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Tilt/Latitude Body


Latitude of the earth

Figure A: Degrees of Latitude
http://www.mrdowling.com/601-grid.html

 

 

The technical definition of latitude is the angular distance north or south from the earth’s equator measured through 90 degrees. Lines of latitude form circles around the earth, with 0 degrees latitude being at the equator and 90° latitude representing the poles. For example, Miami, Florida, is located at approximately 26 degrees North latitude while New York, New York, is located at approximately 41 degrees North latitude.

While there are other factors that affect general climate in an area (terrain, location relative to mountains/oceans, and height above/below sea level, for example), latitude is an important factor in determining what type of climate a location will have. For example, we can expect Miami’s climate to be much warmer than that of New York since it is at a lower latitude and is located closer to the equator.  Locations at lower latitudes receive stronger and more direct sunlight than locations near the poles.  Energy input from the sun is the main driving force in the atmosphere.

As mentioned earlier, there are other factors that influence the weather on the earth.  One of these is the tilt of the earth. The earth's axis of rotation is tilted about 23.5 degrees compared to the plane of the earth's orbit around the sun.   The earth’s tilt is responsible for the seasons we experience.

Seasons
Figure B: Seasons of the Year

The earth moves around the sun in an elliptical fashion, and one complete orbit around the sun takes one year. An interesting fact is that it is not the proximity of the earth to the sun that determines the season; we are actually closest to the sun in January, not July.  Instead, the tilt of the earth is the key. When the Northern Hemisphere is tilted towards the sun, the Southern Hemisphere is tilted away from the sun. This leads to summer in the Northern Hemisphere and winter in the Southern Hemisphere as the Northern Hemisphere experiences the most direct sunlight and solar heating as shown in Figure C. 

At this point, the earth's angle to the sun allows it to be summer in the Northern Hemisphere and Winter in the Southern Hemisphere.
Figure C: Northern Hemisphere Summer/Southern Hemisphere Winter
Image from wikipedia

During winter in the Northern Hemisphere, the Southern Hemisphere is tilted towards the sun, which now experiences summer shown in Figure D. The Southern Hemisphere takes in more of the sun’s rays than the Northern Hemisphere, and the days last longer in the Southern Hemisphere. Meanwhile, in the Northern Hemisphere, the days become shorter and the temperatures become cooler.  The sunlight is weaker and less direct, so there is less energy being absorbed by the earth and atmosphere.

At this point, the earth's angle to the sun allows it to be winter in the Northern Hemisphere and Summer in the Southern Hemisphere.
Figure D: Northern Hemisphere Winter/Southern Hemisphere Summer
Image from wikipedia

During spring and fall, the earth is in a transition phase shown in Figure E. What usually marks the occurrence of spring and fall astronomically is the equinox. The equinox occurs when the sun is directly focused on the earth’s equator and causes 12 hours of daytime hours and 12 hours of nighttime hours across the entire earth.  There are two types of equinoxes that occur: the vernal and the autumnal. The vernal equinox marks the beginning of spring for the Northern Hemisphere and the beginning of fall for the Southern Hemisphere. As time passes, the Northern Hemisphere gradually receives more of the sun’s rays and also experiences longer daylight hours. The autumnal equinox marks the beginning of fall in the Northern Hemisphere and spring in the Southern Hemisphere. The Northern Hemisphere gradually receives less of the sun’s rays over time and also experiences less daylight hours. In addition to revolving around the sun, the earth rotates counter-clockwise on its own axis. This rotation allows us to experience day and night.

Climatologists usually use full months to represent the seasons.  Winter is considered December, January and February; spring is March through May; summer is June through August; and fall or autumn is September through November. 

At this point, the earth's angle to the sun allows it to be either Spring or Fall for the Southern and Northern Hemispheres.
Figure E: Autumnal (Fall) Equinox/Vernal (Spring) Equinox
Image from wikipedia

Last modified date: Friday, July 27, 2012 - 10:02am