Head in the Clouds - Owain Wyn Evans, Gavin Pretor-Pinney, Amanda Maycock

0:28Hello, I'm Brian Cox. He's dark, dark with industrial plumes. You've not bought your clogs again, have you? Because they made a right racket last time. I couldn't wear them standing on those volcanoes looking enigmatic, could I? Because the clicking would spoil the atmosphere. They're not made for going over cooled lava, are they? No. No. They made it wood. It's the worst possible thing to wear, to be honest, walking through lava, isn't it? Isn't it? There must be something... Well, paper, I suppose. Oh, no. Oh, of course, we only had paper shoes in Oldham. Yeah, whatever. Anyway, today we're looking to the sky, but not as far as Brian likes to look.

1:06It's kind of parochial level of looking to the sky. We're going to go, well, really the level of clouds, the clouds that, of course, so often hindered your series Stargazing. Why were there always clouds there? Was it Dara O 'Brien's head? Because I think because of the roundness of the head, they might have attracted clouds closer. Today we're asking, how do clouds help in maintaining... Maintaining, I can't say maintaining. I'll do it if you want. Here we go. You do it, you do it. Today we're asking how do clouds help in maintaining a healthy atmosphere? What can clouds, which are so beautiful and so wonderful, and sometimes they shine with ice crystals, what can they teach us about the climate?

1:44Now you've got to do my line, doing me. To guide us through.

1:52That's Bernard Mann. To guide us through. Oh, she's joking. Guides through, we're joined by a climate scientist. Don't worry, it's all right, the show's going to be OK. To guide us through, we're joined by a climate scientist, a cloud appreciator and a drummer. Oh, but so much more than a drummer. And they are. My name's Gavin Preeti-Pinney. I'm member number one and the founder of the Cloud Appreciation Society, which I started 20 years ago, and it brings people together from all around the world, 120 countries. we've got members in, all united in the belief that, well, clouds aren't something to complain about.

2:29They're actually one of the most evocative and dynamic and maybe you could say poetic aspects of nature. And the most wonderful thing I've seen in a morning sky is a morning glory. Which you'll be relieved. No! It is a cloud formation that forms in a remote part of northern Queensland, Australia. It's a cloud that glider pilots surf, just like surfers on an ocean wave. It travels across the Gulf of Carpentaria through the night and it arrives first thing in the morning on the Queensland coast. And I went there and I watched this cloud arrive. I rushed up into a plane with all the other gliders and watched them as they surfed up and down this cloud as the sunrise was breaking over the top of it.

3:21It was an absolute glorious and beautiful sight. Hello, I'm Amanda Maycock. I'm an atmospheric scientist and a professor from the University of Leeds. I use computer models to simulate the movement of the air within the Earth's atmosphere, including clouds and how it affects the Earth's climate. The most wonderful thing I saw in this morning's sky, there weren't many clouds around up in Leeds today, was actually Venus, which is visible at the moment. And Venus is another beautiful, cloudy planet, but a bit less hospitable than Earth because the clouds are made of sulphuric acid and they've contributed to a runaway greenhouse effect that means the surface temperature is more than 450 degrees Celsius.

4:03So that was the beautiful thing I saw this morning. Don't worry, you'll have those sulphuric acids before you know it. They're working really hard in the US. And also... LAUGHTER I'm Owyne Wyn Evans, used to be a weather presenter. Now I am a TV and radio presenter, and I'm also a drummer. I got the name The Drumming Weatherman when I played the drums to the BBC News music in lockdown, and it went viral, and then I went on to play the drums for 24 hours for a Children in Need drum-a-thon, whilst every so often also doing the weather. LAUGHTER And my husband was thrilled to have the drum kit out of the house for 24 hours.

4:43And I was thrilled to throw the drum kit into a skip after the drum-a-thon. And the most wonderful thing that I've seen in a morning sky is a gigantic pepper pig balloon. Stay with me on this one. I live in Penarth, which is near the water in South Wales. And me and Aaron were going for a walk one morning and saw this kind of orb over the water. I thought, Aaron, what's that? Aaron, that looks like Peppa Pig. Or was it Daddy Pig, actually? As the balloon approached, it was indeed Peppa Pig. And it was drifting up the coast towards Swansea. Stranger things have drifted up the coast towards Swansea.

5:23And it turned out to be a child's balloon, which was somehow kind of amplified and expanded by the view across the sea. And Peppa Pig drifted towards us, and off she went. Last scene off the coast of Barrie. as I think a lot of hopes and dreams have. So there we go. And this is our panel.

