Abstract
A simple and inexpensive fully automated all-sky imaging system based on a commercial digital camera with a fish-eye lens and a rotating polarizer is presented. The system is characterized and two examples of applications in atmospheric physics are given: polarization maps and cloud detection. All-sky polarization maps are obtained by acquiring images at different polarizer angles and computing Stokes vectors. The polarization in the principal plane, a vertical cut through the sky containing the Sun, is compared to measurements of a well-characterized spectroradiometer with polarized radiance optics to validate the method. The images are further used for automated cloud detection using a simple color- ratio algorithm. The resulting cloud cover is validated against synoptic cloud observations. A Sun coverage parameter is introduced that shows, in combination with the total cloud cover, useful correlation with UV irradiance.
© 2009 Optical Society of America
Full Article | PDF ArticleMore Like This
Francisco J. Olmo, Alberto Cazorla, Lucas Alados-Arboledas, Miguel A. López-Álvarez, Javier Hernández-Andrés, and Javier Romero
Appl. Opt. 47(34) H182-H189 (2008)
Laura M. Eshelman, Martin Jan Tauc, Taiga Hashimoto, Kendra Gillis, William Weiss, Bryan Stanley, Preston Hooser, Glenn E. Shaw, and Joseph A. Shaw
Appl. Opt. 59(21) F41-F52 (2020)
Nathan J. Pust and Joseph A. Shaw
Appl. Opt. 47(34) H190-H198 (2008)