Downward wave coupling between the stratosphere and troposphere under future anthropogenic climate change

Sandro W. Lubis*, Katja Matthes, Nili Harnik, Nour Eddine Omrani, Sebastian Wahl

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Downward wave coupling (DWC) is an important process that characterizes the dynamical coupling between the stratosphere and troposphere via planetary wave reflection. A recent modeling study has indicated that natural forcing factors, including sea surface temperature (SST) variability and the quasi-biennial oscillation (QBO), influence DWC and the associated surface impact in the Northern Hemisphere (NH). In light of this, the authors further investigate how DWC in the NH is affected by anthropogenic forcings, using a fully coupled chemistry-climate model CESM1(WACCM). The results indicate that the occurrence of DWC is significantly suppressed in the future, starting later in the seasonal cycle, with more events concentrated in late winter (February and March). The future decrease in DWC events is associated with enhanced wave absorption in the stratosphere due to increased greenhouse gases (GHGs), which is manifest as more absorbing types of stratospheric sudden warmings (SSWs) in early winter. This early winter condition leads to a delay in the development of the upper-stratospheric reflecting surface, resulting in a shift in the seasonal cycle of DWC toward late winter in the future. The tropospheric responses to DWC events in the future exhibit different spatial patterns, compared to those of the past. In the North Atlantic sector, DWC-induced circulation changes are characterized by a poleward shift and an eastward extension of the tropospheric jet, while in the North Pacific sector, the circulation changes are characterized by a weakening of the tropospheric jet. These responses are consistent with a change in the pattern of DWC-induced synoptic-scale eddy-mean flow interaction in the future.

Original languageEnglish
Pages (from-to)4135-4155
Number of pages21
JournalJournal of Climate
Volume31
Issue number10
DOIs
StatePublished - 1 May 2018

Funding

FundersFunder number
German–Israeli Foundation for Scientific Research and DevelopmentGIF1151-83.8/2011
Helmholtz University
International Meteorological Institute
German-Israeli Foundation for Scientific Research and Development
GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
Stockholms Universitet
Helmholtz Association

    Keywords

    • Atmospheric circulation
    • Climate change
    • Coupled models
    • Planetary waves
    • Stratosphere-troposphere coupling
    • Stratospheric circulation

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