Lapse Rate or Cold Point: The Tropical Tropopause Identified by In Situ Trace Gas Measurements

Although the tropopause is a well-established concept, its definition and physical properties remain an active research topic. In the tropics, both the World Meteorological Organization established lapse rate tropopause definition and the minimum in the temperature profile (the cold point) are used to determine the tropopause height. We examine the differences produced by these two definitions using high-resolution airborne in situ measurements of temperature, water vapor, and ozone in the tropical tropopause layer from a recent experiment over the western Pacific using the National Aeronautics and Space Administration (NASA) Global Hawk unmanned aircraft system. When the two definitions do not produce the same tropopause height, which is in about half of the cases, the combined temperature and trace gas analysis shows that the lapse rate definition better identifies the transition from the troposphere to the stratosphere.