This study presents the response of the atmosphere and ionosphere to the precipitation of energetic electrons from the Earth’s outer radiation belt into the atmosphere during a weak magnetic storm on February 1–4, 2015. Information on the spectra of precipitating energetic electrons was obtained from experimental data from the polar satellite Meteor-M2 using integral electron channels with energies >100 keV, >300 keV and >2 MeV. To recover atmospheric response we use one-dimensional radiative-convective model with interactive neutral and ionic chemistry. It is shown that the strongest response in variations of ionization rates, ozone, as well as ozone-depleting atmospheric components occurs during the main phase of the storm and at the beginning of the recovery phase, when the most intense precipitation occurs during substorm activity. It has been established that mesospheric ozone loss up to 24

Extreme solar particle events (ESPEs) are caused by rare, enormously strong solar eruptions and can produce globally detectable spikes in tree-ring radiocarbon 14C, known as Miyake events, which serve as precise chronological tie-points and indicators of extreme solar activity. After production, radiocarbon is subjected to the complex carbon cycle, including large-scale atmospheric transport, which is crucially important for fast and strong Miyake events with highly inhomogeneous 14C production. A new 3D dynamical model, SOCOL:14C-Ex, of the radiocarbon atmospheric production and transport is presented here, which can model fast changes in the 14C atmospheric concentrations with high temporal and spatial resolution. Precise response curves of Δ^14C to a reference ESPE (100xGLE#69) were computed for various event dates. They can be directly applied to analyse Miyake events under different conditions. Seven strong events over the past 14 millennia (AD 993, AD 774, 664 BC, 5260 BC, 5411 BC, 7177 BC, and 12351 BC) were analysed by fitting the reference curves to the available annual D14C data, identifying the most probable values and confidence intervals of their parameters – strength, event's date and background level. By applying corrections for the geomagnetic and atmospheric (CO2) factors, the strengths of the corresponding ESPEs were assessed. The strongest ESPE is confirmed to be that of 12351 BC, while that of AD 774 remains the strongest event during the Holocene. To conclude, a new tool, based on the radiocarbon atmospheric transport model SOCOL:14C-Ex, is presented to analyse fast changes in the ^14C production.

The Arctic stratosphere during the first half of the 2024/25 winter was characterized by an exceptionally strong polar vortex, comparable to the coldest winter of 2019/20 with record ozone depletion. In mid-February 2025, enhanced propagation of planetary wave activity over northeastern Eurasia led to a deceleration of the wind in the upper stratosphere, followed by downward wave reflection into the troposphere over Canada, northern USA, and northwestern Eurasia. This stratosphere-troposphere interaction resulted in significant surface cooling in these regions and drove the Arctic Oscillation (AO) index to a winter minimum of −5. Such strong AO anomalies, exceeding −2σ, have been observed in February over the past 25 years only in 2010, 2021, and 2025. A major sudden stratospheric warming (SSW) event in early March was preceded by a prolonged preconditioning stage of the polar vortex, characterized by intensified stratospheric vacillations between zonal winds and planetary waves. During the SSW, enhanced wave activity propagation into the stratosphere was identified over northeastern Eurasia and Europe. The amplified upward wave flux over Europe was linked to the eastward redistribution of wave activity fluxes in the upper troposphere over the North Atlantic, originating from the wave reflection region over North America. Using lidar sounding and spectral measurements of excited hydroxyl molecules OH* temperature, the stratosphere and upper mesosphere temperature variations in February–March 2025 were analyzed. Simulation with the CCM (chemistry–climate model) SOCOLv3 estimated the total chemical ozone loss in the Arctic stratosphere in winter 2024/25 as ∼50

To improve diagnostics and prediction of changes caused by increased impact of anthropogenic activity, it is necessary to increase the comparative analysis of measurements and modeling of ozone-one of the climatically important atmospheric gases due to the decisive influence of stratospheric ozone on the radiation balance of the Earth-atmosphere system and the role of tropospheric ozone, the third most significant anthropogenic factor contributing to the greenhouse effect. This task is particularly relevant for Russia, as its geographical location makes it more vulnerable to climate change than other countries, whereas its regional tendencies in ozone variability have not yet been studied in sufficient detail. An analysis of IKFS-2 tropospheric ozone content (TrOC) measurements for 2015-2022 revealed that in Siberian, Far Eastern, North Caucasian, and Southern federal districts of Russia TrOC maximum, caused by photochemical formation of ground-level ozone, is observed in July (up to 30-35 DU for monthly means in surface-400 hPa layer). In Northwestern federal district, TrOC maximum (up to 25-30 DU), determined by meridional transport, is observed in late spring. No statistically significant linear trends in TrOC are detected. The WRF-Chem model qualitatively describes the seasonal variations of TrOC as well as the anomalous increase in TrOC caused by forest fires. The variability of total ozone content (TOC) is analyzed by OMI (2005-2023) and IKFS-2 (2015-2022) measurements as well as by SOCOLv3 simulations. Ozone negative anomalies in spring (up to 15% for monthly means) are generally observed with positive Arctic oscillation index values and a westerly phase of Quasi-biennial oscillations. For the 2008-2022 period, a statistically significant increase in TOC (+1.6-1.7% per year) is obtained for European Russia and Western and Central Siberia in November.

