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February 13

UV index

This thing interests me, and I don't know it (it's not homework): in which time of the year is the UV index highest in any given place? Is it arund the summer solstice, which is in June in northern hemisphere and in December in southern hemisphere, or is it in July in northern hemisphere and in January in southern hemisphere, when temperatures are highest? --40bus (talk) 15:58, 13 February 2024 (UTC)[reply]

See Ultraviolet index. I expect the UV Index at any geographical position to be at its annual highest value when the sun is at the greatest elevation - the summer solstice. Dolphin (t) 16:27, 13 February 2024 (UTC)[reply]

But the high-latitude ozone hole peaks in early spring, in low latitude the Sun height changes of Earth's axis cause smaller incoming solar radiation changes than elsewhere cause trigonometry so the strong 1-year wet and dry season cycle and milder seasonal ozone strength cycle might overpower the small axis tilt effect and make it not the time of highest noon Sun (which is not the solstice less than 23.44 degrees from the Equator. Sagittarian Milky Way (talk) 18:00, 13 February 2024 (UTC)[reply]

Sun Safety Monthly Average UV Index 2006-2023 from the United States Environmental Protection Agency shows similar results for June and July. Alansplodge (talk) 12:41, 15 February 2024 (UTC)[reply]

Some relevant considerations also are to be found in that article Record solar UV irradiance in the tropical Andes. As can be expected, peak values were measured between the end of December, and January (2004). --Askedonty (talk) 13:38, 15 February 2024 (UTC)[reply]

Peak rain time is afternoon, Andes might often pierce the clouds, the ITCZ usually lags the Sun zenith latitude and it only has to be sunny in late December once to be a record. Sagittarian Milky Way (talk) 14:12, 15 February 2024 (UTC)[reply]

Yes, that's why the team hit bonanza. But no residual glacier, which is a course other latitudes tend to be following lately [1]. --Askedonty (talk) 14:52, 15 February 2024 (UTC)[reply]

Also the Sun is closest to Earth in early January. Sagittarian Milky Way (talk) 14:57, 15 February 2024 (UTC)[reply]

However the zenith noon latitude is only December solstice at the Tropic of Capricorn, slightly norther it'll be zenith twice a year and the early January one will be at the nearest part of Earth's orbit but not even get peak doldrums. Also it's dry as fuck there. Atacama Desert, nothing to block UV not even tropospheric ozone pollution. Sagittarian Milky Way (talk) 15:05, 15 February 2024 (UTC)[reply]

In NYC the summer month percent of possible sunshine is 57 59 63 (frontal thunderstorms decline after June, frontless land heating thunderstorms likely peak July). Avg UV index 7 8 8 8 6 MJJAS according to Wikipedia, maybe enough of the country is similar to make June and July the national average peak. Sagittarian Milky Way (talk) 14:19, 15 February 2024 (UTC)[reply]

Wilson-Effect

Does the Wilson-Effect apply to other properties or just hight (how large somebody is)? 2A02:8071:60A0:92E0:C1E2:268B:CB67:A6BA (talk) 22:07, 13 February 2024 (UTC)[reply]

What Wilson effect? There's one concerning sun spots: Wilson effect. There's one concerning inheritability of IQ: [2]. You seem to be talking about yet another one. Please try to ask a proper question. --Wrongfilter (talk) 22:22, 13 February 2024 (UTC)[reply]

This refers to an increase in heritability of IQ with age, not of height:

Thomas J. Bouchard (October 2013). "The Wilson effect: The increase in heritability of IQ with age". Twin Research and Human Genetics 16(5):923–30. PMID 23919982

Reportedly, looking at a proxy for general cognitive ability instead of IQ, some researchers found the opposite effect for the age bracket of 50–69 years:

Matthew A. Sarraf, Michael Anthony Woodley of Menie, Mateo Peñaherrera-Aguirre (February 2023). "The anti-Wilson effect: The decrease in heritability of general cognitive ability, as proxied by polygenic expressivity, with advanced age". Personality and Individual Differences 202:111969. doi:10.1016/j.paid.2022.111969

--Lambiam 09:22, 14 February 2024 (UTC)[reply]

I've known about that for a long time and am surprised it still is just a citation in Heritability of IQ and not even named there. Yes I would expect height to follow a similar pattern but haven't seen anything about it. NadVolum (talk) 14:12, 14 February 2024 (UTC)[reply]

Children develop at different rates for all sorts of reasons, including non-genetic reasons like nutrition. So children of a particular age are more variable in IQ and height than older age groups that have reached full adulthood. This is what causes the heritability to be higher in older age groups; there is less non-genetic variation, so the proportion of total variation explained by genetic variation is higher. Hence I would expect the Wilson effect to exist in most traits that show developmental changes with age during childhood. A character like baldness might show the opposite pattern. JMCHutchinson (talk) 22:18, 14 February 2024 (UTC)[reply]