Signatures of Anomalous Transport in the 2019/2020 Arctic Stratospheric Polar Vortex

Abstract

The exceptionally strong and long‐lived Arctic stratospheric polar vortex in 2019/2020 resulted in large transport anomalies throughout the fall‐winter‐spring period from vortex development to breakup. These anomalies are studied using Aura MLS N2O, H2O, and CO long‐lived trace gas data, ACE‐FTS CH4 data, and meteorological and trace gas fields from reanalyses. Anomalies are strongest throughout the winter in the lower through the middle stratosphere (from about 500K through 700K), with record low (high) departures from climatology in N2O and CH4 (H2O). CO shows extreme high anomalies in midwinter through spring down to about 550K. Descent rates, vortex confinement, and trace gas distributions in the preceding months indicate that early winter anomalies in N2O and H2O arose primarily from entrainment of air with already‐anomalous values into the vortex as it developed in fall 2019 followed by descent of those anomalies to lower levels within the vortex. Trace gas anomalies in midwinter through the late vortex breakup in spring 2020 arose primarily from inhibition of mixing between vortex and extravortex air because of the exceptionally strong and persistent vortex. Persistent strong N2O and H2O gradients across the vortex edge demonstrate that air within the vortex and its remnants remained very strongly confined through late April (mid‐May) in the middle (lower) stratosphere. These results are important for understanding the evolution of trace gas distributions, which affects both polar chemical processing and radiative processes related to climate.

Introduction to Special Collection “The Exceptional Arctic Stratospheric Polar Vortex in 2019/2020: Causes and Consequences”

“…Also critical to polar processing and ozone loss is the degree of confinement of air that is primed for ozone depletion inside the polar vortex, and how it is transported within the vortex. In addition to the metrics already discussed of exceptional polar vortex strength and longevity (Figures 1e and 1f; Lawrence et al, 2020;Manney et al, 2020, also show diagnostics that are indicative of unusually low mixing), Manney, Millán, et al (2022) discussed the unusual transport throughout the 2019/2020 winter, showing that, in early winter, unusual long-lived trace gas distributions arose primarily from descent of preexisting anomalies entrained into the vortex as it formed, whereas springtime trace gas anomalies arose primarily from inhibited mixing into the polar regions related to the late polar vortex breakup. Further, Curbelo et al (2021) explored aspects of the evolution of and transport within the polar vortex during a vortex-split event in the lower to middle stratosphere in the period preceding the springtime vortex breakup.…”

“…In addition to the metrics already discussed of exceptional polar vortex strength and longevity (Figures 1e and 1f; Lawrence et al., 2020; Manney et al., 2020, also show diagnostics that are indicative of unusually low mixing), Manney, Millán, et al. (2022) discussed the unusual transport throughout the 2019/2020 winter, showing that, in early winter, unusual long‐lived trace gas distributions arose primarily from descent of preexisting anomalies entrained into the vortex as it formed, whereas springtime trace gas anomalies arose primarily from inhibited mixing into the polar regions related to the late polar vortex breakup. Further, Curbelo et al.…”

“…Studies in this special collection focusing on observations and/or modeling of chemical ozone loss in the Arctic in 2019/2020 use satellite data sets including those from: the Aura Microwave Limb Sounder (MLS) (Feng et al., 2021; Grooβ & Müller, 2021; Manney, Millán, et al., 2022; Manney et al., 2020; Wohltmann et al., 2020, 2021), the Atmospheric Chemistry Experiment‐Fourier Transform Spectrometer (Bognar et al., 2021; Grooβ & Müller, 2021; Manney et al., 2020), the Aura Ozone Monitoring Instrument (Bernhard et al., 2020), the TROPOspheric Monitoring Instrument, the Global Ozone Monitoring Experiment‐2, the SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY, and the Ozone Mapping and Profiler Suite—Limb Profiler (last four by Weber et al., 2021). In addition, several studies use ground‐and/or balloon‐based data sets (Bognar et al., 2021; Wohltmann et al., 2020).…”

M2‐SCREAM: A Stratospheric Composition Reanalysis of Aura MLS Data With MERRA‐2 Transport

“…(2022) utilized the high horizontal resolution of the M2‐SCREAM water vapor and N 2 O fields to analyze complex transport patterns during the Arctic stratospheric polar vortex breakup in the spring of 2020. Our comparisons of M2‐SCREAM against GLORIA and FPH data (Section 6.1) demonstrate the utility of the reanalysis for studies of small‐scale (∼1 km) vertical structures important for furthering our understanding of the UTLS. Consistency between the tracer fields and assimilated meteorological data allows a comprehensive view of dynamics and transport on scales ranging from decades (Section 6.5) to hours (Manney et al., 2022). It can also elucidate relations between composition, temperature and dynamics.…”

“…Consistency between the tracer fields and assimilated meteorological data allows a comprehensive view of dynamics and transport on scales ranging from decades (Section 6.5) to hours (Manney et al., 2022). It can also elucidate relations between composition, temperature and dynamics.…”