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Journal articleEastwood JP, Phan TD, Drake JF, et al., 2026, , The Astrophysical Journal, Vol: 996, ISSN: 0004-637X
The Heliospheric Current Sheet (HCS) is a fundamental feature of the heliosphere, playing a key role organizing the magnetic structure of the solar wind. In contrast to observations previously made through the majority of the heliosphere, Parker Solar Probe has recently revealed that the HCS is typically reconnecting in the inner heliosphere. This provides a new opportunity to study reconnection dynamics in large-scale current sheets and assess how this is different from smaller systems such as Earth’s magnetosphere. We use Parker data to explore HCS reconnection energy partition in two case studies from Encounter 07 and 08. In both cases, we find that in the exhaust, the proton enthalpy flux density is largest, with significant contributions from the proton kinetic energy flux density and electron enthalpy flux density. In contrast, the exhaust Poynting flux density is small in both events. The size and stability of the HCS allows for a control volume analysis to be performed, thus allowing us to estimate changes in energy flux during reconnection. This analysis shows that energy is primarily transferred from the magnetic field to the protons, manifested as the kinetic energy of the exhaust and proton heating. Although the exhaust electron enthalpy flux density is significant, the incoming and outgoing electron enthalpy fluxes are found to be similar, and there is minimal electron heating. The small contribution of the Poynting flux in the outflow may be an important feature of HCS reconnection, with implications for reconnection in large-scale solar and astrophysical current sheets more generally.
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Journal articleBerland GD, Hill ME, Kouloumvakos A, et al., 2026, , ASTROPHYSICAL JOURNAL, Vol: 996, ISSN: 0004-637X
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Journal articleGiacalone J, Trotta D, Mitchell DG, et al., 2026, , Astrophysical Journal, Vol: 996, ISSN: 0004-637X
On 2023 March 13, Parker Solar Probe was located about 0.23 au from the Sun when it was crossed by a very fast interplanetary shock. The intensities of ∼0.08–10 MeV energetic protons were markedly enhanced at the shock crossing. At energies from ∼0.1 to 1 MeV, the intensity at the shock was 3–4 orders of magnitude larger than it was ∼4 hr prior. In this study, we investigate the possible source of particles that led to this enhancement. Pre-existing high-energy particles that were present during the few-hour period prior to the shock could possibly serve as a source, assuming they are accelerated to even higher energies by the shock. We apply a “seeds test”—which determines the expected enhancement at the shock—to test this. We find that none of the pre-existing particle populations identified can account for the observed enhancement at the shock. The solar wind itself provides a very abundant source. To test whether shock-heated thermal solar wind could account for the source, we perform a series of self-consistent hybrid plasma simulations of this event and make direct comparisons with the observed particle spectra and magnetic field. We conclude that shock-heated solar wind protons are the source of energetic particles in this event. The direct comparisons of our simulations and observations also suggest that the shock was moving about 1350 km s<sup>−1</sup> and had an Alfvén Mach number of about 4, both of which are considerably lower than previously estimated.
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Journal articleCamacho H, Rotermund KM, Slosar A, et al., 2026, , Open Journal of Astrophysics, Vol: 9
LuSEE-Night is a pathfinder radio telescope on the lunar far side employing four 3-m monopole antennas arranged as two horizontal cross pseudo-dipoles on a rotational stage and sensitive to the radio sky in the 1-50 MHz frequency band. LuSEE-Night measures the corresponding 16 correlation products as a function of frequency. While each antenna combination measures radiation coming from a large area of the sky, their aggregate information as a function of phase in the lunar cycle and rotational stage position can be deconvolved into a low-resolution map of the sky. We study this deconvolution using linear map-making based on the Wiener filter algorithm. We illustrate how systematic effects can be effectively marginalised over as contributions to the noise covariance and demonstrate this technique on beam knowledge uncertainty and gain fluctuations. With reasonable assumptions about instrument performance, we show that LuSEE-Night should be able to map the sub-50 MHz sky at a ∼5-degree resolution.
