Preprints
https://doi.org/10.5194/egusphere-2024-471
https://doi.org/10.5194/egusphere-2024-471
23 Feb 2024
 | 23 Feb 2024

Variability and trends in the PV-gradient dynamical tropopause

Katharina Turhal, Felix Plöger, Jan Clemens, Thomas Birner, Franziska Weyland, Paul Konopka, and Peter Hoor

Abstract. The dynamical tropopause as a transport barrier between the tropical upper troposphere and extratropical lowermost stratosphere is characterized by steep gradients in potential vorticity (PV) along an isentropic surface. Hence, the latitudinal separation between the dynamical tropopause in the northern and southern hemispheres can be used as a metric of upper tropospheric width for assessing climate change impacts. Here, we obtain the PV gradient-based dynamical tropopause (PVG tropopause) from four meteorological satellite-era reanalyses (ERA5, ERA-Interim, JRA-55, MERRA-2) and investigate its climatology, variability and long-term trends ranging from 1980 to 2017. Our results show a distinct seasonal cycle with larger PV values and a poleward movement of the PVG tropopause in summer. The climatological tropopause PV values are substantially different between different reanalyses, but the tropopause latitude is similar. Significant inter-annual variability in the PVG tropopause latitude is related to El Niño Southern Oscillation (ENSO) and weaker variability also to the Quasi-Biennial Oscillation (QBO), and is consistently represented in reanalyses. In particular, El Niño causes equatorward shifts of the PVG tropopause, hence a decrease of upper tropospheric width. Long-term trends in the PVG tropopause over the period 1980–2017 exhibit a distinct vertical structure with poleward shifts below 340 K potential temperature, equatorward shifts between 340–370 K and poleward shifts between 370–380 K, implying an expansion of the troposphere at lower levels, a narrowing at upper levels and an expansion near the tropical tropopause.

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Katharina Turhal, Felix Plöger, Jan Clemens, Thomas Birner, Franziska Weyland, Paul Konopka, and Peter Hoor

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-471', Anonymous Referee #1, 01 Apr 2024
    • AC1: 'Reply on RC1', Katharina Turhal, 08 Jul 2024
  • RC2: 'Comment on egusphere-2024-471', Anonymous Referee #2, 26 Apr 2024
    • AC2: 'Reply on RC2', Katharina Turhal, 08 Jul 2024
Katharina Turhal, Felix Plöger, Jan Clemens, Thomas Birner, Franziska Weyland, Paul Konopka, and Peter Hoor

Data sets

PV-gradient (PVG) tropopause: Time series 1980--2017 in four reanalyses Katharina Turhal https://doi.org/10.5281/zenodo.10529153

Katharina Turhal, Felix Plöger, Jan Clemens, Thomas Birner, Franziska Weyland, Paul Konopka, and Peter Hoor

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Short summary
The tropopause separates the troposphere, the lowest atmospheric layer where weather occurs, from the stratosphere. We computed the PV-gradient (PVG) tropopause, which is based on transport barriers between both layers. In 1980–2017, the PVG tropopause shifted poleward at lower altitudes and equatorward above. These shifts may signify height-dependent changes in atmospheric transport, influencing the distribution of pollutants and, e.g., greenhouse gases responsible for global warming.