atmospheric features

Summary of Module One: Earth's Atmosphere

Overview

This module introduces the Earth's atmosphere, focusing on its composition, interactions with other Earth systems, patterns, and layers.

1. Atmospheric Composition

  • The atmosphere consists primarily of:

    • Nitrogen: ~78%

    • Oxygen: ~21%

    • Argon: ~0.9%

    • Trace Gases: <0.1% (including carbon dioxide)

    • Water Vapor: 0.01% to 4% (average ~1%)

  • 5 main gassses of the atmosphere

    • Nitrogen, Oxygen, Argon, Water, Carbon Dioxide

  • The focus is on the lower 100 kilometers of the atmosphere, where the composition remains relatively consistent.

2. Interacting Systems

The atmosphere interacts with:

  • Biosphere: Humans and built environments

  • Hydrosphere: Oceans, lakes, and other water bodies

  • Lithosphere: Land components of the Earth

3. Atmospheric Patterns

  • Weather: Short-term atmospheric conditions (temperature, precipitation, etc.)

    • Example: Hurricane Felix (2007)

  • Climate: Long-term weather patterns averaged over 30 years or more

    • Example: Arid conditions in the Mojave Desert

Comparison of Weather and Climate

  • Weather: Day-to-day variations; predicted using short-term models (days to weeks).

  • Climate: Long-term averages; simulated for future projections (decades to centuries). 30 years or more

4. Atmospheric Layers

  • Troposphere: Closest layer to Earth's surface; where most weather and clouds occur. 0 to about 11000 m

  • Stratosphere: Above the troposphere; contains the ozone layer and is where airplanes typically fly.

  • Mesosphere: Not the focus of this course.

Temperature Trends

  • Temperature decreases in the troposphere and increases in the stratosphere due to ozone absorption.

Conclusion

The module covers the essential features of the atmosphere, including its composition, interactions with other systems, weather and climate patterns, and the troposphere and stratosphere layers.

(peaceful music) - Welcome to module one, Earth's Atmosphere. This section is on atmospheric features. We're gonna give an overview of the many parts of the atmosphere that are included in this course. The first section is thinking about atmospheric composition. What is the atmosphere? The second section will think about what the atmosphere interacts with, the other Earth systems that interact with the atmosphere. And the third is the types of patterns in the atmosphere, including climate patterns and weather patterns. And then we're gonna look at atmospheric layers. And our focus on this course is in the troposphere and the stratosphere. These all are part of our learning objective to describe the atmospheric composition and structure. The atmospheric composition is summarized here, and we have a graph showing how that composition varies with altitude. I'm gonna ask you to focus on just the bottom 100 kilometers. And what you can see is, throughout that whole distance, nitrogen is about 78%, and oxygen is about 21%. So the gray nitrogen covers more than three-quarters of the graph, and then oxygen's over on the right. And that's not a surprise, because we know that's the composition of the atmosphere we breathe. And that turns out to be pretty consistent for the whole first hundred kilometers of the atmosphere. In addition to those two components, there's a little more than 0.9% argon, and less than 0.1% trace amounts of carbon dioxide and other gases. And these four types of components constitute what we call the dry atmosphere, because they don't have water yet. If we add the water, which is, of course, present in the atmosphere, we add between 0.01% and 4% of water, or on average, about 1% water vapor is present in the atmosphere. So that's what our composition is, below a hundred kilometers. As you can see, above a hundred kilometers, the composition changes, and you have different components other than molecular, nitrogen, and oxygen. The interacting systems of the atmosphere are the biosphere, by which we mean humans and the built environment, and the hydrosphere, by which we mean oceans, as well as lakes and other bodies of water, and then there's the lithosphere, which are the land components of the earth system. We can think about the patterns of the atmosphere as well, and weather is the first one we'll think about. Weather is the state of the atmosphere, such as the degree to which it's hot or cold, wet or dry, calm or stormy, clear or cloudy. And this image shows a huge storm, Hurricane Felix, seen from low earth orbit in September, 2007. So this is an example of weather. On the other hand, we also wanna think about another pattern of the atmosphere that we call climate. It's the long-term weather pattern in an area, typically averaged over 30 years or more. And so here is a figure with high clouds above the Mojave Desert, but as you can see, it's a very arid region. So clearly not a lot of water, not a lot of precipitation, and generally some pretty hot temperatures. So those are both part of the climate pattern. Comparing weather and climate, we can see here the main differences. Weather refers to day-to-day temperature, precipitation, and other atmospheric conditions, including wind, whereas climate is the long-term average of atmospheric conditions over longer periods of time. So weather is predicted by forecast models, where we're trying to use the information we have to predict a few days to a week or two in advance. Climate simulations are thinking about what's gonna happen a hundred years in the future. So we're simulating climate based on our understanding of the principles and the forces contributing to how climate is controlled. Weather is on the scale of three weeks or so into the future. Climate is usually more than a year, and often 50 to a hundred years in the future. Weather is thinking about a specific location or set of locations. Climate is the average over our region. Weather, we often focus on extreme events. On the other hand, in climate, we're thinking about averages for 30 years or more. The atmospheric layers that we're gonna focus on in this course are the troposphere and the stratosphere. So the troposphere is shown in this diagram way at the bottom. It is the closest layer to the Earth's surface, and it is where most weather and most clouds are found. It's because that's also where most of the water is. So we'll come back to that point when we think specifically about the troposphere. Then there is a layer above that called the stratosphere, and that's the second layer we'll focus on. And you can see the ozone layer is there, and airplanes are often flying at that level. And then on top of that is the mesosphere, and we won't focus on that in this course, but on the right hand side of the graph, what you can see is a red line, and that line is actually showing us the average temperature of the atmosphere at that altitude. So you can see in the troposphere, it's decreasing, and then it kind of goes straight up for a while. And then in the stratosphere, it starts heating because of the ozone, so it's increasing. And so we're gonna think about what causes those aspects of the atmospheric structure. So just to wrap up, the atmospheric features include the atmospheric composition, its interactions with different systems, the atmospheric patterns, including climate and weather, and then atmospheric layers, where we started the troposphere down near the surface, and then we think about the stratosphere above that. And this is our basic description of the atmospheric composition and structure.