Understanding Weather: Winds (3rd Ed, 1992)

[Music] Wesley calling Wesley. The Weather Bureau of Investigation is calling Wesley. Are you there, Wesley? This is Wesley, sir. Are you ready for another day of training? Yes, sir. You're doing well, Wesley. Soon you'll be a real agent like all of us at the WBI, not just an agent in training. What is my assignment today, sir? Wins. Wesley, come in, please. Wesley. Yes, sir. How's your study of wind going? Well, you've given me a very oops difficult assignment, sir. I have. Well, if I may say so, sir, it's very difficult to study something that's invisible. Air is invisible whether it's moving or not. Yes, I know. So, you can't see the wind. So, what have you been doing these past several days? Observing the wind, sir. But in the only way I can, not by watching the wind, but by watching what it does. A good solution, Wesley. Any conclusions? Did you get the videotape I sent in yesterday? Yes. If you would show it on my Weather Watch channel, I'd be glad to explain what I've observed so far about the wind. I spent some time in the city watching the wind blowing. It was easy to see the wind's effect on things near the ground. Things blew one way, then they blew the other way. The wind seemed to keep changing directions. Of course, with all the buildings in the city, I guess the moving air doesn't have a clear path. It has to go around things. I guess that could change the wind's direction. Very good thinking, Wesley. And then I spent some time in the open country. The wind didn't seem to change direction as much there. Probably because there weren't so many buildings. And then I looked up at the clouds. They were moving. A wind must have been blowing them. That just reminded me that winds blow above the ground. And generally wind speed increases with height. We've speeded up your tape to emphasize that fact. Well, that's my report so far, sir. Keep watching your weather watch, Wesley. I have something else to show you from our video files. Is that a passenger jet? Yes. It's about 7 miles up. Listen to the captain speaking. We'll be cruising at an altitude of 35,000 ft. Our flight time to New York will be only 3 hours because the jetream will be giving us a strong tailwind. Any questions, Wesley? Yes, sir. The jetream? That's a new one on me. What is it? I hoped you'd ask. At high altitudes, usually higher than where you see clouds, there are narrow currents of fastm moving air. Winds? Yes, winds, called jet streams, move generally toward the east at high speeds, sometimes as fast as 250 mph. Wow, sir. That's a lot stronger than the winds that were blowing in the city or the country or out here right now. But sir, I have a question about the wind. Yes, Wesley. I knew the wind blows at different speeds and in different directions, but what starts the wind blowing in the first place? I was hoping you'd ask Wesley. Hop on your bike and pedal over to our WBI substation just up the road. They'll give you a special instrument when you arrive. Take it into the lunchroom kitchen. I'm in the kitchen, sir. Is this the special instrument they were supposed to give me? It's just a toy. A pin wheel. Yes. Uh, just a little joke, Wesley. But the pin wheel will do the job quite well. What job, sir? You'll see, Wesley. First, blow on it and tell me what [Music] [Applause] happens. Blowing on it makes it turn, sir. I knew that moving air turns the pin wheel. Yes. Which means the pin wheel can function nicely as a detector of moving air. A wind detector. That's quite right, Wesley. Well, is it very windy in the kitchen now? Windy? No, sir. Not a breeze stirring. A calm day in the kitchen. Yes, sir. Why don't you walk over to the big oven? The oven? Yes, sir. It's hot. I asked the receptionist to turn it on while you were riding over there. Hold your pin wheel just above the oven and open the door slowly. The pin wheel's moving, sir. Now, Wesley, is the air in the oven the same temperature as the air in the kitchen? No, sir. The oven air is warmer. Any conclusions from your observations, Wesley? Well, it seems like Yes. It seems that when air at one temperature comes in contact with air at another temperature, that can make air start moving. That can make winds. Yes, very good, Wesley. Winds are caused by temperature differences in the air. So, an oven could cause temperature differences in a kitchen, but outdoors, outdoors, there is something that can change the temperature of things. I guess that must be the sun. That's quite right, Wesley. And uneven heating by the sun will result in temperature differences. Uneven heating? Yes. You're at Lookout Point, aren't you? Yes, sir. I'm at the edge of a cliff overlooking the ocean. And what do you