Talk:Rain

Portland rainfall inacurate

Portland's rainfall is 35 inches per year, not 45 as the editor suggests —Preceding unsigned comment added by Jamesj2 (talk • contribs) 19:57, 22 October 2009 (UTC)

Major expansion

This article was missing a lot of information, and some information is still needed. Much has been added and reorganized. After several more references are added, the info in the lead is reconciled with the article below, and the rainfall climatology information by continent is fairly complete we can think about GANing it. Let me know if anything else significant is missing from this article. Thegreatdr (talk) 21:12, 2 January 2010 (UTC)

Down to 4 paragraphs needing references. Think all the necessary content is already here. Thegreatdr (talk) 16:13, 15 January 2010 (UTC)

I have shuffled the sections a bit, but I did not remove or alter any information. I think that the article has a better flow this way. Nergaal (talk) 10:57, 3 February 2010 (UTC)

Global precipitation trend - up or flat?

The following statements in the "Human Influence" section seem to be contradictory: "Increasing temperatures tend to increase evaporation which leads to more precipitation. As average global temperatures have risen, average global precipitation has also increased." "Globally there has been no statistically significant overall trend in precipitation over the past century..."

I plead utter ignorance as to which is correct. Both statements come from reference [56], viz. EPA citing IPCC FAR WG1. But that doesn't (in my mind, at least) mitigate the apparent contradiction.

Anyone more knowledgeable who knows of a reliable source to back up one or the other statement? Or reconcile the two?

Thanks. LijeBailey (talk) 21:12, 27 February 2010 (UTC)

There's a surprise. A consensus document has contradictions. In this case, that is a real problem. I made an effort to resolve the situation. Thegreatdr (talk) 04:38, 28 February 2010 (UTC)

Inches?

How is it determined how many inches of rain is going to fall/has fallen? Inches over what measurement of land? If someone knows the answer to this maybe it should be on the main page? —Preceding unsigned comment added by 24.160.179.228 (talk) 04:12, 15 June 2010 (UTC)

• Using a Rain gauge. Why, there is nothing notable about them? Pyrotec (talk) 08:49, 15 June 2010 (UTC)

I've changed the article (a bit late, I know) to hopefully clear this up some... see the measurement section. -RunningOnBrains^(talk) 09:40, 5 May 2012 (UTC)

Deserts inaccuracy/vandalism

In the section under Deserts, someone has listed the Willamette Valley of Oregon as one of four drier regions of the United States. It fact it is one of the wettest; the rainfall map linking from their reference will attest to that. Or ask anyone who lives here; June has already given us 2.81" in 18 days so far. {{editsemiprotected}}

159.121.4.169 (talk) 20:53, 15 June 2010 (UTC)

Done Favonian (talk) 19:15, 18 June 2010 (UTC)

Causes

All (or very nearly all) of the "causes" section here is identical to that in Precipitation (meteorology) and that I think is bad. Since the causes stuff here isn't rain-specifc (same applies to snow) I think it is better in ppn. so the stuff here should be removed; and we should just link across William M. Connolley (talk) 20:58, 26 September 2010 (UTC)

Wettest places

"Cherrapunji situated on the southern slopes of the Eastern Himalaya in Shillong, India is one of the wettest places on Earth, with an average annual rainfall of 11,430 mm (450 in). "

I don't know what those mountains are called where Cherrapunji is, but it is NOT the Eastern Himalaya.Eregli bob (talk) 15:12, 8 February 2011 (UTC)

I think the section could do with bullet points for each of the places, rather than lumping them together in one paragraph (I don't know how to do them myself though).

¬¬¬¬ — Preceding unsigned comment added by Meltingpot (talk • contribs) 17:40, 19 February 2013 (UTC)

Paragraph form is usually preferred to inline lists. In any event, the table seems to accomplish much the same thing that a bullet list would, doesn't it? Rivertorch (talk) 19:33, 19 February 2013 (UTC)

The wettest places is not very good. As long as we are talking about estimates (cause people dont live in the most extreme places to run a weather station). Ålfotbreen in Norway has around 5,600 mm a year. Source http://www.ub.uib.no/elpub/2005/h/406004/Hovedoppgave.pdf. This is probably a wetter place than the one in Montenegro. Lolper11 (talk) 12:29, 4 March 2013 (UTC)

The wettest places section of this article should be an independent entry. There is a wealth of information regarding wettest places on each continent, causes of extreme rainfall, dispute between wettest locations, and potential undiscovered wettest locations. More than enough to create a standalone article.

