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!

Details of the Atmosphere 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.

Properties of Air Density Pressure Altitude 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!)

Puzzle AND Air pressure decreases as altitude increases THEN… If denser air exerts MORE pressure than less dense air AND Air pressure decreases as altitude increases THEN… How does air pressure affect density?

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

Energy in the Atmosphere

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

Energy in the Atmosphere 25% is reflected by clouds and gas 20% is absorbed by gases in the atmosphere (ozone absorbs UV) 5% is reflected back by the surface into the atmosphere 50% absorbed by Earth’s surface (heats land and water)

Why is the sky blue? 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!

The Greenhouse Effect 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!)

Temperature and Heat Transfer 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)

Types of Heat Transfer __________________ __________________

Wind 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)

Other Weather Items 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)