Clearness index explained

The clearness index is a measure of atmosphere clearness. It is calculated as the fraction of the actual total solar radiation on the surface of the Earth during a certain period over the theoretical maximum (i.e., clear sky) radiation during the same period.^{[1] [2]} The clearness index is a dimensionless quantity and can vary from 0 (sky is completely covered) to 1 (perfectly sunny).^[3]

See also

• Cloud cover

Notes and References

1. Web site: NASA POWER Docs Methodology Energy Fluxes Derived Parameters - NASA POWER Docs . power.larc.nasa.gov . 3 March 2022.
2. Web site: Physical models used > Irradiation models > Clearness Index . www.pvsyst.com . 3 March 2022.
3. Web site: Clearness Index . www.homerenergy.com . 3 March 2022.