5:51Gavin, we should start with you. Why did you feel a cloud appreciation society was so important? It's because people do like to complain about them a bit. You don't need, like, a sort of kitten appreciation society because everyone loves them. You need something that's a society that has a kind of mission to shift people's perspective about the sky. At least that's what I felt. So really, I just felt someone needed to stand up for clouds, basically. Let's get this out of the way. What's your favourite formation? It's got to be a pillious. Fair enough. That's a very strong answer.

6:28Amanda, to move back to the science. That's not science? Move back to the science. We had a man talking about a Peppa Pig balloon. You've got to bring them gently back to the science. I was saying, what's your favourite cloud? Did you say favourite cloud? I said favourite formation, Brian. Is there a technical difference between that? Have I made a terrible mistake? Formation is just a general term, because, I mean, basically, they're all clouds, these random appearances in the sky, but humans are amazing at spotting patterns, and so when we started to classify clouds in a scientific way, 1802 around then, and it was actually an Englishman called Luke Howard, a Quaker from Tottenham, he was spotting patterns and he started to give them Latin names, so he came up with the cumulus and cirrus and stratus, and these names just basically say what the clouds look like, and you say it in Latin, sounds fancy, makes it sound scientific.

7:29See, Brian, you've put too much effort in learning physics. Amanda, how do clouds, at the most basic level, how do clouds form? So, a cloud forms when a parcel of air becomes saturated and some of the moisture that it contains condenses. So where does that come from, the moisture in the air? Well, if you imagine standing and drawing a sort of square around your feet that was sort of one metre squared and you weighed all of the water above your head, there's on average about 25 kilograms of water all the way up to the top of the atmosphere, which doesn't sound like a lot, certainly a lot less than the rest of the mass of the air, but it is enough to form these clouds.

8:07So basically, the evaporation mainly comes from over the oceans. We've got the vast oceans that provide that source. And the sun heats the surface of the earth. The air warms up, warm air rises. It moves up through the atmosphere. And as it does so, it cools and it expands. And it's that expansion and cooling that can cause the air to become saturated. and that's the point at which the cloud droplets can begin to form. But they don't just form by themselves, they need something to cling on to, as it were, and they tend to form around little things we can't see, specks in the air, they might be bits of dust, bits of pollen, fungal spores from trees, and the water molecules condense around those little particles and start to grow a droplet.

8:45And then where does the structure come from? Because we've heard that there are... Is there a number for how many different types of classified cloud formations? Yeah, well, there are 10 basic type, the genera, the main types. And those are the ones you'll have heard of at school, cumulus, cirrus stratus, cumulonimbus, the superstar, you know, the storm cloud that produces thunder and lightning and hail. But then there are lots of these additional ones, which are sometimes just a feature that looks just like a curl, like a tiny breaking wave, which would be called a fluctose cloud feature. There's a whole bunch of them.

9:26I think there's about, when you combine them all, there's probably about 80, something like that. And one of them actually came from the Cloud Appreciation Society. Yeah, one of the official types. So what is giving the clouds these different characteristics, broadly speaking? So there's two main sort of types of particle that we can find within clouds. There's liquid water droplets and then there are ice crystals. and so a lot of the appearance and the differences in appearance come from how much liquid water they contain or how much ice crystals they contain so the high altitude ice clouds where it's very cold they have this kind of wispy appearance they get sort of stretched out by the winds so the winds are obviously blowing the clouds around you can often see that on a windy day you'll see them being blown along the lower altitude clouds which are made from liquid water the sort of fluffy cumulus type clouds they're sort of formed because of the liquid water within them.

10:17So, Owen, what about for you? I know technically you'd be called a weather forecaster, but you weren't actually forecasting weather. Yeah, that's right. Yeah. I came from a background of journalism. When I joined BBC Weather, the Met Office were providing the sort of data, if you like. So I was trained up by them and then later studied through the Open University, meteorology through a couple of modules, just because I think we love the weather here in the UK. It's the first point of kind of conversation for a lot of people. You know, if you don't know what to say, it was lovely outside. Oh, it's terrible, isn't it?

10:55Not always that camp, by the way. Terrible weather. But I think that for me, the clouds are the things that a lot of people, you know, it's that thing that you can see. And I remember when I was doing the weather in lockdown there was nothing to talk about because people weren't really going out so the producers would give me three minutes to fill on the weather I'm like Hans like everyone's inside but people would then start to see like you were saying earlier Gavin about you know the clouds you start to see shapes or faces and I think that's what's amazing about clouds it almost gives people a little bit of creativity especially cumulus clouds the fluffy cotton wool ones.

