User blog:Cerne/Air, water, and temperature

NOTE: This blog entry was originally scheduled for Tuesday night, May 29th, but II left it on my screen for the following morning and most of what I had was deleted when some idiot who shall remain nameless decided to play around with my CPU before I could post it. Luckily the first three paragraphs were backed up. Everything else was re-typed from memory and then expanded from there.

Here I am going to type a brief (heheh, yeah...) bit about water cycles and how they correspond with temperature. What determines whether rising air will be warm or cool, dry or moist/humid, etc. And while it is still too early to be typing about it yet, I am going to describe how water cycles work in my conworld's atmosphere; how they not only correspond with temperature but also altitude, latitude, and atmospheric content.

OK, first off, I'll admit I wasn't thinking about typing a blog entry on this subject before today but I got thinking about it during a conversation with someone I know in person about regulating heat in warm weather - I'm thinking around 31 ºC or 88 ºF because that was how hot it was today (Tuesday, May 29th) - so I got thinking about how air would circulate in a larger context pertaining to changes in temperature, particularly during seasonal changes and in accordance with latitude and altitude. I still don't think I have it exactly right so don't quote me on any of this.

The principle is that lighter air will rise while heavier air will fall. This can depend on a few things: most notably the size of the given area within which you are making your comparison, the temperature mean outside of the given area, and atmospheric content. On the surface of a planet with an atmosphere, like Earth, the lighter air will continue to rise until it reaches the higher reaches of the atmosphere. These upper areas have less atmospheric density due to less gravitational pull. Less atmospheric density means more empty space between the atmospheric particles for heat energy from the sun to travel through, which in turn means it takes longer for said areas to heat up, consequently making that area colder than the area below it.

An atmosphere that contains larger and/or thicker particles will also be denser than an atmosphere with the same amount of particles if they are smaller and lighter, and will therefore be warmer, but the circumstances for this can still depend on how strong the surface gravity is: a planet that has a lot of heavy atmospheric particles may still have a sharp gradient in atmospheric temperature if its gravity keeps most of those particles close to the surface while letting the lighter particles escape into the higher altitudes. There will be more on this later.

Anyway, where you have liquid water on the surface of the planet, you will get what is known as a water cycle:

Basically, a water cycle is a circulation of air that rises up unto the atmosphere and then falls back down again. This happens because the circulated air contains water particles (H2O) that change their state depending on the surrounding temperature. In warmer temperatures these particles evaporate into a gaseous form (vapour). In cooler temperatures they condense into liquid water. Moist air is heavier than dry air because it contains water vapour, so air that is saturated with water vapour will stay near the surface at first. If temperatures are cool enough, the water vapour may turn into mist or fog before it gets too far off the ground. The warmer the temperature, however, the more these particles will separate and the higher they will rise into the atmosphere. Once they reach a certain altitude, they will start to condense and form liquid water in the form of rain. Or they may remain in the atmosphere and create clouds. This cycle will repeat itself as long as temperatures remain above 0 ºC or 32 ºF so we may conclude under these circumstances that warm air rises and cool air falls. Therefore, warm air is lighter than cool air.

Below 0 ºC or 32 ºF things happen differently.

Once water condenses into ice or snow, the air around it is no longer considered to be "wet." The air surrounding it is then considered to be "dry" and the onlly way liquid water can return to the higher atmosphere and complete the water cycle is when it evaporates from a large body of water like an ocean or a very large lake. Air circulating upward from land will be dry, and that makes it lighter but also cooler. Any moisture that goes back up will make the air warmer, because water moderates the surrounding temperature. But it will also be heavier than the dry air coming up from the land. In this case, while moist air still circulates upward, it is now heavier than the air circulating downward. In this case we can then say that warm air is heavier than cool air.

The significance of this comparison will be brought up shortly but first I want to go back and look at Geoff's Climate Cookbook again. Particularly the part about high- and low-pressure areas. In the summer, low pressure areas form over land and high pressure areas form over water. In the winter, high pressure areas form over land and low pressure areas form over water. According to another source, low pressure means more moderate temperatures and more cloud cover while high pressure means more extreme temperature (for that season) and less cloud cover. Putting this in context with what I just typed in the two preceding paragraphs, we can see that a low pressure system on land would make sense because more moisture is being picked up via the lighter warm air and is creating more cloud cover, which in turn would create milder temperatures, though in larger landmasses there would be less moisture to be picked up and therefore less cloud cover, leading to more extreme temperatures. All in all, we could say that low pressure means warm air being lighter than cool air. Conversely, during the winter, a landmass having a high pressure system would make sense because less moisture is being picked up. Less cloud cover is being created and more cold air is being released back down, creating greater extremes, so we could say that high pressure means warm air being heavier than cold air. We could also look at oceanic high and low pressure systems; high pressure during the summer means more warm air conflicting with more cool air to create wind storms and hurricanes while low pressure during the winter means more thunder and rain storms out at sea and along maritime coasts from all of those moisture-filled clouds running into each other. And of course these four instances - oceanic summer, terrestrial summer, oceanic winter, terrestrial winter - could have the opposite in air pressure as well, but temperature and the size of the land are major determinants in how these instances will play out so more often than not the instance in question will be unique for its season.

