Weather Theory

22 77 11 88 %% %% nn ee gg oo NNii tt rr OO xx yy gg ee nn Atmosphere The atmosphere is a blanket of air made up of a mixture of 1% gases that surrounds the Earth and reaches almost 350 miles from the surface of the Earth. This mixture is in constant motion. If the atmosphere were visible, it might look like an ocean with swirls and eddies, rising and falling air, and waves that travel for great distances. Life on Earth is supported by the atmosphere, solar energy, and the planet’s magnetic fields. The atmosphere absorbs energy from the sun, recycles water and other chemicals, and works with the electrical and magnetic forces to provide a moderate climate. The atmosphere also protects life on Earth from high energy radiation and the frigid vacuum of space. Figure 12-1. Composition of the atmosphere. Composition of the Atmosphere In any given volume of air, nitrogen accounts for 78 percent atmosphere have been identified using thermal characteristics of the gases that comprise the atmosphere, while oxygen (temperature changes), chemical composition, movement, makes up 21 percent. Argon, carbon dioxide, and traces and density. [Figure 12-2] of other gases make up the remaining one percent. This volume of air also contains some water vapor, varying from The first layer, known as the troposphere, extends from 6 zero to about five percent by volume. This small amount of to 20 kilometers (km) (4 to 12 miles) over the northern and water vapor is responsible for major changes in the weather. southern poles and up to 48,000 feet (14.5 km) over the [Figure 12-1] equatorial regions. The vast majority of weather, clouds, storms, and temperature variances occur within this first The envelope of gases surrounding the Earth changes layer of the atmosphere. Inside the troposphere, the average from the ground up. Four distinct layers or spheres of the temperature decreases at a rate of about 2 °Celsius (C) every Thermosphere 280,000 feet Mesosphere 160,000 feet Stra T t r o o s p p o h s e p r h e ere 20,000 feet Figure 12-2. Layers of the atmosphere.