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Journal articleKang H, Choi Y, 2025,
Estimating Tropical Upper‐Level Cloud Feedback Based on Radiative‐Convective Equilibrium Framework
, Geophysical Research Letters, Vol: 52, ISSN: 0094-8276<jats:title>Abstract</jats:title> <jats:p> Tropical upper‐level cloud (TUC) feedback remains highly uncertain because TUC fraction and its radiative effect respond in complex ways to sea surface temperature (SST) warming. Using a radiative–convective equilibrium (RCE) model, we isolate the radiative impact of TUC changes by adjusting the relative occurrence of clouds and water vapor across the tropics. The resulting TUC feedback parameter, estimated from RCE experiments with observationally constrained versus CMIP6‐derived TUC fractions, is more negative for observational inputs (−1.66 to −1.24 W m <jats:sup>−2</jats:sup> K <jats:sup>−1</jats:sup> ) and spans a much broader range for CMIP6 inputs (−1.34 to +1.78 W m <jats:sup>−2</jats:sup> K <jats:sup>−1</jats:sup> ). The stronger negative feedback with observational inputs likely reflects a larger reduction in TUCs with SST warming. In contrast, CMIP6‐based parameters indicate weaker radiative effects of SST‐driven TUC reductions, suggesting that climate models may underestimate this negative feedback. </jats:p>
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Journal articleLivadiotis G, Cuesta ME, Khoo LY, et al., 2025,
Entropy transfer from solar radio bursts to energetic particles.
, Sci Adv, Vol: 11Space plasma thermodynamics is thought to be affected by wave activity. Here, we show that solar radio bursts (SRBs) can transfer entropy to solar energetic protons (SEPs), affecting their thermodynamics. In particular, our analysis (i) detects the statistically significant SEP density fluctuations, associated with SRB activity that triggers a systematic increase in the thermodynamic kappa; (ii) estimates the polytropic index of SEPs, which is anticorrelated with kappa, serving as an independent measure to validate the increase in kappa; (iii) derives the entropy transfer by using its theoretical relationship with kappa; and (iv) compares SRB wave intensity with the entropy transferring to SEPs to demonstrate their wave-particle coupling. We lastly expose the thermodynamic association between type III SRB wave intensity and SEP entropy transfer as well as their respective coupling, thus developing a paradigm for further systematic investigations among other types of wave activity and particle populations.
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Journal articlePugsley G, Gryspeerdt E, Nair V, 2025,
Cloud fraction response to aerosol driven by nighttime processes
, Proceedings of the National Academy of Sciences of USA, ISSN: 0027-8424 -
Journal articleDriver OGA, Stettler MEJ, Gryspeerdt E, 2025,
The ice supersaturation biases limiting contrail modelling are structured around extratropical depressions
, Atmospheric Chemistry and Physics (ACP), Vol: 25, Pages: 16411-16433, ISSN: 1680-7316Contrails are ice clouds formed along aircraft flight tracks, responsible for much of aviation's climate warming impact. Ice-supersaturated regions (ISSRs) provide conditions where contrail ice crystals can persist, but meteorological models often mispredict their occurrence, limiting contrail modelling. This deficiency is often treated by applying local humidity corrections. However, model performance is also affected by synoptic conditions (such as extratropical depressions).Here, composites of ERA5 reanalysis data around North Atlantic extratropical depressions enable a link between their structure and ISSR modelling. ISSRs are structured by these systems: at flight levels, ISSRs occur less frequently in the dry intrusion – descending upper-tropospheric air – than above warm conveyors – where air is lifted. Both ERA5 reanalysis and in situ aircraft observations show this contrast, demonstrating that the model reproduces the fundamental relationship. Individual-ISSR modelling performance (quantified using interpretable metrics) is also structured. Of the rare ISSRs diagnosed in the location associated with the dry intrusion, fewer are confirmed by in situ observations (20 %–25 % precision drop compared to the warm conveyor) and fewer of those observed were diagnosed (13 %–19 % recall drop). Scaling humidity beyond the occurrence rate bias dramatically increases the recall at low precision cost, demonstrating the potential value of scaling approaches designed with different intentions. However, the failure of scaling to improve precision, or the performance in the dry intrusion, implies that there is a need to account for the synoptic weather situation and structure in order to improve ISSR forecasts in support of mitigating aviation's climate impact.
