How robust are stratospheric age of air trends from different reanalyses?

Ploeger, Felix; Legras, Bernard; Charlesworth, Edward; Yan, Xiaolu; Diallo, Mohamadou; Konopka, Paul; Birner, Thomas; Tao, Mengchu; Engel, Andreas; Riese, Martin

doi:10.5194/acp-2018-1281

Cited by 17 publications

(39 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure 3 provides useful context for interpreting these differences, as high values of H 2 O CH 4 are accompanied by systematically older stratospheric air in CLaMS-MRA. Note that consistent climatological mean age differences within the same model framework are presented by Ploeger et al (2019). The lower panels of Fig.…”

Section: Extraction Of Variability At Multiple Timescalessupporting

confidence: 66%

“…Figure 1 provides example regression results for SWV on the 400 K isentropic surface in the tropics (20 • S-20 • N) based on the SWOOSH monthly merged satellite dataset. This time series approximates that of H 2 O values entering the stratosphere (H 2 O e ) at the base of the "tropical pipe" (Plumb, 1996), and is characterized by a climatological annual mean of 3.83 ppmv and a negative trend of 0.22 ppmv decade −1 . The regression model explains over 80 % of the variance in H 2 O e .…”

Section: Extraction Of Variability At Multiple Timescalesmentioning

confidence: 79%

See 1 more Smart Citation

Multitimescale variations in modeled stratospheric water vapor derived from three modern reanalysis products

Tao¹,

Konopka²,

Ploeger

et al. 2019

Atmos. Chem. Phys.

Self Cite

View full text Add to dashboard Cite

Abstract. Stratospheric water vapor (SWV) plays important roles in the radiation budget and ozone chemistry and is a valuable tracer for understanding stratospheric transport. Meteorological reanalyses provide variables necessary for simulating this transport; however, even recent reanalyses are subject to substantial uncertainties, especially in the stratosphere. It is therefore necessary to evaluate the consistency among SWV distributions simulated using different input reanalysis products. In this study, we evaluate the representation of SWV and its variations on multiple timescales using simulations over the period 1980–2013. Our simulations are based on the Chemical Lagrangian Model of the Stratosphere (CLaMS) driven by horizontal winds and diabatic heating rates from three recent reanalyses: ERA-Interim, JRA-55 and MERRA-2. We present an intercomparison among these model results and observationally based estimates using a multiple linear regression method to study the annual cycle (AC), the quasi-biennial oscillation (QBO), and longer-term variability in monthly zonal-mean H2O mixing ratios forced by variations in the El Niño–Southern Oscillation (ENSO) and the volcanic aerosol burden. We find reasonable consistency among simulations of the distribution and variability in SWV with respect to the AC and QBO. However, the amplitudes of both signals are systematically weaker in the lower and middle stratosphere when CLaMS is driven by MERRA-2 than when it is driven by ERA-Interim or JRA-55. This difference is primarily attributable to relatively slow tropical upwelling in the lower stratosphere in simulations based on MERRA-2. Two possible contributors to the slow tropical upwelling in the lower stratosphere are suggested to be the large long-wave cloud radiative effect and the unique assimilation process in MERRA-2. The impacts of ENSO and volcanic aerosol on H2O entry variability are qualitatively consistent among the three simulations despite differences of 50 %–100 % in the magnitudes. Trends show larger discrepancies among the three simulations. CLaMS driven by ERA-Interim produces a neutral to slightly positive trend in H2O entry values over 1980–2013 (+0.01 ppmv decade−1), while both CLaMS driven by JRA-55 and CLaMS driven by MERRA-2 produce negative trends but with significantly different magnitudes (−0.22 and −0.08 ppmv decade−1, respectively).

show abstract

Section: Extraction Of Variability At Multiple Timescalessupporting

confidence: 66%

Section: Extraction Of Variability At Multiple Timescalesmentioning

confidence: 79%

Multitimescale variations in modeled stratospheric water vapor derived from three modern reanalysis products

Tao¹,

Konopka²,

Ploeger

et al. 2019

Atmos. Chem. Phys.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Figure 3 provides useful context for interpreting these differences, as high values of H 2 O CH4 are accompanied by systematically older stratospheric air in CLaMS-MRA. Note that a consistent climatological mean age differences within the same model framework are presented in Ploeger et al (2019). The lower panels of Fig.…”

supporting

confidence: 59%

Multi-timescale variations of modelled stratospheric water vapor derived from three modern reanalysis products

