Climatological impact of the Brewer–Dobson circulation on the N<sub>2</sub>O budget in WACCM, a chemical reanalysis and a CTM driven by four dynamical reanalyses
<p>The Brewer–Dobson circulation (BDC) is a stratospheric circulation characterized by upwelling of tropospheric air in the tropics, poleward flow in the stratosphere, and downwelling at mid and high latitudes, with important implications for chemical tracer distributions, stratospheric heat a...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2020-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/20/12609/2020/acp-20-12609-2020.pdf |
| _version_ | 1818403437978583040 |
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| author | D. Minganti S. Chabrillat Y. Christophe Q. Errera M. Abalos M. Prignon D. E. Kinnison E. Mahieu |
| author_facet | D. Minganti S. Chabrillat Y. Christophe Q. Errera M. Abalos M. Prignon D. E. Kinnison E. Mahieu |
| author_sort | D. Minganti |
| collection | DOAJ |
| description | <p>The Brewer–Dobson circulation (BDC) is a stratospheric circulation characterized by upwelling of tropospheric air in the tropics, poleward flow in the stratosphere, and downwelling at mid and high latitudes, with important implications for chemical tracer distributions, stratospheric heat and momentum budgets, and mass exchange with the troposphere.
As the photochemical losses of nitrous oxide (<span class="inline-formula">N<sub>2</sub>O</span>) are well known, model differences in its rate of change are due to transport processes that can be separated into the mean residual advection and the isentropic mixing terms in the transformed Eulerian mean (TEM) framework.
Here, the climatological impact of the stratospheric BDC on the long-lived tracer <span class="inline-formula">N<sub>2</sub>O</span> is evaluated through a comparison of its TEM budget in the Whole Atmosphere Community Climate Model (WACCM), in a chemical reanalysis of the Aura Microwave Limb Sounder version 2 (BRAM2) and in a chemistry transport model (CTM) driven by four modern reanalyses: the European Centre for Medium-Range Weather Forecasts Interim reanalysis <span class="cit" id="xref_paren.1">(ERA-Interim; <a href="#bib1.bibx23">Dee et al.</a>, <a href="#bib1.bibx23">2011</a>)</span>, the Japanese 55-year Reanalysis <span class="cit" id="xref_paren.2">(JRA-55; <a href="#bib1.bibx59">Kobayashi et al.</a>, <a href="#bib1.bibx59">2015</a>)</span>, and the Modern-Era Retrospective analysis for Research and Applications version 1 <span class="cit" id="xref_paren.3">(MERRA; <a href="#bib1.bibx93">Rienecker et al.</a>, <a href="#bib1.bibx93">2011</a>)</span> and version 2 <span class="cit" id="xref_paren.4">(MERRA-2; <a href="#bib1.bibx44">Gelaro et al.</a>, <a href="#bib1.bibx44">2017</a>)</span>.
The effects of stratospheric transport on the <span class="inline-formula">N<sub>2</sub>O</span> rate of change, as depicted in this study, have not been compared before across this variety of datasets and have never been investigated in a modern chemical reanalysis.
We focus on the seasonal means and climatological annual cycles of the two main contributions to the <span class="inline-formula">N<sub>2</sub>O</span> TEM budget: the vertical residual advection and the horizontal mixing terms.</p>
<p>The <span class="inline-formula">N<sub>2</sub>O</span> mixing ratio in the CTM experiments has a spread of approximately <span class="inline-formula">∼20 <i>%</i></span> in the middle stratosphere, reflecting the large diversity in the mean age of air obtained with the same CTM experiments in a previous study.
In all datasets, the TEM budget is closed well; the agreement between the vertical advection terms is qualitatively very good in the Northern Hemisphere, and it is good in the Southern Hemisphere except above the Antarctic region.
The datasets do not agree as well with respect to the horizontal mixing term, especially in the Northern Hemisphere where horizontal mixing has a smaller contribution in WACCM than in the reanalyses.
WACCM is investigated through three model realizations and a sensitivity test using the previous version of the gravity wave parameterization.
The internal variability of the horizontal mixing in WACCM is large in the polar regions and is comparable to the differences between the dynamical reanalyses.
The sensitivity test has a relatively small impact on the horizontal mixing term, but it significantly changes the vertical advection term and produces a less realistic <span class="inline-formula">N<sub>2</sub>O</span> annual cycle above the Antarctic.
