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Blowin' in the Wind, Issue #048 Weather Seasons Change and Consistency - November 1, 2007
October 31, 2007
Predicable Weather Seasons Change ItWe all understand that the year has four seasons. A season is a portion of each year characterized by typical weather conditions or trends, where we watch the weather seasons change . Each season has weather a least a bit different from those in the preceding or following seasons. You know the list - summer, fall, winter, and spring. In addition to the general changes associated with these names, many regions have established various seasons by the events that have plagued them in the past during the same periods annually. You may have heard the terms of "rainy season", or "hurricane season". Now for a brief explanation of the ever-changing seasons and why we experience them.
We all understand that the earth rotates around the sun. However, not everyone knows of the impact the earth's tilt. This tilt results in the seasons we experience. Areas on the globe receive predictable changes in the amount of solar energy each place can receive, and that helps make the seasons and their changes quite consistent from year to year.
What changes?Sun angle, solar intensity, sunrise/sunset times, temperatures, humidity, cloud cover, precipitation, as well as wind speeds and prevailing direction for starters. One season may produce a larger amount of rain, while the next can be dry for instance. A brisk breeze may chime through the trees during the fall, and a sharp cold may nip our noses in the winter. At least somewhere. We may be subjected to severe thunderstorms, hurricanes, long days of rain, snow, drought and other adverse conditions, usually in their appropriate seasons.
Ultimately, all of this comes from the earth's rotation around the sun, the angle in which the planet tilts, and areas in most direct contact with the sun's rays. A region's proximity to the equator impacts the variability of conditions from one season to the next in addition to annual average temperatures. And, as people in temperate regions well know, seasons with longer days are generally warmer than those with shorter days.
We normally the first day of spring...Officially, we use the solstices and equinoxes to define the changing of the seasons. The equinox means that the day and night have an roughly equal amount of hours. It occurs at the instant the plane containing the earths equator passes through the centre of the sun, thus putting the sun from one celestial hemisphere into the other. The vernal equinox takes place when the sun moves from the southern hemisphere into the northern, and the autumnal equinox happens when the sun moves back south again, from a terrestrial perspective. They signal the beginning of spring and fall (in the northern hemisphere) respectively.
The two solstices occur when the sun has travelled as far as it will go any one direction and turns around to come back the other way, with the summer solstice in June and the winter solstice in December. They indicate the start of summer and winter respectively.
In conclusion, understand that each season we experience is directly related to many different things, but first of all the location and tilt at which the earth rests. These seasons normally bring about changes in weather (including day length, temperature, types and frequency of storms), and last approximately three months each. Why can we expect certain conditions and patterns at the same time each year? The reason for that is that while the earth moves about the sun, the tilt of the earth remains more-or-less consistent.
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