Post on 05-Jan-2016
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