Tao¹,

Konopka²,

Ploeger³

et al. 2019

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. Stratospheric water vapor (SWV) plays important roles in the radiation budget and ozone chemistry and is a valuable tracer for understanding stratospheric transport. Meteorological reanalyses provide variables necessary for simulating this transport; however, even recent reanalyses are subject to substantial uncertainties, especially in the stratosphere. It is therefore necessary to evaluate the consistency among SWV distributions simulated using different input reanalysis products. In this study, we evaluate the representation of SWV and its variations on multiple timescales using simulations over the period 1980&#8211;2013. Our simulations are based on the Chemical Lagrangian Model of the Stratosphere (CLaMS) driven by horizontal winds and diabatic heating rates from three recent reanalyses: ERA-Interim, JRA-55 and MERRA-2. We present an inter-comparison among these model results and observationally-based estimates, using a multiple linear regression method to study the annual cycle (AC), the quasi-biennial oscillation (QBO), and longer-term variability in monthly zonal-mean H2O mixing ratios forced by variations in the El-Nino&#8211;Southern Oscillation and the volcanic aerosol burden. We find reasonable consistency among simulations of the distribution and variability of SWV with respect to the AC and QBO. However, the amplitudes of both signals are systematically weaker in the lower and middle stratosphere when CLaMS is driven by MERRA-2 than when it is driven by ERA-Interim or JRA-55. This difference is primarily attributable to relatively slow tropical upwelling in the lower stratosphere in simulations based on MERRA-2. Two possible contributors of the slow tropical upwelling in the lower stratosphere are found to be the large long-wave radiative effect and the unique assimilation process in MERRA-2. The impacts of ENSO and volcanic aerosol on H2O entry variability are qualitatively consistent among the three simulations despite differences of 50&#8211;100&#8201;% in the magnitudes. Trends show larger discrepancies among the three simulations. CLaMS driven by ERA-Interim produces a neutral to slightly positive trend in H2O entry values over 1980&#8211;2013 (+0.01&#8201;ppmv&#8201;decade-1), while both CLaMS driven by JRA-55 and CLaMS driven by MERRA-2 produce negative trends but with significantly different magnitudes (&#8722;0.22&#8201;ppmv&#8201;decade-1 and &#8722;0.08&#8201;ppmv&#8201;decade-1, respectively).

show abstract

“…The consistency in the magnitude and sign of the upwelling changes between the reanalyses is encouraging and shows that the changes exhibited by MERRA‐2 (and M2GMI) are also exhibited by another reanalysis product. We stress that this result is not obvious given that the TEM circulation can exhibit large differences among different reanalysis products depending on the pressures and latitudes sampled (e.g., Abalos et al, ; Chabrillat et al, ; Ploeger et al, ; Seviour et al, ; see Figure S4). Those studies, however, focused on different regions (e.g., tropical lower stratosphere and high‐latitude middle stratosphere), so our results indicate that MERRA‐2 and ERA‐I are overall consistent, at least with respect to upwelling changes over the NH subtropics.…”

Section: Resultsmentioning

confidence: 86%

Mechanisms Linked to Recent Ozone Decreases in the Northern Hemisphere Lower Stratosphere

et al. 2020

View full text Add to dashboard Cite

Previous studies have robustly identified a decrease since 1998 in lower stratospheric (LS) ozone in the Northern Hemisphere (NH). While this ozone decrease is qualitatively explained as resulting from changes in the large-scale circulation, there is not yet a quantitative mechanistic explanation of these changes. Here, we explore the drivers of recent ozone changes using two different configurations of the Goddard Earth Observing System (GEOS) general circulation model. The first configuration of GEOS includes a full chemistry module and is constrained with meteorological fields from the Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2). This configuration (M2GMI) is used to analyze an idealized tracer that covaries closely with ozone on interannual and decadal timescales, revealing that recent ozone decreases in the NH subtropics are associated with a poleward expansion of upwelling in the NH LS, with reduced (enhanced) downwelling over northern subtropics (midlatitudes). The second configuration of GEOS is a free-running version of the GEOS Chemistry Climate Model (CCM) that is used to perform a 10-member ensemble of free-running simulations. Comparisons of the two configurations reveal that, while the free-running model can produce negative ozone changes in the NH LS, the magnitude of these changes is significantly weaker, relative to both M2GMI and MERRA-2; moreover, these weaker ozone decreases are consistent with weaker simulated changes in the residual circulation. Finally, we examine the GEOS model results in the broader context of the hindcast simulations performed as part of Phase 1 of the Chemistry Climate Modeling Initiative. We show that the majority of the free-running simulations considered here also exhibit weaker long-term residual circulation changes, compared to reanalyses.

show abstract

How robust are stratospheric age of air trends from different reanalyses?

Cited by 17 publications

References 51 publications

Multitimescale variations in modeled stratospheric water vapor derived from three modern reanalysis products

Multitimescale variations in modeled stratospheric water vapor derived from three modern reanalysis products

Multi-timescale variations of modelled stratospheric water vapor derived from three modern reanalysis products

Mechanisms Linked to Recent Ozone Decreases in the Northern Hemisphere Lower Stratosphere

Contact Info

Product

Resources

About