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

Related Publications


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. ONLINE.
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.
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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. 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.


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.

Voyles JW. 2007. ACRF Instrumentation Status: New, Current, and Future September – October 2007. DOE ARM Climate Research Facility. DOE/SC-ARM/P-07-002.8.


Sabburg JM and CN Long. 2004. "Improved sky imaging for studies of enhanced UV irradiances." Atmospheric Chemistry and Physics, 4, 10.5194/acp-4-2543-2004.

Berendes TA, DA Berendes, RM Welch, EG Dutton, T Uttal, and EE Clothiaux. 2004. "Cloud cover comparisons of the MODIS daytime cloud mask with surface instruments at the north slope of Alaska ARM site." IEEE Transactions on Geoscience and Remote Sensing, 42(11), 10.1109/tgrs.2004.835226.


Lane DE, K Goris, and RC Somerville. 2002. "Radiative Transfer through Broken Clouds: Observations and Model Validation." Journal of Climate, 15(20), 10.1175/1520-0442(2002)015<2921:rttbco>;2.

Uttal T, JA Curry, MG McPhee, DK Perovich, RE Moritz, JA Masalanik, PS Guest, HL Stern, JA Moore, R Turenne, A Heiberg, MC Serreze, OG Persson, CA Paulson, C Halle, JH Morison, PA Wheeler, H Welch, MD Shupe, K Stamnes, RW Lindsey, WS Pegau, TC Grenfeld, and JM Intrieri. 2002. "Surface Heat Budget of the Arctic Ocean." Bulletin of the American Meteorological Society, 83(2), 10.1175/1520-0477(2002)083<0255:shbota>;2.

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