wsi: Whole Sky Imager

The whole-sky imager (WSI) is an automated imager used for assessing and documenting cloud fields and cloud field dynamics. The WSI is a ground-based electronic imaging system that monitors the upper hemisphere. It is a passive, i.e., non-emissive, system that acquires images of the sky dome through three spectral filters (neutral, red, and blue).

From these sky images, we can assess the presence, distribution, shape, and radiance of clouds over the entire sky using automated cloud decision algorithms and related processing. The current WSI model (EO System 6) is capable of image acquisition under daylight, moonlight, and starlight conditions.



  • Fixed
  • AMF1
  • AMF2
  • AMF3


Dong X, A Schwantes, B Xi, and P Wu. 2015. "Investigation of the marine boundary layer cloud and CCN properties under coupled and decoupled conditions over the Azores." Journal of Geophysical Research: Atmospheres, 120(12), doi:10.1002/2014JD02, 10.1002/2014jd022939.
Research Highlight


Zhang Y and SA Klein. 2013. "Factors Controlling the Vertical Extent of Fair-Weather Shallow Cumulus Clouds over Land: Investigation of Diurnal-Cycle Observations Collected at the ARM Southern Great Plains Site." Journal of the Atmospheric Sciences, 70(4), 10.1175/jas-d-12-0131.1.
Research Highlight


Huo J and DR Lu. 2012. "Comparison of Cloud Cover from All-Sky Imager and Meteorological Observer." Journal of Atmospheric and Oceanic Technology, 29(8), 10.1175/jtech-d-11-00006.1.


Jeong M and Z Li. 2010. "Separating real and apparent effects of cloud, humidity, and dynamics on aerosol optical thickness near cloud edges." Journal of Geophysical Research – Atmospheres, 115(D7), D00K32, 10.1029/2009jd013547.


Cazorla A, JE Shields, ME Karr, FJ Olmo, A Burden, and L Alados-Arboledas. 2009. "Technical Note: Determination of aerosol optical properties by a calibrated sky imager." Atmospheric Chemistry and Physics, 9(17), 10.5194/acp-9-6417-2009.

Taylor PC and RG Ellingson. 2009. On the use of probability of clear line of sight models in parameterizing surface downwelling longwave radiation in the tropical Western Pacific. In AIP Conference Proceedings, AIP, USA.


Taylor PC and RG Ellingson. 2008. "A Study of the Probability of Clear Line of Sight through Single-Layer Cumulus Cloud Fields in the Tropical Western Pacific." Journal of the Atmospheric Sciences, 65(11), 10.1175/2008jas2620.1.

Barnard JC, CN Long, EI Kassianov, SA McFarlane, JM Comstock, M Freer, and GM McFarquhar. 2008. "Development and evaluation of a simple algorithm to find cloud optical depth with emphasis on thin ice clouds." The Open Atmospheric Science Journal, 2, 10.2174/1874282300802010046.


Matthews S, JM Hacker, J Cole, J Hare, CN Long, and RM Reynolds. 2007. "Modification of the Atmospheric Boundary Layer by a Small Island: Observations from Nauru." Monthly Weather Review, 135(3), 10.1175/mwr3319.1.

Turner DD, A Vogelmann, K Johnson, M Miller, RT Austin, JC Barnard, C Flynn, C Long, SA McFarlane, K Cady-Pereira, SA Clough, JC Chiu, MM Khaiyer, J Liljegren, B Lin, P Minnis, A Marshak, SY Matrosov, Q Min, W O'Hirok, Z Wang, and W Wiscombe. 2007. "Thin Liquid Water Clouds: Their Importance and Our Challenge." Bulletin of the American Meteorological Society, 88(2), 10.1175/bams-88-2-177.

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