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Journal articleDrake JF, Antiochos SK, Bale SD, et al., 2025,
Magnetic Reconnection in Solar Flares and the Near-Sun Solar Wind
, SPACE SCIENCE REVIEWS, Vol: 221, ISSN: 0038-6308- Cite
- Citations: 2
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Journal articleGrimmich N, Pöppelwerth A, Archer MO, et al., 2025,
Investigation of the occurrence of significant deviations in the magnetopause location: solar-wind and foreshock effects
, Annales Geophysicae: atmospheres, hydrospheres and space sciences, Vol: 43, Pages: 151-173, ISSN: 0992-7689Common magnetopause models can predict the location of the magnetopause with respect to upstream conditions from different sets of input parameters, including solar-wind pressure and the interplanetary magnetic field. However, recent studies have shown that some effects of upstream conditions may still be poorly understood since deviations between models and in situ observations beyond the expected scatter due to constant magnetopause motion are quite common. Using data from the three most recent multi-spacecraft missions to near-Earth space (Cluster, THEMIS, and MMS), we investigate the occurrence of these large deviations in observed magnetopause crossings from common empirical models. By comparing the results from different models, we find that the occurrence of these events appears to be model independent, suggesting that some physical processes may be missing from the models. To find these processes, we test whether the deviant magnetopause crossings are statistically associated with foreshocks and/or different solar-wind types and show that, in at least 40 % of cases, the foreshock can be responsible for the large deviations in the magnetopause's location. In the case where the foreshock is unlikely to be responsible, two distinct classes of solar wind are found to occur more frequently in association with the occurrence of magnetopause deviations: the “fast” solar wind and the solar-wind plasma associated with transients such as interplanetary coronal mass ejections. Therefore, the plasma conditions associated with these solar-wind classes could be responsible for the occurrence of deviant magnetopause observations. Our results may help to develop new and more accurate models of the magnetopause, which will be needed, for example, to accurately interpret the results of the upcoming Solar Wind Magnetosphere Ionosphere Link Explorer (SMILE) mission.
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Journal articleSharan S, Dougherty M, Masters A, et al., 2025,
Viability of the early JUICE flyby trajectories to confirm ocean existence at Ganymede
, The Planetary Science Journal, Vol: 6, ISSN: 2632-3338Ganymede is the largest moon in our solar system, and unique in producing its own magnetic field, as well as possibly possessing a subsurface ocean. The data analysis from the Galileo spacecraft provided two models for the internal field—a dipole and quadrupole model or a dipole and induction model. The latter model is preferred due to the number of parameters being less than the former, given that the model discrepancy with respect to the measurements is similar for both. While the recently launched JUpiter ICy moons Explorer (JUICE) mission will focus on Ganymede in its orbital phase providing an in-depth analysis, there are flybys initially around the moon that can be used for internal field studies. We focus on the first three close flybys of the mission in order to assess how effective the expected observation would be for distinguishing between the induction and quadrupole signals and confirm the existence of an ocean. We begin with an analysis of the JUICE and Galileo trajectories in different reference frames and predict the induction signal using the time varying field of Jupiter. A comparison between the two signatures for Galileo flybys agrees with previous results indicating induction to be present. Finally, we display and discuss the feasibility and importance of the three JUICE flybys to observe the induction field and hence confirm the ocean.
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Journal articleLiu Y-H, Hesse M, Genestreti K, et al., 2025,
Ohm's law, the reconnection rate, and energy conversion in collisionless magnetic reconnection
, Space Science Reviews, Vol: 221, ISSN: 0038-6308Magnetic reconnection is a ubiquitous plasma process that transforms magnetic energy into particle energy during eruptive events throughout the universe. Reconnection not only converts energy during solar flares and geomagnetic substorms that drive space weather near Earth, but it may also play critical roles in the high energy emissions from the magnetospheres of neutron stars and black holes. In this review article, we focus on collisionless plasmas that are most relevant to reconnection in many space and astrophysical plasmas. Guided by first-principles kinetic simulations and spaceborne in-situ observations, we highlight the most recent progress in understanding this fundamental plasma process. We start by discussing the non-ideal electric field in the generalized Ohm’s law that breaks the frozen-in flux condition in ideal magnetohydrodynamics and allows magnetic reconnection to occur. We point out that this same reconnection electric field also plays an important role in sustaining the current and pressure in the current sheet and then discuss the determination of its magnitude (i.e., the reconnection rate), based on force balance and energy conservation. This approach to determining the reconnection rate is applied to kinetic current sheets with a wide variety of magnetic geometries, parameters, and background conditions. We also briefly review the key diagnostics and modeling of energy conversion around the reconnection diffusion region, seeking insights from recently developed theories. Finally, future prospects and open questions are discussed.
