Talk:Ice fog

Inconsistent description

Link to the revision I am talking about

In section 1, "In the United States," it is said:

The pogonip fog is so thick you can't even see your hand. Go out in it and you'll be lost in seconds. If it lingers you'll die of starvation or exposure. Breathing pogonip can damage your lungs thus the term white death. [citation needed]

In section 2, "In Siberia", it however is said:

The city of Yakutsk is famous for its ice fogs. The water vapour in the air freezes when there's no wind and produces a thick ice fog. When a person walks through this fog, behind him or her a completely visible tunnel appears, and children going to school often play a game trying to guess who has just passed (here our fat schoolmate, there that tall teacher...)

So ice fog is a deadly nightmare of icy doom — unless when it is not, and then children play with it? —Preceding unsigned comment added by Badpazzword (talk • contribs) 18:57, 14 December 2009 (UTC)

I've lived with pogonip. Where I lived in Nevada, sometimes temps would hover at negative 40 degrees F for a week straight. Pogonip's not just scary, it can be dangerous to go out into, because many times you can't see more than a foot: You can stumble into something unfortunate, freeze, get lost and starve, or die of thirst. 71.22.155.114 (talk) 20:19, 29 April 2012 (UTC)

Visible tunnels

I removed this text:

The water vapour in the air freezes when there's no wind and produces a thick ice fog. When a person walks through this fog, behind him or her a completely visible tunnel appears, and children going to school often play a game trying to guess who has just passed (here our fat schoolmate, there that tall teacher...) (Source: "-46°" (in Italian). Retrieved 2009-02-14.)

The source is a blog, which does not seem very reliable, and the phenomenon described is aerodynamically improbable. -- Beland (talk) 02:38, 28 February 2010 (UTC)

i can confirm that this is untrue, i have experienced it before. — Preceding unsigned comment added by 162.222.253.174 (talk) 15:24, 7 January 2021 (UTC)

Temperatures?

"It can happen only in cold areas of the world since water can remain liquid down to -40 °C (-40 °F)."

Which temperature is wrong? Celsius and Fahrenheit are not the same thing... I'd assume -40°C is the correct temperature. -40°F seems too cold. Jacksonalv (talk) 14:51, 13 August 2010 (UTC)

Actually, they are the same. 86.89.144.60 (talk) 09:18, 6 December 2010 (UTC)

Direct to ice?

The Diamond dust article says "the term ice fog usually refers to a fog that formed as liquid water and then froze". This article says "Pogonip only forms under specific conditions, [...], allowing ice crystals to form in the air". I believe that the later is misleading and should read "Pogonip only forms under specific conditions, [...], allowing water droplets to form in the air, which subsequently freeze into ice crystals". 86.89.144.60 (talk) 09:18, 6 December 2010 (UTC)

Pogonip: Ice Fog or Freezing Fog?

It seems to me that common usage of the term "pogonip" refers more to what is known as "freezing fog" rather than "ice fog". Ice fog is described on this page as forming at temperatures near -40F, and that is hard to reconcile with the word being Shoshonean, since they rarely if ever would have encountered those conditions. I recall (as a teenager) the news media in Reno, Nevada using the word "pogonip" to describe "icy fog" conditions when the temperature certainly did not drop below +20F. Here's a link to a January 2011 media web page predicting pogonip in Nevada's Douglas County in early 2011: http://www.recordcourier.com/article/20110105/NEWS/110109944/1062&ParentProfile=1049 — Preceding unsigned comment added by Gac1959 (talk • contribs) 10:57, 7 January 2011 (UTC)

Agree. Famartin (talk) 13:48, 5 December 2014 (UTC)

Article needs some work

I read the article and the sources, and all of it are extremely vague. I think this article needs a lot of work to get it up to some basic scientific standards. For example, I live in Anchorage Alaska where we get ice fog all the time, yet, being so close to the ocean, the temperature rarely gets below -15F. It actually tends to occur at very specific temperatures here, which are 0F and -10F, because we are so close to the ocean. It occurs when the air is fairly calm but the wind direction is coming from the water, because at those temps the salt water in the ocean wants to freeze but can't, so vast clouds of it come pouring off the water's surface. It happens because the air's relative humidity jumps way beyond 100%, becoming supersaturated.

Water has many unusual properties. It expands when it freezes. It crystalizes in almost every form a crystal can take (depending on many factors like temperature) and when its vapor mixes with air, it doesn't just mix --it dissolves-- forming a gaseous solution that behaves exactly like a liquid solution. It's a misconception that water vapor is a liquid; it's not. It's a gas, and therefore does not freeze even in freezing temperatures for the same reason salt water doesn't freeze. In this case, the solvent (air) keeps the vapor locked in a gaseous state.

Like any solution, how much of the solute it can hold depends a lot on the temperature of the solvent, in this case air. At 40F air can hold quite a bit of vapor, and at -40F it will be much drier. The temperature at which the air reaches 100% saturation is called the dew point, which depends on the humidity of the air. When the temperature of the air drops below its dew point, it becomes supersaturated, and through the process of nucleation, the water vapor precipitates meaning it is literally squeezed out of solution.

Compare it to making rock candy like they showed us in school. You heat up water and add as much sugar as it can dissolve. Cool it down and it becomes supersaturated. It's in a metastable state, meaning it wants to crystallize but can't. Add a seed crystal and boom, suddenly it starts growing. This is how frost forms. If the solution becomes extremely supersaturated, like honey, it becomes unstable and crystals will form spontaneously. This is how things like fog, clouds, rain, and snow form. And ice fog. The crystals literally start forming right in midair. If it's cold enough it goes directly from a gas to a solid without ever crossing through a liquid state.

Different crystals will form under different conditions, relating to temperature, air pressure, calmness or turbulence, etc. This is because crystal nucleation and crystal growth reach their maximums at different temperatures (also not much different from honey) and the conditions correspond to the typical altitudes where clods form. Fog is just a cloud at ground level.

One of the big misunderstanding I see here, which I think was a misinterpretation of the source, is that water in air exists in a liquid state until you hit -40. That's not correct. What the source says, and is correct, is that under just the right conditions, liquid water can exist below its freezing point, which is called supercooling. When supercooled water contacts a single ice crystal it will crystallize almost instantly, and anyone who has left a beer in the freezer a bit too long can attest to that. For a supercooled liquid to form you have to eliminate any points of nucleation, so it only happens under just the right conditions, but under most conditions ice crystals will form when the air is below freezing. Zaereth (talk) 21:14, 28 September 2023 (UTC)