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Journal articleLopez-Marti F, Czaja A, Messori G, et al., 2026, , Quarterly Journal of the Royal Meteorological Society, ISSN: 0035-9009
Extreme precipitation and wind events in Western Europe are often driven by atmospheric rivers (ARs) developing over the North Atlantic Ocean. Even though research has explored AR variability in relation to large-scale atmospheric dynamics and the North Atlantic Storm Track, gaps remain in understanding how oceanic variability influences AR activity, particularly within the eddy-rich environment of the Gulf Stream extension. The enhanced ocean heat transport and mesoscale eddy activity associated with this western boundary current can influence large-scale dynamics, modulate moisture availability in the lower atmosphere, and potentially control the AR activity downstream. In this study, we evaluated ocean mesoscale features, oceanic heat supply, and surface heat fluxes in the Gulf Stream extension region at monthly time-scales. We assessed their downstream impact on AR activity using state-of-the-art observational datasets. Our analysis identified winter and spring as the key seasons for interactions between Gulf Stream conditions and ARs. Higher ocean heat transport and mesoscale sea-surface height (SSH) meandering were associated with a northward shift in downstream AR activity and a positive North Atlantic Oscillation (NAO) pattern, although the atmospheric response is weaker in the latter case. In contrast, stronger than average surface heat fluxes in the Gulf Stream were linked to a southward shift of ARs and a strong negative NAO pattern, suggesting a dominant atmospheric influence that enhanced moisture availability and modulated North Atlantic dynamics. These results show that the Gulf Stream plays an important role in controlling the latitudinal variability of ARs over the Euro-Atlantic sector during winter and spring.
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Journal articleHartinger MD, Archer MO, Masongsong E, et al., 2026, , Frontiers in Astronomy and Space Sciences, Vol: 13
Ultra Low Frequency (ULF) waves with periods of (Formula presented.) 10–1,000 s can lead to space weather impacts such as induced electrical currents in power grids, thus it is important to understand the factors controlling wave dynamics. This is challenging, however, as waves (1) are affected by multiple factors simultaneously, (2) are non-stationary which in some cases precludes use of identification methods that assume stationarity, (3) can occur in superposition with each other making them difficult to separate and identify. Past studies have addressed these challenges through combined audiovisual analysis tools to identify complex but recurring patterns in ULF wave activity that eluded standard visual inspection and automated detection algorithms, as well as through crowd-sourced wave identification. The “Heliophysics Audified: Resonances in Plasmas” NASA citizen science project follows these studies by deploying a Graphical User Interface (GUI) for crowd-sourced ULF wave identification to a large online audience before and during the Heliophysics Big Year (HBY). In this study, we discuss the initial development, beta testing, and deployment of the GUI in April 2023. We further discuss the key initial scientific findings of the HARP project, in particular the discovery by volunteers of anomalous standing Alfvén wave activity with frequency increasing with distance from the Earth. Finally, we discuss participant impacts and lessons learned, as well broader impacts beyond the scope of the original project such as collaborations with museums and musicians. We place these results in context with previous work and discuss implications for future studies.
