University of Oulu

Salminen A, Asikainen T, Maliniemi V & Mursula K 2020. Comparing the effects of solar-related and terrestrial driverson the northern polar vortex. J. Space Weather Space Clim. 10, 56.

Comparing the effects of solar-related and terrestrial drivers on the northern polar vortex

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Author: Salminen, Antti1; Asikainen, Timo1; Maliniemi, Ville2;
Organizations: 1Space Physics and Astronomy Research Unit, University of Oulu, 90014 Oulu, Finland
2Birkeland Centre for Space Science, Department of Physics and Technology, University of Bergen, 5007 Bergen, Norway
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 7.9 MB)
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Language: English
Published: EDP Sciences, 2020
Publish Date: 2020-12-11


Northern polar vortex experiences significant variability during Arctic winter. Solar activity contributes to this variability via solar irradiance and energetic particle precipitation. Recent studies have found that energetic electron precipitation (EEP) affects the polar vortex by forming ozone depleting NOx compounds. However, it is still unknown how the EEP effect compares to variabilities caused by, e.g., solar irradiance or terrestrial drivers. In this study we examine the effects of EEP, solar irradiance, El-Niño-Southern Oscillation (ENSO), volcanic aerosols and quasi-biennial oscillation (QBO) on the northern wintertime atmosphere. We use geomagnetic Ap-index to quantify EEP activity, sunspot numbers to quantify solar irradiance, Niño 3.4 index for ENSO and aerosol optical depth for the amount of volcanic aerosols. We use a new composite dataset including ERA-40 and ERA-Interim reanalysis of zonal wind and temperature and multilinear regression analysis to estimate atmospheric responses to the above mentioned explaining variables in winter months of 1957–2017. We confirm the earlier results showing that EEP and QBO strengthen the polar vortex. We find here that the EEP effect on polar vortex is stronger and more significant than the effects of the other drivers in almost all winter months in most conditions. During 1957–2017 the considered drivers together explain about 25–35% of polar vortex variability while the EEP effect alone explains about 10–20% of it. Thus, a major part of variability is not due to the linear effect by the studied explaining variables. The positive EEP effect is particularly strong if QBO-wind at 30 hPa has been easterly during the preceding summer, while for a westerly QBO the EEP effect is weaker and less significant.

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Series: Journal of space weather and space climate
ISSN: 2115-7251
ISSN-E: 2115-7251
ISSN-L: 2115-7251
Volume: 10
Article number: 56
DOI: 10.1051/swsc/2020058
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: We acknowledge the financial support by the Academy of Finland to the ReSoLVE Center of Excellence (project no. 307411) and to the PROSPECT (project no. 321440), and by the Kvantum institute of the University of Oulu (CAESAR project). V.M. was funded by the Norwegian Research Council under contract 223252/F50.
Academy of Finland Grant Number: 307411
Detailed Information: 307411 (Academy of Finland Funding decision)
321440 (Academy of Finland Funding decision)
Dataset Reference: We thank ECMWF for providing the ERA-40 and ERA-Interim reanalysis datasets (, International service of geomagnetic indices for Ap index (, WDC–SILSO, Royal Observatory of Belgium for the internation sunspot number (, NOAA/ESRL Physical Sciences Division for Nino 3.4 index ( and NASA for the stratospheric aerosol optical depth data (
Copyright information: © A. Salminen et al., Published by EDP Sciences 2020. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.