In meteorology, what does the term 'lapse rate' refer to?

The term 'lapse rate' in meteorology specifically refers to the rate at which temperature decreases with an increase in altitude. This phenomenon occurs because, as you ascend through the layers of the atmosphere, the air becomes less dense and, therefore, cannot hold heat as effectively. The average lapse rate in the troposphere is approximately 6.5 degrees Celsius per kilometer. Understanding the lapse rate is crucial for applications such as weather forecasting and aviation safety, as it affects air stability and the potential for cloud formation.

In contrast to the correct answer, the other options describe different atmospheric characteristics: the rate of temperature increase with altitude represents an inversion situation rather than a lapse rate; the rate at which pressure decreases with altitude refers to the barometric formula and atmospheric pressure changes; and the rate of humidity change with altitude pertains to moisture content in the air, which is a separate concept from the temperature lapse rate.