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Journal articleAndrews MB, Butchart N, Anstey JA, et al., 2026, , EGUsphere, Vol: 2026, Pages: 1-33
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Journal articleShuster JR, Bessho N, Dorelli JC, et al., 2026, , Commun Phys, Vol: 9
The electron diffusion region is central to NASA's Magnetospheric Multiscale (MMS) mission to understand collisionless magnetic reconnection, the plasma physics phenomenon crucial to triggering the explosive energy release of solar flares, powering auroras generated in planetary magnetospheres, and driving sawtooth crashes in laboratory fusion devices. Inside the diffusion region, electron velocity distributions exhibit highly-structured velocity-space signatures critical for elucidating the kinetic mechanisms fueling reconnection. Recent multi-spacecraft analysis techniques enabled observational study of the spatial gradient in the electron velocity distribution, which has been reported in electron-scale current layers to explain the kinetic origins of electron pressure gradients. However, electron gradient distributions have not yet been investigated inside the reconnection diffusion region. In this work, we discover that electron gradient distributions exhibit a smile-shaped velocity-space structure in the electron diffusion region of asymmetric magnetic reconnection at Earth's magnetopause. Characterizing the nature and prevalence of these smile-shaped electron gradient distributions offers a kinetic perspective into how electrons spatially evolve to provide the net electron pressure divergence that self-consistently supports non-ideal electric fields in the electron diffusion region of magnetopause reconnection. These results are relevant to space, astrophysical, and laboratory plasma communities working to understand the long-standing mystery of collisionless magnetic reconnection.
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Journal articleCohen CMS, Alterman BL, Baker DN, et al., 2026, , Space Sci Rev, Vol: 222, ISSN: 0038-6308
The payload of the Interstellar Mapping and Acceleration Probe (IMAP) includes sophisticated in situ instruments to measure solar wind plasma and magnetic fields, suprathermal and energetic particles at 1 au as well as unprecedented remote sensing instruments to observe the energetic neutral atoms (ENAs) in the outer heliosphere and the ultraviolet glow of the interstellar neutral H interacting with the three-dimensional solar wind. This unique combination of sensors on a single platform allows connections to be made between the inner and outer heliosphere to an extent never before possible. This article focuses on the scientific theme of connecting the physics of particle acceleration and transport throughout the heliosphere. Such studies enabled by IMAP are organized into three broad categories: i) fundamental particle acceleration and transport processes, ii) heliospheric variability that affects those processes, and iii) inner heliospheric science.
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Journal articleBadman ST, Stevens ML, Bale SD, et al., 2025, , ASTROPHYSICAL JOURNAL LETTERS, Vol: 995, ISSN: 2041-8205
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Journal articleBowen TA, Ervin T, Mallet A, et al., 2025, , Phys Rev Lett, Vol: 135
Collisionless dissipation of turbulence is important for heating plasmas in astrophysical, space physics, and laboratory environments, controlling energy, momentum, and particle transport. We analyze Parker Solar Probe observations to understand the collisionless heating of the sub-Alfvénic solar wind, which is connected to the solar corona. Our results show that linear resonant heating through parallel-propagating cyclotron waves cannot account for turbulent dissipation in the sub-Alfvénic region, which observations suggest may dissipate turbulence at distances further from the Sun. Instead, we find that stochastic heating can account for the observed ion energization; however, because the dominant contributions arise from infrequent, large-amplitude events, turbulent intermittency must be explicitly incorporated. These observations directly connect stochastic heating via breaking of the proton magnetic moment with the intermittent and inhomogeneous heating of turbulence reported in many previous studies. Our identification of stochastic heating as a dynamic mechanism responsible for intermittent heating of the solar wind has significant implications for turbulent dissipation in the lower corona, other astrophysical environments, and laboratory plasmas.
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Journal articleSharan S, Pais A, Amit H, et al., 2025, , Journal of Geophysical Research: Planets, ISSN: 2169-9097
The magnetic main field (MF) and secular variation (SV) models for Jupiter can be used to gain insights about the internal dynamo and the flow that drives the field. We use two such models computed from Juno observations up to spherical harmonic degrees 16 and 8 for the MF and SV, respectively. We solve the radial magnetic induction equation in the frozen-flux approximation, at the dynamo region outer boundary assuming zero radial velocity for four large-scale physical flow assumptions- unconstrained, toroidal, tangentially geostrophic and columnar. We find flows with root mean square velocity varying between 100 and 400 km/yr (0.3-1.3 cm/s) when the dynamo region spherical boundary is taken at 0.83 Jupiter radius. Equatorially symmetric, toroidal and non-zonal velocity components are larger than the anti-symmetric, poloidal and zonal components, respectively, for almost all cases. Toroidal and tangentially geostrophic flows display similar velocity values and patterns, despite relying on different physical assumptions. The four inverted solutions indicate that the Jovian interior has dominant eastward flows nearthe Great Blue Spot, in agreement with previous studies. In addition, our more complex flow models shed light on some new features such as a large non-zonal component,meridional flows in the southern hemisphere and field-aligned flows in the north. Finally, our unconstrained flow solution suggests upwelling near the south pole, consistent withn thermal wind theory.