Energetic particle precipitation (EPP) provides a key source of atmospheric ionization, particularly during the polar night when solar radiation is absent. This ionization triggers chemical processes that leading to dramatic changes in the chemical and ionic composition of the atmosphere and the ionosphere (for example, layer D). Here, we present the variability of the ion composition of the high-latitude ionosphere simulated using a one-dimensional radiative-convective photochemical model with interactive neutral and ion chemistry.

During the last millennia, prior to the industrialization, long-term climatic variations correlate with low-frequency total solar irradiance (TSI) changes. This long-term correlation does, however, not prove or disapprove a causal relationship. An additional natural forcing is the volcanic activity. The exact magnitudes of these two natural forcings are not known because reconstructions are based on proxy data which include substantial uncertainty. The Maunder Minimum, a period between roughly 1600 and 1700 A.D., is characterized by lower temperatures, low solar activity, and relatively high volcanic activity. There is still a debate on how forcing, i.e., solar vs. volcanic, influenced the climate and to which extend during that time. The amplitude of the TSI decrease is especially uncertain and suggestions range from a few W/m2 to a few tens of W/m2 lower than today’s value. Here we present simulations with the chemistry-climate model SOCOL where different solar forcings ranging from +10 W/m2 to -20 W/m2 in TSI terms are applied. On a global scale, changes in temperature are linear with changes in TSI. On a regional scale, however, the temperature response can be non-linear especially at high latitudes. The mechanisms leading to the non-linear behavior are explored.

This study analyses the wide-band algorithm, Cloud-J v.8.0, from the point of view of the validity of the choice of wide spectral intervals to accelerate the calculations of photolysis rates in the lower and middle atmosphere, considering the features of solar radiation propagation, and to assess the influence of the processes of reflection and scattering on molecules, aerosols, and clouds. The results show that the calculations performed using Cloud-J v.8.0 are in agreement with the data obtained using the high-resolution LibRadtran model. The study also considers the factors influencing the propagation of the solar flux through the atmosphere in Cloud-J v.8.0, which occurs following theoretical concepts. It is shown that the presence of cloud layers can increase photolysis rates by up to 40% in the above-cloud layer and decrease them by up to 20% below the cloud layer. The presence of volcanic aerosol can increase the photolysis rates in the upper part of the layer and above it by up to 75% and decrease them by up to 75% in the underlying atmosphere. Rayleigh scattering can both enhance photolysis rates in the troposphere and reduce them at large zenith angles. Thus, Cloud-J offers a robust method for modelling atmospheric photodissociation processes with high computational efficiency.

The severe ozone depletion over the Southern polar region, known as the “ozone hole,” is a stark example of global ozone depletion caused by human-made chemicals. This has implications for climate change and increased harmful surface solar UV. Several Chemistry–Climate models (CCMs) tend to underestimate total column ozone (TCO) against satellite measurements over the Southern polar region. This underestimation can reach up to 50% in monthly mean zonally averaged biases during cold seasons. The most significant discrepancies were found in the CCM SOlar Climate Ozone Links version 3 (SOCOLv3). We use SOCOLv3 to study the sensitivity of Antarctic TCO to three key factors: (1) stratospheric heterogeneous reaction efficiency, (2) meridional flux intensity into polar regions from sub-grid scale mixing, and (3) photodissociation rate calculation accuracy. We compared the model results with satellite data from Infrared Fourier Spectrometer-2 (IKFS-2), Microwave Limb Sounder (MLS), and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The most effective processes for improving polar ozone simulation are photolysis and horizontal mixing. Increasing horizontal mixing improves the simulated TCO seasonal cycle but negatively impacts CH4 and N2O distributions. Using the Cloud-J v.8.0 photolysis module has improved photolysis rate calculations and the seasonal ozone cycle representation over the Southern polar region. This paper outlines how different processes impact chemistry–climate model performance in the southern polar stratosphere, with potential implications for future advancements.