Requesting permission to create an independent article of Earth's wettest places -Ivvavik — Preceding unsigned comment added by Ivvavik (talk • contribs) 02:27, 29 August 2018 (UTC)

Typo?

I think this is merely a typo, but I have no idea how it should read.

There is a statement in the article:

"Over the contiguous United States, total annual precipitation increased at an average rate of 6.1 percent per century since 1900"

There has only been one century since 1900.

-john — Preceding unsigned comment added by 63.239.65.11 (talk) 17:01, 19 April 2011 (UTC)

Science News resource "Rain tips balance between forest and savanna: Amount of tree cover can shift suddenly and abruptly"

• Trees have a tipping point: Amount of forest cover can shift suddenly and unexpectedly by Alexandra Witze November 5th, 2011; Vol.180 #10 (p. 5) "Rain tips balance between forest and savanna: Amount of tree cover can shift suddenly and abruptly" November 5th, 2011
• http://www.sciencenewsdigital.org/sciencenews/20111105?pg=7#pg7

Also see Tipping point. 97.87.29.188 (talk) 22:52, 9 November 2011 (UTC)

See Trees. 99.19.43.8 (talk) 00:02, 12 November 2011 (UTC)

Poor Description of Why Rain Falls

This article gives the appearance of being "scientific" and well-written, but it actually does not describe clearly why rain falls. (P.S. - No, it does *not.* Re-read the article *carefully* and you'll see what I mean.) — Preceding unsigned comment added by 68.196.248.241 (talk) 07:33, 11 April 2012 (UTC)

Okay, I'll bite. The article says:

Coalescence occurs when water droplets fuse to create larger water droplets, or when water droplets freeze onto an ice crystal, which is known as the Bergeron process. Air resistance typically causes the water droplets in a cloud to remain stationary. When air turbulence occurs, water droplets collide, producing larger droplets. As these larger water droplets descend, coalescence continues, so that drops become heavy enough to overcome air resistance and fall as rain.

The only thing missing there, as far as I can see, is a mention of gravity, which hardly seems needed. Rivertorch (talk) 00:51, 12 April 2012 (UTC)

---

Coalescence is a fusing of material - for example, water drops. Therefore the first statement says "Coalescence occurs when coalescence occurs." And it's not an explanation of why that happens, it just uses a "big word" to sound more fancy. I'll give you the second one, about the "Bergeron process." It then states that air droplets "descend" as if stating that fact is an explanation. *Why* do they descend? Thermal air currents? Gravity? (etc.) Obviously a threshold is reached where gravity is overcome - but *why* is that threshold reached? What factors are necessary to overcome it? Does it always happen at the same altitude and temperature? Trust me, if you read this article *very* very carefully, you will see that there is hardly any explanation given for rain falling at *all.* It just *appears* to. — Preceding unsigned comment added by 68.196.248.241 (talk) 10:59, 23 April 2012 (UTC)

If I'm reading you correctly, you're looking for a much greater level of detail about the formation of raindrops and the factors that determine the threshold of their precipitation. I'm not sure whether you have a specific idea for achieving that in the article or are just curious. If the latter, tell you what—since this topic is well outside my field of expertise and no one else has responded, why don't you post something at the Reference Desk? (Btw, you can indent your replies by various degrees by adding one or more colons at the beginning of each paragraph. See Help:Talk#Indentation.) Rivertorch (talk) 17:53, 23 April 2012 (UTC)

If that is what is asked for, the user could create a new article called raindrop to provide the additional level of detail. We have good, detailed articles like that for snowflake and hail. It could be a subarticle to both drop and rain. Thegreatdr (talk) 18:23, 23 April 2012 (UTC)

Yes, I was just curious. I'll try to contact the reference desk to ask about it tomorrow. I don't really have the expertise or the time to write about it myself. Thanks for taking the time to respond. — Preceding unsigned comment added by 68.196.248.241 (talk) 04:56, 5 May 2012 (UTC)

