Earth ScienceEarth Science

Chapter 9Chapter 9

Chapter 9Chapter 9

Weather and Climate

Lesson 1Lesson 1What Factors Affect What Factors Affect

Climate?Climate?• Climate is the

normal pattern of weather in an area over many years.

• Climate in an area is affected by:– Earth’s shape– Tilt of its axis– Geographic

features

Uneven HeatingUneven Heating

• The Sun’s rays strike Earth at different angles.

• The closer the angle to the Sun, the warmer the climate in that area.– Example: The Equator

Major Climate ZonesMajor Climate Zones

• Earth has three Major Climate Zones– Tropical, Temperate, and Polar

• Their differences are:– Average temperature– Amount of precipitation (rain,

sleet, snow, or hail)

Tropical Climate ZonesTropical Climate Zones

• Occur at the Equator, or areas just North and South of it

• Warm temperatures all year round

• Often very rainy

Temperate Climate ZonesTemperate Climate Zones

• North and South of the tropics

• Warm summers, with rain as precipitation.

• Winter is cool- very cold, and precipitation falls as snow

• We live in a temperate climate

• Have 4 seasons

Polar ClimatesPolar Climates

• Located close to Earth’s North Pole and South Pole.

• Very cold year round.• Most precipitation falls as snow.

Land and Sea BreezesLand and Sea Breezes

• Unequal heating of land and water causes Land and Sea Breezes.

• Sea Breezes- flow from the WATER towards the land.

• Land Breezes- flows from the LAND toward the water.

Mountain EffectMountain Effect

• Mountains can affect precipitation.

• Most air flows up the windward side of a mountain.– The windward side

receives more precipitation than the leeward side.

Ocean and ClimatesOcean and Climates

• Ocean Currents – Caused by the wind pushing against the

ocean’s surface, moving streams of water.

• Warm ocean currents move warm water away from the equator toward the poles.

• Cold ocean currents move cold water away from the poles and toward the equator.

El NiñoEl Niño

• The name given to a periodic change in the direction of warm ocean currents across the Pacific Ocean.– Occurs every 5-7

years– Can cause change in

climate around the world

Lesson 2Lesson 2How Are Weather Forecasts Made?How Are Weather Forecasts Made?

• Earth’s atmosphere is a mixture of gases that surrounds the planet.

• Changes in the air causes changes in weather.

Structure of the AtmosphereStructure of the Atmosphere

• Divided into four main layers.

• Troposphere- – Closest to Earth– Where almost all

weather occurs– Thinnest layer– Contains 75% of

gases that make up the atmosphere.

StratosphereStratosphere

• Lies above the Troposphere• Air is much colder and drier• Contains most of the Planet’s Ozone layer• Absorbs radiation from the Sun

MesosphereMesosphere• Lies above

Stratosphere

• Coldest layer of Earth’s atmosphere

ThermosphereThermosphere

• Thin layer of Earth’s atmosphere

• First layer struck by sunlight

Air MassesAir Masses

An AIR MASS is a huge volume of air that affects weather in a certain area

– Can be dry OR humid, and warm OR cold, depending on where it forms

FrontsFronts • A front is a boundary between two air masses • When two DIFFERENT air masses meet, they

create a front. – Warm fronts form when warm air moves into an area,

causes light rains – Cold fronts form when cold air moves into an area,

usually has heavy rains

Observing Observing WeatherWeather• Weather is the overall

condition of the atmosphere at a given time and place. – Meteorologists are

scientists who study weather.

– Weather maps display atmospheric conditions.

RADARRADAR• Radar is a useful tool

for observing and forecasting weather

• Can be used to create an image of a storm.– Size, direction, amount

of precipitation and speed of the storm can be determined

Other Weather InstrumentsOther Weather Instruments

Satellites orbiting the Earth measure data in the atmosphere and relay it to Earth

• Thermometers- measure temperature in Celsius or Fahrenheit

• Anemometers- measure wind speed• Barometers- measure air pressure• Rain Gauges- collect and measure amount of

rain, snow, sleet or hail.• Weather Vane- indicates the direction the wind

is blowing