Insolation and the Seasons Unit 6

Solar Radiation and Insolation  Sun emits all kinds of E E.  Most of the E E is visible light.  Sun emits all kinds of E E.  Most of the E E is visible light.

Effects of Atmosphere on Insolation  The insolation reaching the surface is diff. from what reaches the upper atmosphere.  Visible light is mostly transmitted through to the ground.  The insolation reaching the surface is diff. from what reaches the upper atmosphere.  Visible light is mostly transmitted through to the ground.

Absorption of Ultraviolet and Infrared  Almost all UV rays are absorbed by the ozone  Recently ozone has been reduced. Mainly over the poles.  UV rays are a direct cause of skin cancer.  Almost all UV rays are absorbed by the ozone  Recently ozone has been reduced. Mainly over the poles.  UV rays are a direct cause of skin cancer.

 Infrared waves are absorbed by gases in the atmosphere. CO2, CH4, H2O vapor.

Reflection and Scattering  Clouds cause a lot of reflection of insolation. Some E E does make it through, but is scattered.  This is caused by aerosols.  As the amount of aerosols increases the amount of light scattered increases and the less E E reaches Earth.  Clouds cause a lot of reflection of insolation. Some E E does make it through, but is scattered.  This is caused by aerosols.  As the amount of aerosols increases the amount of light scattered increases and the less E E reaches Earth.

Factors that affect Absorption and Reflection  Angle of insolation  Surface characteristics  Angle of insolation  Surface characteristics

Angle of Incidence  The angle at which E E is striking the surface.  Higher the sun the higher the angle = warmer surface and air  The angle at which E E is striking the surface.  Higher the sun the higher the angle = warmer surface and air

Land and Water Heating  H2O heats up more slowly and cools more slowly than land.

Greenhouse Effect  Much of the heat re-radiated back toward space never leaves the atmosphere.  The long infrared waves can be absorbed by the gases in the atmosphere.  Gases are called greenhouse gases.  Much of the heat re-radiated back toward space never leaves the atmosphere.  The long infrared waves can be absorbed by the gases in the atmosphere.  Gases are called greenhouse gases.

 This keeps Earth’s surface at an average temp. of 59 degrees F.  If all heat absorbed was re-radiated the temp. of Earth’s surface would be 0 degrees F.  This keeps Earth’s surface at an average temp. of 59 degrees F.  If all heat absorbed was re-radiated the temp. of Earth’s surface would be 0 degrees F.

Variation of Insolation  Varies by angle of intensity and duration of intensity.  A 90 degree angle is the strongest. 0 degrees is the weakest.  Varies by angle of intensity and duration of intensity.  A 90 degree angle is the strongest. 0 degrees is the weakest.

Effect of Earth’s Shape  Sun’s E reaches Earth in a bundle of parallel rays. If Earth were flat, all angles of insolation would be 90 degrees.

Effect of Latitude  Intensity of insolation is greatest at the equator at each of the equinox.  At the time of the summer solstice, insolation is greatest at 23 1/2 N.  Winter solstice, greatest is at 23 1/2 S.  Intensity of insolation is greatest at the equator at each of the equinox.  At the time of the summer solstice, insolation is greatest at 23 1/2 N.  Winter solstice, greatest is at 23 1/2 S.

Duration of Insolation  The time between sunrise and sunset.  This time varies with latitude and seasons.  U.S.- Longest on June 21, shortest on December 21, and about 12 hrs. on March 21 and September 23.  The time between sunrise and sunset.  This time varies with latitude and seasons.  U.S.- Longest on June 21, shortest on December 21, and about 12 hrs. on March 21 and September 23.

 Surface temp. will increase as long as the amount of E gained is more than the amount of E lost.

Yearly Max. and Min. Temperatures  Max and min temps do not occur on max and min insolation days.  Daily max. and min. are not at solar noon.  Max and min temps do not occur on max and min insolation days.  Daily max. and min. are not at solar noon.

Heat Budget and Climate  Heat budget- the result of the balance between the total amount of energy gained and the total amount of energy lost. (average temp. of an object)

 Long-term changes in heat budget can result in climate changes.

Ice ages, Warm periods  Earth’s heat budget has shifted in the past for long periods of time.  A cold shift creates glaciers that advanced all the way to the middle latitudes. Warm shifts have little glaciers.  Earth’s heat budget has shifted in the past for long periods of time.  A cold shift creates glaciers that advanced all the way to the middle latitudes. Warm shifts have little glaciers.

El Nino and La Ninia  Every 2-10 yrs. The normally cold waters of the eastern Pacific Ocean, off western South America, are replaced with warmer water.  El Nino causes world wide flooding, drought, and heat waves.  Every 2-10 yrs. The normally cold waters of the eastern Pacific Ocean, off western South America, are replaced with warmer water.  El Nino causes world wide flooding, drought, and heat waves.

Global Warming  Since 1860 the world’s average temperature has risen 2 degrees F.  This trend has scientist worried that human interaction with the environment could speed up the rate of warming.  Since 1860 the world’s average temperature has risen 2 degrees F.  This trend has scientist worried that human interaction with the environment could speed up the rate of warming.

Causes of Heat Budget Shifts  Solar E- the E output of the sun is related to sunspot activity. (11 yr. cycles)  When there are a large number of sunspots E from the sun increases by.1 to 1% more.  Solar E- the E output of the sun is related to sunspot activity. (11 yr. cycles)  When there are a large number of sunspots E from the sun increases by.1 to 1% more.

 Change in tilt and orbit of Earth: over periods of thousands of years the tilt of the axis changes a couple of degrees.  The amount of eccentricity also changes.  When the cycle of these two factors change together, summers may be cooler and winters warmer with more precipitation.  Change in tilt and orbit of Earth: over periods of thousands of years the tilt of the axis changes a couple of degrees.  The amount of eccentricity also changes.  When the cycle of these two factors change together, summers may be cooler and winters warmer with more precipitation.

Another Cause  Volcanic eruptions: volcanic ash and other aerosols such as sulfur get into the stratosphere and reflect more E E than normal.