Within the troposphere, temperature generally decreases with altitude. This is due to the fact that Earth’s lower atmosphere is heated significantly by terrestrial radiation.
The standard lapse rate is 1.98°C / 1,000 feet, however, the actual lapse rate may be greater or less than the standard one. A pilot should familiarize themselves with the following types of lapse rates, they will be discussed in more detail in upcoming lessons:
- Environmental Lapse Rate: The environmental lapse rate (ELR), is the rate of decrease of temperature with altitude in the stationary atmosphere at a given time and location.
- Dry Adiabatic Lapse Rate: The lapse rate for a dry atmosphere, which may contain water vapour but which has no liquid moisture present in the form of fog, droplets, or clouds.
- Wet Adiabatic Lapse Rate: The lapse rate for a wet atmosphere, which may contain water vapour and visible moisture in the form of fog, droplets, or clouds.