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Journal articlePanditharatne S, Brindley H, Cox C, et al., 2025,
Retrievals of water vapour and temperature exploiting the far-infrared: application to aircraft observations in preparation for the FORUM mission
, Atmospheric Measurement Techniques, Vol: 18, Pages: 717-735, ISSN: 1867-1381We present the extension of the Rutherford Appleton Laboratory (RAL) Infrared Microwave Sounding (IMS) optimal estimation retrieval scheme to include the use of far-infrared channels in preparation for the upcoming Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) mission. The IMS code has been previously applied to mid-infrared spectral radiances measured by the Infrared Atmospheric Sounding Instrument (IASI) to retrieve temperature and water vapour. Given this, the evolution and evaluation of the extended scheme is performed in two steps. First, clear-sky retrievals of temperature and water vapour are performed on IASI and FORUM simulations. Comparable retrieval biases are observed for retrievals of temperature and water vapour; however, there is an increase of ∼ 1 degree of freedom for water vapour and temperature for the FORUM configuration. Secondly, radiances observed from an aircraft flight in the upper troposphere are modified to match the FORUM spectral characteristics. Retrievals from these radiances using the modified code show a strong agreement with contemporaneous in situ measurements of the atmospheric state, reducing the root-mean-square error (RMSE) by 18 % for water vapour from the a priori, giving confidence in its performance. The extended IMS scheme is now available for use on FORUM observations and can be easily adapted to other far- and mid-infrared instrument configurations.
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Journal articleRivera YJ, Badman ST, Verniero JL, et al., 2025,
Differentiating the Acceleration Mechanisms in the Slow and Alfvénic Slow Solar Wind
, ASTROPHYSICAL JOURNAL, Vol: 980, ISSN: 0004-637X- Cite
- Citations: 6
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Journal articleMitchell JG, Christian ER, de Nolfo GA, et al., 2025,
Delay of Near-relativistic Electrons with Respect to Type III Radio Bursts throughout the Inner Heliosphere
, ASTROPHYSICAL JOURNAL, Vol: 980, ISSN: 0004-637X- Cite
- Citations: 3
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Journal articleAmes F, Ferreira D, Czaja A, et al., 2025,
Ocean stratification impedes particulate transport to the plumes of Enceladus
, Nature Communications, ISSN: 2041-1723 -
Journal articleChitta LP, Huang Z, D'Amicis R, et al., 2025,
Coronal hole picoflare jets are progenitors of both fast and Alfvénic slow solar wind
, ASTRONOMY & ASTROPHYSICS, Vol: 694, ISSN: 0004-6361- Cite
- Citations: 4
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Journal articleKokkola H, Tonttila J, Calderón SM, et al., 2025,
Model analysis of biases in the satellite-diagnosed aerosol effect on the cloud liquid water path
, Atmospheric Chemistry and Physics, Vol: 25, Pages: 1533-1543, ISSN: 1680-7316The response in cloud water content to changes in cloud condensation nuclei remains one of the major uncertainties in determining how aerosols can perturb cloud properties. In this study, we used an ensemble of large eddy simulations of marine stratocumulus clouds to investigate the correlation between cloud liquid water path (LWP) and the amount of cloud condensation nuclei. We compare this correlation directly from the model to the correlation derived using equations which are used to retrieve liquid water path from satellite observations. Our comparison shows that spatial variability in cloud properties and instrumental noise in satellite retrievals of cloud optical depth and cloud effective radii results in bias in the satellite-derived liquid water path. In-depth investigation of high-resolution model data shows that in large part of a cloud, the assumption of adiabaticity does not hold, which results in a similar bias in the LWP–CDNC (cloud droplet number concentration) relationship as seen in satellite data. In addition, our analysis shows a significant positive bias of between 18 % and 40 % in satellite-derived cloud droplet number concentration. However, for the individual ensemble members, the correlation between the cloud condensation nuclei and the mean of the liquid water path was very similar between the methods. This suggests that if cloud cases are carefully chosen for similar meteorological conditions and it is ensured that cloud condensation nuclei concentrations are well-defined, changes in liquid water can be confidently determined using satellite data.
