Tropopause inversion layer and its correlation with relative humidity

To better understand our climate and weather system, knowledge of the processes in the upper troposphere and lower stratosphere (UTLS) is crucial.

An important element in the UTLS region is the tropopause inversion layer (TIL). The TIL is a region of extraordinarily high or overshooting static stability just above the tropopause. Since its discovery, a couple of hypothesis were developed to explain the origin and formation of the TIL. In addition to dynamic mechanisms, such as baroclinic waves, a radiative forcing mechanism is considered, where ozone and water vapor are contributing to the TIL formation and persistence.

To investigate the latter mechanism further, we examine the correlation between the relative humidity with respect to ice, as a measure for water vapor in the UTLS region, and the TIL.

Based on high-resolution radiosonde data of the German Weather Service (DWD) from 2011 to 2019, we are investigating how TIL properties such as the height, strength or thickness of the TIL layer change with temperature and relative humidity over ice. We also investigate seasonal differences of the above-mentioned properties. Furthermore, the results are also compared with ERA5 reanalysis data. We can show that ERA5 can reproduce relevant properties of the TIL as compared to the radiosondes. Thus, ERA5 data can be used for extending the investigations to other geographical locations.