Mesosphere-to-stratosphere descent of odd nitrogen in February–March 2009 after sudden stratospheric warming
We use the 3-D FinROSE chemistry transport model (CTM) and Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) observations to study connections between atmospheric dynamics and middle atmospheric NO<sub>x</sub> (NO<sub>x</sub&am...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2011-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/11/4645/2011/acp-11-4645-2011.pdf |
| _version_ | 1828848287739805696 |
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| author | S.-M. Salmi P. T. Verronen L. Thölix E. Kyrölä L. Backman A. Yu. Karpechko A. Seppälä |
| author_facet | S.-M. Salmi P. T. Verronen L. Thölix E. Kyrölä L. Backman A. Yu. Karpechko A. Seppälä |
| author_sort | S.-M. Salmi |
| collection | DOAJ |
| description | We use the 3-D FinROSE chemistry transport model (CTM) and Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) observations to study connections between atmospheric dynamics and middle atmospheric NO<sub>x</sub> (NO<sub>x</sub> = NO + NO<sub>2</sub>) distribution. Two cases are considered in the northern polar regions: (1) descent of mesospheric NO<sub>x</sub> in February–March 2009 after a major sudden stratospheric warming (SSW) and, for comparison, (2) early 2007 when no NO<sub>x</sub> descent occurred. The model uses the European Centre for Medium-Range Weather Forecasts (ECMWF) operational data for winds and temperature, and we force NO<sub>x</sub> at the model upper altitude boundary (80 km) with ACE-FTS observations. We then compare the model results with ACE-FTS observations at lower altitudes. For the periods studied, geomagnetic indices are low, which indicates absence of local NO<sub>x</sub> production by particle precipitation. This gives us a good opportunity to study effects of atmospheric transport on polar NO<sub>x</sub>. The model results show no NO<sub>x</sub> descent in 2007, in agreement with ACE-FTS. In contrast, a large amount of NO<sub>x</sub> descends in February–March 2009 from the upper to lower mesosphere at latitudes larger than 60° N, i.e. inside the polar vortex. Both observations and model results suggest NO<sub>x</sub> increases of 150–200 ppb (i.e. by factor of 50) at 65 km due to the descent. However, the model underestimates the amount of NO<sub>x</sub> around 55 km by 40–60 ppb. According to the model results, chemical loss of NO<sub>x</sub> is insignificant during the descent period, i.e. polar NO<sub>x</sub> is mainly controlled by dynamics. The descent is terminated and the polar NO<sub>x</sub> amounts return to pre-descent levels in mid-March, when the polar vortex breaks. The break-up prevents the descending NO<sub>x</sub> from reaching the upper stratosphere, where it could participate in catalytic ozone destruction. Both ACE-FTS observations and FinROSE show a decrease of ozone of 20–30 % at 30–50 km from mid-February to mid-March. In the model, these ozone changes are not related to the descent but are due to solar activation of halogen and NO<sub>x</sub> chemistry. |
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| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-12T22:26:55Z |
| publishDate | 2011-05-01 |
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| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-8dbc614722394700afbb36cbe5a0cc552022-12-22T00:09:44ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242011-05-0111104645465510.5194/acp-11-4645-2011Mesosphere-to-stratosphere descent of odd nitrogen in February–March 2009 after sudden stratospheric warmingS.-M. SalmiP. T. VerronenL. ThölixE. KyröläL. BackmanA. Yu. KarpechkoA. SeppäläWe use the 3-D FinROSE chemistry transport model (CTM) and Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) observations to study connections between atmospheric dynamics and middle atmospheric NO<sub>x</sub> (NO<sub>x</sub> = NO + NO<sub>2</sub>) distribution. Two cases are considered in the northern polar regions: (1) descent of mesospheric NO<sub>x</sub> in February–March 2009 after a major sudden stratospheric warming (SSW) and, for comparison, (2) early 2007 when no NO<sub>x</sub> descent occurred. The model uses the European Centre for Medium-Range Weather Forecasts (ECMWF) operational data for winds and temperature, and we force NO<sub>x</sub> at the model upper altitude boundary (80 km) with ACE-FTS observations. We then compare the model results with ACE-FTS observations at lower altitudes. For the periods studied, geomagnetic indices are low, which indicates absence of local NO<sub>x</sub> production by particle precipitation. This gives us a good opportunity to study effects of atmospheric transport on polar NO<sub>x</sub>. The model results show no NO<sub>x</sub> descent in 2007, in agreement with ACE-FTS. In contrast, a large amount of NO<sub>x</sub> descends in February–March 2009 from the upper to lower mesosphere at latitudes larger than 60° N, i.e. inside the polar vortex. Both observations and model results suggest NO<sub>x</sub> increases of 150–200 ppb (i.e. by factor of 50) at 65 km due to the descent. However, the model underestimates the amount of NO<sub>x</sub> around 55 km by 40–60 ppb. According to the model results, chemical loss of NO<sub>x</sub> is insignificant during the descent period, i.e. polar NO<sub>x</sub> is mainly controlled by dynamics. The descent is terminated and the polar NO<sub>x</sub> amounts return to pre-descent levels in mid-March, when the polar vortex breaks. The break-up prevents the descending NO<sub>x</sub> from reaching the upper stratosphere, where it could participate in catalytic ozone destruction. Both ACE-FTS observations and FinROSE show a decrease of ozone of 20–30 % at 30–50 km from mid-February to mid-March. In the model, these ozone changes are not related to the descent but are due to solar activation of halogen and NO<sub>x</sub> chemistry.http://www.atmos-chem-phys.net/11/4645/2011/acp-11-4645-2011.pdf |
| spellingShingle | S.-M. Salmi P. T. Verronen L. Thölix E. Kyrölä L. Backman A. Yu. Karpechko A. Seppälä Mesosphere-to-stratosphere descent of odd nitrogen in February–March 2009 after sudden stratospheric warming Atmospheric Chemistry and Physics |
| title | Mesosphere-to-stratosphere descent of odd nitrogen in February–March 2009 after sudden stratospheric warming |
| title_full | Mesosphere-to-stratosphere descent of odd nitrogen in February–March 2009 after sudden stratospheric warming |
| title_fullStr | Mesosphere-to-stratosphere descent of odd nitrogen in February–March 2009 after sudden stratospheric warming |
| title_full_unstemmed | Mesosphere-to-stratosphere descent of odd nitrogen in February–March 2009 after sudden stratospheric warming |
| title_short | Mesosphere-to-stratosphere descent of odd nitrogen in February–March 2009 after sudden stratospheric warming |
| title_sort | mesosphere to stratosphere descent of odd nitrogen in february march 2009 after sudden stratospheric warming |
| url | http://www.atmos-chem-phys.net/11/4645/2011/acp-11-4645-2011.pdf |
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