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Total solar irradiance (TSI) is a measure of the solar power over all wavelengths per unit area incident on the Earth's upper atmosphere. It is measured perpendicular to the incoming sunlight. [3] The solar constant is a conventional measure of mean TSI at a distance of one astronomical unit (AU).
Irradiance. In radiometry, irradiance is the radiant flux received by a surface per unit area. The SI unit of irradiance is the watt per square metre (W⋅m −2). The CGS unit erg per square centimetre per second (erg⋅cm −2 ⋅s −1) is often used in astronomy. Irradiance is often called intensity, but this term is avoided in radiometry ...
Solar activity and climate. Solar irradiance (yellow) plotted with temperature (red) since 1880. Patterns of solar irradiance and solar variation have been a main driver of climate change over the millions to billions of years of the geologic time scale. Evidence that this is the case comes from analysis on many timescales and from many sources ...
Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere as daylight when the Sun is above the horizon.
Direct irradiance measurements have been available during the last three cycles and are a composite of multiple observing satellites. [41] [42] However, the correlation between irradiance measurements and other proxies of solar activity make it reasonable to estimate solar activity for earlier cycles. Most important among these proxies is the ...
Radiative forcing (or climate forcing[2]) is a concept used in climate science to quantify the change in energy balance in Earth's atmosphere. Various factors contribute to this change in energy balance, such as concentrations of greenhouse gases and aerosols, and changes in surface albedo and solar irradiance.
Pyranometer. A pyranometer (from Greek πῦρ (pyr) 'fire' and ἄνω (ano) 'above, sky') is a type of actinometer used for measuring solar irradiance on a planar surface and it is designed to measure the solar radiation flux density (W/m 2) from the hemisphere above within a wavelength range 0.3 μm to 3 μm. A typical pyranometer does not ...
Pyrheliometer. A pyrheliometer is an instrument that can measure direct beam solar irradiance. [1] Sunlight enters the instrument through a window and is directed onto a thermopile which converts heat to an electrical signal that can be recorded. The signal voltage is converted via a formula to measure watts per square metre.