Atmosphere Basics

Atmosphere basics. Weather is the state of the atmosphere at any given time and place. Climate refers to the overall weather conditions for an extended period of time. In other words, the average weather for a certain place over time. Our atmosphere is composed mostly of nitrogen, 78% of the gas in the atmosphere is nitrogen, 21% is oxygen. Almost 1% is argon, but there are also tiny amounts of other gases like carbon dioxide and helium. This pie graph shows you the distribution of different gases in the atmosphere. Again, nitrogen makes up most of our atmosphere. There are also several things in the atmosphere that change depending on what part of the atmosphere you're in. So we call these variable components. They are important materials because they can affect the weather. The first of those is water vapor, water vapor is the source of the clouds and precipitation. And it can absorb heat that is given off by the earth, so it can trap heat close to the surface, as well as absorb solar energy. We'll talk about more about water vapor later. There are also solid and liquid particles that are suspended in the air, these include things like salt, salt from the sea, find soil, smoke, pollen, microorganisms, and solids released from volcanos. The third variable component is ozone. Ozone is an O three molecule. The oxygen we breathe is O2. So the difference would be an O2 molecule that we breathe means two oxygen atoms chemically combined, where ozone are three oxygen atoms chemically combined. And that O three molecule is able to filter out 95% of the sun's harmful ultraviolet radiation. So the ultraviolet radiation can cause skin cancer can damage your eyes. So our ozone layer protects us from most of that radiation. Years ago, we discovered that there were holes in the ozone layer because it was the O three molecules were being broken down. Scientists figured out that the corals of this was chlorofluorocarbons, also known as CFCs. At one time they were used in the manufacturing of different products for cooling such as air conditioners in your car, refrigerators, freezers, they were used in aerosol, cans like hairspray or spray paint. They were used in many different products and as soon as scientists figured out that the CFCs were breaking the O three molecules down and destroying those that ozone layer, they have been outlawed. So new products no longer contain CFCs. Air pressure is the weight of the air around us. The pressure changes throughout the atmosphere. That's because most of the molecules are concentrated close to earth's surface. So the atmosphere becomes more thin as you move away from the earth in other words, the gas molecules are farther apart as you get farther from the earth. So that means that pressure is highest at earth's surface at sea level, and it decreases with altitude or elevation. So the air pressure on top of a mountain is less than that if you're at sea level. This graph represents pressure changes, notice this dotted line shows that half of all the air molecules in our atmosphere lie below this line. And then all of this part of the atmosphere contains the other half of the molecules. So again the molecules are spread far apart, the further you get from the earth, the molecules are packed much more closely together. At earth's surface. Temperature also changes throughout the atmosphere. And we can divide the Earth's atmosphere into four layers based on whether the temperature is increasing or decreasing. The first layer of the atmosphere is called the troposphere. This is the layer that we live in, the only layer we're used to. It contains most of the mass of the atmosphere because again, most of the gas molecules are held close to earth's surface. All the weather happens in the troposphere. And temperature decreases with elevation, you're probably used to this because if you've ever traveled to the top of a mountain, you'll notice that the temperature gets colder as you climb higher toward the top. In this picture, you can see the mountains are covered with snow, but the base of the mountains, there is no snow or ice, that's because temperature is colder at the tops of these mountains at the higher elevation than it is in the lower elevations. Above the troposphere is the stratosphere. And the stratosphere, temperature increases with elevation because this ozone layer traps so much radiation from the sun that it gets hot. So as you're moving through the troposphere, temperature decreases when you get to the stratosphere temperature starts to increase with elevation. The next layer up is the mesosphere, again temperature starts to decrease with elevation because there is no layer like the ozone layer to trap excess radiation. Temperatures in the mesosphere can decrease to as much as negative 90°C. So parts of the mesosphere are very cold. And the fourth layer up is called the thermosphere, the temperatures here can get as high as 1727°C and get very hot. And in this layer, the temperature is increasing because oxygen and nitrogen in that outer atmosphere absorb all the high energy solar radiation and it is the top of the atmosphere. So it's getting all the solar radiation. This graph shows those four layers and you can see this red line represents temperature. So again, in the troposphere, the temperature is decreasing with elevation. There's a transition period, then the temperature starts to increase again, so this is the stratosphere. Another transition temperature decreases in the med sphere, another transition, and temperature, again, increases in the thermosphere. Temperatures also change throughout the seasons. Seasons happen because of the position of the earth's axis relative to the sun. So let's look at a picture. In this picture, the earth's axis is tilted toward the sun. So notice much of the northern hemisphere is illuminated by the sun. At any given time, half of the earth is illuminated, but when the northern hemisphere is tilted toward the sun, more of it is illuminated than the southern hemisphere. So in this case, the northern