Unit 4 Lesson 7 : Solar Radiation and Earth's Seasons

Insolation: INcoming SOLar radiATION

Insolation=Solar Radiation/Area

Seasons in Northern Hemisphere

- December 21-22 Winter Solstice > March 20-21 Vernal Equinox > June 20-22 Summer Solstice > September 22-23 Autumnal Equinox - December: Shortest day of the year, polar night - March: Day and night roughly equal in length - June: midnight sun, longest day of the year - September: Day and night roughly equal in length

Essential Knowledge

- 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 towards the poles. - The solar radiation received at a location on the earth's surface varies seasonally, with the most radiation received during the locations 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 numbers of hours of daylight in a particular location on the Earth's surface.

Practice

- The diagram to the left shows the Earth tilted at 23.5º on its axis As shown in the diagram, which region is currently experiencing the highest insolation? Answer - Tropic of Capricorn (most perpendicular) - As shown in the diagram to the left, what is the approximate length of day at the Tropic of Capricorn? Answer: Longer than 12 hours

Seasons in the southern hemisphere

- Opposite from northern hemisphere - Equinox days the same - The longest day of the year and midnight sun is december 20 or 21 - The shortest day of the year and polar night is June 20 or 21

Random Information

- Solar radiation in constant - The angle of incidence for the sun's energy varies because of the spherical shape of the earth - A smaller angle of incidence leads to a larger area over which the solar radiation is spread, leading to a smaller insolation value. - The area radiation will have the highest insolation - Different parts of the earth receive different amounts of insolation at different times of the year because of its tilted axis. - The general amount of insolation presents in the northern and southern hemisphere can be predicted because of the regular orbit of the earth around the sun. - The earth has seasons because of its tilted axis

Insolation change due to shape of earth

- The surface most perpendicular to the sen will have the highest concentration of solar radiation per unit area (highest insolation) - The angle of incidence decreases moving towards the poles, increasing area of incidence, which in turn lowers insolation. - Example) flashlight and cardboard, see circle, tilt the paper and it will seem that the flashlight dimmed.