INSOLATION

Here comes the Sun…hehehehehehe

How Does Heat Energy Travel?

• Heat is a form of energy because it can do work.

• There are three ways that heat can travel1.Convection2.Conduction3.Radiation

Angle of Insolation

• Angle of Insolation depends on how high the sun is in the sky.

• As the sun rises and sets the a.o.i. changes, ie, the daily weather cycle.

• We measure the a.o.i from the horizon up to the position of the sun.

• Smaller angle=colder temp• Larger angle (90˚)= warmer temps

A.O.I

A.O.I• The a.o.i also works for the seasonal weather cycle. • In the Northern Hemisphere, the lowest noon time

a.o.i is on Dec. 21 and the highest noon time a.o.i is on June 21.

• These are different because Earth is spherical.• The vertical ray is the most direct amount of insolation

(warmer temps), which always hits in the Tropics.• All other latitudes received indirect, or slanted

amounts of insolation (colder temps).

Duration of Insolation• Duration of Insolation is the length of time from sunrise

to sunset. • When Earth has a greater duration of insolation, the

temperatures increase.• Direct Relationship• D.O.I varies greatly with latitude. • Higher the latitude, the more extreme amounts of d.o.i.• Lower the latitude, the more consistent the amounts of

d.o.i.

Greenhouse EffectSun

Earth’s Atmospheric GasesNitrogen (N2)

Oxygen (O2)

Water (H2O)

Carbon Dioxide (CO2)

Methane (CH4)

Non-Greenhouse

Gases99%

GreenhouseGases

1%

Climate

• Climate:• The atmospheric conditions observed over a

long period of time for a large geographic region.

• Higher Latitude (90 N/S), cooler and drier ̊�• Lower Latitude (Tropics), warmer and moist

Factors That Affect Climate• Latitude• Altitude:• High altitude locations have a cool climate due

to adiabatic (rises, cools, expands) cooling of air as it rises.

• Mountain Ranges:• Windward and Leeward

Factors that Affect Climate

• Oceans/ Large Bodies of Water:• Coastal locations tend to have less temperature

change than inland locations• Reasons for this:1.Water holds heat down longer 2.Water has a higher specific heat, which means it

needs more energy to warm up3.Energy that hits the water causes evaporation

more than heating

Factors That Affect Climate

• Ocean Currents• Wind Belts• Monsoons:• Massive rainy season due to an extreme

change in moisture and pressure between summer and winter (India)

• Typical Storm Tracks

Land v. Water Absorption • The difference between the amount of radiation

could be for one or more of the four following reasons:

1. Water has a higher specific heat than land2. Water reflects lower angle insolation better than

land3. Water is transparent so insolation goes down

further into it4. Convection currents bring insolation further into

the hydrosphere

Reflection of Insolation

• The Poles are colder than the Equator, even though they both get 12 months of sun and 12 months of darkness, because:

1.Snow at the Poles reflect most of the insolation

2.The Sun is lower in the sky at the Poles (a.o.i)3.Sunlight must travel a greater distance

through the atmosphere b/c the Sun is so low in the sky, so it loses energy.

The Insolation-Temperature Lag

• The Insolation-Temperature Lag is the time delay between the maximum and minimum insolation and the maximum and minimum air temperature.

• Ex. Temp at 6AM compared to Temp at 2PM• Ex. Temp of the ocean in June compare to

Temp of the ocean in October.

History of Earth’s Climate

• Earth formed ~4.6 billion years ago• Originally very hot• Sun’s energy output only 70% of present• Liquid water present ~4.3 billion years

History of Earth’s Climate

• Life appeared ~3.8 billion years ago• Photosynthesis began 3.5-2.5 billion years ago– Produced oxygen and removed carbon dioxide

and methane (greenhouse gases)– Earth went through periods of cooling (“Snowball

Earth”) and warming• Earth began cycles of glacial and interglacial

periods ~3 million years ago