4.7 - Solar Radiation and Earth's Season's

Insolation

the amount of solar radiation (energy from sun's rays) reaching an area

- Measured in Watts/m^2

What solar intensity of insolation depends on

1) Angle: how directly rays strike earth's surface

2) The amount of atmosphere sun's rays pass through

higher insolation than higher latitudes

Equator =

Solar intensity and latitude

Solar intensity and season

- 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

• June & December Solstices: N or S hemisphere is maximally tilted toward sun (summer/winter)

• March & Sept. Equinox: N & S hemispheres

equally facing sun

1) Angle of Insolation (which changes intensity)

2) Length of day

3) Season

Tilt of Earth's axis causes variation in ______

Albedo

The proportion of light that is reflected by a surface

- Surfaces with HIGH albedo reflect more light, and absorb less

(ice/snow)

• Absorb less heat

- Surfaces with LOW albedo reflect less light, and absorb more (water, pavement, vegetation)

• Absorb more heat

Albedo & surface temperature

Surface temperature is affected by albedo

- When sunlight is absorbed by a surface, it gives off infrared radiation (heat)

• Areas w/lower albedo, absorb more sunlight light (heat)

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