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Journal articleLewis ZM, Stephenson P, Beth A, et al., 2025, , Monthly Notices of the Royal Astronomical Society, Vol: 541, Pages: 3590-3605, ISSN: 0035-8711
The Rosetta spacecraft escorted comet 67P/Churyumov–Gerasimenko for two years, gathering a rich and variable data set.Amongst the data from the Rosetta Plasma Consortium (RPC) suite of instruments are measurements of the total electron densityfrom the Mutual Impedance Probe (MIP) and Langmuir Probe (LAP). At low outgassing, the plasma density measurements canbe explained by a simple balance between the production through ionization and loss through transport. Ions are assumed totravel radially at the outflow speed of the neutral gas. Near perihelion, the assumptions of this field-free chemistry-free modelare no longer valid, and plasma density is overestimated. This can be explained by enhanced ion transport by an ambipolarelectric field inside the diamagnetic cavity, where the interplanetary magnetic field does not reach. In this study, we explore thetransition between these two regimes, at intermediate outgassing (5.4 × 1026 s−1), when the interaction between the cometaryand solar wind plasma influences the transport of the ions. We use a 3D collisional test-particle model, adapted from Stephensonet al. to model the cometary ions with input electric and magnetic fields from a hybrid simulation for 2.5–3 au. The total plasmadensity from this model is then compared to data from MIP/LAP and to the field-free chemistry-free model. In doing so, wehighlight the limitations of the hybrid approach and demonstrate the importance of modelling collisional cooling of the electronsto understand the ion dynamics close to the nucleus.
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Journal articlePage B, Lecacheux A, Pulupa M, et al., 2025, , RADIO SCIENCE, Vol: 60, ISSN: 0048-6604
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Journal articleVan de Koot EK, Byrne MP, Woollings T, 2025, , Journal of Climate, Vol: 38, Pages: 3185-3199, ISSN: 0894-8755
<jats:title>Abstract</jats:title><jats:p>Tropical cloud feedbacks are an important source of uncertainty in estimates of climate sensitivity. The extent to which changes in atmospheric circulation contribute to these feedbacks remains an open question. Here, all-sky radiative flux observations and an atmospheric reanalysis are used to estimate tropical cloud feedbacks from multidecadal trends (1985–2020) in cloud radiative effect and surface temperature. We decompose the observed feedbacks into dynamic and nondynamic components to quantify the impact of circulation trends. Narrowing and strengthening of tropical ascent lead to substantial dynamic feedbacks on regional scales that are similar in magnitude to the nondynamic feedbacks. However, as previously shown for high- and low-resolution climate models, large dynamic feedbacks in different circulation regimes are connected by the atmospheric mass budget and approximately cancel when averaged across the tropics due to the quasi-linear relationship between cloud radiative effect and vertical velocity. This results in small dynamic contributions to the tropical-mean net, longwave, and shortwave feedbacks. We suggest that this result will hold in future and thus that isolating the nondynamic components associated with individual cloud types can provide important insights into the processes controlling the tropical-mean cloud feedback and its uncertainty. Additionally, we show that feedbacks estimated from multidecadal trends differ from those estimated from interannual variability. We demonstrate that, for dynamic feedbacks, this is because changes are controlled by different mechanisms and this leads to a differing spatial distribution of temperature sensitivity. Finally, we provide new estimates of the uncertain combined tropical anvil area and albedo feedback using both multidecadal trends and interannual variability.</jats:p>
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Journal articleKretzschmar M, Brochot J-Y, Horbury TS, et al., 2025, , ASTRONOMY & ASTROPHYSICS, Vol: 699, ISSN: 0004-6361
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Journal articlePulupa M, Bale SD, Jebaraj IC, et al., 2025, , ASTROPHYSICAL JOURNAL LETTERS, Vol: 987, ISSN: 2041-8205
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- Citations: 2
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Journal articleNiwa Y, Tohjima Y, Terao Y, et al., 2025, , Atmospheric Chemistry and Physics, Vol: 25, Pages: 6757-6785, ISSN: 1680-7316
Atmospheric methane (CH4) growth rates reached unprecedented values in the years 2020-2022. To identify the main drivers of this increase, an inverse modeling study estimated regional and sectoral emission changes for 2016-2022. Three inverse estimates based on different sets of atmospheric CH4 observations (surface observations only, surface and aircraft observations, and GOSAT observations) consistently suggest notable emission increases from 2016-2019 to 2020-2022 in the tropics (15° S-10° N) (10-18 Tg CH4 yr-1) and in northern low latitudes (10-35° N) (ca. 20 Tg CH4 yr-1), the latter of which likely contributed to the growth rate surge from 2020. The emission increase in the northern low latitudes is attributed to emissions in South Asia and northern Southeast Asia, which abruptly increased from 2019 to 2020, and elevated emissions continued until 2022. Meanwhile, the tropical emission increase is dominated by Tropical South America and Central Africa, but emissions were continuously increasing before 2019. Agreement was found in the sectoral estimates of the three inversions in the tropics and northern low latitudes, suggesting the largest contribution of biogenic emissions. Uncertainty reductions demonstrate that the flux estimates in Asia are well constrained by surface and aircraft observations. Furthermore, a sensitivity test with the probable reduction of OH radicals showed smaller emissions by up to 2-3 Tg CH4 yr-1 in each Asian region for 2020, still suggesting notable emission contributions. These results highlight the importance of biogenic emissions in Asian regions for the persistent high growth rate observed during 2020-2022.
