Weather and Climate

Our weather and climate dictates the types of lives we live, the homes we build, and the businesses we operate. Weather describes the day-to-day variations in our atmosphere. The variations are recorded by meteorologists as measurements of temperature, humidity, cloud cover, wind and precipitation. The source of our weather is the Sun. As the Earth spins on its axis at an angle of about 23½ degrees and orbits the Sun, the areas nearest the equators receive more intense radiation than those at the poles. Landmasses also absorb heat more quickly than do oceans. The atmosphere attempts to create a balance between these extremes by moving warm air from the equator to the poles, and by carrying cold air from the poles toward the equator. Through this process, air is redirected by the Earth's rotation, it is slowed down by friction with the land and sea, and is held within the confines of the atmosphere through gravity. These cycles and forces create complex and constantly changing weather patterns. Massive waves of air and clouds that can be thousands of miles wide circulate around the Earth creating areas of high and low-pressure in the atmosphere that result in our weather on the ground.

Another factor that affects our weather is the different properties between the land and ocean. The oceans absorb and release heat slowly, while landmasses heat up quickly during the day and cool rapidly at night. Because of these different properties there is a greater difference between day and night temperatures in coastal areas and inland areas. Land also reradiates heat more effectively than sea. Where there is sufficient moisture clouds will form more rapidly over land than over water.

Seasons also play a role in our weather. The amount of solar energy that reaches a particular area of the Earth determines the season. These variations in the amount of energy that reaches a particular area is due to the Earth's tilt, rotation and orbit around the Sun. It takes the Earth just over 365 days, or one calendar year, to orbit the Sun. The Earth spins on its axis and takes 24 hours to spin around once which creates our night and day. The fact that the Earth is tilted at about 23.5 degrees on its axis creates our seasons. As the Earth orbits the Sun, different areas of the planet are tilted toward the Sun so varying amounts of heat occur around the world at different times of the year. In the Northern Hemisphere, the North Pole is tilted away from the Sun in December, and less light reaches the hemisphere resulting in lower temperatures and shorter days. This creates their winter. While the Earth is continuing its orbit around the Sun, the North Pole begins to tilt toward the Sun. The Sun begins to rise higher in the sky which increases daylight. During the month of March day and night are equal. The amount of sunlight increases until the Sun reaches its maximum height in the sky which occurs on June 21- the summer solstice. At this time the Sun is directly overhead at the Tropic of Cancer and areas north of the Arctic Circle experience 24 hours of daylight. As the Earth continues its orbit around the Sun the North Pole begins to tilt away from the Sun once again. In September the autumnal equinox occurs and daylight begins to decrease until the winter solstice is reached on December 21. When the summer solstice occurs in the Northern Hemisphere, the winter solstice is occurring in the Southern Hemisphere and areas south of the Antarctic Circle have 24 hours of darkness. December 21 is the summer solstice in the Southern Hemisphere, and the Sun is directly overhead at the Tropic of Capricorn. In the Southern Hemisphere the spring equinox occurs in September, and the autumnal equinox in March.

The four seasons occur in the middle and high latitudes of the Earth where the greatest changes in Sunlight and heat occur. In the tropics the length of day and amount of Sunlight vary much less and the only two seasons are wet and dry. When the Sun is directly overhead storm activity and precipitation are at their highest. As this area of intense heat shifts from the Tropic of Cancer to the Tropic of Capricorn maximum rainfall moves with it. This results in the tropical areas receiving a distinct cycle of wet and dry seasons.