Please note that I am not saying I know any of this for sure. I am only making a hypothetical correlation. The more accurate predictions can only be made by researching the topic and gaining a more in-depth understanding of exactly how and why low and high pressure systems arise for any season. Right now I am not actually trying to go into the topic of weather. I am only throwing ideas out there for future reflection and consideration..

Now I want to introduce two different scenarios that utilize the size proponent I brought up earlier. The reason why I said my comparison is significant was because all air on Earth's surface will eventually condense and fall back down if it contains some amount of moisture. Temperatures eventually cool down upon reaching a certain altitude, and water condenses upon reaching the dew point, so warm air is limited in how high it can go in a given space if that space is large enough, as on the surface of a planet. Obvious? Yes, if you took Science in Elementary school. Trivial? Maybe, but then what if the given space in which air can move was limited to a much smaller space? First, imagine a house during the summer. It has one or two living floors, a basement, and an attic. The basement will be the last room to heat up so the air inside it will remain cool longer. The attic will be the first room to heat up, especially if the house has a black tin roof. By placing an electric fan in the attic, you replace the warm air with cool air, Gradually, as cool air starts to replace the warm air, the warm air will rise and be cooled by the electric fan. This, I am told, is the best way to cool your entire house. But what about in the winter? The whole house will be filled with cold, dry air. You can heat it either by running a hydro-electric heater throughout the entire house, starting a fire (in a fireplace) in one area of the house, or by releasing steam into the room as is done in a sauna. Air heats up either by being filled with more heat energy or by becoming denser so that whatever heat energy is contained in it will not need to travel as far before it is reflected by another air particle. If a given closed-off space is below 0 ºC or 32 ºF, any air that is relatively warmer will need to be denser or it will quickly cool down again, unless the entire exterior of the closed-off space is warmer than the interior. Denser air will have more molecules per cubic centimetre so it will be heavier. And, as you know, heavier air does not rise as quickly or as readily as lighter air does. In this instance, then, warm air will be lower off the ground than will cool air. If your home's power should go off in the middle of winter, you will be warmer in a downstairs room than an upstairs room and you will be warmer sleeping on the floor than on a bed that is raised off the ground (provided the bed doesn't have any blankets).

So that is pretty much it for what I wanted to say about air circulation and temperature in general. My conworld does have weather and climate but there are a few factors to think about when attempting to predict it: I still don't really know whether my planet will have a thicker atmosphere than Earth does or not but I did plan on increasing the amount of water vapour in it. This might make it thicker, as might more carbon dioxide and sulphide compounds like hydrogen sulphide and sulphur oxide, as well as a higher quantity of noble gases like argon.
 * 1) axial inclination is a lot less than that of Earth, so seasons are less distinct from each other;
 * 2) distance from its sun is proportionately farther than Earth is from our sun, so mean global temperature will be lower;
 * 3) someone suggested on an online bulletin board that since my planet had faster rotation velocity and lower gravity it would have more than three circulation cells, and furthermore that some of these cells would be on top of the others.

What I am thinking, though - at least for the lower atmosphere (up to what would be the cloud layer on Earth), is that there will be two layers of atmospheric circulation: one from sea level to some undecided point above it, and a second layer on top of it. The first layer would be composed mainly of water, with some carbon dioxide and oxygen, and the second layer would be composed of thinner concentrations of oxygen and then carbon dioxide in that respect. The first layer would be a lot denser so it would make conditions warmer and more cloudy (lack of better word) while the second layer would be less dense and would be cooler. There could be a figure-eight type of inter-circulation between the two layers, where some gases go up to the second layer while others stay in the first layer. Water could certainly go all the way up and create a cloud layer proportionately as high in altitude as it does on Earth (maybe even higher due to the lower gravity) if it weren't for the lower global temperature mean on this planet so temperature could be the primary reason why water condenses so much closer to ground level.

For analogy, typical gametophyte forests on this planet would be very similar to the cloud forests of Central and South America. Other vegetation areas would be somewhat sparser (Note: no angiosperms -> no grass).

This has mostly been an exploration of ideas and speculation on atmospheric circulation, water cycles, and the effect that temperature has on them to create weather. As such, if I really want to get into this at a later time, I may need to go more in-depth and bring in more references than I did this time. Nothing is being decided upon for sure yet. Until then, I'm going to end the entry here.

Thanks for reading.