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The ENSO Signal in the Stratosphere

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Calvo Fernández, Natalia and García Herrera, Ricardo and García, Rolando R. (2008) The ENSO Signal in the Stratosphere. Annals of the New York Academy of Sciences, 1146 . pp. 16-31. ISSN 0077-8923

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Official URL: http://dx.doi.org/10.1196/annals.1446.008




Abstract

Although the El Nino-Southern Oscillation (ENSO) is a tropospheric phenomenon, its effects are also observed in the stratosphere. Traditionally, the study of ENSO above the troposphere has been difficult because of the lack of global observations at high altitudes and also because of the presence of other sources of variability whose signals are difficult to disentangle from ENSO effects. Recent work with general circulation models that isolate the ENSO signal have demonstrated its upward propagation into the stratosphere. Here we review the literature in this field and show results from the most recent version of the Whole Atmosphere Community Climate Model to illustrate the propagation and the mechanisms whereby the signal manifests itself in the stratosphere. The ENSO signal propagates upward to about 40 km by means of large-scale Rossby waves. The propagation is strongly influenced by the zonal mean zonal winds. Most of the strong ENSO events tend to peak in the boreal winter and so the ENSO signal is observed mainly at high latitudes during the Northern Hemisphere winter where the winds are westerly and allow Rossby wave propagation. The ENSO signal is also identified at polar latitudes in the Northern Hemisphere winter in the form of warmer temperatures and weaker winds during a strong El Nino event. This signal shows a zonally homogeneous behavior from the intensification of the stratospheric meridional circulation (in which air rises in the tropics and moves toward the winter pole where it descends) forced by anomalous propagation and dissipation of Rossby waves at middle latitudes during strong ENSO events.


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© 2008 New York Academy of Sciences. European Meteorology Society Annual Meeting (7. 2007. El Escorial). European Conference on Applications of Meteorology (8. 2007. El Escorial, Spain). This work has been funded by the Spanish Ministry of Education and Science and the Fulbright Commission in Spain. The WACCM3 simulations discussed here were carried out at the Barcelona Supercomputing Center, Barcelona, Spain, and at the National Center for Atmospheric Research (NCAR), Boulder, CO, USA. NCAR is sponsored by the US National Science Foundation.

Uncontrolled Keywords:Sea-Surface Temperature, General-Circulation Model, Northern-Hemisphere Stratosphere, Niño Southern-Oscillation, El-Niño, Equatorial Pacific, Interannual Variability, Atmospheric Response, Tropospheric Circulation, Winter Stratosphere
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
Sciences > Physics > Atmospheric physics
ID Code:25586
Deposited On:28 May 2014 08:28
Last Modified:10 Dec 2018 15:05

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