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Journal articleWilson III LB, Mitchell JG, Szabo A, et al., 2025, , ASTROPHYSICAL JOURNAL, Vol: 987, ISSN: 0004-637X
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- Citations: 1
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Journal articleGoodwin P, Williams RG, Ceppi P, et al., 2025, , Journal of Geophysical Research (JGR): Atmospheres, Vol: 130, ISSN: 2169-897X
Climate feedbacks, including Planck, surface albedo, water vapor-lapse rate (WVLR) and cloud feedbacks, determine how much surface temperatures will eventually warm to balance anthropogenic radiative forcing. Climate feedbacks remain difficult to constrain directly from temporal variation in observed surface warming and radiation budgets due to the pattern effect and low signal-to-noise ratio, with only order 1°C historic rise in surface temperatures and high uncertainty in aerosol radiative forcing. This study presents a new method to analyze climate feedbacks from observations by empirically fitting simplified reduced-physics relations for outgoing radiation at the top of the atmosphere (TOA) to observed spatial variation in climate properties and radiation budgets. Spatial variations in TOA outgoing radiation are dominated by the dependence on surface temperature: around 91% of the spatial variation in clear sky albedo, and 77% of spatial variation in clear sky TOA outgoing longwave radiation, is functionally explained by variation in surface temperatures. These simplified and observationally constrained relations are then differentiated with respect to spatial contrasts in surface temperature to reveal the Planck, fixed-cloud albedo (饾渾albedo) and WVLR (饾渾WVLR) climate feedbacks spatially for both clear sky and all sky conditions. The resulting global all sky climate feedback values are 饾渾WVLR = 1.28 (1.13–1.45 at 66%) Wm鈦²K鈦¹, and 饾渾albedo = 0.64 (0.53–0.74) Wm−2 for the period 2003–2023, reducing to 0.35 (0.29–0.41) Wm鈦²K鈦¹ under 4°C warming after cryosphere retreat. Our findings agree well with complex Earth system model evaluations based on temporal climate perturbations, and our approach is complementary.
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Journal articleTurc L, Archer MO, Zhou H, et al., 2025, , Geophysical Research Letters, Vol: 52, ISSN: 0094-8276
Solar wind directional discontinuities can generate transient mesoscale structures such as foreshock bubbles and hot flow anomalies (HFAs) upstream of Earth's bow shock. These structures can have a global impact on near-Earth space, so understanding their formation conditions is essential. We investigate foreshock transient generation at a rotational discontinuity using a global 2D hybrid-Vlasov simulation. As expected, a foreshock bubble forms on the sunward side of the discontinuity. Later, when the discontinuity reaches the shock, new structures identified as HFAs develop, despite the initial discontinuity not being favorable to HFA formation. We demonstrate that the foreshock bubble provides the necessary conditions for their generation. We then investigate the evolution of the transient structures and the large-scale bow shock deformation they induce. Our results provide new insights on the formation and evolution of foreshock transients and their impact on the shock.
