SOLENA – Solar effects on natural climate variability in the North Atlantic and Arctic (completed)

• Tartaglione, Nazario; Toniazzo, Thomas; Otterå, Odd Helge & Orsolini, Yvan Joseph Georges Emile G. (2023). Equilibrium Climate after Spectral and Bolometric Irradiance Reduction in Grand Solar Minimum Simulations. Climate. ISSN 2225-1154. 12(1). doi: 10.3390/cli12010001. Full text in Research Archive Show summary

  In this study, we use the Whole Atmosphere Community Climate Model, forced by present-day atmospheric composition and coupled to a Slab Ocean Model, to simulate the state of the climate under grand solar minimum forcing scenarios. Idealized experiments prescribe time-invariant solar irradiance reductions that are either uniform (percentage-wise) across the total solar radiation spectrum (TOTC) or spectrally localized in the ultraviolet (UV) band (SCUV). We compare the equilibrium condition of these experiments with the equilibrium condition of a control simulation, forced by perpetual solar maximum conditions. In SCUV, we observe large stratospheric cooling due to ozone reduction. In both the Northern Hemisphere (NH) and the Southern Hemisphere (SH), this is accompanied by a weakening of the polar night jet during the cold season. In TOTC, dynamically induced polar stratospheric cooling is observed in the transition seasons over the NH, without any ozone deficit. The global temperature cooling values, compared with the control climate, are 0.55±0.03 K in TOTC and 0.39±0.03 K in SCUV. The reductions in total meridional heat transport outside of the subtropics are similar in the two experiments, especially in the SH. Despite substantial differences in stratospheric forcing, similarities exist between the two experiments, such as cloudiness; meridional heating transport in the SH; and strong cooling in the NH during wintertime, although this cooling affects two different regions, namely, North America in TOTC and the Euro–Asian continent in SCUV.

• Pérot, Kristell & Orsolini, Yvan J. (2021). Impact of the major SSWs of February 2018 and January 2019 on the middle atmospheric nitric oxide abundance. Journal of Atmospheric and Solar-Terrestrial Physics. ISSN 1364-6826. 218. doi: 10.1016/j.jastp.2021.105586. Full text in Research Archive Show summary

  The Arctic middle atmosphere was affected by major sudden stratospheric warmings (SSW) in February 2018 and January 2019, respectively. In this article, we report for the first time the impact of these two events on the middle atmospheric nitric oxide (NO) abundance. The study is based on measurements obtained during two dedicated observation campaigns, using the Sub-Millimetre Radiometer (SMR) aboard the Odin satellite, measuring NO globally since 2003. The SSW of February 2018 was similar to other, more dynamically quiet, Arctic winters in term of NO downward transport from the upper mesosphere–lower thermosphere to lower altitudes (referred to as energetic particle precipitation indirect effect EPP-IE). On the contrary, the event of January 2019 led to one of the strongest EPP-IE cases observed within the Odin operational period. Important positive NO anomalies were indeed observed in the lower mesosphere–upper stratosphere during the three months following the SSW onset, corresponding to NO volume mixing ratios more than 50 times higher than the climatological values. These different consequences on the middle atmospheric composition are explained by very different dynamical characteristics of these two SSW events.

• Guttu, Sigmund; Orsolini, Yvan; Stordal, Frode; Otterå, Odd Helge; Omrani, Nour-Eddine & Tartaglione, Nazario [Show all 9 contributors for this article] (2021). Impacts of UV irradiance and medium-energy electron precipitation on the North Atlantic oscillation during the 11-year solar cycle. Atmosphere. ISSN 2073-4433. 12(8). doi: 10.3390/atmos12081029. Full text in Research Archive Show 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.

