Climatology and trends in the forcing of the stratospheric zonal-mean flow
The momentum budget of the Transformed Eulerian-Mean (TEM) equation is calculated using the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-40) and the National Centers for Environmental Prediction (NCEP) Reanalysis 2 (R-2). This study outlines the considerable contributio...
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| Format: | Article |
| Language: | en_US |
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Copernicus GmbH
2015
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| Online Access: | http://hdl.handle.net/1721.1/96881 https://orcid.org/0000-0001-5533-6570 |
| _version_ | 1811093651878576128 |
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| author | Weare, B. C. Monier, Erwan |
| author2 | Massachusetts Institute of Technology. Center for Global Change Science |
| author_facet | Massachusetts Institute of Technology. Center for Global Change Science Weare, B. C. Monier, Erwan |
| author_sort | Weare, B. C. |
| collection | MIT |
| description | The momentum budget of the Transformed Eulerian-Mean (TEM) equation is calculated using the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-40) and the National Centers for Environmental Prediction (NCEP) Reanalysis 2 (R-2). This study outlines the considerable contribution of unresolved waves, deduced to be gravity waves, to the forcing of the zonal-mean flow. A trend analysis, from 1980 to 2001, shows that the onset and break down of the Northern Hemisphere (NH) stratospheric polar night jet has a tendency to occur later in the season in the more recent years. This temporal shift follows long-term changes in planetary wave activity that are mainly due to synoptic waves, with a lag of one month. In the Southern Hemisphere (SH), the polar vortex shows a tendency to persist further into the SH summertime. This also follows a statistically significant decrease in the intensity of the stationary EP flux divergence over the 1980–2001 period. Ozone depletion is well known for strengthening the polar vortex through the thermal wind balance. However, the results of this work show that the SH polar vortex does not experience any significant long-term changes until the month of December, even though the intensification of the ozone hole occurs mainly between September and November. This study suggests that the decrease in planetary wave activity in November provides an important feedback to the zonal wind as it delays the breakdown of the polar vortex. In addition, the absence of strong eddy feedback before November explains the lack of significant trends in the polar vortex in the SH early spring. A long-term weakening in the Brewer-Dobson (B-D) circulation in the polar region is identified in the NH winter and early spring and during the SH late spring and is likely driven by the decrease in planetary wave activity previously mentioned. During the rest of the year, there are large discrepancies in the representation of the B-D circulation and the unresolved waves between the two reanalyses, making trend analyses unreliable. |
| first_indexed | 2024-09-23T15:48:30Z |
| format | Article |
| id | mit-1721.1/96881 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T15:48:30Z |
| publishDate | 2015 |
| publisher | Copernicus GmbH |
| record_format | dspace |
| spelling | mit-1721.1/968812022-10-02T04:13:51Z Climatology and trends in the forcing of the stratospheric zonal-mean flow Weare, B. C. Monier, Erwan Massachusetts Institute of Technology. Center for Global Change Science Massachusetts Institute of Technology. Joint Program on the Science & Policy of Global Change Monier, Erwan Monier, Erwan The momentum budget of the Transformed Eulerian-Mean (TEM) equation is calculated using the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-40) and the National Centers for Environmental Prediction (NCEP) Reanalysis 2 (R-2). This study outlines the considerable contribution of unresolved waves, deduced to be gravity waves, to the forcing of the zonal-mean flow. A trend analysis, from 1980 to 2001, shows that the onset and break down of the Northern Hemisphere (NH) stratospheric polar night jet has a tendency to occur later in the season in the more recent years. This temporal shift follows long-term changes in planetary wave activity that are mainly due to synoptic waves, with a lag of one month. In the Southern Hemisphere (SH), the polar vortex shows a tendency to persist further into the SH summertime. This also follows a statistically significant decrease in the intensity of the stationary EP flux divergence over the 1980–2001 period. Ozone depletion is well known for strengthening the polar vortex through the thermal wind balance. However, the results of this work show that the SH polar vortex does not experience any significant long-term changes until the month of December, even though the intensification of the ozone hole occurs mainly between September and November. This study suggests that the decrease in planetary wave activity in November provides an important feedback to the zonal wind as it delays the breakdown of the polar vortex. In addition, the absence of strong eddy feedback before November explains the lack of significant trends in the polar vortex in the SH early spring. A long-term weakening in the Brewer-Dobson (B-D) circulation in the polar region is identified in the NH winter and early spring and during the SH late spring and is likely driven by the decrease in planetary wave activity previously mentioned. During the rest of the year, there are large discrepancies in the representation of the B-D circulation and the unresolved waves between the two reanalyses, making trend analyses unreliable. National Science Foundation (U.S.) (Grant ATM0733698) 2015-05-04T12:37:43Z 2015-05-04T12:37:43Z 2011-12 2011-11 Article http://purl.org/eprint/type/JournalArticle 1680-7324 1680-7316 http://hdl.handle.net/1721.1/96881 Monier, E., and B. C. Weare. “Climatology and Trends in the Forcing of the Stratospheric Zonal-Mean Flow.” Atmospheric Chemistry and Physics 11, no. 24 (2011): 12751–12771. https://orcid.org/0000-0001-5533-6570 en_US http://dx.doi.org/10.5194/acp-11-12751-2011 Atmospheric Chemistry and Physics Creative Commons Attribution http://creativecommons.org/licenses/by/3.0/ application/pdf Copernicus GmbH Monier |
| spellingShingle | Weare, B. C. Monier, Erwan Climatology and trends in the forcing of the stratospheric zonal-mean flow |
| title | Climatology and trends in the forcing of the stratospheric zonal-mean flow |
| title_full | Climatology and trends in the forcing of the stratospheric zonal-mean flow |
| title_fullStr | Climatology and trends in the forcing of the stratospheric zonal-mean flow |
| title_full_unstemmed | Climatology and trends in the forcing of the stratospheric zonal-mean flow |
| title_short | Climatology and trends in the forcing of the stratospheric zonal-mean flow |
| title_sort | climatology and trends in the forcing of the stratospheric zonal mean flow |
| url | http://hdl.handle.net/1721.1/96881 https://orcid.org/0000-0001-5533-6570 |
| work_keys_str_mv | AT wearebc climatologyandtrendsintheforcingofthestratosphericzonalmeanflow AT moniererwan climatologyandtrendsintheforcingofthestratosphericzonalmeanflow |