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Journal articleRen T, Yang P, Brindley HE, et al., 2025, , Geophysical Research Letters, Vol: 52, ISSN: 0094-8276
A database of temperature-dependent hexagonal ice aggregate optical properties in the far-infrared (FIR) spectrum is developed to support FIR missions, particularly the current Polar Radiant Energy in the Far InfraRed Experiment and the upcoming Far-infrared-Outgoing-Radiation Understanding and Monitoring. Based on this data set, simulations of the brightness temperatures (BTs) in the 100–667 cm−1 FIR region are conducted for an anvil-like ice cloud in a tropical atmosphere. The results show nonnegligible impact of ice cloud temperature on simulated BTs, which can be as large as 3 K due to the difference between fixed 160 or 270 K cloud temperature and the benchmark counterpart, varying in accordance with the ambient temperature profile for a cloud residing between 249.6 and 199.6 K. To enhance the accuracy of FIR radiative transfer modeling, it is recommended to incorporate temperature-dependent optical properties of ice clouds.
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Journal articleKartavykh Y, Rodriguez-Garcia L, Heber B, et al., 2025, , ASTRONOMY & ASTROPHYSICS, Vol: 699, ISSN: 0004-6361
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Journal articleDakeyo J-B, Demoulin P, Rouillard A, et al., 2025, , ASTROPHYSICAL JOURNAL, Vol: 986, ISSN: 0004-637X
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Journal articleHuang J, Larson DE, Ervin T, et al., 2025, , ASTROPHYSICAL JOURNAL LETTERS, Vol: 986, ISSN: 2041-8205
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- Citations: 3
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Journal articlePhan TD, Romeo OM, Drake JF, et al., 2025, , ASTROPHYSICAL JOURNAL, Vol: 986, ISSN: 0004-637X
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Journal articleSeo G-Y, Min S-K, Lee D, et al., 2025, , NPJ CLIMATE AND ATMOSPHERIC SCIENCE, Vol: 8, ISSN: 2397-3722
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Journal articleHamilton CW, Mcewen AS, Keszthelyi L, et al., 2025, , The Planetary Science Journal, Vol: 6, ISSN: 2632-3338
Jupiter’s moon Io is a highly compelling target for future exploration that offers critical insight into tidal dissipation processes and the geology of high heat flux worlds, including primitive planetary bodies, such as the early Earth, that are shaped by enhanced rates of volcanism. Io is important for understanding the development of volcanogenic atmospheres and mass exchange within the Jupiter system. However, fundamental questions remain about the state of Io’s interior, surface, and atmosphere, as well as its role in the evolution of the Galilean satellites. The Io Volcano Observer (IVO) would advance answers to these questions by addressing three key goals: (A) determine how and where tidal heat is generated inside Io, (B) understand how tidal heat is transported to the surface of Io, and (C) understand how Io is evolving. IVO was selected for Phase A study through the NASA Discovery program in 2020, and, in anticipation of the next New Frontiers (NF) opportunity, an enhanced IVO-NF mission concept would increase the Baseline mission from 10 flybys to 20, with an improved radiation design; employ a Ka-band communication system to double IVO’s total data downlink; add a wide-angle camera for color and stereo mapping; add a dust mass spectrometer; and lower the altitude of later flybys to enable new science. This study compares the architecture, instrument suite, and science objectives for Discovery (IVO) and NF (IVO-NF) missions to Io. IVO can achieve outstanding science results at the Discovery level, but we advocate for continued prioritization of Io for NF.
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Journal articleGrillakis M, Voulgarakis A, 2025, , Communications Earth & Environment, Vol: 6, ISSN: 2662-4435
Forest fires can significantly impact the hydrological regime of river basins, affecting short-term flood propensity and long-term water resource availability until vegetation is reestablished. While basin-level studies have extensively investigated these impacts, regional and global-scale assessments remain limited. Here we use a comprehensive global dataset of river discharge observations to systematically assess the hydrological response to wildfires for a range of hydrologically homogenous world regions and biomes. Our analysis reveals contrasting hydrological impacts by region, with high-latitude discharge ratios declining by 7.5% and 16% in the first and second year after wildfire, respectively, while Northern mid-latitude regions showing a marginal 3.3% median increase in discharge ratio the first-year post-fire. Sub-tropical and equatorial regions display negative and positive effects, respectively. We further discuss how potential ecological and hydroclimatic factors, along with human river and watershed management, shape these diverse hydrological responses per hydroclimatic region.