• Guttu, Sigmund; Orsolini, Yvan J.; Stordal, Frode; Otterå, Odd Helge & Omrani, Nour-Eddine (2021). The 11 year solar cycle UV irradiance effect and its dependency on the Pacific Decadal Oscillation. Environmental Research Letters. ISSN 1748-9326. 16(6). doi: 10.1088/1748-9326/abfe8b. Full text in Research Archive Show summary

  The stratospheric, tropospheric and surface impacts from the 11 year ultraviolet solar spectral irradiance (SSI) variability have been extensively studied using climate models and observations. Here, we demonstrate using idealized model simulations that the Pacific Decadal Oscillation (PDO), which has been shown to impact the tropospheric and stratospheric circulation from sub-decadal to multi-decadal timescales, strongly modulates the solar-induced atmospheric response. To this end, we use a high-top version of the coupled ocean–atmosphere Norwegian Climate Prediction Model forced by the SSI dataset recommended for Coupled Model Intercomparison Project 6. We perform a 24-member ensemble experiment over the solar cycle 23 in an idealized framework. To assess the PDO modulation of the solar signal, we divide the model data into the two PDO phases, PDO+ and PDO−, for each solar (maximum or minimum) phase. By compositing and combining the four categories, we hence determine the component of the solar signal that is independent of the PDO and the modulation of the solar signal by the PDO, along with the solar signal in each PDO phase. Reciprocally, we determine the PDO effect in each solar phase. Our results show that the intensification of the polar vortex under solar maximum is much stronger in the PDO− phase. This signal is transferred into the troposphere, where we find a correspondingly stronger polar jet and weaker Aleutian Low. We further show that the amplification of the solar signal by the PDO− phase is driven by anomalous meridional advection of solar-induced temperature anomalies over northern North America and the North Pacific, which contributes to a decreased meridional eddy heat flux and hence to a decreased vertical planetary wave flux into the stratosphere.

• Tartaglione, N.; Toniazzo, T.; Orsolini, Y. & Otterå, O.H. (2020). Impact of solar irradiance and geomagnetic activity on polar NOx, ozone and temperature in WACCM simulations. Journal of Atmospheric and Solar-Terrestrial Physics. ISSN 1364-6826. 209. doi: 10.1016/j.jastp.2020.105398. Full text in Research Archive Show summary

  The response of the atmosphere to solar irradiance and geomagnetic activity is analyzed in experiments with the Whole Atmosphere Community Climate Model (WACCM) under idealized forcings. Four experiments are carried out combining high (H) and low (L) solar radiative forcing with high (7) and low (3) geomagnetic activity: H7 (with high radiative forcing and high geomagnetic activity), H3, (high/low), L7 (low/high), and L3 (low/low). The comparison between these experiment is used to assess the effects of solar radiative forcing and geomagnetic activity mainly on the stratosphere. A two-step Monte Carlo-based statistical test, which defines an impact score, is used to assess statistically significant impacts on regional scales, on pressure levels, for a few key model variables, like NOx, ozone, and temperature. Under low solar forcing (L7/L3), a statistically significant relationship between geomagnetic activity and NOx is found in both hemispheres and for all seasons. An equally strong relationship is lacking for ozone and temperature when analyzing these fields on isobaric levels. A statistically significant impact on stratospheric ozone is only seen in austral winter and spring. However, vertical cross sections show statistically significant impact on temperature and ozone mainly in the southern hemisphere (SH) during austral winter and the following spring. Significant and persistent signals in both SH NOx and ozone concentrations are only produced when the effect of high solar forcing is added to high geomagnetic activity (H7). In this case, statistically significant differences are also found for mesospheric temperatures, ozone and NOx. This latter result appears also under low geomagnetic activity as a result of solar forcing alone, suggesting that solar irradiance significantly affects NOx, ozone and stratospheric temperatures and, in some seasons, even tropospheric temperature. In summary, geomagnetic activity primarily affects NOx and ozone concentrations in the SH. Solar maximum conditions can reduce the amount of NOx in the stratosphere because of higher ozone production. Thus, we conclude that correlations between changes in solar irradiance and geomagnetic activity are important with respect to their effects on the atmosphere. In particular, geomagnetic activity can modulate atmospheric ozone concentrations and other associated stratospheric and tropospheric variables under conditions of high solar activity.

