Weather basics

Our daily weather—warm, sunny, windy, cold, rainy, snowy—is dependent on many factors in the earth’s atmosphere. The atmosphere surrounds Earth, going up for more than 300 miles until it blends in with space. This protective atmosphere has five layers, including the stratosphere, which uses ozone to absorb ultraviolet radiation from the sun before it reaches Earth.

The layer closest to Earth is called the troposphere and contains 80% of the gases (such as nitrogen and oxygen) that are in the atmosphere. It also contains water vapor, or water in its gas state (like steam), which can form clouds. The temperature in the troposphere decreases with height, so weather at the top of this layer will be much colder.

Weather can change rapidly just from day to day, but we usually notice the biggest changes with each season. Did you realize that in winter, the sunlight reaching Earth is weaker than in summer? This is because the light is less direct: it reaches the earth at an angle. You can demonstrate this with a ball and a flashlight to represent the earth and sun.

Hold the flashlight so its beam shines straight down on the ball. Note what the spot of light looks like on the “earth.” Now, bring the light down so that it hits the ball at an angle. What does the light spot look like now? The area of the spot expands, but the light is not as strong as it was with the more direct beam. The difference between winter and summer light is caused in the same way, by the angle of the sun and earth.

In addition, the days are shorter in winter, allowing less time for sunlight to heat up the earth, whereas the long summer days allow much more heat to penetrate.

Climate is based on the average weather in an area over a long period of time, and therefore is fairly unchanging—unlike the daily weather. The main types of climate are polar, desert, tundra, tropical, equatorial, Mediterranean, temperate, and continental.

Tropical regions are warm year-round and have a wet and dry season; equatorial regions are always warm and moist, providing ideal rainforest conditions. Temperate regions are generally cool year-round; continental regions are hot in summer and cold in winter.

Both of these climates can be found in the northern regions of the Unites States. Polar climates are so cold and dry that little plant life can grow there; plants in the desert, however, are specially designed to store water so that they can survive off of little rainfall. Tundra regions have strong winds and low winter temperatures.