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  2. Solar irradiance - Wikipedia

    en.wikipedia.org/wiki/Solar_irradiance

    Global distribution of incoming shortwave solar radiation averaged over the years 1981–2010 from the CHELSA-BIOCLIM+ data set [1] The shield effect of Earth's atmosphere on solar irradiation. The top image is the annual mean solar irradiation (or insolation) at the top of Earth's atmosphere (TOA); the bottom image shows the annual insolation ...

  3. Ultraviolet index - Wikipedia

    en.wikipedia.org/wiki/Ultraviolet_index

    A UV index reading of 3 to 5 means moderate risk of harm from unprotected sun exposure. Stay in shade near midday when the sun is strongest. If outdoors, wear sun-protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. Generously apply broad spectrum SPF 50+ sunscreen every 1.5 hours, even on cloudy days, and after swimming or ...

  4. Solar constant - Wikipedia

    en.wikipedia.org/wiki/Solar_constant

    The solar "constant" is not a physical constant in the modern CODATA scientific sense; that is, it is not like the Planck constant or the speed of light which are absolutely constant in physics. The solar constant is an average of a varying value. In the past 400 years it has varied less than 0.2 percent. [2]

  5. Sunlight - Wikipedia

    en.wikipedia.org/wiki/Sunlight

    The solar constant is a measure of flux density, is the amount of incoming solar electromagnetic radiation per unit area that would be incident on a plane perpendicular to the rays, at a distance of one astronomical unit (AU) (roughly the mean distance from the Sun to Earth).

  6. Actinometer - Wikipedia

    en.wikipedia.org/wiki/Actinometer

    John Herschel further developed actinometers in the 19th century, including a design involving photochemical reactions to measure sunlight intensity, which was a significant step forward. Herschel's actinometer involved observing the rate of a chemical reaction under sunlight, which allowed for more precise quantification of solar energy.

  7. Air mass (solar energy) - Wikipedia

    en.wikipedia.org/wiki/Air_mass_(solar_energy)

    For example, when the sun is more than about 60° above the horizon (<30°) the solar intensity is about 1000 W/m 2 (from equation I.1 as shown in the above table), whereas when the sun is only 15° above the horizon (=75°) the solar intensity is still about 600 W/m 2 or 60% of its maximum level; and at only 5° above the horizon still 27% of ...

  8. Solar zenith angle - Wikipedia

    en.wikipedia.org/wiki/Solar_zenith_angle

    It is the complement to the solar altitude or solar elevation, which is the altitude angle or elevation angle between the sun’s rays and a horizontal plane. [1] [2] At solar noon, the zenith angle is at a minimum and is equal to latitude minus solar declination angle. This is the basis by which ancient mariners navigated the oceans. [3]

  9. Solar luminosity - Wikipedia

    en.wikipedia.org/wiki/Solar_luminosity

    Evolution of the solar luminosity, radius and effective temperature compared to the present-day Sun. After Ribas (2010) [1] The solar luminosity (L ☉) is a unit of radiant flux (power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun.