Dr. Felix Plöger – Stratospheric Water Vapor – Low Concentrations but Strong Impacts

CESOC continues the seminar series “My Research” this Winter term 2023/24 with

Dr. Felix Plöger

from the Institute of Energy and Climate Research (IEK), Jülich Research Centre,
talking on their work

“Stratospheric Water Vapor – Low Concentrations but Strong Impacts”

Read the Abstract below

Date: 12 January 2024
Time: 15:30 CEST
Place: Online

The talk lasts about 30 minutes with the possibility to ask questions afterwards.
It will be held via Zoom and is open to any interested person within the CESOC research disciplines (any Earth system sciences, mathematics or computer science).
Please contact info[@]cesoc.net, if you would like to participate.

Full Schedule could be found here

Stratospheric Water Vapor – Low Concentrations but Strong Impacts
Felix Plöger
Institute for Energy and Climate Research: Stratosphere (IEK–7), Forschungszentrum Jülich, Jülich, Germany;
Institute for Atmospheric and Environmental Research, University of Wuppertal, Wuppertal, Germany

Water vapor plays an important role in many aspects of the climate system, by affecting
radiation, cloud formation, atmospheric chemistry and dynamics. Even the low stratospheric
water vapor content induces an important climate feedback. In this presentation, I report crucial
sensitivity of the atmospheric circulation in the stratosphere and troposphere to the abundance
of water vapor in the lowermost stratosphere. First, I review the processes controlling the
concentrations of stratospheric water vapor, its long-term changes and shorter-term variability,
such as caused by the recent Hunga-Tonga eruption. In particular, I investigate the model
representation of stratospheric water vapor and show that current climate models simulate
substantial moist biases in the lowermost stratosphere. These prevailing stratospheric moist
biases in current models are likely caused by the model transport scheme, and can be
significantly reduced by employing a less diffusive Lagrangian scheme. Based on a mechanistic
climate model experiment and inter-model variability I further show that, in general, increases in
lowermost stratospheric water vapor decrease local temperatures, and thereby cause an upward
and poleward shift of subtropical jets, a strengthening of the stratospheric circulation and a
poleward shift of the tropospheric eddy-driven jet. Furthermore, also regional water vapor
increases, like a common moist bias above the Pacific in climate models, may affect regional
circulation systems and may cause an eastward shift of the upper-level Asian monsoon
circulation and a strengthening of the Pacific westerly ducts. Overall, the effects of stratospheric
moist biases in current models on atmospheric circulation are of similar magnitude as climate
change effects. Hence, lowermost stratospheric water vapor exerts a first order effect on
atmospheric circulation and improving its representation in models offers promising prospects for
future research.