Instrument : Whole Sky Imager (WSI)

Note: wsi is currently inactive and/or retired.

Active Dates
1995.09.20 - 1999.02.02

Instrument Categories
Cloud Properties

Picture of the Whole Sky Imager (WSI)

General Overview

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.

Output Value-Added Products

This instrument is an input to the following value-added products, which provide improved measurements or derived quantities.

  • wsicloud : WSI: derived, cloud numbers, area, perimeter, & more
  • wsicloudden : WSI: stationary (JPEG) images based on optical density retrieval
  • wsicloudspec : WSI: stationary (JPEG) images based on spectral retrieval
  • wsicloudsummary : WSI: cloud and aerosol info, classification summary data
  • wsicloudsummarygif : WSI: images (GIF) relating to cloud, aerosol summary data
  • wsifilesummary : WSI: images (GIF) and text representations of data existence

Output Datastreams

  • 02wsipartradiance : WSI: calibrated red or clear images and house keeping data, 2-min intervals
  • 02wsipartradjpg : WSI: stationary calibrated red or clear quicklook images (JPEG), 2-min intervals
  • 02wsipartradmpg : WSI: calibrated red or clear quicklook movies (MPEG), 2-min intervals
  • 10wsipartradjpg : WSI: stationary calibrated red or clear quicklook images (JPEG), 10 min intervals
  • 10wsipartradmpg : WSI: calibrated red or clear quicklook movies (MPEG), 10 min intervals
  • wsifullradiance : WSI: calibrated radiances for each pixel, with multiple filters
  • wsipatchsummary : WSI: radiances from red image for three patches (avg and SD)

Primary Measurements

The following measurements are those considered scientifically relevant.


North Slope Alaska
NSAC1 Browse DataCentral Facility, Barrow AK retired
NSAC2 Browse DataCentral Facility, Atqasuk AK retired
Southern Great Plains
SGPC1 Browse DataCentral Facility, Lamont, OK retired
SGPL3 Browse DataBlackwell/Tonkawa Airport, OK retired
Tropical Western Pacific
TWPC1 Browse DataCentral Facility, Manus I., PNG retired
TWPC2 Browse DataCentral Facility, Nauru Island retired
TWPC3 Browse DataCentral Facility, Darwin, Australia retired
 retired = Originating instrument has been retired at this location


Douglas Sisterson
Argonne National Laboratory
(630) 252-5836