johnson, Monette E. Karr, Art R. Burden, and Justin G. Baker "Daylight visible/NIR whole-sky imagers for cloud and radiance monitoring in support of UV research programs", Proc. SPIE 5156, Ultraviolet Ground- and Space-based Measurements, Models, and Effects III, (4 November 2003); https://doi.org/10.1117/12.509062

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