The decrease in temperature with an increase in altitude is primarily due to the way air interacts with the atmosphere and the distribution of heat within it. This phenomenon is known as the lapse rate.
1. Adiabatic Cooling: As air rises higher in the atmosphere, it expands due to the decrease in atmospheric pressure at higher altitudes. As the air expands, it does work against the surrounding air molecules, leading to a decrease in its temperature. This process, known as adiabatic cooling, causes the air to cool approximately 1°C per 100 meters (or 5.4°F per 1000 feet) of ascent, referred to as the dry adiabatic lapse rate.
2. Heat Transfer: Another reason for the decrease in temperature with altitude is the diminishing effect of the ground on the air. Near the surface, the air is in direct contact with the warmed Earth, absorbing heat through conduction and convection. As you ascend, the air loses this direct contact with the warm surface, leading to a decrease in temperature.
3. Radiative Cooling: Additionally, at higher altitudes, there's less atmospheric mass above, which means there's less air to absorb and retain heat. Consequently, the radiative cooling effect increases as altitude rises, contributing to lower temperatures.
These factors combined lead to a consistent decrease in temperature with an increase in altitude throughout most of the Earth's atmosphere. However, in certain atmospheric layers, like the stratosphere, temperatures might increase with altitude due to the absorption of solar radiation by ozone molecules. This creates a temperature inversion, where the usual decrease in temperature with altitude temporarily reverses.