• Tartaglione, Nazario; Toniazzo, Thomas; Orsolini, Yvan & Otterå, Odd Helge (2020). A note on the statistical evidence for an influence of geomagnetic activity on Northern Hemisphere seasonal-mean stratospheric temperatures using the Japanese 55-year Reanalysis. Annales Geophysicae. ISSN 0992-7689. 38, p. 545–555. doi: 10.5194/angeo-38-545-2020. Full text in Research Archive Show summary

  We employ JRA-55 (Japanese 55-year Reanalysis), a recent second-generation global reanalysis providing data of high quality in the stratosphere, to examine whether a distinguishable effect of geomagnetic activity on Northern Hemisphere stratospheric temperatures can be detected. We focus on how the statistical significance of stratospheric temperature differences may be robustly assessed during years with high and low geomagnetic activity. Two problems must be overcome. The first is the temporal autocorrelation of the data, which is addressed with a correction of the t statistics by means of the estimate of the number of independent values in the series of correlated values. The second is the problem of multiplicity due to strong spatial autocorrelations, which is addressed by means of a false discovery rate (FDR) procedure. We find that the statistical tests fail to formally reject the null hypothesis, i.e. no significant response to geomagnetic activity can be found in the seasonal-mean Northern Hemisphere stratospheric temperature record.

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• Orsolini, Yvan J.; Guttu, Sigmund; Stordal, Frode; Otterå, Odd Helge & Omrani, Nour-Eddine (2022). The 11 year solar cycle UV irradiance effect and its dependency on the Pacific Decadal Oscillation.
• Guttu, Sigmund; Orsolini, Yvan J.; Stordal, Frode; Otterå, Odd Helge & Omrani, Nour-Eddine (2021). The 11 year solar cycle UV irradiance effect and its dependency on the Pacific Decadal Oscillation.
• Orsolini, Yvan J.; Guttu, Sigmund; Stordal, Frode; Otterå, Odd Helge; Omrani, Nour-Eddine & Tartaglione, Nazario [Show all 9 contributors for this article] (2021). Impacts of UV Irradiance and Particle Precipitation on the North Atlantic Oscillation During the 11-year Solar Cycle.
• Orsolini, Yvan J. & Pérot, Kristell (2021). Impact of the Major Ssws of February 2018 and January 2019 on the Middle Atmospheric Nitric Oxide Abundance.
• Guttu, Sigmund; Orsolini, Yvan J.; Stordal, Frode; Limpasuvan, Varavut & Marsh, Daniel R. (2020). Impact of Medium-Energy Electron Precipitation on Ozone and Middle Atmosphere Dynamics in WACCM Simulations.
• Orsolini, Yvan J. (2020). Solar Impact on Climate through Energetic Particle Precipitation.
• Orsolini, Yvan; Guttu, Sigmund; Stordal, Frode & Limpasuvan, Varavut (2019). Impact of Medium-energy Electron Precipitation on Ozone and Middle Atmosphere Dynamics in WACCM Simulations.
• Guttu, Sigmund & Orsolini, Yvan (2019). Impact of Medium-energy Electron Precipitation on Ozone and Middle Atmosphere Dynamics in WACCM simulations.
• Pérot, K.; Orsolini, Yvan; Grieco, F. & Murtagh, D. (2019). Study of Energetic Particle Precipitation Effects, based on 15 Years of NO Observations by Odin/SMR.
• Zhang, Jiarong; Limpasuvan, Var; Orsolini, Yvan; Espy, Patrick Joseph & Hibbins, Robert (2019). Semidiurnal Tidal Perturbations during SSW in SuperDARN and WACCM-X.
• Guttu, Sigmund; Orsolini, Yvan; Stordal, Frode; Limpasuvan, Varavut & Marsh, D. (2019). Impact of medium-energy electron precipitation on ozone and middle atmosphere dynamics in WACCM simulations.
• Orsolini, Yvan (2018). Chemical impacts of energetic particle precipitation in the polar mesosphere-lower thermosphere.
• Tartaglione, Nazario; Orsolini, Yvan; Otterå, Odd Helge & Toniazzo, Thomas (2018). Impact of the solar and geomagnetic activity on atmospheric variables: A study with WACCM.
• Orsolini, Yvan; Smith-Johnsen, Christine; Marsh, Dan & Stordal, Frode (2018). Chemical impacts of energetic particle precipitation in the middle atmosphere.
• Tartaglione, Nazario; Toniazzo, Thomas; Otterå, Odd Helge & Orsolini, Yvan (2017). Stratospheric ozone distribution and its influence on the atmospheric circulation.
• Orsolini, Yvan (2017). Modelling the impact of energetic particle precipitation on the middle atmosphere, and implications for climate.

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