GEOG 1112 Lecture 3 Notes

How much of Earth’s energy is from the sun?

greater than 99%

>99%

The amount (intensity) of sunlight striking the Earth…

varies spatially (over space or area) with latitude & varies temporally (over time) with the seasons (day length) and between day and night

What do variations of sunlight on Earth cause?

they cause unequal heating of the Earth’s surface

Unequal heating of the Earth’s surface drives…

the ocean currents form winds, which transports energy across the globe.

Earth movements are…

rotation on its axis

Revolution is

around the sun

Rotation is…

spinning of the Earth on its axis. Makes 1 turn every 24 hours.

Because the earth is rotating, the same side of the planet…

is not always facing the Sun and solar intensity varies

The Earth turns…

counterclockwise

What forms between the area of light (daytime) and dark (nighttime)

A circle of illumination

What is revolution?

this is the movement of the Earth in its orbit around the Sun.

The Sun’s energy output is…

constant

What forms between the area of light (daytime) and dark (nighttime)?

A circle of illumination

What is the movement of the Earth in its orbit around the sun?

revolution

Solar radiation varies with

seasons and latitude

Earth’s orbit is…

elliptical

What does it mean for the Earth’s orbit to be elliptical?

it means that at one part of the year, it is closer to the sun than the opposite end of the orbit and solar intensity varies.

What are the two points on the Earth?

1. Perihelion

2. Aphelion

What is Perihelion?

this is when the Earth and Sun are closest to each other

When does Perihelion occur?

it occurs on January 4th

What is Aphelion?

this is when the Earth and Sun are the furthest apart.

When does Aphelion occur?

it happens on July 4th

What is the result of Perihelion?

this causes a higher solar intensity

What is the result of Aphelion?

this causes a little lower solar intensity

What causes Earth’s seasons?

they are due to Earth’s orientation to the Sun, thus, the varying angle the Sun’s rays strike the Earth’s surface.

Seasons are brought about by or due to…

1. Revolution

2. Rotation

3. Tilt of the Earth on its Axis

4. Axial parallelism

5. Sphericity

Earth’s orientation to the Sun is a result of the…

tilt on its axis or the inclination of the axis

What degree currently is the inclination of the axis?

23.5 degrees

Other major factors of Earth’s orientation?

1. its revolution around the Sun

2. daily rotation on its axis

Another factor controlling solar intensity at the surface?

• the Earth’s axial parallelism (orientation of the North Pole of the Earth toward a specific star

• the fact that Earth is a sphere (sphericity)

Summer has…

• longer days (with a higher solar altitude)

• more intense sunlight

• more energy

Winter is the opposite of summer, with…

• shorter days

• lower solar altitude

• less intense sunlight

• less energy

What is solar altitude?

it is the angle of the Sun above the horizon at any given latitude.

What five factors cause the astronomical seasons?

1. revolution

2. rotation

3. tilt (inclination)

4. axial parallelism

5. sphericity

When does the March equinox occur?

March 21-22

What does the March equinox mean for the Northern Hemisphere?

Marks the start of Spring

What does the March Equinox mean for the Southern Hemisphere?

marks the start of Fall

When does the June Solstice occur?

June 21-22

What does the June solstice mean for the Northern Hemisphere?

it marks the start of summer

What does the June equinox mean for the southern hemisphere?

marks the start of Winter

When is the September Equinox?

September 22-23

What does the September Equinox mean for the Northern Hemisphere?

marks the start of Fall

What does the September Equinox mean for the southern hemisphere?

it marks the start of Spring

When is the December Solstice?

December 21-22

What does the December Solstice mean for the Northern Hemisphere?

marks the start of Winter

What does the December Solstice mean for the Southern Hemisphere?

marks the start of Summer

Winter months

December, January, February

Spring Months

March, April, May

Summer months

June, July, August

Fall/Autumn Months

September, October, November