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Journal articleRiddell-Young B, Michel SE, Lan X, et al., 2025, , Proc Natl Acad Sci U S A, Vol: 122
Methane (CH4) is the second most important greenhouse gas and has been rising following a brief period of stabilization from 1999 to 2006. Determining the cause of this rise is critical for reducing emissions and predicting future climate sensitivity. The carbon and hydrogen stable isotopic composition of atmospheric CH4 is controlled by variability in isotopically distinguishable emission categories and fractionating sink processes. While most studies using atmospheric δ13C-CH4 data suggest a dominantly microbial source for recent CH4 growth, this understanding is not uniform, and uncertainties remain [S. Schwietzke et al., Nature 538, 88-91 (2016), S. Basu et al., Atmos. Chem. Phys. 22, 15351-15377 (2022), J. Thanwerdas, M. Saunois, A. Berchet, I. Pison, P. Bousquet, Atmos. Chem. Phys. 24, 2129-2167 (2024)]. Here, we present a harmonized global measurement record of atmospheric δD-CH4 and estimate emissions from 1999 to 2022 with global isotope mass balance calculations using both carbon and hydrogen isotopic ratios. We conduct thorough uncertainty analyses to separate absolute magnitude and emission trend uncertainties and find with high confidence that trends in δ13C-CH4 and δD-CH4 observations are both consistent with an entirely microbial emission driver of the post-2006 CH4 rise, while fossil fuel emissions have remained relatively stable.
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Journal articleNakamura R, Dudok de wit T, Jones GH, et al., 2025, , Annales Geophysicae, Vol: 43, Pages: 855-879, ISSN: 0992-7689
Europe hosts a large and highly active community of scientists working in the broad domain of Heliophysics. This broad discipline addresses plasmas in the regions of space and atmosphere influenced by the Sun and solar wind. However, this community has historically been fragmented, both geographically and thematically, which has limited the potential for strategic coordination, collaboration, and growth. This has recently prompted a grass-roots community-building effort to foster communication and interactions within the European Heliophysics Community (EHC). This white paper outlines the motivation, priorities, and initial steps towards establishing the EHC, and presents a vision for the future of Heliophysics in Europe. As a crucial first step of this endeavour, a dedicated EHC website is now available: https://www.heliophysics.eu/ (last access: November 2025).
