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Journal articleLi J-H, Khotyaintsev YV, Graham DB, et al., 2025, , GEOPHYSICAL RESEARCH LETTERS, Vol: 52, ISSN: 0094-8276
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Journal articleMuro GD, Cohen CMS, Xu Z, et al., 2025, , SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS, Vol: 23
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ReportClarke B, Barnes C, Keeping T, et al., 2025,
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Journal articleVon Salzen K, Akingunola A, Cole JNS, et al., 2025, , Nature Communications, Vol: 16, ISSN: 2041-1723
Over the past several decades, the proportion of solar radiation reflected back into space has declined, accelerating the accumulation of heat within the Earth system. Here we show that the marine cloud reflectivity decreased on average by 2.8 ± 1.2% per decade in the combined North Atlantic and Northeast Pacific regions between 2003 and 2022. The majority of the Earth System Models we analyzed simulated a significantly weaker cloud reflectivity decrease and warming of the sea surface in these regions than observed. In contrast, our simulations using an improved aerosol-climate model reproduce the spatial extent and magnitude of the observed cloud reflectivity decrease. We show that reductions in sulfur dioxide and other aerosol precursors accounted for 69% (range 55−85%) of the cloud reflectivity decrease through aerosol-cloud interactions, consistent with the observed aerosol and cloud trends. This raises the prospect of a continuing cloud reflectivity decrease and an associated warming impact in these regions, given that the emission reductions are projected to persist over the next few decades. Further research is needed to assess whether near-term climate scenarios should be revised to account for the weak cloud reflectivity reductions in the Earth System Models.
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Journal articleSparks N, Toumi R, 2025, , Environmental Research Letters, Vol: 20, ISSN: 1748-9326
The projection of hurricane activity under climate change is challenging. The 911今日黑料 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鈼 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 articleErgun RE, Qi Y, Vo T, et al., 2025, , ASTROPHYSICAL JOURNAL, Vol: 993, ISSN: 0004-637X
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Journal articleGrimmich N, Settino A, Nykyri HK, et al., 2025, , Planetary and Space Science, Vol: 267, ISSN: 0032-0633
Across 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, , ASTROPHYSICAL JOURNAL LETTERS, Vol: 993, ISSN: 2041-8205
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Journal articleHalekas JS, Whittlesey P, Larson DE, et al., 2025, , ASTROPHYSICAL JOURNAL, Vol: 993, ISSN: 0004-637X
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Journal articleBeth A, Galand M, Jia X, et al., 2025, , Monthly Notices of the Royal Astronomical Society, Vol: 544, Pages: 95-112, ISSN: 0035-8711
Icy 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 articleMcComas DJ, Christian ER, Schwadron NA, et al., 2025, , SPACE SCIENCE REVIEWS, Vol: 221, ISSN: 0038-6308
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Journal articleGuillaume-Castel R, Ceppi P, Dorrington J, et al., 2025, , GEOPHYSICAL RESEARCH LETTERS, Vol: 52, ISSN: 0094-8276
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Journal articleErvin T, Mallet A, Eriksson S, et al., 2025, , ASTROPHYSICAL JOURNAL LETTERS, Vol: 992, ISSN: 2041-8205
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Journal articleBreul P, Ceppi P, Nowack P, 2025, , Atmospheric Chemistry and Physics (ACP), Vol: 25, Pages: 11991-12005, ISSN: 1680-7316
Stratocumulus 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 articleTsui EYL, Toumi R, 2025, , Atmospheric Science Letters, Vol: 26, ISSN: 1530-261X
The 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 articleWaters CL, Eastwood JP, Fargette N, et al., 2025, , Journal of Geophysical Research: Space Physics, Vol: 130, ISSN: 2169-9380
Magnetic 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 articleCargill PJ, Hood AW, Johnson D, 2025, , Monthly Notices of the Royal Astronomical Society, Vol: 542, Pages: 3385-3394, ISSN: 0035-8711
Conductive 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 articleDesai RT, Perrin J, Meredith NP, et al., 2025, , SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS, Vol: 23
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Journal articleDing M, Lim SZJ, Yu X, et al., 2025, , MACHINE LEARNING-SCIENCE AND TECHNOLOGY, Vol: 6
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Journal articleTrotta D, Horbury TS, Giacalone J, 2025, , ASTRONOMY & ASTROPHYSICS, Vol: 702, ISSN: 0004-6361
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Journal articleArcher M, Evans V, Eastwood J, et al., 2025, , Space Weather, ISSN: 1539-4956
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Journal articleAuestad H, Shibu A, Ceppi P, et al., 2025, , GEOPHYSICAL RESEARCH LETTERS, Vol: 52, ISSN: 0094-8276
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Conference paperLin J, Gryspeerdt E, Clark R, 2025, , 9th Conference on Neural Information Processing Systems (NeurIPS 2025)
There has been great progress in improving numerical weather prediction and climate models using machine learning. However, most global models act at akilometer-scale, making it challenging to model individual clouds and factors such as extreme precipitation, wind gusts, turbulence, and surface irradiance. Therefore, there is a need to move towards higher-resolution models, which in turn require high-resolution real-world observations that current instruments struggle to obtain. We present Cloud4D, the first learning-based framework that reconstructs a physically consistent, four–dimensional cloud state using only synchronized ground-based cameras. Leveraging a homography-guided 2D-to-3D transformer, Cloud4D infers the full 3D distribution of liquid water content at 25 m spatial and 5 s temporal resolution. By tracking the 3D liquid water content retrievals over time, Cloud4D additionally estimates horizontal wind vectors. Across a two-month deployment comprising six skyward cameras, our system delivers an order-of-magnitude improvement in space-time resolution relative to state-of-the-art satellite measurements, while retaining single-digit relative error (< 10%) against collocated radar measurements. Code and data are available on our projectpage https://cloud4d.jacob-lin.com/.
