The Troposphere

You, along with many other living things, live in the layer of the atmosphere called the troposphere. The troposphere (TROH puh sfeer) is the lowest layer of Earth's atmosphere. This layer contains almost all of the atmosphere's water vapor and suspended particles, which are important in the formation of clouds and precipitation. Most weather takes place in the troposphere. Weather is the condition of the atmosphere in a particular place at a particular time.

The height of the troposphere ranges from about 9 kilometers above the poles to 16 kilometers above the tropics. The average height of the troposphere is about 12 kilometers.

In the troposphere, temperature generally decreases as altitude increases. Though it varies somewhat, the rate of decrease averages about 6.5 Celsius degrees per kilometer. For example, if it is 20°C where you are on Earth's surface, then it is probably about 7°C at an altitude of 2 kilometers above you. This characteristic of the troposphere accounts for the extremely low temperatures that Hillary and Tenzing had to withstand when they scaled Mount Everest.

Figure 4 Barometers measure air pressure. A Changes in air pressure cause the airtight chamber of this aneroid barometer to flex in and out. B Changes in air pressure cause the level of mercury in the open glass tube of this antique mercury barometer to move up or down.