Heat and WindHeat and Wind

Heating of Earth Heating of Earth (start demo)(start demo)

• It is radiation from the sun that heats Earth.It is radiation from the sun that heats Earth.•This This solar radiationsolar radiation or heat affects both or heat affects both weatherweather and and climate.climate.•Weather is the condition of Earth’s atmosphere at a particular time and Weather is the condition of Earth’s atmosphere at a particular time and place.place.

•Climate is the average, year-after-year conditions of temperature, Climate is the average, year-after-year conditions of temperature, precipitation, winds, and clouds in an area.precipitation, winds, and clouds in an area.

•As weAs we have learned previously, the sun heats different places on earth have learned previously, the sun heats different places on earth at different rates, this unequal heating is due to the tilt of Earth’s axis at different rates, this unequal heating is due to the tilt of Earth’s axis causing sunshine to strike Earth at different anglescausing sunshine to strike Earth at different angles..

•Differences in the amount of heat an area on Earth receives can cause Differences in the amount of heat an area on Earth receives can cause differences in air pressure. differences in air pressure.

•Differences in air pressureDifferences in air pressure cause everything from wind to the cause everything from wind to the movement of hot and cold air masses from one place to another.movement of hot and cold air masses from one place to another.

Heat and WindHeat and Wind

Convection CurrentsConvection Currents

Heating Differences in air pressure Wind & movement of air massesHeating Differences in air pressure Wind & movement of air masses

• Remember, Remember, hot air riseshot air rises and and cool aircool air sinkssinks. .

• It is these It is these convection currentsconvection currents in the air that is responsible for in the air that is responsible for moving air up and down in the atmosphere.moving air up and down in the atmosphere.

Heat and WindHeat and Wind

Pressure CellsPressure Cells

• When hot air rises from an area, the air pressure decreases, causing When hot air rises from an area, the air pressure decreases, causing what we call a what we call a low pressurelow pressure cell. (page 399, figure 6) cell. (page 399, figure 6)

• The cold air from another area then rushes into fill the void, creating aThe cold air from another area then rushes into fill the void, creating a high pressurehigh pressure cell. cell.

Low PressureLow Pressure High PressureHigh Pressure

• Land is made of rock, and Land is made of rock, and rock heats up faster than waterrock heats up faster than water, so during the , so during the

day it is hotter inland than on the coast, but day it is hotter inland than on the coast, but rock also cools off faster than rock also cools off faster than waterwater, so during the night it is cooler inland than on the coast. (observe , so during the night it is cooler inland than on the coast. (observe demo)demo)

• Since large bodies of water like oceans and big lakes hold their heat and Since large bodies of water like oceans and big lakes hold their heat and cool off slowly even at night, a city by the ocean will be warmer at night and cool off slowly even at night, a city by the ocean will be warmer at night and during the winter than inland cities.during the winter than inland cities.

• Since land heats up faster than water, cities by the ocean will be cooler Since land heats up faster than water, cities by the ocean will be cooler during the day and during the summer than inland cities.during the day and during the summer than inland cities.

Exploring Earth (The Atmosphere in Motion)(The Atmosphere in Motion)

Heat and WindHeat and Wind

Air Movement Between Land and SeaAir Movement Between Land and Sea

Heat and WindHeat and Wind

WindWind

• There are two types of wind: local winds and global windsThere are two types of wind: local winds and global winds• Local windLocal wind is the movement of cool air known as a is the movement of cool air known as a sea breezesea breeze

rushing into an area of high pressure where hot air has risen to rushing into an area of high pressure where hot air has risen to higher elevations.higher elevations.

• This hot air then moves back to the area where the cool air came This hot air then moves back to the area where the cool air came from, creating a convection cell (current).from, creating a convection cell (current).

Heat and WindHeat and Wind

Which one heats up faster, land or water?Which one heats up faster, land or water?

Which one cools off faster, land or water?Which one cools off faster, land or water?

What is caused by differences in air pressure?What is caused by differences in air pressure?

What is responsible for moving air up and down in the atmosphere?What is responsible for moving air up and down in the atmosphere?

Does cool air create a high pressure or low pressure cell?Does cool air create a high pressure or low pressure cell?

Which one is cooler at night, a city at the beach or one that is located inland?Which one is cooler at night, a city at the beach or one that is located inland?