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.
Seasons & Climate Regions - 2
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.
Seasons & Climate Regions – 3
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
a 23.5°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.
Seasons & Climate Regions – 4
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.
Seasons & Climate Regions – 5
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.
Seasons & Climate Regions – 6
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.
Seasons & Climate Regions – 7
Summer
begins on the summer 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)