EGU23-9439, updated on 06 Nov 2023
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

A Modern Approach to a Stability-Based Definition of the Tropopause

Emily Tinney1, Cameron Homeyer1, Lexy Elizalde2, Dale Hurst3,4, Anne Thompson5,6, Ryan Stauffer5, Holger Vömel7, and Henry Selkirk8,9
Emily Tinney et al.
  • 1School of Meteorology, University of Oklahoma, Norman, Oklahoma, United States of America (
  • 2South Dakota School of Mines and Technology, Rapid City, South Dakota, United States of America
  • 3Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, Colorado, United States of America
  • 4NOAA/Global Monitoring Laboratory, Boulder, Colorado, United States of America
  • 5NASA Goddard Space Flight Center, Greenbelt, Maryland, United States of America
  • 6Joint Center for Environmental Systems Technology, University of Maryland, Baltimore County, Baltimore, Maryland, United States of America
  • 7National Center for Atmospheric Research, Boulder, Colorado, United States of America
  • 8Earth Science Division, NASA Headquarters, Washington, D.C., United States of America
  • 9Agile Decision Sciences, LLC, Beltsville, Maryland, United States of America

Definition of the tropopause has remained a focus of atmospheric science since its discovery near the beginning of the twentieth century. An accurate identification of the tropopause is a vital component to upper troposphere and lower stratosphere research, especially for studies that seek to assess and quantify the two-way exchange of air across the tropopause, which in turn impacts our understanding and prediction of Earth’s radiation budget and climate. Few universal definitions (those that can be reliably applied globally and to both common observations and numerical model output) exist and many definitions with unique limitations have been developed over the years. The most commonly used universal definition of the tropopause is the temperature lapse-rate definition established by the World Meteorological Organization (WMO) in 1957 (the LRT). Despite its widespread use, there are recurrent situations where the LRT definition fails to reliably identify the tropopause. Motivated by increased availability of coincident observations of stability and composition, we reexamine the relationship between stability and composition change in the tropopause transition layer and identify areas for improvement in a stability-based definition of the tropopause. Six locations with long-term (up to 40+ years) balloon observations of temperature, ozone, and water vapor were selected for analysis to offer a variety of environments, including tropical, subtropical, extratropical, and polar environments. Data from these sites are then used to identify covariability between several metrics of atmospheric stability and composition. We show that the vertical gradient of potential temperature is a superior stability metric to identify the greatest composition change in the tropopause transition layer, which we use to propose a new universally applicable potential temperature gradient tropopause (PTGT) definition. A comparison of the PTGT and LRT applied to both observations and reanalysis output will be shown. Overall, our results reveal that the PTGT largely agrees with the LRT, but more reliably identifies tropopause-level composition change when the two definitions differ greatly.

How to cite: Tinney, E., Homeyer, C., Elizalde, L., Hurst, D., Thompson, A., Stauffer, R., Vömel, H., and Selkirk, H.: A Modern Approach to a Stability-Based Definition of the Tropopause, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9439,, 2023.