Representation, evolution and validation of the stratopause and stratospheric contraction in reanalyses data

Recent work using models from the Chemistry-Climate Model Initiative shows that the stratopause is descending and that the stratosphere has contracted substantially over the last decades, being the increasing concentrations of greenhouse gases (GHGs) the main driver. This stratospheric contraction is not a mere response to stratospheric cooling, as changes in both tropopause and stratopause pressure contribute significantly to it.

Here we present the evolution over the last decades of the stratopause and stratospheric thickness in the main reanalyses datasets: MERRA-2, JRA-55, and ERA5.1. We compare them to model results with WACCM-X and satellite observations (GOMOS, MLS and SABER). For our computations, we consider the discontinuity problems in temperature at stratopause heights suitable to affect its structure and behaviour due to the assimilation of new observational data as they become available.

Our results show that there is high variability in the percentages of stratopauses and their height, a significant dependence on the latitude and dataset for the stratopause height and limitations of JRA-55 to represent elevated stratopause cases (probably linked to sudden stratospheric warnings) over the polar regions because of its low-top compared to other reanalyses.