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Journal articleYufei Y, Timothy H, Domenico T, et al., 2025,
Ion-scale solitary structures in the solar wind observed by Solar Orbiter and Parker Solar Probe
, Astrophysical Journal Letters, Vol: 994, ISSN: 2041-8205We investigate a class of ion-scale magnetic solitary structures in the solar wind, characterized by distinct magnetic field enhancements and bipolar rotations over spatial scales of several proton inertial lengths. These structures are revisited using high-resolution data from the Solar Orbiter and Parker Solar Probe missions. Using a machine learning-based method, we identified nearly a thousand such structures, providing new insights into their evolution and physical properties. Statistical analysis shows that these structures are more abundant closer to the Sun, with occurrence rates peaking around 30 - 40 Rsun and decreasing farther out. High-cadence measurements reveal that these structures are predominantly found in low-beta (beta <1) environments, with consistent fluctuations in density, velocity, and magnetic field. Magnetic field enhancements are often accompanied by plasma density drops, which, under near pressure balance, limit field increases. This leads to small fractional field enhancements near the Sun (approximately 0.01 at 20 Rsun), making detection challenging. Magnetic field variance analysis indicates that these structures are primarily oblique to the local magnetic field. Alfvénic velocity-magnetic field correlations suggest that most of these structures, unlike most near-Sun solar wind fluctuations, exhibit sunward-directed Alfvenic polarization in the plasma frame. We compare these findings with previous studies, discussing possible generation mechanisms and their implications for the turbulent cascade in the near-Sun Alfvénic solar wind. While these structures might be Alfvénic solitons, vortices, or flux ropes, we refrain from a definitive classification pending further evidence. Further high-resolution observations and simulations are needed to fully understand their origins and impacts.
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Journal articleLi J-H, Khotyaintsev YV, Graham DB, et al., 2025,
Solar Orbiter Observations of a Self-Consistent Ion-Scale Magnetic Hole at 0.9AU
, GEOPHYSICAL RESEARCH LETTERS, Vol: 52, ISSN: 0094-8276 -
Journal articleDasgupta B, Menoud M, van der Veen C, et al., 2025,
Harmonisation of methane isotope ratio measurements from different laboratories using atmospheric samples
, Atmospheric Measurement Techniques, Vol: 18, Pages: 6591-6607<jats:p>Abstract. Establishing interlaboratory compatibility among measurements of stable isotope ratios of atmospheric methane (δ13C-CH4 and δD-CH4) is challenging. Significant offsets are common because laboratories have different ties to the VPDB or SMOW-SLAP scales. Umezawa et al. (2018) surveyed numerous comparison efforts for CH4 isotope measurements conducted from 2003 to 2017 and found scale offsets of up to 0.5 ‰ for δ13C-CH4 and 13 ‰ for δD-CH4 between laboratories. This exceeds the World Meteorological Organisation Global Atmospheric Watch (WMO-GAW) network compatibility targets of 0.02 ‰ and 1 ‰ considerably. We employ a method to establish scale offsets between laboratories using their reported CH4 isotope measurements on atmospheric samples. Our study includes data from eight laboratories with experience in high-precision isotope ratio mass spectrometry (IRMS) measurements for atmospheric CH4. The analysis relies exclusively on routine atmospheric measurements conducted by these laboratories at high-latitude stations in the Northern and Southern Hemispheres, where we assume each measurement represents sufficiently well-mixed air at the latitude for direct comparison. We use two methodologies for interlaboratory comparisons: (I) assessing differences between time-adjacent observation data and (II) smoothing the observed data using polynomial and harmonic functions before comparison. The results of both methods are consistent, and with a few exceptions, the overall average offsets between laboratories align well with those reported by Umezawa et al. (2018). This indicates that interlaboratory offsets remain robust over multi-year periods. The evaluation of routine measurements allows us to calculate the interlaboratory offsets from hundreds, in some cases thousands of measurements. Therefore, the uncertainty in the mean inter
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Journal articleMuro GD, Cohen CMS, Xu Z, et al., 2025,
Energy-Dependent SEP Fe/O Abundances During the May 2024 Superstorm
, SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS, Vol: 23 -
ReportClarke B, Barnes C, Keeping T, et al., 2025,
Climate change enhanced intensity of Hurricane Melissa, testing limits of adaptation in Jamaica and eastern Cuba
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Journal articleVon Salzen K, Akingunola A, Cole JNS, et al., 2025,
Reduced aerosol pollution diminished cloud reflectivity over the North Atlantic and Northeast Pacific
