Twenty-first century trends in mixing barriers and eddy transport in the lower stratosphere



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Ábalos Sánchez, Marta and Cámara Illescas, Álvaro de la (2020) Twenty-first century trends in mixing barriers and eddy transport in the lower stratosphere. Geophysical research letters, 47 (21). ISSN 0094-8276

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Future trends in isentropic mixing in the lower stratosphere remain largely unexplored, in contrast with other aspects of stratospheric tracer transport. This study examines trends in effective diffusivity κ_(eff), a measure of the potential of the flow to produce isentropic mixing, in recent chemistry-climate model simulations. The results highlight substantial reduction of κ_(eff) in the upper flanks of the subtropical jets from fall to spring, which are strengthened in response to greenhouse gas increases. This contrasts with stronger eddy transport, associated with increased wave drag in the region, peaking in summer near the critical lines. The key role of changes in tracer meridional gradients in addition to transport barriers for isentropic mixing trends is evidenced. The projected ozone recovery leads to enhanced κ_(eff) in polar austral spring and summer, associated with a weaker and shorter-lived austral polar vortex by the end of the 21st century.

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© 2020 American Geophysical Union. We acknowledge insightful comments from Hella Garny and an anonymous reviewer that have helped improve the paper. This study has been funded by the Spanish Ministry of Science and Innovation under grants CGL2017-83198-R (STEADY) and PID2019-109107GB-I00 (DYNWARM) and by the Santander-UCM grant PR87/19-22679 (STRATWARS). MA is supported by the Program Atracción de Talento de la Comunidad de Madrid (2016-T2/AMB-1405). We are thankful to D. Kinnison (NCAR) for carrying out the WACCM simulations. The authors acknowledge support from NCAR and CISL high-performance computing (HPC) systems.

Uncontrolled Keywords:Brewer-Dobson circulation; Parameterization; Troposphere; Decline
Subjects:Sciences > Physics > Atmospheric physics
ID Code:63609
Deposited On:22 Jan 2021 13:14
Last Modified:25 Jan 2021 11:57

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