hemisphere is in the daylight for a longer period of time, and we have very long days. You probably know that we have longer days during the summer. So this would represent the position of the earth's axis and the sun during the summer. Also notice that during the summer, the sun is shining most directly on the northern hemisphere. It's kind of like if you stand right in front of a heater, you're getting all the direct energy and this part of the globe is being heated very efficiently. Down here in the southern hemisphere, they are kind of getting the heat and energy from the sun at an angle. So it's skimming across them. It's not heating them as efficiently as it's heating the northern hemisphere at this time. So we have summer because we are being heated very efficiently. We are tilted toward the sun. The next picture shows winter, notice now the earth's axis is tilted away from the sun. So in this case, the southern hemisphere is getting the most direct energy more of it is illuminated than the northern hemisphere, so they have hot temperatures in the south, long days, and the northern hemisphere where we live, we're getting more indirect light and heat. So we are not being heated efficiently. And our temperature is cool. So the temperature of the atmosphere depends on the angle of which you are receiving solar radiation, the more direct the radiation is, the more efficiently a place will be heated. Temperature is actually just a measure of how rapidly the molecules are moving. So when air warms up, those gas molecules are moving faster. Temperature can be measured in degrees Fahrenheit, degrees Celsius, or kelvins. Heat is the energy that's transferred from one material to another because of a temperature difference. And in nature everything likes to be equal, leveled out. So anytime something's colder or warmer, energy wants to move to try to balance out the indifference. And there are three ways that energy can be transferred throughout our atmosphere. There's a radiation conduction and convection. We're going to talk about each of these. Radiation is any energy that's transferred through space by electromagnetic waves. So radiation includes the electromagnetic spectrum. So gamma rays x-rays, ultraviolet rays, the visible light we can see infrared, which just means heat, microwaves, and radio waves are all types of electromagnetic radiation. So we get all of our energy from the sun in the form of radiation. Our sun emits various wavelengths of ultraviolet or ultra, electromagnetic waves, including ultraviolet, visible light, infrared, gamma rays, and x-rays. Of all of that energy that comes from the sun to the earth, 50% is absorbed by earth's surface. 35% of the radiation is reflected back into space, and 15% is absorbed by our atmosphere. Let's talk about the portion of the radiation that is absorbed. The greenhouse effect is the natural heating of earth's surface and atmosphere when solar radiation is absorbed by our atmosphere. Its nickname the greenhouse effect because it works, just like a greenhouse, someone builds for plants. Greenhouses for plants are made of glass. They allow the sun's energy to come in through the glass, that energy is absorbed by the soil and the plants inside the greenhouse, and that heat can escape back out through the glass. So it keeps the greenhouse nice and warm. The same thing happens to your car. If you've ever noticed even on a cold day, if your sun is if your car is sitting in the sun, the sun's energy can come in through the glass, the things in your car absorb that energy, and they release it back at a different wavelength and that glass won't allow that heat to escape back out. So even your car can remain hot. So the greenhouse effect is a good thing for all the living things on earth. Because if our atmosphere didn't trap some of that heat, when you, when the earth turns away from the sun and you're in nighttime, the temperatures would drop to negative degrees well below freezing, and many life forms wouldn't be able to sustain that extreme drop in temperature. So the greenhouse effect is necessary to regulate temperature so that plants and animals can survive on earth. Not all gases trap energy. The two most important are two main greenhouse gases are water vapor and carbon dioxide. So they are kind of like that glass they can allow the radiation in, but they trap that heat close to the earth. This explains why a cloudy night, the temperatures don't drop as much as a clear night, because clouds contain so much water vapor, those thick clouds act as an extra thick blanket to keep in even more heat than normal. So you'll notice if you wake up on a cloudy morning, it won't feel cool outside, it'll still feel kind of warm 'cause those clouds of trap so much heat. While we're talking about the greenhouse effect, we'll also mention global warming, so remember greenhouse effect is a good thing. It's natural, and we need it to keep the temperatures from dropping to hold at night. It's also often confused with global warming. Global warming happens when there's too much water vapor carbon dioxide in the air. And the greenhouse effect becomes stronger than it naturally should be. This can cause temperatures on earth to increase. This picture shows different ways that too much greenhouse gas can be added to the atmosphere, notice the factories, the deforestation right here, and the cars, and we're going to talk about those. Humans main effects on global warming are the removal of too many trees. Trees are the natural way we can get carbon dioxide out of the atmosphere. Trees take in carbon dioxide for photosynthesis and they release oxygen as a byproduct. So when we cut down too many trees or burn too many trees, that's our only way of getting carbon dioxide out of the atmosphere. So more stays in the atmosphere. Also, the burning of anything releases carbon dioxide into the air. So when we burn entire forests, it releases lots of carbon dioxide, and then you have fewer trees to take in the excess carbon dioxide. And again, any time you burn