, NATURE COMMUNICATIONS, Vol: 16 -
Journal articleSparks N, Toumi R, 2025,
The impact of global warming on U.S. hurricane landfall: a storyline approach
, Environmental Research Letters, Vol: 20, ISSN: 1748-9326The projection of hurricane activity under climate change is challenging. The Imperial College Storm Model (IRIS) was used to analyse the impact of global warming on North Atlantic hurricane landfall through a storyline approach. The storyline assumes increases of potential intensity (PI) as the cause of change with no changes to tracks or basin frequency. This allows study of both recenttrends and projections for the first time in a consistent way. The observed hurricane intensification is simulated but underestimated. For a +2◦C global warming scenario hurricanes of intensity Category 4 and above become 62% more likely in the basin and nearly twice (92%) more likely at landfall. The future number of hurricanes, their decay and tracks are uncertain and their impact is examined by sensitivity studies. Reduction of the basin count offsets warming driven landfall frequency increases only for weaker hurricanes. The increased frequency and fraction of the most damaging landfalling hurricanes is controlled by changes in PI.
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Journal articleGrimmich N, Settino A, Nykyri HK, et al., 2025,
Comparison of Kelvin–Helmholtz waves observed simultaneously at the dawn and dusk flanks of the Earth’s magnetopause
, Planetary and Space Science, Vol: 267, ISSN: 0032-0633Across the Earth’s magnetopause, unless the magnetic fields stabilise the boundary, the velocity shear between the magnetospheric plasma and the shocked plasma of the solar wind can lead to the Kelvin–Helmholtz instability. This instability can develop into large-scale surface waves and vortices at the magnetopause, causing the different plasma regions to mix, which plays an important role in the transfer of energy across the magnetopause. We know from spacecraft observations and simulations that the way Kelvin–Helmholtz waves grow and evolve can be different at dawn and dusk. However, very few studies have directly observed this phenomenon on both flanks of the magnetopause simultaneously, nor have they provided a consistent explanation for the question of symmetrical or asymmetrical dawn–dusk growth of the waves. By combining measurements from the THEMIS and Cluster missions, we can report here on an event where such a simultaneous observation of the Kelvin–Helmholtz waves is possible.For this event, we investigate and compare the typical wave parameters and the plasma mixing on the two flanks. Our results suggest an asymmetric evolution of the Kelvin–Helmholtz waves at dawn and dusk. Comparing these results with previous studies of simultaneously observed events and linking them to solar wind conditions further shows that this asymmetric growth seems to occur during the Parker spiral IMF, but probably only if the magnetic fields are strong enough to effectively stabilise the boundary at the dusk flank due to field line draping.
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Journal articleCuesta ME, Fraschetti F, Livadiotis G, et al., 2025,
Distinct Solar Energetic Particle Shock Intensity-Diffusion Coefficient Relationships in the Inner Heliosphere
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 993, ISSN: 2041-8205 -
Journal articleBeth A, Galand M, Jia X, et al., 2025,
Ion-neutral chemistry at icy moons: the case of Ganymede
, Monthly Notices of the Royal Astronomical Society, Vol: 544, Pages: 95-112, ISSN: 0035-8711Icy moons orbiting giant planets are often described as airless bodies though they host an exosphere where collisions between neutral species are scarce. In the case of Ganymede, the neutral composition is dominated by H2O, H2, and O2. Past observations by Galileo showed that Ganymede hosts an ionosphere and those by Juno revealed the presence of H+3 , an ion species onlystemming from ion-neutral collisions. H+3 detection suggests that ions and neutrals might still collide and be the source of new ion species on icy moons. We examine Ganymede’s ability to host a more diverse ionosphere in terms of ion composition than previously thought and predict its variety. We upgraded our test-particle code of Ganymede’s ionosphere, formerly collisionless,to include ion-neutral collisions in a probabilistic manner. The updated code is applied to three Galileo flybys of Ganymede that were investigated in the absence of chemistry. Both sets of simulations have been compared and the effect of ion-neutral chemistry has been assessed. We show that in the case of an exosphere predominantly composed of H2O, H2, and O2, theionosphere is made not only of their associated cations but also of H+3 , H3O+, and O2H+. Simulations reveal that, depending on the location, the contribution of H+3 and H3O+ to the ion composition may be significant. Strong dayside/nightside and Jovian/anti-Jovian asymmetries in the ion composition are identified. Our findings are key to interpreting Juno and future JUICEion mass spectrometer data sets.
