Atmospheric Temperature

Averaging atmospheric temperatures over all latitudes and across an entire year gives us the average vertical temperature profile. This plot is sometimes called a standard atmosphere. The average vertical temperature profile suggests four distinct layers (Figure 1). In the first layer, called the troposphere, average atmospheric temperature drops steadily from its value at the surface, about 290K (63°F; 17°C) until it reaches of minimum of around 220K (−64°F; −53°C) at a level about 6.2 mi (10 km) high. This level, known as the tropopause, is just above the cruising altitude of large commercial jet aircraft. The drop of temperature with height, called the lapse rate, is nearly steady throughout the troposphere at 43.7°F (6.5°C) per 0.6 mi (1 km). At the tropopause, the lapse rate abruptly shrinks to very low values. Atmospheric temperature is roughly constant over the next 12 mi (20 km), then begins to rise with increasing altitude up to about 31 mi (50 km). This region of increasing temperatures is the stratosphere. At the top of the layer, called the stratopause, temperatures are nearly as warm as the surface values. Between about 31–50 mi (50–80 km) lies the mesosphere, where atmospheric temperature resumes its drop with altitude and reaches a very cold minimum of 180K (−136°F; −93°C) at the top of the layer (the mesopause), around 50 mi (80 km). Above the mesopause is the thermosphere, which as its name implies is a zone of high gas temperatures. In the very high thermosphere (about 311 mi (500 km) above Earth's surface) gas temperatures can reach from 500–2,000K (441–3,141°F; 227–1,727°C), depending on how active the sun is. However, these figures are somewhat misleading. Temperature is a measure of the energy of the gas molecules' motion. Although they have high energies, the molecules in the thermosphere are present in very low numbers, less than one millionth of the amount present on average at Earth's surface. If a person were in the thermosphere, it would feel to them much more like the icy cold of space because such a small number of energetic gas molecules would be unable to transfer much of their heat energy.

To add more information to the temperature graph, one can plot atmospheric temperature as a function of both latitude and altitude. Figures 2 and 3 show such plots, with latitude as the x coordinate and altitude as the y.