Rocket emissions thin the stratospheric ozone layer. To understand if significant ozone losses could occur as the launch industry grows, we examine two scenarios. Our ‘ambitious’ scenario (2040 launches/year) yields a −0.29% depletion in annual-mean, near-global total column ozone in 2030. Antarctic springtime ozone decreases by 3.9%. Our ‘conservative’ scenario (884 launches/year) yields −0.17% annual, near-global depletion; current licensing rates suggest this scenario may be exceeded before 2030. Ozone losses are driven by the chlorine produced from solid rocket motor propellant, and black carbon which is emitted from most propellants. The ozone layer is slowly healing from the effects of CFCs, yet global-mean ozone abundances are still 2% lower than measured prior to the onset of CFC-induced ozone depletion. Our results demonstrate that ongoing and frequent rocket launches could delay ozone recovery. Action is needed now to ensure that future growth of the launch industry and ozone protection are mutually sustainable.

We compare enhancements of mesospheric volume mixing ratios of hydroperoxyl radical HO2 and nitric acid HNO3, as well as ozone depletion in the Northern Hemisphere (NH) polar night regions during energetic particle precipitation (EPP) in January of 2005 and 2012. We utilize mesospheric observations of HO2, HNO3, and ozone from the Microwave Limb Sounder (MLS/Aura). During the second half of January 2005 and 2012, the GOES satellite identified strong solar proton events with virtually the same proton flux parameters. Geomagnetic disturbances in January of 2005 were stronger, with Dst decreasing up to 100 nT compared to January 2012 while the Dst drop did not exceed 70 nT. Comparison of observations made with the MLS/Aura shows the highest change of HO2 and HNO3 concentrations and also the deepest ozone destruction at the latitudinal range from 60∘ NH to 80∘ NH inside the north polar vortex right after the spike in energetic particle flux registered by GOES satellites. MLS/Aura observations show HNO3 maximum enhancements of about 1.90 ppb and 1.66 ppb around 0.5 hPa (about 55 km) in January 2005 and January 2012, respectively. The HOx increases lead to short-term ozone destruction in the mesosphere, which is seen in MLS/Aura ozone data. The maximum HO2 enhancement is about 1.05 ppb and 1.62 ppb around 0.046 hPa (about 70 km) after the onset of EPP in the second half of January 2005 and January 2012, respectively. Ozone maximum depletion is observed around 0.02 hPa (about 75 km). Ozone recovery after EPP was much faster in January 2005 than in January 2012.

Orographic gravity waves (OGW) have a significant impact on the global atmospheric circulation, providing the transfer of energy and momentum within the atmospheric layers from the surface to the lower thermosphere. Most modern numerical models of the global climate, due to the specifics of the problems being solved, are not able to resolve the atmospheric wave of the meso- and lower scale on their spatial grid. Therefore, various parameterization schemes for wave effects are developed to take into account the impact of OGW. This study is devoted to a detailed description of the new version of the OGW parameterization created on the basis of solving the wave energy balance equation taking into account the Earth rotation. The new version of the parameterization was implemented into the chemistry-climate model SOCOL3 and numerical experiments were carried out using both the previous and the new versions of the parameterization. It is shown, in particular, that the new version of the OGW parameterization allows for more detailed calculation of wave accelerations and heat inflows, especially in the lower stratosphere, while the OGWs propagate to greater heights of the thermosphere than in the previous parameterization, which better corresponds to observations. As a result, this allows us to obtain more realistic profiles of the mean wind and temperature calculated by the model SOCOL3 with the new parameterization, and the possibilities for fine-tuning the new parameterization provide a significant expansion of a range of scenarios for numerical experiments.

We present new opportunities for modeling cosmogenic isotopes using the chemistry-climate model (CCM) SOCOL, including recent advancements in the modeling of 10Be and 14C. A state-of-the-art SOCOL-AERv2 model (coupled with the CRAC production model) has been developed to simulate cosmogenic isotope atmospheric transport and deposition. The model incorporates all relevant atmospheric processes, enabling precise calculations of isotope concentrations across different locations and times. Validation of SOCOL-AERv2-Be against 10Be data from five Antarctic and Greenland ice cores demonstrates a reasonable agreement, capturing large-scale atmospheric dynamics while averaging synoptic-scale variability. This work reveals that most 10Be production occurs in the stratosphere, with >60% of 10Be deposited on the Earth's surface within a year. Additionally, a simplified parameterization of the full-model results is introduced, offering quick and practical estimates for polar regions. Extending these capabilities, the new SOCOL:14C-Ex model allows for the study of extreme solar particle events (ESPEs) beyond the Holocene based on 14C, which was previously limited by the lack of models applicable to glacial climates. Using this model we analyzed the strongest known ESPE, dated to approximately 12350 BC. This event, nearly twice as powerful as the widely studied 775 AD event, likely occurred between January and April 12350 BC, with a peak in early March. These developments demonstrate how advanced chemistry-climate modeling with the SOCOL framework opens new frontiers in understanding cosmogenic isotopes, solar-terrestrial interactions, and the climatic implications of extreme solar events.