11:36What about Gavin was saying about that there's a negative attitude towards clouds? I imagine when you were mainly doing the kind of, you know, the presenting of the weather, you would get letters of complaint as if you yourself had created the weather. I mean, did you get that? Yes. I still do. I haven't done the weather for three years and people say, oh, didn't forecast this, did you? So I would say, hon, if I forecast this three years ago, I'd be monetising this skill somehow. It would happen a lot when we get, we would get bad weather as well, you know, There were really bad storms and we'd get weather warnings.

12:10The yellow warning is the lowest. Then it goes up to amber warning, which is my drag name as well. I do think weather presenters are a bit too apologetic. They sort of seem to feel that and they feel a bit guilty when they say, you know, there's going to be a lot of cloud around in an apologetic tone. I would like to hear a bit more detail about what cloud is going to be around. I'd like to know how the formations are going to be changing through the afternoon, what sort of shapes we're going to be seeing. I'd like some more detail and a bit more positivity. I'd love that. I'd love that. We could do, like, a kind of a what shapes will we see today in the clouds, like a little bat, maybe.

12:54Did you used to send to... Because they only used to have one shape of magnet for the cloud, didn't they? Whatever, whether it was a stormy cloud, whatever. It was a bit of a sad day when they stopped using those magnets, But, I mean, that is the cumulus cloud, the one that's in the cartoon. And it's like the sort of generic cloud, the cumulus. If you close your eyes and think of a cloud, it's one of these puffy white cumuluses that form on a sunny day. They feel the most solid. The word cloud comes from the old English word clud, which means a rock or a boulder. It's where we get the clod of earth, that term from.

13:30These feel like solid things, cumulus clouds. Do you know what I mean? and that's why I think they're kind of iconic for us. They have very, very distinctive shapes and the edge of them is very well-defined, which seems counterintuitive. It's just this phenomena where water is condensing. So why do they have such a well-defined shape? So it's often because there's a sort of barrier of the air to be mixed from within the cloud to the surrounding cloud. So there's differences in temperature, differences in density between different air masses that are nearby each other. So that's what provides this kind of rather crisp looking shape often.

14:04The base of the cloud will be where the kind of layer of the atmosphere starts to become saturated. I mentioned before the saturation is a sort of necessary condition. So, again, that's something that will have a sort of well-defined base to it. And then at the top of the cloud, you'll move into drier air, warmer air above. But they're not sort of stationary things. What's actually happening in reality is that there's constant evaporation and condensation occurring, you know at the base of the cloud so the the base of the cloud the little droplets will be continuously evaporating and then at the top of the cloud they'll be condensing and reforming so they're very sort of dynamic structures so is that because i sometimes i do find it fascinating when you're when you're looking you know on on a day where the wind is moving a cloud and you look at that cloud and you think it has remained in that shape and yet so so actually within what appears to be that kind of you know the the stationary nature of the shape itself there is still all manner of movement going on there?

14:59Yeah, absolutely. There's a lot of motion that's happening within the clouds. In fact, that's one of the reasons why a cloud doesn't just fall out of the sky. So a typical cumulus cloud, the ones we're talking about, might weigh somewhere between about 250 or 400 tonnes, something like a sort of typical 747 aircraft, something like that. There's a lovely gasp over there. People have got slightly more scared of clouds than they used to. What if they fall? Chicken lick it? How big would that be? So a 400 ton one cumulus cloud. Yeah. So that would be of the order of a sort of cubic kilometre or something like that, one and a half kilometres cubic.

15:32That's a sort of typical size of a cumulus cloud. But, you know, of course, the gravity isn't acting on the cloud as a whole. It's acting on the individual tiny little droplets, which are of the order of a few thousandths of a millimetre across within the cloud. And so actually they only fall very, very slowly, perhaps, you know, a centimetre per second or something like that. And you actually have motion within the cloud, upward motion, which sort of basically sustains the altitude of those droplets so they don't just drop out and fall down. They collide and coalesce with each other. They join up and become bigger droplets and eventually once they're heavy enough they can actually fall out and become precipitation.

16:06This is the magic of clouds comes from the special nature of water that's naturally found in the three states of solid, liquid and gas And that is really the secret of this kind of poetic and beautiful quality of clouds, because they can appear and disappear at will, because one of those states, the gas one, is invisible. And so we're at the triple point of these three states on Earth, in the atmosphere of Earth. And so the clouds are revealing the changes, revealing the invisible movements of the air. These movements of the winds are happening the whole time. We only see them when they just nudge that water to shift state from the gas form we can't see to the liquid or the solid.

