Why does the tropopause stop the environmental lapse rate?
It doesn’t. The first thing to remember is that the tropopause is just the name for a notional boundary in the atmosphere. As air rises through the atmosphere it cools at a standard rate, approximately 6.8 degrees for every 1Km in height. The tropopause lies at the point where the heat of the rising air matches the heat of the surrounding atmosphere. This is known as the Equilibrium level. In meteorology, the equilibrium level (EL), or level of neutral buoyancy (LNB), is the height at which a rising parcel of air is at a temperature of equal warmth to it. This means that unstable air is now stable when it reaches the equilibrium level and convection stops. This level is often near the tropopause and can be indicated as the anvil of a thunderstorm due to the fact that it is where the thunderstorm updraft is usually cut off, except in the case of overshooting tops.
