The Atmosphere and Weather

Weather: The condition of Earth’s atmosphere at a particular time and

place.

Atmosphere: The envelope of gases that surrounds the planet.

Composition of the Atmosphere

The atmosphere makes conditions on Earth suitable for living things!

Nitrogen An essential building block of all living organisms Nitrogen cycles throughout the atmosphere and environment

Carbon Dioxide Plants use this to make food This is produced when fuels are burned Made from 1 carbon atom and 2 oxygen (CO2)

Oxygen Plants and animals use it to release energy from their food. Oxygen is used in fuel (Cars, fires) It makes up our ozone layer (O3)that protects earth from harmful UV

rays.

Details of the Atmosphere

Density The amount of mass (molecules) in a given area

Pressure The force pushing on an area Air pressure: the weight of a column of air pushing down

on an area (the atmosphere is heavy!) Denser air exerts MORE pressure than less dense air

Altitude The distance above sea level Air pressure decreases as altitude increases (INVERSE

relationship!)

Properties of Air

If denser air exerts MORE pressure than less dense air

AND Air pressure decreases as altitude

increases THEN…

How does air pressure affect density?

Puzzle

As air pressure decreases, so does density! (direct relationship!)

Answer

Energy in the Atmosphere

This energy travels to earth in the form of electromagnetic waves (these can be visible light, infrared radiation or UV radiation)

Energy from the Sun

Energy in the Atmosphere

50% absorbed by Earth’s surface (heats land and water)

20% is absorbed by gases

in the atmosphere (ozone

absorbs UV)

5% is reflected back by the surface into the atmosphere

25% is reflected by clouds and gas

Dust and gases reflect light in the atmosphere in all directions (this is called scattering)

Short wavelengths (blue) are scatttered more than long wavelengths (red), so the light looks blue!

Why is the sky blue?

Even though most energy is radiated back into the atmosphere, it cannot reach space!

Instead it gets absorbed mostly by carbon dioxide in the atmosphere

Now the heat is held inside the atmosphere like a blanket warming the Earth = greenhouse effect

This is a NATURAL process keeping Earth at a good temperature (however, too much carbon dioxide means too much heat…global warming!)

The Greenhouse Effect

Temperature : The average amount of motion of each particle in a substance (the faster they’re moving, the more energy, the higher temperature!)

Thermometers measure temperature because as the liquid inside of it is heated, the particles move faster and spread out (rise up the column)

Heat is transferred through radiation, conduction or convection (this is REVIEW)

Temperature and Heat Transfer

Types of Heat Transfer

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Unequal heating of the atmosphere causes differences in air pressure .

Differences in air pressure cause the air to move.

Wind: horizontal movement of air from an area of high pressure to low pressure.

Winds can be local (blown over short distances) or global (occur over large area)

Wind

Humidity: a measure of the amount of water vapor in the air. (Warm air holds more water vapor than cold air)

Clouds: Form when water vapor in the air condenses to form liquid water or ice crystals. (For water vapor to condense, tiny particles must be present so the water has a surface to condense on!)

Precipitation: Any form of water that falls from the clouds and reaches Earth’s surface (rain, sleet, snow, hail)

Other Weather Items