University of Oulu

Guttu, S.; Orsolini, Y.; Stordal, F.; Otterå, O.H.; Omrani, N.-E.; Tartaglione, N.; Verronen, P.T.; Rodger, C.J.; Clilverd, M.A. Impacts of UV Irradiance and Medium-Energy Electron Precipitation on the North Atlantic Oscillation during the 11-Year Solar Cycle. Atmosphere 2021, 12, 1029.

Impacts of UV irradiance and medium-energy electron precipitation on the North Atlantic Oscillation during the 11-year solar cycle

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Author: Guttu, Sigmund1; Orsolini, Yvan2,3; Stordal, Frode1;
Organizations: 1Department of Geosciences, University of Oslo, 0315 Oslo, Norway
2Norwegian Institute for Air Research, 2007 Kjeller, Norway
3Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim, Norway
4NORCE Norwegian Research Centre AS, 5008 Bergen, Norway
5Bjerknes Centre for Climate Research, 5007 Bergen, Norway
6Geophysical Institute, University of Bergen, 5007 Bergen, Norway
7Space and Earth Observation Centre, Finnish Meteorological Institute, 00101 Helsinki, Finland
8Sodankylä Geophysical Observatory, University of Oulu, 99600 Sodankylä, Finland
9Department of Physics, University of Otago, Dunedin 9016, New Zealand
10British Antarctic Survey (UKRI-NERC), Cambridge BIQQ 1ZZ, UK
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 4.8 MB)
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Language: English
Published: Multidisciplinary Digital Publishing Institute, 2021
Publish Date: 2021-10-28


Observational studies suggest that part of the North Atlantic Oscillation (NAO) variability may be attributed to the spectral ultra-violet (UV) irradiance variations associated to the 11-year solar cycle. The observed maximum surface pressure response in the North Atlantic occurs 2–4 years after solar maximum, and some model studies have identified that atmosphere–ocean feedbacks explain the multi-year lag. Alternatively, medium-to-high energy electron (MEE) precipitation, which peaks in the declining phase of the solar cycle, has been suggested as a potential cause of this lag. We use a coupled (ocean–atmosphere) climate prediction model and a state-of-the-art MEE forcing to explore the respective roles of irradiance and MEE precipitation on the NAO variability. Three decadal ensemble experiments were conducted over solar cycle 23 in an idealized setting. We found a weak ensemble-mean positive NAO response to the irradiance. The simulated signal-to-noise ratio remained very small, indicating the predominance of internal NAO variability. The lack of multi-annual lag in the NAO response was likely due to lagged solar signals imprinted in temperatures below the oceanic mixed-layer re-emerging equatorward of the oceanic frontal zones, which anchor ocean–atmosphere feedbacks. While there is a clear, yet weak, signature from UV irradiance in the atmosphere and upper ocean over the North Atlantic, enhanced MEE precipitation on the other hand does not lead to any systematic changes in the stratospheric circulation, despite its marked chemical signatures.

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Series: Atmosphere
ISSN: 2073-4433
ISSN-E: 2073-4433
ISSN-L: 2073-4433
Volume: 12
Issue: 8
Article number: 1029
DOI: 10.3390/atmos12081029
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: S.G., Y.O., F.S., O.H.O., N.-E.O., and N.T. have been funded by the Norwegian Research Council through project 255276 (Solar effects on natural climate variability in the North Atlantic and Arctic). The work of P.T.V. is supported by the Academy of Finland (project no. 335555 ICT-SUNVAC).
Copyright information: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (