ir·​ra·​di·​ance | \ i-ˈrā-dē-ən(t)s How to pronounce irradiance (audio) \

Definition of irradiance

2 : the density of radiation incident on a given surface usually expressed in watts per square centimeter or square meter

Examples of irradiance in a Sentence

Recent Examples on the Web The device can be mounted at any angle on a floating platform to optimize incident solar irradiance and can readily be integrated with commercial solar-thermal systems. Caroline Delbert, Popular Mechanics, "The Army Is Building an Anti-Gravity, Water-Purifying Solar Panel," 15 July 2020 During that time the solar irradiance decreased by one-quarter of one percent. Jeff Berardelli, CBS News, "10 common myths about climate change — and what science really says," 27 Feb. 2020 The next thing to determine is to think about the solar irradiance. Rhett Allain, WIRED, "The Physics of NASA's New Mars Helicopter," 16 May 2018 With this size, irradiance, length of a day, and an efficiency of 25 percent, that would give a total energy of about 40,000 Joules. Rhett Allain, WIRED, "The Physics of NASA's New Mars Helicopter," 16 May 2018 The solar cycle also plays a minor role in climate, as variations in irradiance can cause slight changes in average sea-surface temperatures and precipitation patterns. Shannon Hall, Scientific American, "The Sun Is Spitting Out Strange Patterns of Gamma Rays—and No One Knows Why," 28 Mar. 2018 From fiber optics to solar irradiance, watch how this @ISS_Research is seeking to offer benefits back on Earth and expand space exploration. Sabrina Eaton,, "NASA Glenn experiments head to International Space Station," 15 Dec. 2017 That was a problem for the U.S. federal research facility Pacific Northwest National Laboratory (PNNL), which needed something that could carry lots of equipment to measure solar irradiance, three-dimensional windspeed, and analyze air particulates. David Hambling, Popular Mechanics, "The Winter-Proof Drone That Will Watch the Arctic," 13 July 2017 Most of all, evolution seems fond of using moonlight as mood lighting: Many species of all shapes and sizes use the moon’s ghostly irradiance, and its 29.5-day waxing and waning, to cue various phases of reproduction. National Geographic, "Sex, Death, and Pollination: How the Moon Changes Life on Earth," 6 July 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'irradiance.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of irradiance

1599, in the meaning defined at sense 1

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The first known use of irradiance was in 1599

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Cite this Entry

“Irradiance.” Dictionary, Merriam-Webster, Accessed 17 May. 2021.

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More Definitions for irradiance


ir·​ra·​di·​ance | \ ir-ˈād-ē-ən(t)s How to pronounce irradiance (audio) \

Medical Definition of irradiance

: the density of radiation incident on a given surface usually expressed in watts per square centimeter or square meter

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