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Solar irradiance (also Insolation, from Latin ''insolare'', to expose to the sun)〔(【引用サイトリンク】Insolation – Definition of insolation by Merriam-Webster )〕〔(【引用サイトリンク】Online Etymology Dictionary )〕 is the power per unit area produced by the Sun in the form of electromagnetic radiation. Irradiance may be measured in space or at the Earth's surface after atmospheric absorption and scattering. Total solar irradiance (TSI), is a measure of the solar radiative power per unit area normal to the rays, incident on the Earth's upper atmosphere. The solar constant is a conventional measure of mean TSI at a distance of one Astronomical Unit (AU). Irradiance is a function of distance from the Sun, the solar cycle, and cross-cycle changes.〔Michael Boxwell, ''Solar Electricity Handbook: A Simple, Practical Guide to Solar Energy'' (2012), p. 41–42.〕 Irradiance on Earth is most intense at points directly facing (normal to) the Sun. == Units == The unit recommended by the World Meteorological Organization is the megajoule per square metre (MJ/m2) or joule per square millimetre (J/mm2).〔(【引用サイトリンク】World Meteorological Organization – WMO )〕 An alternate unit of measure is the Langley (1 thermochemical calorie per square centimeter or 41,840 J/m2) or irradiance per unit time. The solar energy business uses watt-hour per square metre (Wh/m2). Divided by the recording time, this measure becomes insolation, another unit of irradiance. Insolation can be measured in space, at the edge of the atmosphere or at a terrestrial object. Insolation can also be expressed in Suns, where one Sun equals 1000 W/m2 at the point of arrival, with kWh/m2/day expressed as hours/day.〔(U.S. Solar Radiation Resource Maps ) retrieved 29 October 2012〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Solar irradiance」の詳細全文を読む スポンサード リンク
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