Question

what is meant by normal lapse rate

Answer 1

In lapse rate. …air—commonly referred to as the normal, or environmental, lapse rate—is highly variable, being affected by radiation, convection, and condensation; it averages about 6.5 °C per kilometre (18.8 °F per mile) in the lower atmosphere (troposphere).

Answer 2

In troposphere temperature decreases at an average rate of 6.4°C for every 1000m ascent.This is called normal lapse rate.