In this region, all reanalyses show a large wintertime <span class="inline-formula">N<sub>2</sub>O</span> decrease, which is mainly due to horizontal mixing.
This is not seen with WACCM, where the horizontal mixing term barely contributes to the TEM budget.
While we must use caution in the interpretation<span id="page12610"/> of the differences in this region (where the reanalyses show large residuals of the TEM budget), they could be due to the fact that the polar jet is stronger and is not tilted equatorward in WACCM compared with the reanalyses.</p>
<p>We also compare the interannual variability in the horizontal mixing and the vertical advection terms between the different datasets.
As expected, the horizontal mixing term presents a large variability during austral fall and boreal winter in the polar regions.
In the tropics, the interannual variability of the vertical advection term is much smaller in WACCM and JRA-55 than in the other experiments.
The large residual in the reanalyses and the disagreement between WACCM and the reanalyses in the Antarctic region highlight the need for further investigations on the modeling of transport in this region of the stratosphere.</p> |
| first_indexed | 2024-12-14T08:24:15Z |
| format | Article |
| id | doaj.art-190815d24ecd424d897df2e23cdbaeeb |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-14T08:24:15Z |
| publishDate | 2020-11-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-190815d24ecd424d897df2e23cdbaeeb2022-12-21T23:09:41ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242020-11-0120126091263110.5194/acp-20-12609-2020Climatological impact of the Brewer–Dobson circulation on the N<sub>2</sub>O budget in WACCM, a chemical reanalysis and a CTM driven by four dynamical reanalysesD. Minganti0S. Chabrillat1Y. Christophe2Q. Errera3M. Abalos4M. Prignon5D. E. Kinnison6E. Mahieu7Royal Belgian Institute for Space Aeronomy, BIRA-IASB, 1180 Brussels, BelgiumRoyal Belgian Institute for Space Aeronomy, BIRA-IASB, 1180 Brussels, BelgiumRoyal Belgian Institute for Space Aeronomy, BIRA-IASB, 1180 Brussels, BelgiumRoyal Belgian Institute for Space Aeronomy, BIRA-IASB, 1180 Brussels, BelgiumEarth Physics and Astrophysics Department, Universidad Complutense de Madrid, 28040 Madrid, SpainInstitute of Astrophysics and Geophysics, University of Liège, 4000 Liège, BelgiumNational Center for Atmospheric Research, Boulder, 80301 CO, USAInstitute of Astrophysics and Geophysics, University of Liège, 4000 Liège, Belgium<p>The Brewer–Dobson circulation (BDC) is a stratospheric circulation characterized by upwelling of tropospheric air in the tropics, poleward flow in the stratosphere, and downwelling at mid and high latitudes, with important implications for chemical tracer distributions, stratospheric heat and momentum budgets, and mass exchange with the troposphere. As the photochemical losses of nitrous oxide (<span class="inline-formula">N<sub>2</sub>O</span>) are well known, model differences in its rate of change are due to transport processes that can be separated into the mean residual advection and the isentropic mixing terms in the transformed Eulerian mean (TEM) framework. Here, the climatological impact of the stratospheric BDC on the long-lived tracer <span class="inline-formula">N<sub>2</sub>O</span> is evaluated through a comparison of its TEM budget in the Whole Atmosphere Community Climate Model (WACCM), in a chemical reanalysis of the Aura Microwave Limb Sounder version 2 (BRAM2) and in a chemistry transport model (CTM) driven by four modern reanalyses: the European Centre for Medium-Range Weather Forecasts Interim reanalysis <span class="cit" id="xref_paren.1">(ERA-Interim; <a href="#bib1.bibx23">Dee et al.</a>, <a href="#bib1.bibx23">2011</a>)</span>, the Japanese 55-year Reanalysis <span class="cit" id="xref_paren.2">(JRA-55; <a href="#bib1.bibx59">Kobayashi et al.</a>, <a href="#bib1.bibx59">2015</a>)</span>, and the Modern-Era Retrospective analysis for Research and Applications version 1 <span class="cit" id="xref_paren.3">(MERRA; <a href="#bib1.bibx93">Rienecker et al.</a>, <a href="#bib1.bibx93">2011</a>)</span> and version 2 <span class="cit" id="xref_paren.4">(MERRA-2; <a href="#bib1.bibx44">Gelaro et al.