ORCID
https://orcid.org/0009-0009-8793-8125
Date of Award
Spring 2025
Language
English
Embargo Period
4-22-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
College/School/Department
Department of Atmospheric and Environmental Sciences
Program
Atmospheric Science
First Advisor
Andrea Lopez Lang
Committee Members
Ryan Torn, Brian Rose, Steven Cavallo
Subject Categories
Atmospheric Sciences
Abstract
Variability in the high-latitude wintertime stratospheric flow, often referred to as the stratospheric polar vortex, can precede anomalous conditions in tropospheric flow on subseasonal-to-seasonal (S2S) timescales and impact surface weather. The range of stratospheric impacts on tropospheric conditions range from shifts in the North Atlantic storm tracks, formation of cold spells, and development of extreme precipitation. Impacts of stratospheric variability are known to persist for up to 60 days, providing ample windows of opportunity in forecasting on S2S timescales. This dissertation focuses on the stratospheric impacts on tropopause-level processes, such as Rossby wave breaking (RWB) events and tropopause polar vortices (TPVs), to improve understanding of the processes involved in the communication of stratospheric anomalies below the tropopause.
RWB represents nonlinear mixing of stratospheric and tropospheric air masses, and often is a precursor to high-impact weather in the troposphere. Eddy momentum fluxes associated with RWB are known to displace the regions of accelerated flow in the troposphere. Stratospheric variability has been shown to change the life cycles of Rossby waves, but it is not clear to what effect changes in RWB lifecycles promote meridional displacements in extratropical jets. This dissertation examines the role of stratosphere-induced RWB changes on meridional displacements in the extratropical jet, specifically in the North Atlantic region. Anticyclonic RWB events, associated with positive momentum fluxes, were most frequently found over Eurasia after strong vortex events. Meanwhile, cyclonic RWB events, associated with negative momentum fluxes, increased in the North Atlantic after weak vortex events. Stratosphere- induced RWB changes are found to enhance displacements in the North Atlantic jet position, iii where increased AWB frequencies in strong vortex events shift the North Atlantic jet poleward and increased CWB frequencies in weak vortex events shift the North Atlantic jet equatorward.
TPVs are long-lived, (i.e., weeks), tropopause-based cyclonic features that exist within the high-latitude regions. TPVs are frequently removed from the Arctic in cases of highly amplified midlatitude flow, allowing for the creation or intensification of surface cyclones and accelerations in the midlatitude jet stream. Given the overlapping effects of TPVs and stratospheric variability, it is hypothesized that the characteristics of TPVs can be impacted in periods of extreme stratospheric variability. While TPV characteristics, such as average lifetime, size, and amplitude remained consistent between all periods of stratospheric variability, the tracks of TPVs were found to be sensitive to precursor stratospheric strength. Specifically, the highest amplitude TPVs were most frequently observed poleward of the North Atlantic jet after strong vortex events, while TPV frequency decreased in the same domain after weak vortex events.
To better understand the joint effects of stratospheric variability, RWB and TPVs on tropopause level flow in the North Atlantic, a composite analysis was conducted. However, the climatological relationships between stratospheric variability, RWB, and TPVs are hard to discern. In comparing case studies of the 2018 SSW and 2020 strong vortex event, it is evident that TPVs act to enhance the zonal components of the flow in strong vortex events, and enhance the meridional component of the flow in weak vortex events. RWB processes then evolve in response to the strengthened or weakened states of North Atlantic flow. This dissertation concludes that variability in stratospheric polar vortex conditions impact synoptic-scale processes on the tropopause, and these processes can lead to variability in North Atlantic flow regimes on subseasonal-to-seasonal timescales.
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Paquette, Cameron R., "The Response of Tropopause Phenomena to Stratospheric Variability: Rossby Wave Breaking and Tropopause Polar Vortices" (2025). Electronic Theses & Dissertations (2024 - present). 130.
https://scholarsarchive.library.albany.edu/etd/130
