The Sun, Seasons and Weather

• understand that energy from the Sun is the primary driver of weather on Earth.

• describe the revolution and tilt of Earth’s rotational

• account for seasons in both hemispheres

Key WordsSpring (vernal) equinox Fall (autumnal) equinoxLatitude/Longitude SolsticeTropic of Cancer Tropic of Capricorn

The Earth rotates on its axis once a day.

The axis is tilted at an angle of 23.5 degrees.

The Earth revolves around the Sun once a year. At any time - half of Earth is in sunlight and half in

darkness.

Earth rotates in an easterly direction

Insolation – because of (spherical) shape of the Earth, sun shines at different angles over different parts.

Equator - sun’s energy is more direct - HOT Poles - sun’s energy is spread out over a larger area - COOL

Affects the weather and climate of that part of the earth.

summer

winter

When the Earth’s axis is tilted the most towards or away from the Sun’s rays.

Winter Solstice – north titled away – December 21

Summer Solstice – north tilted towards – June 21

Summer Solstice – Long days, short nights.

Winter Solstice – Short days, long nights.

When Earth’ s axis is perpendicular to the Sun’s rays - exactly half of Earth is reached:

Spring Equinox – about March 21Fall Equinox – about September 23

Everywhere receives 12 hours of daylight.

SPRING/FALL

At the equator, the daily period of daylight is the same, everyday of the year.

The poles have the greatest range in temperature.

Higher latitudes (Canada) have greater variations in solar radiation received over the year, creating greater seasonal differences (Cuba).

Sunlight variations in the Southern Hemisphere are reversed – as are the seasons.

Tropic of Cancer – most northerly location that receives direct (vertical) sunlight in summer.

Arctic Circle – most northerly location reached by any sunlight in winter.

Tropic of Capricorn and Antarctic Circle are the corresponding lines for the Southern hemisphere.

Longitude is measured east - west from 0o line through Greenwich, England (prime meridian).

Latitude is measured north - south from the equator.