4.7 Solar Radiation and Earth's Seasons

Explain how the sun's energy affects the Earth's surface.

- Incoming solar radiation (insolation) is the Earth's main source of energy and is dependent on season and latitude. - The angle of the sun's rays determines the intensity of the solar radiation. Due to the shape of the Earth, the latitude that is directly horizontal to the solar radiation receives the most intensity. - The highest solar radiation per unit area is received at the equator and decreases toward the poles. - The solar radiation received at a location on the Earth's surface varies seasonally, with the most radiation received during the location's longest summer day and the least on the shortest winter day. - The tilt of Earth's axis of rotation causes the Earth's seasons and the number of hours of daylight in a particular location on the Earth's surface.

Surface temperature is affected by... HOW?

- albedo ●When sunlight is absorbed by a surface, it gives off infrared radiation (heat) ○Areas w/lower albedo, absorb more sunlight light (heat)

Identify which season is taking place in the Northern hemisphere in this diagram. Describe how the tilt of the earth's axis is responsible for earth's seasons.

....

●Solar intensity of insolation (W/m2) depends on:

a.Angle: how directly rays strike earth's surface b.The amount of atmosphere sun's rays pass through ●Equator = higher insolation than higher latitudes

Insolation

the amount of solar radiation (energy from sun's rays) reaching an area Measured in Watts/m2

Describe BLANK Solstices and BLANK Equinox

○June & December Solstices: N or S hemisphere is maximally tilted toward sun (summer/winter) ○March & Sept. Equinox: N & S hemispheres equally facing sun

Tilt of Earth's Axis Causes Variation in:

●Angle of Insolation (which changes intensity) ●Length of day ●Season

Solar Intensity & Season - How does Insolation cause different seasons

●Orbit of earth around sun & tilt on axis changes angle of sun's rays ●This causes varying insolation, varying length of day, and seasons ●Tilt of earth's axis stays fixed during orbit

low vs high albedo

●Surfaces with higher albedo reflect more light, and absorb less (ice/snow) ○Absorb less heat ●Surfaces with low albedo reflect less light, and absorb more (water) Absorb more heat

Albedo

●the proportion of light that is reflected by a surface

Urban Heat Island:

●urban areas are hotter than surrounding rural area due to low albedo of blacktop ●Polar regions are colder due to higher albedo