ATMOSPHERE

ATMOSPHERE, WEATHER, AND CLIMATE

Weather: the condition of the atmosphere
- What is happening in the atmosphere at a certain point in time
Climate: the state of weather over long periods of time
- Long-term
- Averages and extremes

The atmosphere: layers of gases (and tiny particles floating in those gases) surrounding and protecting Earth
- Main components: nitrogen, oxygen, argon
- Minor components: water vapor, carbon dioxide, methane

Layers of the atmosphere:

(characterized mainly by temperature)

Exosphere ⬇
Thermosphere ⬇ 78% nitrogen, 21% oxygen [fixed ratio] Air has more weight/density with increasing gravity (at ground-level) The higher in altitude you go: The lower the temperature The lower the pressure	Not many glasses Where satellites orbit and the auroras can be found Widest layer Increase with altitude Oxygen molecules in the upper region of the thermosphere absorb shortwave UV radiation from the sun Ionsophere exists within this layer
Mesosphere ⬇	Coldest layer Most meteorites burn up in this layer because it is the first layer (from space) to have atmospheric gases, causing friction with fast flying objects’ heat There are noctilucent clouds (or night-shining clouds that can be seen) Provides protection from metiorites, comets, or space rocks
Stratosphere ⬇	Above troposphere: 11 to 48 km above sea level Temperature consistent until about halfway up, when it starts to rise with altitude Where the good ozone (O3) is that protects us from UV-B and UV-c radiation No weather here
Troposphere ⬇	Lowest: up to 11 km above sea level 80% of Earth’s air mass Weather occurs here Temperature drops at higher altitudes Where airplanes fly Thinnest at north & south pole Densest at this layer Contains ¾ of the mass of the entire atmosphere Provides the oxygen we breathe & other gases that keep Earth at a livable temperature Lower region is warm because Earth’s surface absorbs radiation and transfers it to the surrounding air Hadley cells exist in this layer

Ionosphere:

Gases are excited by solar radiation to form ‘ions’ which have an electrical charge
Parts of the ionosphere overlap with Earth’s magnetosphere (area around Earth where charged particles feel Earth’s magnetic field)
Charged particles get affected by the magnetic fields of both Earth and the sun, causing auroras to happen
- Auroras happen when high-energy particles from the sun interact with the atoms in this layer of our atmosphere
Grows and shrinks depending on the energy it absorbs from the sun

Diagrams:

Albedo:

The percentage of incoming sunlight that is reflected from a surface
A white surface has a HIGHER albedo than a black surface (such as ice or snow covered surfaces)
Asphalt absorbs heat during the day and releases it at night

HEAT	TEMPERATURE
The amount of energy possessed by a material arising from the internal motions of its atoms or molecules	The average kinetic energy of a material’s atoms or molecules

Principle of Heat Transfer:

Heat always flows from the hotter region to the cooler one

METHODS OF HEAT TRANSFER
Conduction	The transfer of heat through matter by molecular activity
Convection	The transfer of heat by mass movement or circulation within a fluid substance
Radiation	The transfer of heat in the form of electromagnetic waves

What is the primary mechanism that heats up the atmosphere?

Solar radiation reaches Earth and is absorbed by the planet's surface (land and oceans), which then heats up.
This warmed surface then releases infrared radiation and transfers heat to the lower atmosphere through several mechanisms:
- Radiation: The warm surface emits infrared radiation, some of which is absorbed by greenhouse gases in the atmosphere.
- Conduction: Direct heat transfer from the warm surface to the air molecules in contact with it.
- Convection: Hotter to cooler areas

Density: The amount of matter in a given volume

Density ⬆ & Pressure ⬆	Directly Related
More air molecules packed into a given space exert a greater force (pressure) on the surrounding air.
Density ⬇& Temperature ⬆	Inversely Related
When air is heated, the molecules gain energy and move faster. This causes them to spread out, occupying more space.
Temperature ⬆& Pressure ⬇	Directly Related (only at constant value)
Higher temperatures often correlate with lower atmospheric pressure. As air warms, it expands and rises. This rising air creates a region of lower air density above, leading to lower pressure.

