Weather satellites are used in measuring daily cloud cover. Technological advancements have made it possible to launch satellites in space to observe and collect cloud data from beyond the Earth's atmosphere. A low-tech alternative is to use a spherical mirror, or "sky mirror," to gauge cloud coverage.
Cloud formation impacts daily weather patterns and the general climatic conditions on Earth. Clouds provide a cooling mechanism for the planet at daytime, while trapping heat during the night. These visible masses of condensed water vapor greatly influences the amount of precipitation an area receives, often driving the development of other phenomena, including snow, storms, hail and tornadoes. Understanding cloud formations and coverage is a crucial aspect in meteorology.
The Terra and Aqua satellites of the National Aeronautics and Space Administration, or NASA, gathers cloud data on a daily basis. These satellites capture real-time images, which are then analyzed by meteorologists to make weather predictions. Reliable weather forecasts are essential to the various aspects of daily living.
Cloud coverage can also be measured by any observer on Earth. A usual method is to visualize the sky as a "pie" that is partitioned into eight equal parts, with the zenith as the middle of the pie. Each slice is referred to as an "okta," where a clear sky denotes 0 oktas. When all 8 oktas are filled, the sky is said to be overcast.