Rocket emissions damage the stratospheric ozone layer, which protects life from harmful solar radiation. To understand if significant ozone losses could occur as the launch industry grows, we examine two scenarios of industry aspirations. Our ‘ambitious’ scenario (2,040 launches/year) leads to a -0.29% depletion in annual-mean, near-global total column ozone, relative to a simulation with no rocket launches. Antarctic springtime ozone decreases by 3.9%. Our ‘conservative’ scenario (884 launches/year) leads to a -0.17% annual depletion; current licensing rates suggest this scenario may be exceeded sooner than 2030. Ozone losses are mostly driven by the reactive chlorine produced from solid rocket motor propellant, and black carbon which is emitted from most propellants in contemporary use. The ozone layer is slowly healing from the effects of anthropogenic CFCs, yet ozone abundances are still 2% lower than those measured prior to the onset of CFC-induced ozone depletion. Our results demonstrate that ongoing and frequent rocket launches could delay ozone recovery. Action is needed now to ensure that future growth of the launch industry and ozone protection are mutually sustainable.

We utilized the Earth System model SOCOLv4 to assess the impacts of the Hunga Tonga-Hunga Ha’apai eruption comprehensively. To accurately estimate the model's performance in terms of water vapour and aerosol plume transport during the initial year, we conducted a multi-member ensemble of free-running simulations and additional simulations employing atmospheric dynamics specified to the ERA5 reanalysis data. These simulations were compared with satellite and reanalysis products. The free-running ensemble simulations with only SO2 (no additional H2O) emissions showed the importance of the two species interaction for the resulting sulphate aerosol evolution, in agreement with previous studies. Furthermore, our primary free-running ensemble simulations, comparing scenarios with and without the eruption event, unravelled a negative response in polar stratospheric ozone levels and temperature. Importantly, these changes were found to be coupled to polar vortex dynamics confirming a larger ozone hole during the austral winter and spring of 2023.

Lower stratospheric ozone between 60°S and 60°N has continued to decline since 1998, despite the reduction of ozone‐depleting substances following the Montreal Protocol. Previous studies have shown that, while chemistry‐climate models reproduce the negative ozone trend in the tropical lower stratosphere as a response to increased upwelling, they fail to capture the ozone decline in northern midlatitudes. This study revisits recent lower stratospheric ozone trends over the period 1998–2018 using two types of simulations from the new Chemistry Climate Model Initiative 2022 (CCMI‐2022): REF‐D1, with observed sea surface temperatures, and REF‐D2, with simulated ocean. The observed negative trend in midlatitudes falls within the range of model trends, especially when considering simulations with observed boundary conditions. There is a large spread in the simulated midlatitudes ozone trends, with some simulations showing positive and others negative trends. A multiple linear regression analysis shows that the spread in the trends is not explained by the different linear response to external forcings (solar cycle, global warming, and ozone‐depleting substances) or to the main variability modes (El Niño‐Southern Oscillation and the quasi‐biennial oscillation) but is instead attributed to internal atmospheric variability. Moreover, the fact that some models show very different trends across members, while other models show similar trends in all members, suggests fundamental differences in the representation of the internal variability of ozone transport across models. Indeed, we report substantial intermodel differences in the ozone‐transport connection on interannual timescales and we find that ozone trends are closely coupled to transport trends.

