21 Nov 2023
 | 21 Nov 2023
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

The extratropical tropopause inversion layer and its correlation with relative humidity

Daniel Köhler, Philipp Reutter, and Peter Spichtinger

Abstract. This study investigates the influence of relative humidity with respect to ice on the extratropical tropopause inversion layer (TIL). Initially, measurements from radiosondes at a location in Germany were compared with the ERA5 reanalysis data from the ECMWF at the same geographic location. A high level of agreement was observed, with the expected limitation that ERA5 cannot resolve sharp changes in variables like humidity and stability at the tropopause as finely.

When examining the TIL with respect to mean relative humidity over ice in the upper troposphere, a clear relationship with stability becomes evident. Moister profiles, on average, exhibit significantly higher maximum values of the Brunt-Väisälä frequency N 2, indicating a more stable stratification of the tropopause in these cases. This result holds true in both radiosonde measurements and ERA5 data. Considering the thickness of the TIL layer, an inverse pattern emerges. In this case, moister and more stable TILs exhibit a lower thickness.

The strong agreement between radiosondes and ERA5 allows for geographical and seasonal analyses using ERA5 data alone. These analyses reveal consistent relationships in various extratropical regions of the Northern Hemisphere under different meteorological conditions. Differences in the strength of the dependence of TIL properties on relative humidity over ice are evident.

Daniel Köhler et al.

Status: open (until 02 Jan 2024)

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  • RC1: 'Comment on egusphere-2023-2440', Anonymous Referee #1, 08 Dec 2023 reply

Daniel Köhler et al.

Daniel Köhler et al.


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Short summary
In this work, the influence of humidity on the properties of the tropopause is studied. The tropopause is the interface between the troposphere and the stratosphere and represents a barrier for the transport of air masses between the troposphere and the stratosphere. We consider not only the tropopause itself, but a layer around it called the tropopause inversion layer (TIL). It is shown that the moister the underlying atmosphere, the stronger this layer acts as a barrier.