Cirrus clouds are found here in the atmosphere(Artiom Vallet / Unsplash)This week on Science Behind the Forecast, learn about those cotton candy-like formations, cirrus clouds. LPM’s Bill Burton talks about them with meteorologist Tawana Andrew.This transcript was edited for clarity and length.T awana Andrew: Good morning. Today we're continuing our cloud series.Bill Burton: Today we're talking about some thin, wispy clouds. Cirrus clouds, specifically. What do we need to know about them?TA: They kind of look like when you take cotton candy and you just pull it apart, it looks all thin and stringy.BB: I'm going to have to do an experiment now.TA: Listen, find cotton candy and share it with me. That's the way to go.BB: Will do.TA: They're light, they're wispy, they float really high up in the atmosphere, and they can be found at altitudes between 10,000 and 25,000 feet in more polar locations. For our area, we typically see them between 16,000 and 45,000 feet. That's a mid-latitude situation.In the tropics, they could be as high as 60,000 feet. The reason for that is that the troposphere, where most of our weather occurs, is thicker near the equator than the poles. So there's a little bit more space for them to go up. Due to their presence very, very high in the atmosphere, cirrus clouds are almost exclusively made of ice crystals. These ice crystals form when water vapor transitions to a solid, becoming the ice. This often happens on condensation nuclei like dust or pollen, or maybe even some hair that makes it that far up.BB: I was not expecting hair.TA: It just has to be really, really, really, really small, and that will work as a condensation nuclei. An airborne sampling mission across the entire globe found that dust-initiated cirrus clouds accounted for 34% to 71% of all cirrus clouds outside of the tropics. You have that dust coming off, let's say, the Sahara, making it high enough in the atmosphere. The moisture solidifies onto that, and then you start to get cirrus clouds. That's one way that they can form, and they will appear as delicate white fibers or bands of clouds. The shape of a cirrus cloud is often a result of the wind at the upper levels of the atmosphere manipulating it into different shapes and strands. Kind of like Play Doh in the upper levels of the atmosphere.BB: Since they're so thin and wispy, I'm guessing they're not really rain clouds.TA: No, they are not rain clouds. They sometimes can be a sign of precipitation to come, but they're usually not a sign of precipitation themselves. They tend to actually have a net cooling effect. We think clouds overhead make cooler days. But because cirrus clouds are higher up in the atmosphere and they're colder than the clouds closer to the ground, and the planet surface itself, what they tend to do is that they radiate less heat into space while trapping heat way more effectively than the lower level clouds. On average, you can have a net warming effect on those days, especially when you have more cirrus clouds overhead, and they're usually seen during quiet weather, like what we have going on right now, where you just don't have much going on.You'll see plenty of those cirrus clouds overhead at times, but if they start to take over the skies and are followed by cirrostratus clouds, that layer of thin clouds high in the atmosphere, is often a sign of an approaching system, most of the time, an approaching warm front. If you see cirrostratus clouds taking over the skies, then you know that the weather is going to start to change, and there could be some precipitation heading your way. ...read more read less