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Journal articleWong HL, Palacios R, Gryspeerdt E, 2025, , Journal of Open Source Software, Vol: 10, ISSN: 2475-9066
Aviation turbulence is atmospheric turbulence occurring at length scales large enough (ap proximately 100m to 1km) to affect an aircraft (Sharman, 2016). According to the National Transport Safety Board (NTSB), turbulence experienced whilst onboard an aircraft was theleading cause of accidents from 2009 to 2018 (NTSB, 2021). Clear air turbulence (CAT) is a form of aviation turbulence which cannot be detected by the onboard weather radar. Thus, pilots are unable to preemptively avoid such regions. In order to mitigate this safety risk, CAT diagnostics are used to forecast turbulent regions such that pilots are able to tactically avoidthem.rojak is a parallelised Python library and command-line tool for using meteorological data to forecast CAT and evaluating the effectiveness of CAT diagnostics against turbulence observations. Currently, it supports,1. Computing turbulence diagnostics on meteorological data from the European Centrefor Medium-Range Weather Forecasts’s (ECMWF) ERA5 reanalysis on pressure levels(Hersbach, 2023). Moreover, it is easily extendable through a software update to supportother types of meteorological data.2. Retrieving and processing turbulence observations from Aircraft Meteorological DataRelay (AMDAR) data archived at the National Oceanic and Atmospheric Administration(NOAA)(NCEP Meteorological Assimilation Data Ingest System (MADIS), 2024) andAMDAR data collected via the Met Office MetDB system (Met Office, 2008)3. Computing 27 different turbulence diagnostics, such as the three-dimensional fronto genesis equation (Bluestein, 1993), turbulence index 1 and 2 (Ellrod & Knapp, 1992),negative vorticity advection (Sharman et al., 2006), and Brown’s Richardson tendencyequation (Brown, 1973).4. Converting turbulence diagnostic values into the eddy dissipation rate (EDR) — the International Civil Aviation Organization’s (ICAO) official metric for reporting turbulence (Meteorological Service for International Air Navigati
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Journal articleWarwick L, Oetjen H, Murray J, et al., 2025, , Earth and Space Science, Vol: 12, ISSN: 2333-5084
This paper describes the first field deployment of the Far INfrarEd Spectrometer for Surface Emissivity far-infrared Fourier transform spectrometer to an Arctic environment and shows retrievals of the emissivity of ice and snow in the wavenumber range 400–1,200 cm−1 at viewing angles of 35° and 50°. The retrieved ice emissivity shows a variation of 0.05 between the peak value at around 950 cm−1 and the minimum value at around 750 cm−1. The emissivity is also between 0.01 and 0.02 lower for the higher viewing angle. The emissivity of snow is higher and shows less variation with both viewing angle and wavenumber but it is 0.01 less than one below 900 cm−1. This has implications for remote sensing and climate modeling in this wavenumber range as it implies that both the spectral and angular variation of emissivity must be taken into account. The retrieved ice emissivity agrees well with the emissivity modeled using Fresnel equations. The retrieved snow emissivity agrees well with modeled snow emissivity but further independent measurements of the snow physical properties are needed to test the performance of the model in the far infrared.
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Journal articleStedman M, Hunt SE, De Vis P, et al., 2025, , IEEE Transactions on Geoscience and Remote Sensing, Vol: 63, ISSN: 0196-2892
A new generation of satellites designed for low-uncertainty, SI-traceable measurements—termed“SITSats”—marks a major advancement in Earth observation (EO) capability. These missions aim to enhance the performance and interoperability of the EO “system of systems.” Among them, the ESA Earth Watch Traceable Radiometry Underpinning Terrestrial- and Helio-Studies (TRUTHS) mission is designedto serve as a “gold-standard” radiometric reference for cross-calibrating EO sensors in the solar reflective domain. In this work, uncertainties in cross-calibration comparisons arising from sensor characterization and design are investigated. A processing chain to prepare collocated data for uncertainty-quantified comparison is presented. This includes steps to perform spectral band adjustment and spatial resampling. Using the TRUTHS hyperspectral imaging spectrometer (HIS)as the reference and Sentinel-2 multispectral imager (MSI) as the target, a simulation study based on high-resolution imagery assesses achievable comparison performance. A subset of uncertainty effects driven by sensor characterization is propagated through the spectral and spatial processing using a Monte Carlo approach. Sentinel-2 data are assumed at 10-m resolution, which is most sensitive to the errors considered. The results highlight the importance of sensor characterization, particularly inherent in-flight wavelength knowledge for target sensors, in such comparisons. Results from the simulation analysis give uncertainty estimates (k = 1) of 0.31% (blue), 0.50% (green), and 0.23% (red) for the combined error effectsarising from sensor characterization and geolocation uncertainty for comparisons over the Libya-4 desert pseudo-invariant calibration sites (PICS) using an instantaneous 205-m square comparison region. Results for more heterogeneous scenes, such as rainforest, still achieve uncertainties of 0.6%–1.2% for the red–green–blue (RGB) ban