</a>, <a href="#bib1.bibx44">2017</a>)</span>. The effects of stratospheric transport on the <span class="inline-formula">N<sub>2</sub>O</span> rate of change, as depicted in this study, have not been compared before across this variety of datasets and have never been investigated in a modern chemical reanalysis. We focus on the seasonal means and climatological annual cycles of the two main contributions to the <span class="inline-formula">N<sub>2</sub>O</span> TEM budget: the vertical residual advection and the horizontal mixing terms.</p> <p>The <span class="inline-formula">N<sub>2</sub>O</span> mixing ratio in the CTM experiments has a spread of approximately <span class="inline-formula">∼20 <i>%</i></span> in the middle stratosphere, reflecting the large diversity in the mean age of air obtained with the same CTM experiments in a previous study. In all datasets, the TEM budget is closed well; the agreement between the vertical advection terms is qualitatively very good in the Northern Hemisphere, and it is good in the Southern Hemisphere except above the Antarctic region. The datasets do not agree as well with respect to the horizontal mixing term, especially in the Northern Hemisphere where horizontal mixing has a smaller contribution in WACCM than in the reanalyses. WACCM is investigated through three model realizations and a sensitivity test using the previous version of the gravity wave parameterization. The internal variability of the horizontal mixing in WACCM is large in the polar regions and is comparable to the differences between the dynamical reanalyses. The sensitivity test has a relatively small impact on the horizontal mixing term, but it significantly changes the vertical advection term and produces a less realistic <span class="inline-formula">N<sub>2</sub>O</span> annual cycle above the Antarctic. In this region, all reanalyses show a large wintertime <span class="inline-formula">N<sub>2</sub>O</span> decrease, which is mainly due to horizontal mixing. This is not seen with WACCM, where the horizontal mixing term barely contributes to the TEM budget. While we must use caution in the interpretation<span id="page12610"/> of the differences in this region (where the reanalyses show large residuals of the TEM budget), they could be due to the fact that the polar jet is stronger and is not tilted equatorward in WACCM compared with the reanalyses.</p> <p>We also compare the interannual variability in the horizontal mixing and the vertical advection terms between the different datasets. As expected, the horizontal mixing term presents a large variability during austral fall and boreal winter in the polar regions. In the tropics, the interannual variability of the vertical advection term is much smaller in WACCM and JRA-55 than in the other experiments. The large residual in the reanalyses and the disagreement between WACCM and the reanalyses in the Antarctic region highlight the need for further investigations on the modeling of transport in this region of the stratosphere.</p>https://acp.copernicus.org/articles/20/12609/2020/acp-20-12609-2020.pdf |
| spellingShingle | D. Minganti S. Chabrillat Y. Christophe Q. Errera M. Abalos M. Prignon D. E. Kinnison E. Mahieu Climatological impact of the Brewer–Dobson circulation on the N<sub>2</sub>O budget in WACCM, a chemical reanalysis and a CTM driven by four dynamical reanalyses Atmospheric Chemistry and Physics |
| title | Climatological impact of the Brewer–Dobson circulation on the N<sub>2</sub>O budget in WACCM, a chemical reanalysis and a CTM driven by four dynamical reanalyses |
| title_full | Climatological impact of the Brewer–Dobson circulation on the N<sub>2</sub>O budget in WACCM, a chemical reanalysis and a CTM driven by four dynamical reanalyses |
| title_fullStr | Climatological impact of the Brewer–Dobson circulation on the N<sub>2</sub>O budget in WACCM, a chemical reanalysis and a CTM driven by four dynamical reanalyses |
| title_full_unstemmed | Climatological impact of the Brewer–Dobson circulation on the N<sub>2</sub>O budget in WACCM, a chemical reanalysis and a CTM driven by four dynamical reanalyses |
| title_short | Climatological impact of the Brewer–Dobson circulation on the N<sub>2</sub>O budget in WACCM, a chemical reanalysis and a CTM driven by four dynamical reanalyses |
| title_sort | climatological impact of the brewer dobson circulation on the n sub 2 sub o budget in waccm a chemical reanalysis and a ctm driven by four dynamical reanalyses |
| url | https://acp.copernicus.org/articles/20/12609/2020/acp-20-12609-2020.pdf |
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