Earth’s Weather and Climate

Our Weather and Climate• Weather

– The condition of the atmosphere at a certain time and place.

– Changes daily• Climate

– The overall weather patterns of an area

– Changes occur over long periods of geologic time

Solar Energy

• Earth receives energy from the sun by radiation.

• Radiation is the transfer of energy as electromagnetic waves.

• The suns radiation enters Earth as• Visible light • Infrared waves - heat• Ultraviolet radiation

Solar Energy from the Sun

Energy from the sun is transferred around Earth by radiation and convection.

Energy from the

sun creates convection currents

in the atmosphere and oceans

Convection Currents

• Convection is the transfer of thermal energy by the circulation of liquids and gases.

• Warm air or water rises– It’s less dense

• Cool air or water sinks– It’s more dense

Ocean CurrentsWarm water rises and cooler water sinks

Wind and Ocean Currents

Influence Earth’s Weather and Climate

Temperature of Our Oceans

– Ocean water cools down and warms up much slower than land or air.

– Oceans keep temperatures for nearby land much more moderate.

• Temperatures are less extreme• Doesn’t get too cold or too hot

– This keeps coastal areas cooler in the summer and warmer in the winter.

Land and Sea Breezes

• Winds caused by uneven heating of air above ocean water and land.

• Land heats up and cools down much faster than ocean water.

• Land gets much hotter during the day and much cooler at night.

Coastal Areas experience Sea Breezes during the day

• Sea Breezes

Coastal Areas also Experience Land Breezes at Night

• Land Breezes

Sea Breezes by DayLand Breezes by Night

Valley and Mountain Breezes

Ocean Currents

• Stream like movements of water in oceans

• Heat is transferred around the world by ocean currents through convection.– Over ½ the heat that reaches the Earth from the

sun is absorbed by the oceans surface.

Surface Currents• Currents at or near the

surface of the ocean• Caused by WINDS!

• Affect weather and climate for coastal regions around the world.– Warm currents originate at the

Equator– Cold currents originate at the

Poles

Deep Water Currents

• Deep currents far below the surface of the ocean.

• Water is cold and salty which makes it more dense and sinks to the ocean floor.

Currents Trade Places• Water from deep currents get warmer as they

reach the equator and starts to rise.

• Water from surface currents get colder as they reach the poles and starts to sink

• Heat is transferred by convection currents, in our oceans. Warm water rises and cold water sinks

Ocean Water Currents

Changes in Ocean Currents– El Nino – the warming of water in the Pacific Ocean

– La Nina – the cooling of water in the Pacific Ocean

Causes Changes in WeatherEl Nino Weather • Rain and flooding along

the Pacific Coast• Tornadoes and

thunderstorms in South US

• Fewer than normal hurricanes in the Atlantic

La Nina Weather• Snow and rain on the

west coast• Cold weather in Alaska• Warm weather in the

rest of the USA• Drought in the south

west• More hurricanes in the

Atlantic

Wind currents

Warm air rises and cool air sinks

Wind Currents• Created by differences in

Air pressure

• Caused by unequal heating of the Earth from the sun

• Equator – Warm, less dense air– Low air pressure

• Poles – Cold, more dense air– High air pressure

Atmospheric/Air Pressure• The force of the air

pushing on any surface.• Measured in Millibars• Decreases with altitude• Changes with air

temperatures• Creates wind!

Barometer – Measures Air Pressure

Air Pressure Weather MapIsobars – Lines on a weather map that show

equal Atmospheric Pressure

• H = High Pressure L = Low Pressure

Convection Cells of Air Create Winds

Jet StreamsHigh-speed winds that can reach up to

500 km/hour high up in the sky.

Wind Speed• Measured by an anemometer

Digital

Weather Map showing Isobars and Windspeed/Direction

Air Masses – large bodies of air that have similar temperature and

moisture throughout

Types of Air Masses

• Continental - form over land; dry• Maritime - form over water; wet

and• Tropical - form in a tropical region;

warm• Polar – form in a polar region; cold

Air Masses• mP – Maritime Polar

Cold and Wet

• cP – Continental Polar Cold and dry

• mT – Maritime Tropical Warm and Wet

• cT – Continental Tropical

Warm and Dry

Air Masses

Fronts

• Boundary that forms between two different air masses– 4 types of fronts: Cold, Warm, Occluded,

Stationary

Cold Front

• When a cold air mass replaces a warm air mass

• Produces colder temperatures and more precipitation

Warm Front•When a warm air mass replaces a cold air mass.•Creates warmer temperatures and some precipitation.

Weather Map

Humidity

The amount of moisture or water vapor in the air.

Relative Humidity

• Relative Humidity – the amount of moisture the air contains compared with the maximum amount it can hold at a particular temperature.

Measuring Humidity• Psychrometer

– Measures Relative Humidity

• Hygrometer– Measures Humidity

Psychrometer

Severe Weather

• Weather that can cause property damage and even death.– Thunderstorms

– Tornadoes – Hurricanes

Thunderstorms• Intense weather systems that produce strong

winds, heavy rain, lightning and thunder

• Occur when warm, moist air rises rapidly in an unstable atmosphere.

• Can cause high winds, hail, flash floods, and tornadoes.

Tornadoes• A rotating column of air that has high wind speeds

and low central pressure that touches the ground.

• Starts as a funnel cloud formed from a cumulonimbus cloud

• Produced by thunderstorms

• 75% occur in the US

Wall Cloud

Wall Cloud – Take Cover

Hurricanes

• Most powerful storms on Earth• Form in warm ocean waters by the equator• Fueled by warm water

and moist air• Die out over cold water

and land

Hurricanes, Typhoons, CyclonesForm in warm ocean waters by the equator