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Journal articleErgun RE, Qi Y, Vo T, et al., 2025,
Electron Acceleration in Magnetic Reconnection-driven Turbulence in the Earth's Magnetotail
, ASTROPHYSICAL JOURNAL, Vol: 993, ISSN: 0004-637X -
Journal articleHalekas JS, Whittlesey P, Larson DE, et al., 2025,
Electrons in the Collisionally Young Solar Wind: Parker Solar Probe Observations
, ASTROPHYSICAL JOURNAL, Vol: 993, ISSN: 0004-637X -
Journal articleMcComas DJ, Christian ER, Schwadron NA, et al., 2025,
Interstellar Mapping And Acceleration Probe: The NASA IMAP Mission
, SPACE SCIENCE REVIEWS, Vol: 221, ISSN: 0038-6308- Cite
- Citations: 3
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Journal articleGuillaume-Castel R, Ceppi P, Dorrington J, et al., 2025,
ENSO Diversity Explains Interannual Variability of the Pattern Effect
, GEOPHYSICAL RESEARCH LETTERS, Vol: 52, ISSN: 0094-8276 -
Journal articleErvin T, Mallet A, Eriksson S, et al., 2025,
The Impact of Alfvénic Shear Flow on Magnetic Reconnection and Turbulence
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 992, ISSN: 2041-8205 -
Journal articleBreul P, Ceppi P, Nowack P, 2025,
The importance of stratocumulus clouds for projected warming patterns and circulation changes
, Atmospheric Chemistry and Physics (ACP), Vol: 25, Pages: 11991-12005, ISSN: 1680-7316Stratocumulus clouds are thought to exert a strong positive radiative feedback on climate change, but recent analyses suggest that this feedback is widely under-represented in global climate models. To assess the broader implications of this model error for the simulated climate change responses, we investigate the impact of Pacific stratocumulus cloud feedback on projected warming patterns, equilibrium climate sensitivity and tropical atmospheric circulation under increased CO2 concentrations. Using the Community Earth System Model, with modifications to enhance low-cloud-cover sensitivity to sea surface temperature (SST) anomalies in Pacific stratocumulus regions, we find increased tropical SST variability and persistence, a higher equilibrium climate sensitivity, an enhanced east–west warming contrast across the tropical Pacific, and a stronger slowdown of the Walker circulation under 4×CO2 conditions. Our findings are supported by inter-model relationships across CMIP6 4×CO2 simulations. These results underscore the importance of accurately representing cloud feedback in climate models to predict future climate change impacts not only globally but also on a regional scale, such as warming patterns or circulation change.
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Journal articleCargill PJ, Hood AW, Johnson D, 2025,
Heating and cooling at a coronal magnetic null
, Monthly Notices of the Royal Astronomical Society, Vol: 542, Pages: 3385-3394, ISSN: 0035-8711Conductive cooling of the solar corona at a magnetic null is examined. An initial equilibrium is set up, balancing thermal conduction and a constant spatially uniform coronal heating. The heating is then turned off and the subsequent conductive cooling calculated. An equation for the cooling is obtained using the method of separation of variables and it is shown that the equations for the equilibrium between conduction and heating, and the time-dependent cooling are mathematically identical with a simple change of variables. Thus, the properties of the cooling phase are automatically determined by the equilibrium state. For a two-dimensional null, the characteristic cooling time-scale increases over that in a straight field by a factor of between 2 and 5, with a scaling determined by the ratio of the average and base areas of a flux element. There is no explicit dependence on the very large areas that can arise near the null.
