Seasons & Climate Regions
There are different temperatures on earth because all parts do not get the same amounts of radiant energy from the sun. This difference in radiant energy is caused from sunlight striking the earth at different angles. The different angles are causes by the tilt and curvature.
Sunlight at the equator hits the earth at 90° or straight on. This means all the energy is concentrated or focused directly on this area. higher angle = less area = more radiant energy = more heat energy = highest temperatures
Sunlight at the polar regions hits at a very low angle. Most radiant energy skims by without touching and is not concentrated in any one spot.
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When referencing the earth, always look down from above. The earth spins counterclockwise on its axis (north and south poles). This is why the sun always rises in the East and sets in the West. One rotation on its axis is called a day (about 24 hours). The earth also revolves around the sun in a counterclockwise direction when looking down from above. One rotation is called a year (about 365 days).
Seasons are periods of time within a year when the temperature stays about the same. A change in the season means a change in temperature. Seasons are caused by the tilt of the earth as its goes around the sun.
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The earth’s tilt affects:
temperature variation in one spot in one year – seasons,
the greater the tilt, the larger the variation
amount of daylight
climate regions
Our earth is currently tilted at about a23.5°angle. During some parts of the year, the tilt leans toward the sun (summer). During some parts the year, the tilt leans away (winter). Seasons are opposite in the northern and southern hemispheres. The earth’s tilt is currently decreasing. A 40,000 year cycle will bring the tilt from 24.5° to about 21.5°. A greater tilt means hotter summers (and colder winters), because the added heat is trapped by the atmosphere. So, global temperatures increase as the tilt increases, and ice ages match up with a lower tilt. Paeloclimatology uses ice core samples, tree rings, coral reefs, and various other methods to study the history of earth’s temperature. Studies show that the earth’s climate both rises and decreases over long cycles.
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Distinct climate regions are caused by the tilt. Climate is a combination of temperature and precipitation over an area. The tropics are around the equator between 23.5° south and 23.5° north latitudes. The tropic of Cancer is 23.5° north latitude, and the tropic of Capricorn is 23.5° south latitude. There are no seasons in the tropics. Every day gets about 12 hours of sunlight (exactly 12 at the equator).
The temperate climate regions are between 23.5° and 66.5°. There are distinct seasons here. The sub tropics are part of the temperate region. They have mild seasons and are mostly dry. They are between 23.5° and 35°. Central Ohio is about 40° north latitude. The polar regions are between 66.5° and 90° latitude. There are no seasons here. It is always cold and dry. The arctic circles are 66.5° latitude.
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The earth averages 93 million miles from the sun. On July 3-4 the earth is at its farthest distance from the sun at 94.5 million miles, called the aphelion. On January 2-3, the earth is at its closest point to the sun at 91.5 million miles, called the perihelion. For this reason, the southern hemisphere of earth tends to have hotter summers and colder winters, while the seasons in the northern hemisphere (United States) are not as harsh as those in the south (Australia).
On June 21st (the summer solstice) the northern hemisphere leans the most toward the sun. There are more hours of daylight on this day than any other. Ohio latitudes receive about 14-16 hours of daylight. The north polar climate regions receive 24 hrs of daylight this day, and the tropics 12.
On December 21st (the winter solstice) the northern hemisphere leans the most away from the sun. There are fewer hours of daylight on this day than any other. Ohio latitudes receive about 7-10 hours of daylight. The north polar climate regions receive 0 hours of daylight and the tropics 12.
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On March 20 or 21 (the Spring or Vernal equinox) and September 22 or 23 (the Fall or Autumnal equinox), the earth’s axis not leaning toward or away from the sun. On these days, all parts of the earth receive 12 hours of daylight and 12 hours of darkness. Ohio gains or loses between 5 ½ and 7 ½ minutes of daylight every day.
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Summer
begins on thesummer solstice (21 June)
24 hrs of sunlight north of arctic circle;
longest day of the year in Ohio;
14-16 hours of daylight in Ohio;
sun angle is 90° at Tropic of Cancer;
ends on the Autumnal equinox (September 22)
Spring
begins on the Vernal Equinox (20 March);
12 hours of sunlight everywhere;
sun angle is 90° everywhere;
ends on the Summer Solstice (21 June)
Fall
begins on the Autumnal equinox (22 September);
12 hours of sunlight everywhere;
sun angle is 90° at equator;
ends on the Winter solstice (21 December)
Winter
begins on the Winter Solstice (21 December);
24 hours of darkness above arctic circle; shortest day of the year;
7-10 hours of daylight in Ohio;
sun angle is 90° at Tropic of Capricorn;
ends on the Vernal equinox (20 March)