Interannual variability in effective diffusivity in the upper troposphere/lower stratosphere from reanalysis data

Ábalos, Marta; Legras, Bernard; Shuckburgh, Emily

doi:10.1002/qj.2779

Cited by 37 publications

(55 citation statements)

References 54 publications

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“…The isentropic mixing trends seen in JRA‐55 and in the model imply an upward shift in the region of isentropic mixing due to the enhanced EP flux propagation into the stratosphere (Figure ). Our sensitivity runs with fixed ODS demonstrate that the observed trends in austral winter isentropic mixing are caused by the ozone hole, as previously hypothesized in Abalos et al ().…”

Section: Antarctic Ozone Depletion Impact On the Bdcsupporting

confidence: 86%

New Insights on the Impact of Ozone‐Depleting Substances on the Brewer‐Dobson Circulation

et al. 2019

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It has recently been recognized that, in addition to greenhouse gases, anthropogenic emissions of ozone‐depleting substances (ODS) can induce long‐term trends in the Brewer‐Dobson circulation (BDC). Several studies have shown that a substantial fraction of the residual circulation acceleration over the last decades of the twentieth century can be attributed to increasing ODS. Here the mechanisms of this influence are examined, comparing model runs to reanalysis data and evaluating separately the residual circulation and mixing contributions to the mean age of air trends. The effects of ozone depletion in the Antarctic lower stratosphere are found to dominate the ODS impact on the BDC, while the direct radiative impact of these substances is negligible over the period of study. We find qualitative agreement in austral summer BDC trends between model and reanalysis data and show that ODS are the main driver of both residual circulation and isentropic mixing trends over the last decades of the twentieth century. Moreover, aging by isentropic mixing is shown to play a key role on ODS‐driven age of air trends.

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Section: Antarctic Ozone Depletion Impact On the Bdcsupporting

confidence: 86%

New Insights on the Impact of Ozone‐Depleting Substances on the Brewer‐Dobson Circulation

et al. 2019

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“…These secondary peaks at older transit times (here 2.5, 3.5, 4.5 years) indicate an increased impact of in-mixing of old extratropical air on the tropical composition, consistent with enhanced subtropical mixing during westerly QBO phase (e.g. Shuckburgh et al, 2001;Abalos et al, 2016). This enhanced mixing results from shifts in the critical lines, allowing Rossby waves to propagate further equatorward and into the tropics.…”

Section: Residual Circulation and Mixing Effects On Age Spectramentioning

confidence: 55%

Seasonal and inter-annual variability of lower stratospheric age of air spectra

2016

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Abstract. Trace gas transport in the lower stratosphere is investigated by analysing seasonal and inter-annual variations of the age of air spectrum -the probability distribution of stratospheric transit times. Age spectra are obtained using the Chemical Lagrangian Model of the Stratosphere (CLaMS) driven by ERA-Interim winds and total diabatic heating rates, and using a time-evolving boundary-impulseresponse (BIER) method based on multiple tracer pulses. Seasonal age spectra show large deviations from an idealized stationary uni-modal shape. Multiple modes emerge in the spectrum throughout the stratosphere, strongest at high latitudes, caused by the interplay of seasonally varying tropical upward mass flux, stratospheric transport barriers and recirculation. Inter-annual variations in transport (e.g. quasibiennial oscillation) cause significant modulations of the age spectrum shape. In fact, one particular QBO phase may determine the spectrum's mode during the following 2-3 years.

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“…[] and with the well‐known behavior of quasi‐isentropic mixing between low and middle latitudes [e.g., Pierrehumbert and Yang , ; Bowman and Carrie , ]. We note that this layered behavior occurs primarily below the subtropical jet core, and is consistent with the weaker transport across the jet core [ Haynes and Shuckburgh , ; Abalos et al ., ], which provides a simple explanation for why the subtropical dry air does not typically extend above ~9 km (340 K; i.e., this process sets the vertical scale of the dry layers). Such behavior would not be expected as a result of tropical subsidence.…”

Section: Summary and Discussionmentioning

confidence: 99%

Dry layers in the tropical troposphere observed during CONTRAST and global behavior from GFS analyses

et al. 2016

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The Convective Transport of Active Species in the Tropics (CONTRAST) experiment was an aircraft‐based field campaign conducted from Guam (14°N, 145°E) during January–February 2014. Aircraft measurements included over 80 vertical profiles from the boundary layer to the upper troposphere (~15 km). A large fraction of these profiles revealed layered structures with very low water vapor (relative humidity <20%) and enhanced ozone, primarily in the lower‐middle troposphere (~3–9 km). Comparing CONTRAST water vapor measurements with co‐located profiles from National Centers for Environmental Prediction Global Forecast System (GFS) analyses, we find good agreement for dry layers, including profile‐by‐profile comparisons and statistical behavior. We then utilize GFS data to evaluate the frequency of occurrence and 3‐D structure of dry layers for the CONTRAST period to provide perspective to the campaign measurements and evaluate the global climatological behavior based on a longer record. GFS data show that dry layers occur ~50–80% of the time in the subtropical troposphere, maximizing on the equatorward side of the subtropical jets in the winter hemisphere. Subtropical dry layers occur most frequently over isentropic levels ~320–340 K, which extend into the extratropical upper troposphere‐lower stratosphere (UTLS). Similar statistical behavior of dry, ozone‐rich layers is found in long‐term balloon measurements from Reunion Island (21°S, 56°E). The climatologically frequent occurrence of dry, ozone‐rich layers, plus their vertical and spatial structures linked to the subtropical jets, all suggest that dry layers are linked to quasi‐isentropic transport from the extratropical UTLS and suggest a ubiquitous UTLS influence on the subtropical middle troposphere.

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Interannual variability in effective diffusivity in the upper troposphere/lower stratosphere from reanalysis data

Cited by 37 publications

References 54 publications

New Insights on the Impact of Ozone‐Depleting Substances on the Brewer‐Dobson Circulation

New Insights on the Impact of Ozone‐Depleting Substances on the Brewer‐Dobson Circulation

Seasonal and inter-annual variability of lower stratospheric age of air spectra

Dry layers in the tropical troposphere observed during CONTRAST and global behavior from GFS analyses

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