AskDefine | Define sunlit

Dictionary Definition

sunlit adj : lighted by sunlight; "the sunlit slopes of the canyon"; "violet valleys and the sunstruck ridges"- Wallace Stegner [syn: sunstruck]

User Contributed Dictionary



sun + lit


  1. illuminated by sunlight

Extensive Definition

Sunlight, in the broad sense, is the total spectrum of the electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the atmosphere, and the solar radiation is obvious as daylight when the Sun is above the horizon. This is usually during the hours known as day. Near the poles in summer, sunlight also occurs during the hours known as night and in the winter at the poles sunlight may not occur at any time. When the direct radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and heat. Radiant heat directly produced by the radiation of the sun is different from the increase in atmospheric temperature due to the radiative heating of the atmosphere by the sun's radiation. Sunlight may be recorded using a sunshine recorder. The World Meteorological Organization defines sunshine as direct irradiance from the Sun measured on the ground of at least 120 W·m−2.
Direct sunlight gives about 93 lumens of illumination per watt of electromagnetic power, including infrared, visible, and ultra-violet.
Sunlight is a key factor in the process of photosynthesis.


To calculate the amount of sunlight reaching the ground both the elliptical orbit of the earth and the earth's atmosphere have to be taken into account. The extraterrestrial solar illuminance (Eext), corrected for the elliptical orbit by using the day number of the year, known as the Julian date (Jd), is: Eext=Esc(1+0.034 * cos(2pi(Jd-2)/365))
The solar illuminance constant (Esc), is equal to 128 Klux. The direct normal illuminance, (Edn), corrected for the attenuating effects of the atmosphere is given by: Edn=Eext*e-cm
Where c is the atmospheric extinction coefficient and m is the relative optical air mass.


  1. Hartmann, Thom (1998). The Last Hours of Ancient Sunlight. London: Hodder and Stoughton. ISBN 0-340-82243-0.
  2. MF Holick & M Jenkins (2004) UV Advantage, Simon & Schuster.
  3. Outlaw, PC (2008). PC Outlaw Management Team. Grand Rapids, Mi. 49418
sunlit in Danish: Sollys
sunlit in Korean: 햇빛
sunlit in Indonesian: Sinar matahari
sunlit in Dutch: Daglicht
sunlit in Japanese: 太陽光
sunlit in Norwegian: Sollys
sunlit in Portuguese: Luz solar
sunlit in Simple English: Sunlight
sunlit in Serbian: Сунчева свјетлост
sunlit in Contenese: 太陽光
sunlit in Chinese: 太阳光

Synonyms, Antonyms and Related Words

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