Summary of Earth-Sun Relationships

 

• Seasonal and temporal variations in solar radiation about the Earth affect changes in climate due to:

     • A varied angle of incoming solar rays (angle of incidence).

     • A varied length of daylight hours throughout a year.

• The length of daylight hours gradually decreases or increases as one moves poleward, and is dependent upon the hemisphere (northern or southern), and the time of year.

• The distance of the Earth to the Sun varies, and does not directly affect temperature variations at the surface. If this were the case, our northern hemisphere summers would be in January (Perihelion, 91,500,000 miles), and winter would be in July (Aphelion, 94,500,000 miles). It follows that northern hemisphere winter is principally a function of a lower Sun angle, and shorter daylight hours.

• Although the southern hemisphere possesses a greater surface area of water (~81%) than the northern hemisphere (~61%), when the angle of incidence is directed toward the southern hemisphere during its summer season, summer temperatures are not warmer than in the northern hemisphere in part because water has a high specific capacity. It takes considerably more energy to raise the temperature of water, than land surfaces.

• The Sun’s rays only strike the Earth’s surface at 90˚ between 23.5˚ north (Tropic of Cancer) and 23.5˚ south latitudes (Tropic of Capricorn). At all other latitudes, the Sun’s solar zenith (angle of the noonday sun) will be less than 90˚.

• The solar zenith will be 90˚ at the Tropic of Cancer on the June Solstice in the northern hemisphere.

• The solar zenith will be 90˚ at the Tropic of Capricorn on the December Solstice in the northern hemisphere.

• On the Spring and Fall Equinox periods, the Sun’s solar zenith will be 90˚ at the Equator, and just rising over the horizon at the North Pole. In the southern hemisphere the Sun is beginning to lower below the horizon at the South Pole.

• On the Equinox periods, the solar zenith (angle of the noonday Sun) can be determined by subtracting the latitude of location from 90˚.

• On the Equinox periods, the latitude of location can be determined by subtracting the solar zenith from 90˚.

• The North Pole and the axis of inclination are constantly directed toward the north star (Polaris). Earth wobble and other anomalous movements are not considered in this generalization.

• The Earth rotates and revolves counterclockwise as viewed from a position in space above the North Pole.

• A slight bulging at the Equator is due in part to rotation and centrifugal force acting upon a planet that is covered by approximately 71% water.

• Rotation creates tidal forces acting upon the Earth’s oceans which result in daily shifts in sea level.

• Objects tend to be shifted to the right in the northern hemisphere, and to the left in the southern hemisphere due to Coriolis Effect. This Effect is most pronounced at the poles, and approaches 0 at the Equator.

• Seasonal conditions are opposite in each respective hemisphere. When it is summer in the northern hemisphere, it is winter in the southern hemisphere.