observe? Well, it's a nice sunny day. I see the ocean and the shore. Is everything you see in the sunlight? Yes, sir. So, I guess that can't be an example of uneven heating, can it? Yes, it can be. And it is. For instance, the ocean heats up more slowly than the nearby land. So, even though both are getting the same amount of sunlight, the land will heat up more than the water. But what about the air? The sun's heating all the air the same, isn't it? Not really. Uh, you see, it's not the sun that has the most direct effect on the temperature of the air. Air is mostly heated by whatever is under it. So if the land is heated more than the water, the air directly over the land will be warmer than the air directly over the water. And what happens is that the warmer air over the land rises. That allows the cooler air from the ocean to move in under the rising air and take its place. Moving air, that's wind. And there is a wind blowing from the ocean toward the land. I can feel it. And I can see the trees moving, too. Now, you've observed the effect of uneven heating over small areas. Let me show you uneven heating over a large area. Pedal over to the spaceport. It's just a few miles away. There's a shuttle about to be launched, and I want you to be on it. I'll let them know you're coming. [Music] getting the angles out, but I got them in to use them before we run. Pitch 212 y. [Applause] Oh, sorry. Wesley, how are you doing? Kind of okay, sir. This is my first time in zero G. Well, grab hold of something and have a good look at the Earth down there through one of the windows. Wow, Earth is beautiful and round, too. Like a ball. Yes, sir. I knew that. But I can't see all of it now. But just glance at your weather watch. Oh, yes. Now it looks more like a ball. But did you know that the earth is heated unevenly by the sun? Really, sir? Regions at the poles don't get as much energy from the sun as regions at the equator do. Oh, sure. I knew that. So, that means that air over the poles should be a lot colder than air over the equator. That's quite right. So, there must be a wind that blows from the north pole toward the equator. Well, there would be, except that the Earth's rotation changes things. I can explain what happens more effectively on Earth rather than out there in space. So, I'll have a sailboat waiting for you at the dock when the mission is completed. How soon will that be, sir? In about a week. Oh, has your stomach settled down yet, Wesley? Just about, sir. Well, I hope this little trip out on the ocean won't cause you any problems. Me, too, sir. Any observations concerning the wind? Well, the wind seems to be blowing steadily in pretty much one direction from the east. And if you stayed in this part of the ocean for a long time, you'd find that the wind's direction never changes much. That's because you're in a system of winds that blow almost all year from the same direction. Certain wind patterns happen often enough that they're given special names. You're in the system of winds called the trade winds. They're rather gentle winds. Now, I've instructed the captain to sail northward so you could observe a different system, the westerlys. They blow in the opposite direction and are much stronger and uneven. Will there be stronger wind there? Rougher seas? Probably yes, Wesley. Is that going to cause a problem? I believe so, sir. Do we really have to go? Well, maybe not. I think I can explain the various systems in about a minute with a map. Oh, thank you, sir. Observe your weather watch. Here's the Earth, the poles, the equator. You're about here now. In this band that reaches almost down to the equator, the winds blow from the east to the west. These are the trade winds. In a band to the north, the system of winds blows generally from the west to the east. These are the westerlys. These systems are duplicated south of the equator. And in polar regions, there are systems of winds called the polar easterlys. I think I understand, sir. Then you can return to land. Thank you, sir. Contact me again when your color is improved and we'll review what you've learned. Sir, this is Wesley calling in. Yes, Wesley. Uh, where are you? At the lookout point where we first started talking about the wind. Oh, that's a lovely spot. And uh, what have you learned about the wind since then? Well, you can't see the wind, which is just moving air, but you can see what it does. Temperature differences start air moving in a kitchen or on the whole earth. And I know about the wind systems and their special names. Very good, Wesley. And I've learned one more thing, sir, that's very important to me. What's that, Wesley? Well, wind on water can be fun for a while, but I like wind on land a lot better. [Music]