Impacts of UV Irradiance and Medium-Energy Electron Precipitation on the North Atlantic Oscillation during the 11-Year Solar Cycle.

Guttu, S.; Orsolini, Y.; Stordal, F.; Otterå, O.H.; Omrani, N.; Tartaglione, N.; Verronen, P.T.; Rodger, C.J.; Clilverd, M.A. ORCID: https://orcid.org/0000-0002-7388-1529. 2021 Impacts of UV Irradiance and Medium-Energy Electron Precipitation on the North Atlantic Oscillation during the 11-Year Solar Cycle. [in special issue: Dynamics and Chemistry of the Middle and Upper Atmosphere and Its Response to External Forcing—Observations and Models] Atmosphere, 12 (8), 1029. 21, pp. https://doi.org/10.3390/atmos12081029

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Abstract/Summary

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.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.3390/atmos12081029
ISSN:	2073-4433
Additional Keywords:	11-year solar cycle; energetic particle precipitation; North Atlantic Oscillation; climate models
Date made live:	17 Aug 2021 08:59 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/530896

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.3390/atmos12081029

ISSN:

2073-4433

Additional Keywords:

11-year solar cycle; energetic particle precipitation; North Atlantic Oscillation; climate models

Date made live:

17 Aug 2021 08:59 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/530896