16:59That's a very beautiful thought, actually, is that they make the atmosphere visible. They're the face of the atmosphere. They're expressions on the face of the atmosphere. And so they can reveal the moods, the ever-shifting moods of the atmosphere. and we just intrinsically know how to read those moods. Ask a child when they see a cloud that is dark with a base that's low and they know what's going to happen. They know that that's very likely to produce rain. You know, we've always known that, right back to, I imagine, you know, when we were living in caves. Now we know the science of it, we know why, but there's always been this shifting expression on the atmosphere that, you know, I think we need to be more in tune with.

17:42I think it is good for the mental health and your well-being to be engaged with the sky personally. What's the physics of that? So why are rain clouds dark? First of all, I mean, clouds look white, most of them, liquid clouds look white, because they're scattering the incoming radiation that's coming from the sun, and they scatter that radiation quite equally across different wavelengths of light, and that's why they look white. Often if you see a kind of grey cloud, it's sometimes a shadowing effect, so it's kind of the cloud's own shadow so if it's a very large kind of low cloud as you said it's basically kind of shadowing and you can't see that scattering effect as well how bright they look is sort of dependent on how they're made so if you have lots of small little droplets within the cloud then it is very good at scattering that light it'll look very bright and very white as the droplets grow and become larger then it sort of becomes less effective at the scattering And it's the tallness of the cloud that's super important when it comes to a dark base because a cloud that's tall has a dark base because the light doesn't really get through.

18:48And a cloud that's tall is much more likely to produce precipitation because it often starts with the droplets starting to freeze at the top. It starts as snow, melts on the way down, maybe lands as rain. but that tallness is crucial to a lot of precipitation. One of the things that I love about clouds as well, you mentioned there about how they appear white because they scatter the wavelengths of colour but ray-ly scattering which is what makes the sky blue because the sky isn't physically blue because at night time you can see through it up to the stars, right? and then in the morning when the sun is lower in the sky and the light is sort of grazing the atmosphere of the earth, those wavelengths are scattered again and you get more of the reds coming through because the red wavelength is kind of...

19:43Could we describe it a bit like a wibbly-wobbly wave? Is that right? Just a wave. Has that ever been said before? Just a wave. Just a wave, Brian, yeah. I didn't need to unnecessarily add wibbly-wobbly then. There's no un-wibbly-wobbly wave. LAUGHTER To be superfluous... I think Owen was saying that this one was wibblier and wobblier, and I think the wibblier wobbliness of this... Does he mean the amplitude or the frequency? No, I mean the wibbly wobbliness. I think it's a longer wave, yeah. It's a longer wave, there we go. So it is more wibbly and less wobbly? Well, yes. Is it more wobbly and less wobbly?

20:19Oh, I can't remember. Brian, I know you've got a question for Owen, because as usual last Tuesday, you were with Gloria Estefan and the Miami Sound Machine. And so I was on the radio with, and it was Gloria Estefan and Bob Mortimer. Just duetting as usual. Yeah, and Bob Mortimer said, I have a question, a question. I said, what is it? And he said, you know, if you get a crisp packet and you open it and you eat all the crisps on an aeroplane and then open the aeroplane window and drop the crisp packet and it falls onto a cloud, will it sit there on the top of the cloud? That was a specific question.

20:57Can I just, though, mention, by the way, if you are an aeroplane, please don't open the window. No, no. It's just that we will get letters. If you're an assessor, you'll be all right. But I had to think for a moment. That's quite a nice question. So what was your answer, then? Let's find out if Brian's answer is right, and then I'll cover you, I want it. OK. So, I mean, they look so crisp, especially when you're in a plane and when the cumulus clouds are below you. But, like, you have that kind of boundary in between what's cloud and not. It feels solid, doesn't it? Yeah, it looks solid. Solid.

21:23But then when you fly through those, you see it's just like, you know, flying through a cloud of smoke or like, you know, Friday night in my house when I've got the dry ice on. So I think the... Which the cat despises. I love that, the dry ice. Is that what it is? Like, put the dry ice on. I think it would fall through it. Yeah, I came to the conclusion that it would fall through. But it's a good physics question. Yeah, the layer right at the top of the cloud is often quite turbulent because the clouds emit radiation. And so that can actually drive motions along the tops of the clouds. So I actually think it would probably get transported around by the air currents rather than being held up by the water droplets of the cloud.