The formation of nitric oxide (NO) by geomagnetic activity and EUV photoionization in the upper mesosphere and lower thermosphere, and its subsequent impact on ozone, contributes to the natural forcing of the climate system, and has been recommended to be included in chemistry-climate model experiments since CMIP6. We compare NO concentrations in the mesosphere and thermosphere simulated by five high-top chemistry-climate models – WACCM-X, EMAC, HAMMONIA, WACCM-D and KASIMA – with satellite observations during a period of low geomagnetic and solar forcing in January 2010. We find disagreements ranging from several orders of magnitude in the high-latitude winter lower thermosphere to about one order of magnitude in the low-latitude thermosphere. Possible reasons for this are explored by analyzing formation and loss reactions of NO at 12:00 UT on 9 January 2010. Two processes that interact with each other are identified as likely sources of these discrepancies, quenching of N(2D) by atomic oxygen in the mid-thermosphere, and meridional transport and mixing from the mid-thermosphere to the lower thermosphere. In the mid-thermosphere, the amount of atomic oxygen available from dissociation of molecular oxygen balances N(4S) and N(2D) via quenching of N(2D). N(4S) can then be transported or mixed into the lower thermosphere, where it efficiently destroys NO, leading to lower values of NO there. In winter, downward and poleward transport of N(4S) from the low and mid-latitude middle thermosphere into the high-latitude lower thermosphere modulates the NO lifetime. This transport is affected by gravity waves, and therefore depends on each models' gravity wave drag scheme and their resolved gravity wave spectra.

In the paper, we examine the atmospheric part of the global electric circuit. When studying large-scale currents in the atmosphere flowing from the ionosphere to the ground, the ionosphere and Earth’s surface can be considered as ideal conductors with high accuracy. These currents are determined by the ground-ionosphere voltage and the spatial distribution of conductivity in the atmosphere. We employ a one-dimensional model of atmospheric electric fields and currents in which currents are assumed to be nearly vertical. Then it is possible to reduce the spatial distribution of conductivity to longitude and latitude distribution of conductivity of atmospheric columns. By integrating the conductivity over the entire Earth surface, we obtain the total conductivity of the atmosphere. Inside clouds, air conductivity decreases due to the ion attachment to water drops. Using available data on decrease in local conductivity within individual clouds, we analyze the effect of cloud density in latitude, longitude, and height on geographical distribution of conductivity and total conductivity of the atmosphere. By the example of 2009, it is shown that cloudiness reduces the total conductivity of the atmosphere by 20 %. Its variations during the day and year are so small that the model fair-weather electric field varies only by 2 % due to cloudiness. Judging by the results obtained, the influence of clouds on atmospheric conductivity does not explain the diurnal and seasonal cycles of the fair-weather electric field strength (Carnegie diagram).

The January 2022 Hunga Tonga–Hunga Ha’apai (HT) eruption injected sulfur dioxide and unprecedented amounts of water vapour (WV) into the stratosphere. Given the manifold impacts of previous volcanic eruptions, the full implications of these emissions are a topic of active research. This study explores the dynamical implications of the perturbed upper-atmospheric composition using an ensemble simulation with the Earth system model SOCOLv4. The simulations replicate the observed anomalies in the stratospheric and lower-mesospheric chemical composition and reveal a novel pathway linking water-rich volcanic eruptions to surface climate anomalies. We show that in early 2023 the excess WV caused significant negative anomalies in tropical upper-stratospheric and mesospheric ozone and temperature, forcing an atmospheric circulation response that particularly affected the Northern Hemisphere polar vortex (PV). The decreased temperature gradient leads to a weakening of the PV, which propagates downward similarly to sudden stratospheric warmings (SSWs) and drives surface anomalies via stratosphere–troposphere coupling. These results underscore the potential of HT to create favorable conditions for SSWs in subsequent winters as long as the near-stratopause cooling effect of excess WV persists. Our findings highlight the complex interactions between volcanic activity and climate dynamics and offer crucial insights for future climate modelling and attribution.

We evaluate changes in the daily doses of surface ultraviolet radiation (UV) necessary for vitamin D production (UVpD) during the 21st century caused by the evolution of the Earth’s climate and the atmospheric ozone layer. Experiments with the Earth system model SOCOLv4 (version 4 of the Solar-Climate Ozone Links Chemistry-Climate Model) and an atmospheric radiative transfer model indicated a significant (20–80%) decrease in UVpD doses at the Earth’s surface between 2015–2024 and 2090–2099 in middle latitudes in both hemispheres and an increase of 30–40% in some areas of lower latitudes. These changes are driven by strong greenhouse gas growth and ozone-depleting substance reductions. The experiments also provided estimates of the relative contributions of the total ozone column (TOC), cloud parameters, and surface albedo changes to the corresponding variations in UVpD daily doses. Outside the tropics, the primary factor contributing to the decrease in UVpD doses (50% to 80%) is the increase in TOC. Changes in cloud parameters account for 20% to 30% of the decrease, while the decline in surface albedo contributes less than 20%. However, in the polar regions of the Northern Hemisphere, this contribution can reach up to 50%. In the lower latitudes, diminishing TOC and liquid water column of cloud (LWCC) provide the main contributions to the increase in UVpD doses.