I like the idea of a rain and raindrop article. The problem with wanting to know how "rain" forms is apparent from reading the article; there are dozens of separate phenomena which can work alone or in concert to form rain. If we have a raindrop article, we can have all the "why" here, and the "what" there. I may start it tomorrow. -RunningOnBrains^(talk) 09:08, 5 May 2012 (UTC)

CULTURE

Good now I have your attention. now I am wondering if there are any cultural aspects of rain, I am pretty sure there are; its just that I don't know how to cite sources.--Commander v99 (talk) 21:51, 11 April 2012 (UTC)

See Wikipedia:Citing sources for information about how to cite sources. You don't have to SHOUT to get your fellow Wikipedians' attention, btw. Rivertorch (talk) 00:24, 12 April 2012 (UTC)

Commonly used categories?

E.g., the widely-used "www.weather.com" refers to "Light Rain," then "Showers." What do these mean? Which is heavier, longer, etc.? Is there a common taxonomy that can be listed in a table, or some discussion of the various phrases used? Thanks! Benefac (talk) 10:03, 17 July 2013 (UTC)

Really depends from country to country and even between organisations (eg. Bureau of Meteorology's Glossary and Weather Words). Bidgee (talk) 12:19, 17 July 2013 (UTC)

"Phantom Rain"? Wikipedia has an article about VIRGA and for consistencies sake I suggest at least mentioning here that "Phantom Rain" is called VIRGA. GodsGoodCountry (talk) 20:43, 27 July 2014 (UTC)

Rate?

In the sentence "total annual precipitation increased at an average rate of 6.1 percent since 1900", should this perhaps read instead "total annual precipitation has increased by 6.1 percent since 1900"? I can't think of a meaning for this sentence where either "average" or "rate" makes sense. Vaughan Pratt (talk) 16:06, 10 September 2014 (UTC)

Hyetograph

Can a link be added to Hyetograph — Preceding unsigned comment added by 141.244.172.122 (talk) 09:20, 29 January 2015 (UTC)

"euphemisms" -->"slang expressions"

several informal synonyms for violent rain are listed. These are denoted "euphemisms" I think a more accurate characterization would be "slang expressions" The expressions quoted don't fit the definition of a euphemism.Imlikewhoa (talk) 16:46, 12 September 2015 (UTC)

include volume fraction in "intensity" section

In the "intensity" section after the listing of light, moderate, heavy, violent categories, I suggest to add

In violent (50mm/hour) rain with large (5mm) raindrops, about 3 parts per million of the air volume (or 3 parts per thousand of its mass) is liquid water.

---

justification:

the volume fraction is the ratio of the rain intensity (50mm/(24*60 sec) or 34 x 10^-6 meters/sec) to the raindrop velocity. elsewhere in the article 5 mm raindrops are said to fall at about 10 meters/sec. The volume fraction is thus (34/10) x 10^-6 . Imlikewhoa (talk) 17:17, 12 September 2015 (UTC)

I am linking in from a different perspective, Rain gutter. Rainfall intensity is measures in l/s/m² in SI units? I am particularly interested in 0.0208 l/s/m² used as a rule of thumb in the building industry. This section doesn't provide an easy link. Any thoughts, please ping me. --ClemRutter (talk) 10:10, 6 January 2017 (UTC)

The SI unit for l/s/m² is 0.01m³/s. However 1l/s/m² is usually expressed as a rainfall of 1mm in 1second; a very heavy rainfall event! Thus 0.0208 l/s/m² = 0.0208mm of rainfall per second which equates to about 54mm of rain per hour- a very heavy rainfall event. Hope my maths is correct !  Velella  ^{Velella Talk}   10:15, 7 January 2017 (UTC)

snow

snow is happens when the temperature is under 32. — Preceding unsigned comment added by 208.108.81.181 (talk) 13:13, 22 September 2016 (UTC)

No. Snow may occur when the tempertaure drops below 1 degree C (Centrigrade is used by all meterologists, even in the US) but equally super-cooled water may fall as rain at this temperature as may hail. However, much of the time when the temperatuer is below freezing, there are clear skies and no preciptation occurs at all.  Velella  ^{Velella Talk}   01:35, 26 January 2017 (UTC)

Math error in intensity section

Hello,

I am mostly a reader and am not a confirmed user, but I noticed a fairly egregious mathematical misconception in the category "measurement" --> "intensity". A storm (or any event) that has a one percent chance of occurring in a year does not have a fifty percent chance of occurring in 100 years. If it did, it would also follow that the storm had a 100% probability of occurring in 100 years (which probability should not guarantee) and a 150% chance of occurring in 150 years (which doesn't make sense).