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Journal articleDesai MI, Drake JF, Phan T, et al., 2025, , ASTROPHYSICAL JOURNAL LETTERS, Vol: 985, ISSN: 2041-8205
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- Citations: 2
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Journal articleHorner G, Gryspeerdt E, 2025, , Atmospheric Chemistry and Physics, Vol: 25, Pages: 5617-5631, ISSN: 1680-7316
The lifetime of cirrus clouds from deep convection plays an important role in determining their overall cloud radiative effect (CRE). The net CRE of cirrus clouds from deep convection is close to zero over their whole lifetime. This CRE is the result of a near-cancellation of a large shortwave (SW) cooling and large longwave (LW) warming, such that small changes in cirrus properties have the potential to produce a significant net radiative effect. Changes in the atmospheric and sea surface temperature structure, along with changes in anthropogenic aerosol, have been hypothesised to impact the lifetime of detrained cirrus clouds, altering this radiative balance. Constraining the potential CRE response to changes in cirrus lifetime is therefore vital to understand the strength of these proposed climate forcings and feedbacks.This paper tracks the evolution of detrained cirrus clouds along trajectories from deep convection. The total cirrus CRE in the tropics is found to be warming, at 11.2 ± 0.4 W m−2. It is found that cirrus clouds along trajectories from oceanic origin convection have a warming CRE of 10.0 ± 0.4 W m−2. In contrast, cirrus clouds along trajectories from land convection have a warming of 15.9 ± 0.7 W m−2 throughout their lifetime. This contrast is predominantly due to differences in the diurnal cycle of the initial convection over land and ocean.A proposed extension to the lifetime of the detrained cirrus leads to changes in the total cirrus CRE in the tropics. In all cases, doubling the lifetime of the detrained cirrus leads to an increase in the total cirrus CRE of 0.6 ± 0.1 W m−2. Whilst there is uncertainty in the strength of mechanisms responsible for a change in cirrus lifetime, this work provides an important constraint on the impact that any potential lifetime extension may have.
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Journal articleMauritsen T, Tsushima Y, Meyssignac B, et al., 2025, , AGU Advances, Vol: 6, ISSN: 2576-604X
Global warming results from anthropogenic greenhouse gas emissions which upset the delicate balance between the incoming sunlight, and the reflected and emitted radiation from Earth. The imbalance leads to energy accumulation in the atmosphere, oceans and land, and melting of the cryosphere, resulting in increasing temperatures, rising sea levels, and more extreme weather around the globe. Despite the fundamental role of the energy imbalance in regulating the climate system, as known to humanity for more than two centuries, our capacity to observe it is rapidly deteriorating as satellites are being decommissioned.
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Journal articleZomerdijk-Russell S, Jasinski J, Masters A, 2025, , JGR: Space Physics, Vol: 130, ISSN: 2169-9402
Uranus provides a key missing piece for fundamentally understanding solar wind-magnetospheric interactions due to its location in the outer solar system. Whether the viscous-like interaction overtakes global magnetic reconnection as the dominant process at the magnetopause of the outer planets remains unresolved. Here, we present theoretical predictions of dayside reconnection voltages applied to the Uranian system under different magnetospheric configurations to assess the effectiveness of global magnetic reconnection in the driving of Uranus' magnetosphere. We find the median model-predicted dayside reconnection voltage applied to Uranus' magnetosphere is 22.4 kV. Over just one full planetary rotation, the reconnection voltages are found to vary by tens of kV under Uranus' magnetospheric configuration during its solstice and equinox seasons with fixed solar wind conditions. However, we do not find a significant difference between average voltages at the different seasons, despite the large differences in magnetospheric configuration between solstice and equinox at Uranus. An increase from ∼17 to ∼31 kV in the modeled reconnection voltages is observed when the strength of the interplanetary magnetic field is increased corresponding to expected conditions during solar maximum. Our results suggest that variability resulting from the planet's diurnal rotation and changing solar wind conditions, are more important in controlling the reconnection voltages than seasonal dependencies.
