Basic Geoscience

Unit 5 Lecture

Radiant Energy

• Radiant energy comes from the sun and travels through space to heat the earth

• This heating of the earth is called radiation

Absorption of Energy

• Dark surfaces absorb more light, which converts into heat

• Light colored surfaces reflect light and remain cooler than darker surfaces

Energy From the Sun

• 50% of the sun’s energy is absorbed by the surface of earth

• 20% is absorbed by the earth’s atmosphere• 30% is reflected by the earth’s atmosphere

and surface total

Energy From the Sun

• There are 3 ways for heat to move:• 1. conduction• 2. convection• 3. radiation• Heat always moves from hot objects to cooler

objects

Conduction

• Near the earth’s surface, heat moves through matter

• By contact with solids• This is conduction• Ex: hot air touching the warm dirt

Radiation

• Radiation are waves of energy that travel through a vacuum

• Outer space is a vacuum• Shortwave radiation (powerful) comes from

the sun• Long wave radiation is released by the earth

back into the atmosphere

Convection

• Convection is heat being transferred through gases or liquids

• Convection currents are formed because warm air expands and rises, cool air contracts and sinks

Winds and Air Pressure

• Air movement is determined by differences in air pressure

• Horizontal air movement is called wind• This is the most common.• Vertical air movement are called updrafts and

downdrafts.

• Highs= cold, heavy air• Lows= warm, light air• Air moves from high pressure to low pressure.• The greater the difference in pressure, the

faster the wind moves.

Air Currents

• Hot air expands and rises• Cool air contracts and sinks

The Big Idea

• Trade winds- reliable winds above and below the equator

• Doldrums- area between the trade winds where there is little wind

• Prevailing Westerlies- winds between the polar area and the trade winds (also called anti trade winds because they move in the opposite direction)

• Horse latitudes- located between the westerlies and the trade winds

• Little wind occurs here• Polar Easterlies- cold and dense, slow winds

Sea and Land Breezes

• A breeze coming from the sea towards land is a sea breeze.

• This happens during the day.• A breeze coming from the land towards the

sea is a land breeze.• This happens during the night.

Mountain and Valley Breezes

• A valley breeze happens when air moves from the valley up a mountain.

• This happens during the day.• A mountain breeze happens when air moves

down from the mountain into the valley.• This happens at night.

Monsoons

• Monsoons are winds that change direction with seasons.

• During summer, the wind moves from the ocean towards the land and causes many rains.

• During winter, the wind moves from the land towards the ocean and is associated with dry air.

Air Masses

• An air mass is a large body of air with certain characteristics of temperature and moisture throughout.

• Masses over land are dry.• Masses over water are moist.

Polar Air Masses

• Polar air masses are cold air masses that form over polar regions.

• cP- cold and dry• Ex: Canada• mP- cold and moist• Ex: north east and west coast of North

America

Tropical Air Masses

• cT- warm and dry• Ex: Mexico• mT- warm and moist• Ex: Caribbean

Boundaries In Air

• Fronts are boundaries where two air masses meet

• This brings changes in the weather

Cold Fronts

• This occurs when cold air pushes under warm because the cold air is more dense

• Causes rainy and cloudy skies

Warm Fronts

• Occurs when warm air pushes over cold air• This front moves slowly• You will see cirrus clouds and precipitation

Stationary Fronts

• This occurs when air masses meet and do not move

• There is little change in the weather when this happens.

Occluded Fronts

• This occurs when warm air is stuck between two cooler air masses.

• The cool air pushes the warm air up• The weather during this time is cloudy, rainy,

and snowing