This issue is addressed in the probability section of the 100 year flood page, which is linked to at the top of the aforementioned subsection. That page cites this link for support "http://www.floods.org/ace-files/documentlibrary/Publications/asfpmpubs-techrep7_2015.pdf"

It should be edited to say that this is a common misconception and that a 1 in 100 year storm has about a one percent chance of occurring each year, but by independence of probability, one or more such storms actually have about a 63% chance of occurring in 100 years.

Brohring (talk) 20:42, 25 January 2017 (UTC)

Semi-protected edit request on 23 January 2019

Change: Rainfall intensity is classified according to the rate of precipitation, which depends on the considered time:[105]

to: Rainfall intensity is classified according to the rate of precipitation, which depends on the considered time[105]. The following categories have been suggested [original reference is missing]:

Reason: Section 4.3 Intensity details important categories for rainfall rates. However, none of the references [105], [106], [107] and [108] explain the mentioned categories. The reference [106] is pointed at for the categories Moderate rain and Heavy rain, but the source AMS fail to provide any references to its categories. Mjunkov (talk) 18:19, 23 January 2019 (UTC)

 Partly done: didn't like using the word "suggested". Both source 106 (American Meteorological Society) and 107 (Met Office) are reliable sources, so this seems to be just a case of different countries using different standards. Roadguy2 (talk) 18:48, 25 February 2019 (UTC)

"Intensity frequency and duration" listed at Redirects for discussion

An editor has asked for a discussion to address the redirect Intensity frequency and duration. Please participate in the redirect discussion if you wish to do so. Steel1943 (talk) 00:27, 22 January 2020 (UTC)

"Pissing it Down" listed at Redirects for discussion

An editor has asked for a discussion to address the redirect Pissing it Down. Please participate in the redirect discussion if you wish to do so. Steel1943 (talk) 18:12, 31 January 2020 (UTC)

" Climate classification systems such as the Köppen classification system use average annual rainfall to help differentiate between differing climate regimes."

This is misleading by excessive specificity, as it implies that "annual" is the precision used by the Koppen system, when (as mentioned later in the article) it uses monthly as well. It's also overly verbose, with questionable word choices. Prefer "Climate classification systems such as the Köppen system use rainfall to help differentiate climates." — Preceding unsigned comment added by 110.28.222.58 (talk) 00:38, 3 May 2021 (UTC)

Incorrect probabilities for return periods

The article states (under the heading Intensity) that a 1 in 10, or 1 in 100 year flood is 50% likely to occur over 10 or 100 years respectively. This is not true. The probability is approximately 65% and 63% respectively.

This can be calculated as 1 minus the probability of no flood. The probability of no flood is a binomial distribution with x=0, n (the number of years) and p (the probability of occurrence in a single year (p=1/n)).

To check this out quickly, use this calculator which will do the calc for you https://www.weather.gov/epz/wxcalc_floodperiod.

Please replace 50% with 65 and 63% for 1 in 10 and 1 in 100 year floods.

Cheers, Fraser 90.248.13.248 (talk) 10:42, 28 October 2021 (UTC)

I've reverted it back to this version (the last correct version December 2016) rather than use the calculator you linked. That version is more easily understandable and directly verified by the sources (as well as being correct). Thanks for bringing it to our attention, it has been wrong since January 2017! SpinningSpark 14:40, 28 October 2021 (UTC)

I agree with the maths but I think the text has the logic backwards. The defn of a 100-y flood is (according to source) that it has a 1% prob in a given year; from this you can deduce that it is likely to occur ~1/century William M. Connolley (talk) 15:37, 28 October 2021 (UTC)