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Journal articleLozinski AR, Kellerman AC, Bortnik J, et al., 2025, , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 130, ISSN: 2169-9380
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Journal articleKim K, Edberg NJT, Modolo R, et al., 2025, , JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS, Vol: 130, ISSN: 2169-9097
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Journal articleColomban L, Agapitov OV, Krasnoselskikh V, et al., 2025, , GEOPHYSICAL RESEARCH LETTERS, Vol: 52, ISSN: 0094-8276
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Journal articleBowen TA, Dunn CI, Mallet A, et al., 2025, , The Astrophysical Journal (ApJ), Vol: 985, ISSN: 0004-637X
Turbulent magnetic field fluctuations observed in the solar wind often maintain a constant-magnitude magnetic field accompanied by spherically polarized velocity fluctuations; these signatures are characteristic of large-amplitude Alfvén waves. Nonlinear energy transfer in Alfvénic turbulence is typically considered in the small-amplitude limit where the constant-magnitude condition may be neglected; in contrast, nonlinear energy transfer of large-amplitude fluctuations remains relatively unstudied. We develop a method to analyze large-amplitude turbulence through studying fluctuations as constant-magnitude rotations in the de Hoffmann–Teller frame, in which the convected electric field of the fluctuations vanishes such that the frame and fluctuations are copropagating. Our analysis reveals signatures of large-amplitude effects deep into the inertial range. While the dominant fluctuations are consistent with spherically polarized large-amplitude Alfvén waves, the subdominant fluctuations are relatively compressible. Signatures of nonlinear interaction between the large-amplitude spherically polarized mode with the subdominant population reveal highly aligned transverse components. In many theoretical models of Alfvénic turbulence, alignment is thought to reduce nonlinearity; our observations suggest that the observed alignment is sufficient to either reduce shear nonlinearity such that non-Alfvénic interactions may be responsible for energy transfer in spherically polarized states, or alternatively that counterpropagating fluctuations maintain anomalous coherence, a predicted signature of reflection-driven turbulence.
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Journal articleAlnussirat ST, Larson DE, Livi R, et al., 2025, , ASTROPHYSICAL JOURNAL, Vol: 985, ISSN: 0004-637X
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Journal articleLi F, Lawrence DM, Rogers BM, et al., 2025, , Geoscientific Model Development, Vol: 19, Pages: 3989-4007, ISSN: 1991-959X
Fire is a global phenomenon and a key Earth system process. Extreme fire events have increased in recent years, and fire frequency and intensity are projected to rise across most regions and biomes, posing substantial challenges for ecosystems, the carbon cycle, and society. The Fire Model Intercomparison Project (FireMIP), launched in 2014, has advanced global fire modeling in Dynamic Global Vegetation Models (DGVMs) and improved understanding of fire's local and direct drivers and its local impacts on vegetation and land carbon budgets through land offline simulations (i.e., uncoupled from the atmosphere). We now bring FireMIP into Coupled Model Intercomparison Project Phase 7 (CMIP7) to: (1) evaluate fire simulations in state-of-the-art fully coupled Earth system models (ESMs); (2) assess fire regime changes in the past, present, and future, and identify their primary natural and anthropogenic forcings and causal pathways within the Earth system, including the associated uncertainties; and (3) quantify the impacts of fires and fire changes on climate, ecosystems, and society across Earth system components, regions, and timescales, and elucidate the underlying mechanisms. FireMIP in CMIP7 will advance the fire and fire-related modeling in fully coupled ESMs, and provide a quantitative, comprehensive, and process-based understanding of fire's role in the Earth system by using models that incorporate critical climate feedbacks and CMIP7 multi-model, multi-initial-condition, and multi-scenario ensemble. This protocol paper presents the motivation, scientific questions, experimental design and rationale, model inputs and outputs, and recommended analysis framework for FireMIP in CMIP7, providing guidance to Earth system modeling teams conductin
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Journal articleCuesta ME, Livadiotis G, Mccomas DJ, et al., 2025, , ASTROPHYSICAL JOURNAL LETTERS, Vol: 984, ISSN: 2041-8205
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- Citations: 2
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Journal articleShen MM, Szalay JR, Pokorny P, et al., 2025, , ASTROPHYSICAL JOURNAL, Vol: 984, ISSN: 0004-637X
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- Citations: 1
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Journal articleVallim D, Grillakis M, Manoudakis S, et al., 2025,
Stakeholder Engagement Drivers: Insights from an Information System Innovation Project Supporting Wildfire Evacuation in Greece
, Proceedings of the International Iscram ConferenceThe Samaria Gorge, a tourist destination in Crete, faces wildfire risk due to its dense forest, topography, number of visitors, and climate. As part of a H2020 project, the Gorge serves as a testing pilot for a new wildfire management platform that integrates technologies to improve fire detection, risk assessment, and resource allocation during a wildfire evacuation. A central component of the project is a multi-stakeholder network, which supports both governance and acceptance of solutions. To understand the drivers of network formation, we used a Social Network Analysis and Exponential Random Graphs Model approaches to identify the drivers of stakeholder collaboration. Our findings indicate that sectoral and wildfire management focus phase are factors driving connections, while the working in intersecting jurisdictions is not. The results highlight the challenges of multi-stakeholder collaboration, suggesting that policy frameworks and information systems need to develop specific mechanisms to encourage stakeholders to bridge collaborative gaps.
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