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Journal articleBreul P, Ceppi P, Simpson IR, et al., 2025, , NATURE REVIEWS EARTH & ENVIRONMENT, Vol: 6, Pages: 824-842
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Journal articleFarahat A, Oliveros JCM, Bale SD, 2025, , AEROSPACE, Vol: 12
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Journal articleKang H, Choi Y, 2025, , Geophysical Research Letters, Vol: 52, ISSN: 0094-8276
<jats:title>Abstract</jats:title> <jats:p> Tropical upper鈥恖evel 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鈥恉erived 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鈥恇ased parameters indicate weaker radiative effects of SST鈥恉riven 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, , SCIENCE ADVANCES, Vol: 11
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Journal articleWilliams RG, Goodwin P, Ceppi P, et al., 2025, , BIOGEOSCIENCES, Vol: 22, Pages: 7167-7186, ISSN: 1726-4170
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Journal articleLee CO, Christian ER, Sandoval L, et al., 2025, , SPACE SCIENCE REVIEWS, Vol: 221, ISSN: 0038-6308
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Conference paperLin J, Gryspeerdt E, Clark R, 2025,
Cloud-stereo: a dataset and benchmark for reconstructing atmospheric clouds from stereo images
, BMVC 2025, Publisher: The British Machine Vision Association and Society for Pattern RecognitionObtaining accurate measurements of clouds is a critical problem in atmospheric physics, as accurate modeling of cloud properties allows us to better understand and predict climate change. Stereo camera networks have shown promise in obtaining such measurements, being able to reconstruct detailed cloud fields over multi-km$^2$ domains. However, previous studies on cloud stereo depth estimation have been limited to using traditional (non-learned) matching techniques, due to the absence of suitable training datasets for this challenging domain. In this work, we present a novel dataset (Cloud-Stereo) specifically tailored for cloud depth estimation. The Cloud-Stereo dataset includes: 1) a synthetic dataset for training, comprising 3000 stereo pairs and simulated dense LiDAR depth data, and 2) a high-accuracy real-world dataset consisting of $\approx 120k$ frames acquired from a stereo camera and Doppler Aerosol LiDAR for testing. Using our dataset we benchmark existing learning and non-learning based stereo depth estimation approaches, and demonstrate that fine-tuning on our dataset can lead to significant accuracy improvement for learned methods. We believe this dataset will enable the training of future, more accurate, methods for cloud field reconstruction, enhancing a unique measurement capability for developing and evaluating atmospheric models. The dataset is available at https://cloud-stereo.jacob-lin.com/.
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Journal articleDriver OGA, Stettler MEJ, Gryspeerdt E, 2025, , Atmospheric Chemistry and Physics (ACP), Vol: 25, Pages: 16411-16433, ISSN: 1680-7316
Contrails 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 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 articleMandikas VG, Voulgarakis A, 2025, , MATHEMATICS, Vol: 13
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Journal articleYufei Y, Timothy H, Domenico T, et al., 2025, , Astrophysical Journal Letters, Vol: 994, ISSN: 2041-8205
We 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 articleDasgupta B, Menoud M, van der Veen C, et al., 2025, , Atmospheric Measurement Techniques, Vol: 18, Pages: 6591-6607, ISSN: 1867-1381
Establishing interlaboratory compatibility among measurements of stable isotope ratios of atmospheric methane (δ<sup>13</sup>C-CH<inf>4</inf> and δD-CH<inf>4</inf>) 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 CH<inf>4</inf> isotope measurements conducted from 2003 to 2017 and found scale offsets of up to 0.5 ‰ for δ<sup>13</sup>C-CH<inf>4</inf> and 13 ‰ for δD-CH<inf>4</inf> 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 CH<inf>4</inf> 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 CH<inf>4</inf>. 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 interlaborator
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