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

References

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