The tropopause is the boundary region between the troposphere and the stratosphere. Atop the troposphere is the tropopause, which is the border between the troposphere and stratosphere. The border between the troposphere and stratosphere, the tropopause, marks where this temperature inversion begins. It lies above the troposphere and is separated from it by the tropopause. These experiments led to his discovery of the tropopause and stratosphere. Smaller-scale explosions penetrating the tropopause generate waves of higher frequency, classified as infrasound. Methane is transported through the cold trap at the tropopause. The boundary between the two, the tropopause, lies at a pressure of . This water is often above the tropopause where little water usually reaches. The tropopause is not a "hard" boundary. At the tropopause, the cloud shape is roughly circular and spread out. The Tropopause represents high-altitude. Often this 'cap' is the tropopause. It is also possible to define the tropopause in terms of chemical composition. The craft was used in a year 2014 "Airborne Tropical Tropopause Experiment".