Description

The impact on aviation of increasing water vapour concentrations in the stratosphere, linked to climate change, have yet to be fully understood. This article explains the phenomenon of convective overshooting of the tropical tropopause layer (TTL) and associated hydration of the lower stratosphere, the terminology, and links to other SKYbrary relevant content.

Tropical Tropopause Layer (TTL)

The TTL is a transition layer in the tropics between the troposphere, where temperature decreases with height, and the stratosphere, where temperature increases with height. The TTL is important as a gateway to the wider stratosphere. 

Cold point tropopause (CPT)

The cold point tropopause is the point in the atmosphere where the temperature reaches its lowest value as air ascends from the troposphere into the stratosphere. The CPT is important because it is where air from the tropopause undergoes final dehydration before entering the stratosphere. The very low temperatures at the tropical CPT reduce water vapour concentration to a few parts per million.