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Journal articleRivera YJ, Klein KG, Wang JH, et al., 2025, , ASTROPHYSICAL JOURNAL LETTERS, Vol: 990, ISSN: 2041-8205
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Journal articleKrasnoselskikh V, Jebaraj IC, Cooper TRF, et al., 2025, , ASTROPHYSICAL JOURNAL, Vol: 990, ISSN: 0004-637X
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Journal articleHuang Z, Velli M, Chandran BDG, et al., 2025, , ASTROPHYSICAL JOURNAL LETTERS, Vol: 990, ISSN: 2041-8205
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Journal articleRovithakis A, Burke E, Burton C, et al., 2025, , Natural Hazards and Earth System Sciences, Vol: 25, Pages: 3185-3200, ISSN: 1561-8633
Our previous studies have shown that fire weather conditions in the Mediterranean and specifically over Greece are expected to become more severe with climate change, impling potential increases in burnt area. Here, we employ the Joint UK Land Environment Simulator (JULES) coupled with the INFERNO fire model driven by future climate projections from the UKESM1 model to investigate the repercussions of climate change and future vegetation changes on burnt area over Greece. We validate modelled burnt area against the satellite-derived GFED5 dataset, and find the model's performance to be good, especially for the more fire-prone parts of the country in the south Greece. For future simulations, we use future climate data following three Shared Socioeconomic Pathways (SSPs), consisting of an optimistic climate change scenario where fossil fuel emissions peak and decline beyond 2020 (SSP126), a middle-of-the-road scenario (SSP370), and a pessimistic scenario where emissions continue to rise throughout the century (SSP8.5). Our results show increased burnt area in the future compared to the present-day period in response to overall hotter and drier climatological conditions. We use an additional JULES-INFERNO simulation in which dynamic vegetation was activated, and find that it features smaller future burned area increases compared to our simulation with static present-day vegetation. For this dynamically changing vegetation simulation the greatest burnt area increases are found for southern Greece, due to higher future availability of flammable and heat-resistant needleleaf trees and the smallest decreases in agricultural areas of northern Greece due to a reduction in the aforementioned tree category.
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Journal articleSakellaris IA, Bartzis JG, Grillakis E, et al., 2025, , FIRE TECHNOLOGY, ISSN: 0015-2684
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Journal articlePanditharatne S, Cox C, Song R, et al., 2025, , Atmospheric Chemistry and Physics, Vol: 25, Pages: 9981-9998, ISSN: 1680-7316
Studies have indicated that far-infrared radiances hold significant information about the microphysics of ice clouds, particularly the ice crystal habit. In support of the European Space Agency's Far-Infrared Outgoing Radiation Understanding and Monitoring mission, we perform the first retrieval on an observation of coincident upwelling far- and mid-infrared radiances taken from an aircraft above a cirrus cloud layer. Four retrievals are performed: including and neglecting the far-infrared portion of the spectrum and assuming two different habit mixes. Results are compared to in situ measurements of the cloud optical thickness, cloud top height, cloud effective radius, and habit distributions. We find that despite the known limitations of ice cloud optical property models, all the retrievals show agreement within the in situ measurements of the cloud optical thickness, cloud top height, and cloud effective radius. However, the inclusion of the far-infrared enables a distinction between two different habits that is not possible using only mid-infrared channels. Furthermore, in this case study, the uncertainty in the retrieval of cloud top height and cloud optical thickness halves with the inclusion of the far-infrared. As with other studies, we also see an additional degree of freedom for the temperature and water vapour retrievals. Our study highlights the need for the improvement of current ice cloud optical models, with the radiance residuals from the converged retrievals still exceeding the instrument uncertainty within the far-infrared. However, it provides observational support for the theoretical improvement that far-infrared observations could bring to retrievals of ice cloud properties.
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Journal articleElsden T, Southwood DJ, Allanson O, et al., 2025, , Journal of Geophysical Research: Space Physics, Vol: 130, ISSN: 2169-9380
The plasmapause in Earth's magnetosphere represents the boundary between the plasma which co-rotates with the Earth (plasmasphere), and the more tenuous plasmatrough outside. The density change across the plasmapause can be large, changing by approximately 1–2 orders of magnitude depending on the prevailing conditions. This would suggest it to be a location where magnetohydrodynamic (MHD) surface waves can form, and indeed, this has been proposed in previous works to explain ultra-low frequency (ULF) wave observations around the plasmapause location. The main question is how such a large scale surface wave on the plasmapause would be excited. In this paper, we propose a model whereby surface waves at the plasmapause are driven by energy input from the magnetopause through solar wind driving. We derive an analytical form for the amplitude of these surface waves with this new driven boundary condition at the magnetopause. The excitation of these waves is then tested in several MHD simulations, where the model geometry, wavenumbers and temporal dependence of the magnetopause driver are varied. We establish that surface waves on the plasmapause can be excited by driving from the magnetopause, and that this still occurs with impulsive and continuous broadband driving. The azimuthal scale of the wave is a critical factor for this excitation, with longer azimuthal scales more favorable for driving larger amplitude surface waves. This mechanism provides new insight for how large scale and large amplitude ULF waves can access the inner magnetosphere, with potential implications for their interaction with radiation belt particles.
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