What Instruments Are Used to Measure Cloud Cover?
In 2008, a group of researchers at Montana State University reported the development of a tool called the Infrared Cloud Imager (ICI), which was designed to collect data on cloud cover. For the novice meteorologist, NASA suggests a few low-tech methods of observing cloud cover, including a spherical sky mirror and a measuring system developed for the naked eye.
The Infrared Cloud Imager uses a combination of satellite images and infrared imaging to provide high-resolution data that can be recorded both day and night: an improvement on methods that rely on human sight, which cannot be used at nighttime. Satellite data can also provide information about cloud cover, but this method is inferior in some ways to human observation.
Human observation has been the traditional method of measuring cloud cover, and there is a specific measurement, the okta, that is used to describe the presence of clouds in the sky. To use oktas, the observer should look straight up at the sky and imagine it is split into eight equal wedges, or oktas, radiating out from a central point directly overhead. If one okta is fully covered and the rest are clear, the sky can be described as having one okta of cloud cover.