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Geomagnetic activity related NOx enhancements and polar surface air temperature variability in a chemistry climate model: modulation of the NAM index

Baumgaertner, Andreas J. G. und Seppälä, A. und Jöckel, Patrick und Clilverd, M. A. (2011) Geomagnetic activity related NOx enhancements and polar surface air temperature variability in a chemistry climate model: modulation of the NAM index. Atmospheric Chemistry and Physics, 11, Seiten 4521-4531. DOI: 10.5194/acp-11-4521-2011.

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Offizielle URL: http://www.atmos-chem-phys.net/11/4521/2011/

Kurzfassung

The atmospheric chemistry general circulation model ECHAM5/MESSy is used to simulate polar surface air temperature effects of geomagnetic activity variations. A transient model simulation was performed for the years 1960�2004 and is shown to develop polar surface air temperature patterns that depend on geomagnetic activity strength, similar to previous studies. In order to eliminate influencing factors such as sea surface temperatures (SST) or UV variations, two nine-year long simulations were carried out, with strong and weak geomagnetic activity, respectively, while all other boundary conditions were held to year 2000 levels. Statistically significant temperature effects that were observed in previous reanalysis and model results are also obtained from this set of simulations, suggesting that such patterns are indeed related to geomagnetic activity. In the model, strong geomagnetic activity and the associated NOx (= NO + NO2) enhancements lead to polar stratospheric ozone loss. Compared with the simulation with weak geomagnetic activity, the ozone loss causes a decrease in ozone radiative cooling and thus a temperature increase in the polar winter mesosphere. Similar to previous studies, a cooling is found below the stratopause, which other authors have attributed to a decrease in the mean meridional circulation. In the polar stratosphere this leads to a more stable vortex. A strong (weak) Northern Hemisphere vortex is known to be associated with a positive (negative) Northern Annular Mode (NAM) index; our simulations exhibit a positive NAM index for strong geomagnetic activity, and a negative NAM for weak geomagnetic activity. Such NAM anomalies have been shown to propagate to the surface, and this is also seen in the model simulations. NAM anomalies are known to lead to specific surface temperature anomalies: a positive NAM is associated with warmer than average northern Eurasia and colder than average eastern North Atlantic. This is also the case in our simulation. Our simulations suggest a link between geomagnetic activity, ozone loss, stratospheric cooling, the NAM, and surface temperature variability. Further work is required to identify the precise cause and effect of the coupling between these regions.

Dokumentart:Zeitschriftenbeitrag
Titel:Geomagnetic activity related NOx enhancements and polar surface air temperature variability in a chemistry climate model: modulation of the NAM index
Autoren:
AutorenInstitution oder E-Mail-Adresse der Autoren
Baumgaertner, Andreas J. G.Andreas.Baumgaertner@dlr.de
Seppälä, A.NICHT SPEZIFIZIERT
Jöckel, PatrickPatrick.Joeckel@dlr.de
Clilverd, M. A.NICHT SPEZIFIZIERT
Datum:12 Mai 2011
Erschienen in:Atmospheric Chemistry and Physics
Referierte Publikation:Ja
In Open Access:Ja
In SCOPUS:Ja
In ISI Web of Science:Ja
Band:11
DOI :10.5194/acp-11-4521-2011
Seitenbereich:Seiten 4521-4531
Status:veröffentlicht
Stichwörter:atmospheric chemistry, geomagnetic activity, nitrous oxide, air temperature, polar atmosphere, middle atmosphere, atmospheric modeling, NAM indexm, chemistry climate model
HGF - Forschungsbereich:Luftfahrt, Raumfahrt und Verkehr
HGF - Programm:Raumfahrt
HGF - Programmthema:Erdbeobachtung
DLR - Schwerpunkt:Raumfahrt
DLR - Forschungsgebiet:R EO - Erdbeobachtung
DLR - Teilgebiet (Projekt, Vorhaben):R - Vorhaben Atmosphären- und Klimaforschung
Standort: Oberpfaffenhofen
Institute & Einrichtungen:Institut für Physik der Atmosphäre > Dynamik der Atmosphäre
Hinterlegt von: Patrick Jöckel
Hinterlegt am:21 Nov 2011 10:23
Letzte Änderung:12 Dez 2013 21:25

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