Investigation of solar induced climate variability in chemistry-climate model simulations
Final Report Abstract
Solar variability on different time scales affects the atmosphere from its uppermost layers, the thermosphere/ionosphere, down to the earth’s surface. Investigating the influence of solar variability with the 11-year sunspot cycle on the mesosphere/stratosphere and the surface climate in climate-chemistry models (CCMs) of the CCM Initiative 1 (CCMI-1) dataset is the subject of this project. The impact of the 11-year variability in solar irradiance in the mesosphere and stratosphere produces a direct signal, with warming from the absorption of solar ultraviolet (UV) radiation by molecular oxygen and ozone and a more intense ozone production with increasing solar activity. However, modelling the downward propagation of the solar signal to the surface remains a challenge. Observational data clearly show an influence on the North Atlantic Oscillation (NAO) during the northern hemisphere winter season, with a trend towards a more positive NAO index at the sunspot cycle’s maximum. The highest solar influence on the NAO pattern is observed with a lag of three to four years after the solar maximum. This project can only support the hypothesis of the "top-down" mechanism that links the solar-induced increase in temperature and ozone in the upper stratosphere/lower mesosphere to the surface for reanalysis data. The reanalyses (EZMWF ERA-20C and CERA-20C) show a maximum signal with a delay of three to four years. CCMI-1 models show no consistent "top-down" mechanism, and the analyzes did not support a time shift of the solar signal for several years. The reason could be the relatively low horizontal resolution of most current CCMs, which does not allow modelling of the relevant processes responsible for connecting the solar signal in the middle atmosphere to the surface, and the delay of the maximum solar signal by several years after the peak of solar activity. Previous modelling studies showing the lag in surface response have used coupled climate models with a higher horizontal resolution of the atmosphere and ocean. The authors argue with an oceanic memory effect that propagates the signal from the highest solar intensity towards the following solar minimum, which may not be able to be modelled by the coarser resolution CCMI-1 CCMs. Likewise, these modelling studies use an amplitude of solar radiation adapted from the SIM instrument, which has now been found to be too large. Future CCMI simulations should be performed with a higher horizontal resolution of the atmosphere and ocean, which could help model the realistic downward propagation of the solar signal to the surface.
Publications
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Solar induced climate variability in CCMI simulations, 9th Annual EMAC Symposium, Jülich, July 2nd –4th 2019
Kunze, Markus & Langematz, Ulrike
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Working Group 1 – Stratospheric Signal, SOLARIS-HEPPA Working Group Meeting, Granada, September 18th –19th 2019
Kunze, Markus & Chiodo, Gabriel
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Quantifying uncertainties of climate signals in chemistry climate models related to the 11-year solar cycle – Part 1: Annual mean response in heating rates, temperature, and ozone. Atmospheric Chemistry and Physics, 20(11), 6991-7019.
Kunze, Markus; Kruschke, Tim; Langematz, Ulrike; Sinnhuber, Miriam; Reddmann, Thomas & Matthes, Katja
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The response of mesospheric H2O and CO to solar irradiance variability in models and observations. Atmospheric Chemistry and Physics, 21(1), 201-216.
Karagodin-Doyennel, Arseniy; Rozanov, Eugene; Kuchar, Ales; Ball, William; Arsenovic, Pavle; Remsberg, Ellis; Jöckel, Patrick; Kunze, Markus; Plummer, David A.; Stenke, Andrea; Marsh, Daniel; Kinnison, Doug & Peter, Thomas
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What is the minimum spectral resolution to model the 11-year solar cycle response in global models?, 10th Annual EMAC Symposium, Online-Zoom- Meeting, May 31st –June 2nd 2021
Kunze, Markus & Langematz, Ulrike
