Introduction: The "Air" and "Sea" That Support Our Lives
Hello everyone! Today, let's start learning about the "Atmosphere and Ocean."
The biggest reason our Earth is so full of life compared to other planets is because of this "atmosphere" (air) and "ocean" (sea).
Meteorological mechanisms might seem difficult at first glance, but they are actually based on the simple rule that "warm air rises, and cold air sinks." Let's take it easy, relax, and think about the familiar sky and sea as we go through this!
1. Atmospheric Structure: The Sky Has Layers!
When you look up, the sky seems to go on forever, but it is actually divided into four layers based on its characteristics. Let’s look at them in order, starting from the ground up.
① Troposphere
The layer from the ground up to about 10–15 km.
・Characteristics: The temperature drops as you go higher (approx. 0.65°C per 100m).
・Key Point: Because the air contains a lot of water vapor, this is the only place where "weather phenomena" like cloud formation and rain occur.
Example: The fact that the summit of Mt. Fuji is cool even in summer is due to the properties of the troposphere.
② Stratosphere
The layer just above the troposphere.
・Characteristics: The temperature rises as you go higher. This is because the ozone layer found in this layer absorbs ultraviolet rays from the sun and releases heat.
・Key Point: The air is stable here, so it is often used as a flight path for airplanes.
③ Mesosphere
・Characteristics: The temperature drops as you go higher again. This is where the coldest part of the atmosphere (approx. -90°C!) is located.
④ Thermosphere
The outermost layer.
・Characteristics: Because it receives strong energy directly from the sun, the temperature becomes extremely high. Auroras also occur in this layer.
[Memory Tip!]
Remember them in rhythm from the bottom up: "Tro-Stra-Me-Ther" (Troposphere, Stratosphere, Mesosphere, Thermosphere)!
How about the phrase: "Trouble is Strategy, the Meaning is Thermal!"
[Points to Remember]
・Weather phenomena only occur in the Troposphere!
・Temperatures rise in the Stratosphere (thanks to ozone) and the Thermosphere (because it's closer to the sun)!
2. Earth’s Heat Budget: The "Wallet" of the Sun and Earth
The Earth maintains a comfortable temperature because there is a balance between the heat received from the sun (income) and the heat escaping from Earth into space (expenditure). This is called the heat budget.
Solar Radiation and Terrestrial Radiation
・Solar Radiation: Energy reaching us from the sun. It arrives mainly in the form of visible light.
・Terrestrial Radiation: Energy released by the Earth into space. It is emitted mainly in the form of infrared radiation.
Greenhouse Effect
A phenomenon where carbon dioxide (\(CO_2\)) and water vapor in the atmosphere absorb some of the infrared radiation emitted by the Earth and re-warm the surface.
Analogy: Greenhouse gases act like a "blanket" for the Earth. Without this, the Earth would be an icy world at about -18°C!
[Common Misconception]
People often think "the greenhouse effect is bad," but in reality, "we can only survive because it exists to a moderate degree." The issue of "global warming" is that the temperature is rising too much because these gases are increasing too much.
3. Atmospheric Circulation: Why Does the Wind Blow?
Looking at the Earth as a whole, the equatorial regions receive a lot of solar heat (heat surplus), while the polar regions (North and South Poles) lack heat (heat deficit). To resolve this temperature difference, air moves on a large scale. This is called the general circulation of the atmosphere.
Three "Cell" Flows
1. Hadley Circulation: Warm air at the equator rises and descends around 30 degrees latitude.
2. Ferrel Circulation: The flow in the mid-latitudes (near Japan).
3. Polar Circulation: The flow of cold air in the polar regions.
Coriolis Force
An apparent force that causes moving objects to curve due to the Earth's rotation.
・In the Northern Hemisphere: It curves to the right relative to the direction of motion.
・In the Southern Hemisphere: It curves to the left relative to the direction of motion.
Due to this force, a strong westerly wind called the westerlies blows constantly over Japan. Thanks to this wind, Japan’s weather changes from west to east!
4. Ocean Structure and Circulation: What's Happening Inside the Sea?
Just like the atmosphere, the sea has different properties depending on its depth.
Layered Structure of Seawater
・Surface Mixed Layer: A layer where the temperature is uniform because it is stirred by the wind.
・Main Thermocline: A layer where the temperature drops rapidly as you go deeper.
・Deep Layer: A layer with very cold, heavy water at about 2–4°C.
Flow of Seawater (Ocean Currents)
There are two main types of ocean currents:
1. Surface Circulation: Surface flows caused by winds (trade winds or westerlies).
The Kuroshio (warm current) and Oyashio (cold current) flowing near Japan are famous examples.
2. Deep Circulation: A deep ocean current that takes thousands of years to circle the Earth, driven by differences in temperature and salinity.
[Trivia]
The deep circulation begins when very cold and salty (heavy) water near the North and South Poles sinks. It acts like a giant, global conveyor belt.
5. El Niño Phenomenon: The Sky and Sea Are Connected!
Finally, let's learn about the "El Niño phenomenon," which occurs through the cooperation of the atmosphere and the ocean.
Normally, near the equator in the Pacific Ocean, warm seawater is gathered on the western side (near Indonesia) by easterly winds (trade winds).
However, if for some reason these easterly winds weaken...
・El Niño Phenomenon: A phenomenon where warm seawater spreads to the eastern side (off the coast of Peru).
・Impact: Abnormal weather (cool summers, warm winters, droughts, etc.) becomes more likely to occur all over the world.
Conversely, the "La Niña phenomenon" is when the easterly winds become too strong and even more warm water accumulates on the western side.
[Point to Remember]
"Wind weakens = El Niño (warm on the east side)"
"Wind strengthens = La Niña (colder on the east side)"
Try to remember these as a pair!
Summary: Key Points for Today
・The atmosphere has a 4-layer structure. We live in the Troposphere.
・The Earth receives heat from the sun and emits it as infrared radiation. Maintaining this balance is crucial!
・Atmospheric circulation and ocean currents occur to bridge the heat gap.
・Due to the Coriolis force, wind in the Northern Hemisphere bends to the right.
・The sea and the air influence each other, as seen in "El Niño."
It might be tough with so many terms at first, but if you think of it all as "the Earth's effort to keep its temperature balanced," it should become a bit easier to visualize. Great work today!