22:11I think the actual turbulent motion, this sort of mixing effect at the top of the clouds, because the clouds are emitting radiation out towards space, would probably hold it up. Are you saying it would move in a wibbly-wobbly fashion? A wibbly-wobbly fashion. He thought he was being... I think he just thought he was being Bob Morton. But it's actually a really good physics question, isn't it? Because as you said, I didn't think of that, actually, the radiation back out again. Is that one of the reasons you feel turbulence when you enter clouds in an aircraft? Yeah, well, that's exactly what you're experiencing.

22:42All of those upward motions I described before that are happening, all of the local currents that are happening within the cloud is basically what causes that turbulence for the aircraft. The top of the cloud in particular, because you've basically got a body which is emitting radiation, emitting thermal radiation, and that's dependent on the temperature at the top of the cloud basically. So how cold the top of the cloud is determines how much energy it's going to emit out. Is it always hotter at a higher temperature than the air, the clear air above it? It depends if it's an unstable atmosphere, because in a stable atmosphere, a thermal might rise from the ground and come back down, because it's not warmer than the surrounding atmosphere, and you don't have clouds forming or storms developing.

23:26But in an unstable atmosphere, as we describe it, the air gets more rapidly cold as you go up. And therefore, if you lift some air from near the ground where it's warm, it comes up, some droplets begin to form as it cools. And remember, every time a tiny droplet forms, a little bit of heat is released, the latent heat as it changes state. And those all add up, even though it's a tiny amount from each tiny droplet. And this is like fuel to keep the buoyancy in an unstable atmosphere. So the droplets form, it gets more buoyant. More droplets form, it gets more buoyant. And you get building, building, building to this enormous cathedral of clouds that is the cumulonimbus storm cloud.

24:08And within that, these currents, vertical currents, are rising rapidly in some areas, precipitation's falling fast in other areas, and sometimes hailstones develop because these particles are going round and round and building up in layers of ice. So Bob Mortimer's crisp packet could have ended up in the middle of a hailstone. It's going to be one of those very famous physics examples that all undergraduates learn in atmospheric physics, isn't it? Mortimer's crisp packet. That was the infinite monkey cage. Just to pick up on that point, because it's an interesting bit of physics, the fact that water droplets forming release energy.

24:53Could you just maybe Amanda just speak about that? Yeah, so going back to Gavin's triple point for water. So any time that water changes phase, so whether it goes from a gas to a liquid or from a liquid to a solid, In that direction, it's basically releasing a little bit of energy, which is to do with the organisation of the water molecules basically within the structure. So once it condenses and it turns to a liquid, that little bit of energy gets released. And as Gavin said, that contributes to a heating in the atmosphere. It's basically this latent heating effect of the clouds as they're forming.

25:24And you get the opposite as well. So you could have ice crystals up at the top of one of these cumulonimbus clouds. They spread out in an anvil, this enormous plume of ice crystals. spreads out hundreds and hundreds of miles. And in one area, those ice crystals can melt and therefore change state in the other way. That makes the air cool a bit. And you can get these sinking pockets that appear as mama clouds on the underside, these pouches of cloud on the underside of one of these cumulonimbus anvil plumes. And they look really distinctive, these pouches of clouds. and they're the result of the cooling, most likely, it's not totally understood, most likely the result of the cooling that happens with the shift in state the other way.

26:12We've all seen those, haven't we, those anvil clouds. Why are they so flat on top of the cloud? So going back to what Gavin talked about with the stability of the atmosphere, so particularly in the tropics, we find a lot of these deep cumulonimbus clouds over the warm tropical oceans. There's a huge amount of fuel and moisture which allows these clouds to get up to altitudes of 18 or 19 kilometres. You know, this is sort of almost twice the height of cruise altitudes of typical aircraft. So these are really tall clouds. And what happens is you hit a sort of boundary. We call it the chopper pause.

26:43It's basically the transition between the lower part of the atmosphere, where all of our weather happens and the clouds form, and the layer above it, which is called the stratosphere. And it's called stratosphere because it's a stratified layer. It's a stable layer. And so the clouds basically get up to this, it's almost like a lid. They can't move above that because the air above is stable. and so they can only spread out and that's why you get these anvil clouds because they then just spread sideways because they can't travel further upwards anymore. And if you see the photographs from the space station where one of the astronauts takes a photo down onto cumulonimbus clouds, it's like they formed underneath a piece of glass because this temperature profile, this temperature inversion, we call it, because it's the opposite of the normal, getting colder as you go up, it starts to get warmer at the top of the troposphere and that's this invisible lid and the cloud you can just see spread out and it just can't go up any.