Talk:Solar irradiance

There are numerous major misconceptions and miss-statements in this article. It needs thorough reworking by experts knowledgeable in solar science. See NASA SORCE at http://lasp.colorado.edu/home/sorce/ etc.DLH (talk) 18:15, 1 January 2015 (UTC)[reply]

Recently this edit by Lfstevens, removed what appears highly cited papers. However the entire manual references belong inline with the content. Thus, i suggest to remove all manual references, and if possible move them to the correct content. Maybe the editor can explain why remove only a few paper studies. prokaryotes (talk) 04:46, 15 August 2015 (UTC)[reply]

See What is the difference between insolation and solar irradiance? http://www.researchgate.net/post/What_is_the_difference_between_insolation_and_solar_irradiance prokaryotes (talk) 19:00, 15 August 2015 (UTC)[reply]

I have no opinion about the answer, but perhaps we should look for something more authoritative? Lfstevens (talk) 07:04, 16 August 2015 (UTC)[reply]

This looks like a more credible source: http://www.volker-quaschning.de/articles/fundamentals1/index.php The distinction they make is "The total specific radiant power, or radiant flux, per area that reaches a Spectrum AM 0 (extraterrestrial) Spectrum AM 1.5 (terrestrial) receiver surface is called irradiance. Irradiance is measured in W/m² and has the symbol E. When integrating the irradiance over a certain time period it becomes solar irradiation. Irradiation is measured in either J/m² or Wh/m², and represented by the symbol H", so I think Irradiance is power per area, "solar irradiation" or insolation is energy per area. Chthonicdaemon (talk) 05:57, 28 September 2015 (UTC)[reply]

Yes, Solar Irradiance and Insolation (Solar Irradiation) are often confused and their meanings and units are conflated in this article. The name of the article needs to be changed to include both ("Solar Irradiance and Irradiation" perhaps), or there should be two articles, one on Solar Irradiance and the other on Solar Irradiation (which is now the preferred way to refer to Insolation). Having them both in the same article might make sense because Irradiation is simply the integral of Irradiance over a given time interval. Indeed the www.volker-quaschning.de source cited here is more credible than the www.researchgate.net source. JDHeinzmann (talk) 11:38, 30 October 2015 (UTC)[reply]

I would be strongly in favour of a separate article on insolation, which can depend on altitude, latitude, cloud cover, wavelength (UV insolation is considerably weaker than IR insolation), nearby reflectors, etc.

Solar irradiance on the other hand is independent of all of those variables except wavelength, with "total" often meaning "over all wavelengths". Nominally it is the irradiance at top of atmosphere, but since both the solar luminosity and distance of Earth from the Sun varies from day to day, different authors implicitly take it to be the mean over one or both of these factors, averaged over a specified period. For example the several articles in Haigh et al's book "The Sun, Solar Analogs and the Climate" use "solar iradiance", "total solar irradiance", and "bolometric irradiance" without definition making it unclear how they differ.

A definition of solar irradiance I'd be fine with is the irradiance from the Sun at a distance of 1 AU from the Sun. (This definition is kept simple by modeling the Sun as a spherically symmetric radiator.) Equivalently solar irradiance is the quotient of solar luminosity by the area of a sphere of radius 1 AU cocentric with the Sun. These are to be understood as instantaneous notions; one can then speak of mean solar luminosity, and hence mean solar irradiance, averaged over a specified period of time. (The article Solar luminosity complicates the notion with a factor of k apparently on the assumption that the notion is defined as the annual mean where distance varies according to Kepler's Second Law while luminosity is either constant or an annual average.)

My understanding of "total" in TSI, based on usage, is as a spectral notion, namely "integrated over all wavelengths"; thus one can say "UV solar irradiance" but not "UV total solar irradiance". Logically "total solar luminosity" would therefore also be a spectral notion, but instead "total" in that context is more often used redundantly to emphasize that luminosity is irradiance integrated over area.

