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
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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.
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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
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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