WEATHER

What causes weather?

Atmospheric pressure
Air movement
- Wind
- Cloud formation
Factors affecting air movement
- Sunlight
- Gravity
- Surface features
- Oceans
Atmospheric pressure/density
- Greater at lower altitude
- Gradients

Vertical air movement:

Due to temperature and pressure changes
Air composed of molecules
Warmer air molecules move around faster and bump into each other more than cooler air molecules
- Spread out -> less dense -> warm air rises
Cooler air above
- Coolds down warm air so that it becomes denser and sinks again

Horizontal air movement (wind):

When warm air rises, it leaves behind an area of low pressure
Air rushes in from higher-pressure areas = wind
Temperature varies across Earth’s surface
Temperature differences lead to winds
- Ex. sea breezes: land warms up faster than ocean -> air rises over land -> air flows from sea to low-pressure area over land
Wind is the primary physical process that redistributes gases in the atmosphere through horizontal and vertical air movements

How does the heating of the earth create wind?

The area of the earth near the equator receives the most solar radiation
The unequal heating of the earth causes global winds

Convection cells:

Larger scale air movement
Permanent pockets of circulating air within the troposhere
Three in each hemisphere: Polar, Ferrel (Mid-Latitude), Hadley
Intertropical Convergence Zone (ITCZ): band where Hadley cells meet
- Low pressure due to air rising -> wind and cloud formation
- Thunderstorms common along ITCZ

CONVECTION CELLS
Polar	Gets least heat from sun Air sinks over the poles, flows toward lower latitudes, rises at around 60-70 degrees N/S, and flows back toward the poles at high altitude
Ferrel	Air rises at high latitudes, flows towards lower latitudes at high altitude, sinks at around 30-40 degrees N/S, and flows back toward higher latitudes along the surface
Hadley	Largest convection cells Equator gets most heat from sun Air rises at equator, flows away from the equator at high altitude, sinks at around 30 to 40 degrees N/S, then flows back toward the equator along the surface

The rotation of the earth and the unequal distribution of land creates three major bands of wind around the globe
- Global winds are also created by the unequal heating of Earth’s surface
- Occur over a large area
- Do not follow a straight path as Earth is rotating
Coriolis effect:
- In the northern hemisphere, global winds curve to the right (west)
- In the southern hemisphere, global winds curve to the left (east)
Latitude: the distance from the equator, measured in degrees, separating the global winds
- Measures the distance north or south of the equator
- Latitude lines start at the equator (0 degrees latitude) and run east and west, parallel to the equator

GLOBAL WIND BELTS
Trade Winds	Blow east to west between the equator and 30 degrees N/S.
Westerlies	Blow west to east between 30/60 degrees N/S.
Easterlies	Blow east to west between 60 north and south latitude and to the poles (90 degrees N/S of the equator).

How do global trade winds affect the ocean?

Global winds drag on the oceans surface, causing surface waves and surface currents
Large spirals of surface currents are created by the combination of global winds, as well as the Coriolis Effect acting on the surface water

These large spirals are called ‘gyres’
- There are five gyres: North Pacific Gyre, South Pacific Gyre, North Atlantic Gyre, South Atlantic Gyre, Indian Ocean Gyre

SURFACE CURRENTS

Since the Earth is spinning on its axis, the air appears to go to the right in the NORTHERN HEMISPHERE and left in the SOUTHERN HEMISPHERE -> CORIOLIS EFFECT
- The effect of the Coriolis force is an apparent deflection of the path of an object that moves within a rotating coordinate system
- The object does not actually deviate from its path, but it appears to do so because of the motion of the coordinate system

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Extra notes:

Remember that gravity’s effect gets stronger going down, so at sea-level, it is more dense as the force of gravity pushes on the air molecules as well as the water molecules [makes it very compact]

This phenomenon is crucial for understanding how atmospheric pressure varies with altitude and how it influences weather patterns.