something, especially fossil fuels, it releases carbon dioxide into the atmosphere. So the coal that we burn in our power plants releases carbon dioxide into the atmosphere. The gasoline you burn in your car releases carbon dioxide into the atmosphere as well. If temperatures increase on earth, it can cause many consequences. A few of the most obvious, if temperatures increase just a little bit, it will cause lots of ice to melt. Some places on earth are cold enough to have huge glaciers or solid ice on tops of mountain peaks and it's cold enough there year round where that water stays in the solid state. If temperatures increase just a little, lots of ice will melt, it will run off into the oceans and cause the sea level to rise and cause coastal flooding in many areas. It will cause more frequent and intense drought. And we'll talk about hurricanes more later, hurricanes get their energy from warm ocean water. So if temperatures on earth increase, you would have more frequent and intense hurricanes. So all that had to do with radiation and how the atmosphere traps some of that radiation. Another way to transfer energy is by conduction. Conduction is the transfer of energy from one molecule to the next. So one molecule has to touch another molecule to pass on that energy. This is a very slow way to transfer energy. An example of conduction could be when the eye of the stove heats apart. So only the molecules that are touching the hot eye of the stove get heated. The same thing happens if you leave a spoon in hot water, the hot water that's touching the spoon will heat it up. In the atmosphere, the air that is touching the soil and the ground gets heated by conduction. But again, this is a very slow way to transfer energy because only the air molecules that are touching the warm rocks or the warm soil are getting heated by conduction. But as soon as those air particles are heated, they become less dense than the air around them. And when things are less dense, they rise, this happens in water, or gases, so convection takes over at this point, convection refers to the heating and cooling of air that creates vertical currents. So when the air warms up, it rises when it cools down, it sinks back, creating a vertical current. Convection is very important to the study of meteorology because it's the cause of most weather on earth. And convection moves mass amounts of energy at a time. It can move lots of heat from the surface and the heat rises into the atmosphere so it moves a lot more energy moves the energy more efficiently than conduction. This picture is showing how you can make a convection current in water. Showing if you put warm red water in the tank, you would see it rise. If you put cold blue water over here, you would see that it sinks in the water. So convection currents are vertical currents where warm water or air is rising, pulls off and sinks back down. Temperature controls mean anything that has an effect on the temperature of the atmosphere. So temperature can change according to your latitude, meaning how close you are to the equator or how far you are from the equator. Temperature changes depending on your proximity to land or water because the heat land heats more quickly than water. Temperature can change depending on your geographic location, what part of the continent you're on, cloud cover, and ocean currents. So first, we'll talk about latitude. Again, latitude just refers to how far you are from the equator. So 0° latitude is the equator. If you are close to the equator, your temperature always tends to be warm because you are getting direct heating from the sun. If you have a high latitude close to 90 degrees north or 90° south, you're in a polar region, you're getting indirect energy from the sun. So these places are never heated as efficiently as places at low latitudes near the equator. This shading just shows you the red is warmer temperatures, yellow gets cooler, and when you're in the polar regions, you have the coolest temperatures. So latitude has the greatest effect on places climate, whether it's usually cold or usually warm. Land heats and cools more quickly than water, and it can also heat to higher temperatures. So this means that if you are in the middle of a continent and there's no water near you, your temperature variations are going to be greater because you don't have that stabilizing effect of the water. Land heats up fast, cools off fast. So temperatures in those places have a greater fluctuation. This is also related to your geographic position. If you are in a place where the wind blows from the ocean onto the land, it regulates your temperature. So in the summer, it helps to keep that the temperature above the land cool in the winter it keeps the temperatures from dropping as much as it would if you weren't. If you weren't next to the land. Here's an example of Eureka, California and New York City. Since the wind blows from the ocean onto the shore here, Eureka's temperature is shown in red, don't fluctuate as greatly as New York City. In New York City, the wind is blowing from the land out to the water, so you don't have the moderating effect of the ocean if you're on the east coast. Altitude means distance relative to sea level, another word for it is elevation, and we talked about how temperature decreases with elevation in the troposphere where we live. So that means that places with higher altitudes are going to have cooler average temperatures. And this picture you see two cities that are very close to one another, they are both on the western coast of the continent. They're at very similar latitudes. So you would think they would have similar temperatures, but notice the temperature difference here, if one place is at a higher elevation, it's going to have a cooler average temperature throughout all the months of the year. Cloud cover affects temperature because clouds reflect lots of solar radiation back into space and therefore it lowers the temperatures and the lower part of the atmosphere. So cloudy days remain cooler than clear days.