Earth as a System

So, a meteorologist studies the atmosphere. But what does that actually mean?

The atmosphere is a gaseous envelope that completely surrounds the Earth. It’s composed of various gases, including nitrogen, oxygen, and trace amounts of other gases.

It’s mostly invisible to the naked eye, but we feel its presence in other ways. It provides breathable air, and blocks harmful radiation from reaching the Earth from space.

Without the atmosphere, life as we know it wouldn’t exist, and the planet would look more like the moon.

The atmosphere is central to weather and climate. In some ways, it is the weather and climate.

Weather is basically how the atmosphere behaves at a given point in time. Wind, for example, is just part of the atmosphere flowing from one place to another.

Again, the moon is a good comparison. It doesn’t have an atmosphere (apart from some minor wispy traces), so there isn’t any wind, or rain, or snow, or clouds.

Just as you can’t have earthquakes without earth, or waterfalls without water, you can’t have weather without an atmosphere.

Despite the importance of the atmosphere to meteorologists, they don’t study it in isolation. The Earth is much more complex than that. It’s a dynamic system tied together by interconnected spheres.

There are four of these spheres in total. Along with the atmosphere, there’s also the hydrosphere, the lithosphere, and the biosphere.

The hydrosphere is all the water on Earth, the lithosphere is the Earth’s solid, rocky crust, and the biosphere encompasses all the organic life forms on Earth.

Unlike the atmosphere, these other three spheres aren’t mediums for weather and climate. But that doesn’t mean they aren’t important. They’re constantly interacting with the atmosphere, and affecting how it behaves.

The Earth is made up of four spheres. If the atmosphere is the first, number two on the list is the hydrosphere. This encompasses all the water on Earth, in all of its different forms.

This includes the oceans and seas, the flowing rivers, the tranquil lakes, the polar ice caps, and even the vapor in the atmosphere. The ocean is the most prominent feature of the hydrosphere, covering almost 71% of the Earth’s total area.

The hydrosphere is a dynamic entity. Its waters are constantly in motion in a process known as the hydrological cycle. This sees water evaporate from the oceans, hang in the atmosphere as clouds, then fall back to the land as rain.

The third of the four spheres is the lithosphere: that’s the planet’s rocky outer layer. It’s the foundation that all of us live on — the ground beneath our feet.

While the atmosphere is gaseous, and the hydrosphere is liquid, the lithosphere is mostly solid.

The surface of the lithosphere is uneven. It features towering mountainous and plunging canyons, some of which lie below sea level. Death Valley's Badwater Basin — the lowest point in North America — is 282 feet (86 meters) lower than the nearby Pacific Ocean.

The final sphere is the biosphere. This term describes all the life on Earth, from plants and animals to fungi and microorganisms.

This life can be found almost anywhere: tropical rainforests, arid deserts, and even at the bottom of the sea. You’re part of the biosphere. All of us are. Every human who ever lived.

The biosphere relies on the atmosphere, the hydrosphere, and the lithosphere. Without them, it couldn’t exist.

Take a tree, for example: it needs the lithosphere for root support, the atmosphere for carbon dioxide, and the hydrosphere for water.

The hydrosphere, the lithosphere and the biosphere are all affected by the atmosphere.

Hot weather evaporates water; strong winds carve mountains; animals need oxygen to breathe.

But just as the atmosphere shapes these spheres, they also shape it back.

Consider the hydrosphere. When water evaporates up into the sky, it forms clouds. These play a vital role in many atmospheric processes. They reflect sunlight into space, cooling the air beneath them. They produce rain, when the water tumbles back to earth.

Large bodies of water, like lakes and oceans, can also influence the atmosphere. They absorb heat from the air, then release it again over time.

Ocean currents can actually transport these areas of heat, and then release them somewhere else.

The lithosphere is just as important as the hydrosphere. Mountain ranges, for example, cause clouds to build up on one side but block them from reaching the other. This phenomenon is known as a rain shadow: when one side of a mountain receives a lot of rain, while the other side is dry.

Finally, there’s the biosphere. Plants release water into the atmosphere through a process known as evapotranspiration. In the Amazon Rainforest, this process takes place on such a massive scale that it actually creates its own rainy season.

Not to mention human behavior. Deforestation and greenhouse gas emissions can significantly alter atmospheric conditions, leading to changes in weather, and causing global warming.

Because of all this, while a meteorologist focuses their studies on the Earth’s atmosphere, they must also study all the interconnections between water, land, and life. From rain shadows all the way to greenhouse gases, each of these spheres plays a major role in the Earth’s climate and weather.

This is the key to meteorology: thinking of the Earth as a vast, complex system. If you’re able to understand this, you should be ready for the rest of the pathway.