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Journal articleWaters CL, Eastwood JP, Fargette N, et al., 2025,
Bridging in situ satellite measurements and simulations of magnetic reconnection using recurrent neural networks
, Journal of Geophysical Research: Space Physics, Vol: 130, ISSN: 2169-9380Magnetic reconnection is inherently structured, with distinct spatial regions such as inflows, outflows, and separatrices playing key roles in energy conversion and particle transport. While in situ spacecraft measurements provide detailed local information, determining where a spacecraft lies within the global reconnection geometry remains a major challenge. Proxy-based methods are often ambiguous, while full reconstructions require strong assumptions and are difficult to apply systematically across events. Here, we present a method that bridges these approaches by using machine learning to infer global structural context from local measurements. We first apply k-means clustering to a 2.5-D particle-in-cell simulation to identify six characteristic symmetric reconnection regions. A recurrent neural network (RNN) is then trained on spacecraft-like trajectories through the simulation to classify time series data into these regions. When applied to Magnetospheric Multiscale (MMS) observations of magnetotail reconnection, this method successfully identifies regional transitions, including inflow, outflow, and separatrix crossings, in agreement with previous reconstructions where available. The approach provides a practical, scalable, and automated framework for determining spatial context in reconnection events without requiring full geometric reconstruction, enabling large-scale and efficient statistical studies of reconnection dynamics across multiple events.
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Journal articleTsui EYL, Toumi R, 2025,
Re‐intensification of seafalling tropical cyclones
, Atmospheric Science Letters, Vol: 26, ISSN: 1530-261XThe study of tropical cyclones re-entering the ocean or making ‘seafall’ has been limited. Here, idealised simulations are used to study the re-intensification of seafalling tropical cyclones. They follow a two-stage fast-slow process driven predominately by a change in surface friction initially and then by heating. The previous land decay causes seafalling tropical cyclones to be larger and intensify more slowly with milder inner-core contraction than in ocean-only cases. Nonetheless, they reach the same intensity but with almost twice the integrated kinetic energy, so that the second landfall made by seafalling tropical cyclones can cause more damage due to their larger footprint of destructive wind.
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Journal articleDesai RT, Perrin J, Meredith NP, et al., 2025,
Multi-MeV Electron Occurrence and Lifetimes in the Outer Radiation Belt and Slot Region During the Maximum of Solar Cycle 22
, SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS, Vol: 23 -
Journal articleDing M, Lim SZJ, Yu X, et al., 2025,
A neural network approach for line detection in complex atomic emission spectra measured by high-resolution Fourier transform spectroscopy
, MACHINE LEARNING-SCIENCE AND TECHNOLOGY, Vol: 6 -
Journal articleArcher M, Evans V, Eastwood J, et al., 2025,
First detection of field-aligned currents using engineering magnetometers from the OneWeb mega-constellation
, Space Weather, ISSN: 1539-4956 -
Journal articleTrotta D, Horbury TS, Giacalone J, 2025,
Variability in energetic particle observations at strong interplanetary shocks: Multi-spacecraft observations
, ASTRONOMY & ASTROPHYSICS, Vol: 702, ISSN: 0004-6361 -
Journal articleAuestad H, Shibu A, Ceppi P, et al., 2025,
The Latent Heating Feedback on the Mid-Latitude Circulation
, GEOPHYSICAL RESEARCH LETTERS, Vol: 52, ISSN: 0094-8276 -
Journal articleHuang Z, Velli M, Chandran BDG, et al., 2025,
Two Types of 1/<i>f</i> Range in Solar Wind Turbulence
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 990, ISSN: 2041-8205 -
Journal articleRivera YJ, Klein KG, Wang JH, et al., 2025,
Observational Constraints on the Radial Evolution of O<SUP>6+</SUP> Temperature and Differential Flow in the Inner Heliosphere
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 990, ISSN: 2041-8205
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