I don't think that's the definition at all, nor does the source say it is the definition. The definition of a 10-y flood is that it has an average recurrence of 10 years. Here's a source that says that. The definition is the recurrence interval, the yearly probability is the inverse of that. Here's a source that says the probability is the inverse of the interval. Really, the definition is in the name, but the two are so directly related that they are equivalent statements. SpinningSpark 16:22, 28 October 2021 (UTC)

I was relying on the ref we use in the article, http://bcn.boulder.co.us/basin/watershed/flood.html, which says The terms "10 year", "50 year", "100 year" and "500 year" floods are used to describe the estimated probability of a flood event happening in any given year... A 10 year flood has a 10 percent probability of occurring in any given year, a 50 year event a 2% probabaility, a 100 year event a 1% probability, and a 500 year event a .2% probability. While unlikely, it is possible to have two 100 or even 500 year floods within years or months of each other. William M. Connolley (talk) 16:57, 28 October 2021 (UTC)

Thinking more slowly: our Return period article says The theoretical return period between occurrences is the inverse of the average frequency of occurrence. For example, a 10-year flood has a 1/10 = 0.1 or 10% chance of being exceeded in any one year and a 50-year flood has a 0.02 or 2% chance of being exceeded in any one year. - which is the defn I picked. But it also says A return period, also known as a recurrence interval or repeat interval, is an average time or an estimated average time between events.... And having thought about it, I think (but am not fully confident) that those two are equivalent, in the long run. However, they are not equivalent to The term 1 in 10 year storm describes a rainfall event which is rare and is only likely to occur once every 10 years which is the text we had before I changed it; at least in part because the "only likely" is ill-defined and so near meaningless William M. Connolley (talk) 21:13, 28 October 2021 (UTC)

"...used to describe the estimated probability" is not the same as "...defined as the estimated probability." You are right about the "only likely" phrase though. SpinningSpark 21:57, 28 October 2021 (UTC)

Furthermore, the first source in that section makes it clear that the probability is only the inverse of return period under a specific condition (that the probability is assumed to be the same in every period). SpinningSpark 23:04, 29 October 2021 (UTC)

@Velella: I think this was your edit. SpinningSpark 14:42, 28 October 2021 (UTC)

Removed section: Outside Earth

I have removed this section on "Outside Earth" because I don't think it fits here. The article is clearly about water droplets and not about rain of other things. This section could perhaps be moved to another article where it may fit better:

Rainfalls of diamonds have been suggested to occur on the gas giant planets, Jupiter and Saturn, as well as on the ice giant planets, Uranus and Neptune. There is likely to be rain of various compositions in the upper atmospheres of the gas giants, as well as precipitation of liquid neon in the deep atmospheres. On Titan, Saturn's largest natural satellite, infrequent methane rain is thought to carve the moon's numerous surface channels. On Venus, sulfuric acid virga evaporates 25 km (16 mi) from the surface. Extrasolar planet OGLE-TR-56b in the constellation Sagittarius is hypothesized to have iron rain. Accordingly, research carried out by the European Southern Observatory shows that WASP-76b can produce showers of burning liquid iron droplets once temperature decreases during the planet's night hours. There is evidence from samples of basalt brought back by the Apollo missions that the Moon has been subject to lava rain. EMsmile (talk) 08:19, 5 May 2023 (UTC)

References

EMsmile (talk) 08:19, 5 May 2023 (UTC)

Good catch. We haven't observed any raining phenomena directly. Maybe we should add back info about Titan though, since that's the only body in the solar system other than the Earth that has liquid on the surface. CactiStaccingCrane (talk) 04:06, 27 May 2023 (UTC)

I don't think we need info about Titan here. It's not what people expect to see when they search for rain. There would be other articles about the universe that could contain that. See also Rain (disambiguation). Interestingly, the first sentence there says Rain is a type of precipitation in which liquid drops of water fall toward the surface of the earth.. Is this a better first sentence than our first sentence which is currently Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity.? EMsmile (talk) 21:13, 13 June 2023 (UTC)

"Euphemism"

In Rain#Intensity, the article says

Euphemisms for a heavy or violent rain include gully washer, trash-mover and toad-strangler.

Those are not really euphemisms;there's nothing offensive about a term like "heavy rain". But what should we call them - or should we just delete them? Nø (talk) 10:09, 19 August 2023 (UTC)

Fixed Vsmith (talk) 15:06, 19 August 2023 (UTC)