Meanwhile there are some egregious errors in this article, such as mixing up energy and power, but I would nevertheless suggest fixing the definitions before fixing the errors since the latter depend on the former. Vaughan Pratt (talk) 17:06, 13 December 2015 (UTC)[reply]

While I can glean/infer the meanings of these terms from the discussion, I'd instead suggest that we refer to an authoritative source and go with that. Can anyone provide one? Lfstevens (talk) 07:43, 14 December 2015 (UTC)[reply]

I've reworded the first part of the article to be more in line with the concept of irradiance, and linked to Irradiance to show the analogy. However, as I was searching for the uses of insolation, I came across Direct insolation which uses the "wrong" definition of insolation (the power instead of the energy). I suggest that we take it as we can, I feel that my edits have at least removed some blatantly incorrect units and perhaps harmonized the page a little better. I think part of the problem comes from the redirect from insolation, which I suppose used to be the name of the page. We'll have to go through all the other pages referencing insolation to fix that as well. Chthonicdaemon (talk) 08:26, 14 December 2015 (UTC)[reply]

Since when does irradiance not depend on "depend on altitude, latitude, cloud cover, wavelength, nearby reflectors, etc."? Irradiance (or radiant flux) is simply the radiant energy that crosses a specified plane per unit time and unit area. Of course this depends on the entire environment, including the source of the radiation.

My understanding has been that "insolation" means the same thing as "solar irradiance," i.e., the irradiance arriving at a surface (in this case the Earth's surface) that originated at the sun. However, the term "insolation" is used primarily in the land surface and solar energy communities. In my field (atmospheric radiative transfer), "irradiance" (the current SI term) or "radiative flux" (the older, now nonstandard term) are most widely used, so I may be wrong. I fail to see why anyone would want to know an instantaneous flux (J/m2). — Preceding unsigned comment added by 140.142.113.201 (talk) 01:56, 1 June 2016 (UTC)[reply]

The first sentence of the article says "Solar irradiance (also Insolation, from Latin insolare, to expose to the sun)[1][2] is the power per unit area produced by the Sun in the form of electromagnetic radiation" but the units stated further along are MJ/m². There are also many ambiguous units like kWh/m²/day and such. I think the units should all be power/area as in the definition. Chthonicdaemon (talk) 04:30, 28 September 2015 (UTC)[reply]

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The Solar potential maps are interesting but it wasn't clear at all that the mapping between colors and irradiation amounts are not the same among them, potentially misleading readers. Suggest re-doing these maps such that the color/irradiation scale is the same. — Preceding unsigned comment added by 71.238.62.176 (talk) 03:39, 8 March 2016 (UTC)[reply]

I tried to make some changes and improvements to this article, in part to update the information but also to include a reference to the Global Solar Atlas (http://globalsolaratlas.info), which is relatively new so therefore not yet well known. These edits were rolled back by another editor because they believed them to be spam, which they are not. However, I do have a potential Conflict of Interest in adding the reference because I was involved in creating the Global Solar Atlas. So I won't attempt to re-add these edits. However, I do think they are relevant, and would encourage someone else to view what I was trying to edit and add and see which of this they feel like adding themselves. Much of the information on this article could do with improving, and I'd be happy to get involved, but I'm wary now after having content deleted. Thanks. --O-Jay (talk) 18:58, 25 December 2016 (UTC)[reply]

Recently I corrected the formula for the declination, but the formula for the average insolation over a day is also incorrect and I can't find where the mistake in the construction of the formula is. On this wiki the formula is ${\displaystyle {\overline {Q}}^{day}={\frac {S_{0}}{\pi }}{\frac {R_{0}^{2}}{R_{E}^{2}}}[h_{0}\sin(\phi )\sin(\delta )+\cos(\phi )cos(\delta )sin(h_{0})]}$, but the correct formula is: ${\displaystyle {\overline {Q}}^{day}={\frac {S_{0}}{\pi }}{\frac {R_{0}^{2}}{R_{E}^{2}}}[\sin(\phi )\sin(\delta )+\cos(\phi )cos(\delta )sin(h_{0})]}$(so without the h₀) ^[1] Xyfonix (talk) 08:36, 9 March 2017 (UTC)[reply]

The web page you cite says that it copied the formula from Wikipedia, specifically the Insolation article that was merged into this one. It is likely the author of that page made a mistake in copying. Actually doing the integration shows that the result with the h is the correct one. StarryGrandma (talk) 08:01, 10 March 2017 (UTC)[reply]