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Journal articleKramer E, Koller F, Suni J, et al., 2025,
Jets Downstream of Collisionless Shocks: Recent Discoveries and Challenges
, SPACE SCIENCE REVIEWS, Vol: 221, ISSN: 0038-6308- Cite
- Citations: 9
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Journal articleWahlund J-E, Bergman JES, Ahlen L, et al., 2025,
The Radio & Plasma Wave Investigation (RPWI) for the JUpiter ICy moons Explorer (JUICE)
, Space Science Reviews, Vol: 221, ISSN: 0038-6308The Radio & Plasma Wave Investigation (RPWI) onboard the ESA JUpiter ICy moons Explorer (JUICE) is described in detail. The RPWI provides an elaborate set of state-of-the-art electromagnetic fields and cold plasma instrumentation, including active sounding with the mutual impedance and Langmuir probe sweep techniques, where several different types of sensors will sample the thermal plasma properties, including electron and ion densities, electron temperature, plasma drift speed, the near DC electric fields, and electric and magnetic signals from various types of phenomena, e.g., radio and plasma waves, electrostatic acceleration structures, induction fields etc. A full wave vector, waveform, polarization, and Poynting flux determination will be achieved. RPWI will enable characterization of the Jovian radio emissions (including goniopolarimetry) up to 45 MHz, has the capability to carry out passive radio sounding of the ionospheric densities of icy moons and employ passive sub-surface radar measurements of the icy crust of these moons. RPWI can also detect micrometeorite impacts, estimate dust charging, monitor the spacecraft potential as well as the integrated EUV flux. The sensors consist of four 10 cm diameter Langmuir probes each mounted on the tip of 3 m long booms, a triaxial search coil magnetometer and a triaxial radio antenna system both mounted on the 10.6 m long MAG boom, each with radiation resistant pre-amplifiers near the sensors. There are three receiver boards, two Digital Processing Units (DPU) and two Low Voltage Power Supply (LVPS) boards in a box within a radiation vault at the centre of the JUICE spacecraft. Together, the integrated RPWI system can carry out an ambitious planetary science investigation in and around the Galilean icy moons and the Jovian space environment. Some of the most important science objectives and instrument capabilities are described here. RPWI focuses, apart from cold plasma studies, on the understanding of how, thr
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Journal articleFlegrova M, Brindley H, 2025,
Two Decades of Fire-Induced Albedo Change and Associated Short-Wave Radiative Effect Over Sub-Saharan Africa
, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, Vol: 130, ISSN: 2169-897X -
Journal articlePayne DS, Swisdak M, Eastwood JP, et al., 2025,
In-situ observations of the magnetothermodynamic evolution of electron-only reconnection
, COMMUNICATIONS PHYSICS, Vol: 8, ISSN: 2399-3650- Cite
- Citations: 4
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Journal articleD'Amicis R, Velli M, Panasenco O, et al., 2025,
On Alfvenic turbulence of solar wind streams observed by Solar Orbiter during March 2022 perihelion and their source regions
, ASTRONOMY & ASTROPHYSICS, Vol: 693, ISSN: 0004-6361- Cite
- Citations: 3
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Conference paperLewis Z, Beth A, Galand M, et al., 2025,
Constraining ion transport in the diamagnetic cavity of comet 67P
<jats:p>Comets are small icy bodies originating from the outer solar system that produce an increasingly dense gas coma through sublimation as they approach perihelion. Photoionisation of this gas results in a cometary ionosphere, which interacts with the impinging solar wind, leading to large scale plasma structures. One such structure is the diamagnetic cavity: the magnetic field-free inner region that the solar wind cannot penetrate. This region was encountered many times by the ESA Rosetta mission, which escorted comet 67P/Churyumov-Gerasimenko for a two-year section of its orbit.Within the diamagnetic cavity, high ion bulk velocities have been observed by the Rosetta Plasma Consortium (RPC) instruments. The fast ions are thought to have been accelerated by an ambipolar electric field, but the nature and strength of this field are difficult to determine analytically. Our study therefore aims to model the impact of various electric field profiles on the ionospheric density profile and ion composition. The 1D numerical model we have developed includes three key ion species (H2O+, H3O+, and NH4+) in order to assess the sensitivity of each to the timescale of plasma loss through transport. NH4+ is of particular interest, as it has been previously shown to be the dominant ion species at low cometocentric distances near perihelion. It is only produced through the protonation of NH3, a minor component of the neutral gas, and we show that this makes it particularly sensitive to the electric field.We also compare the simulated electron density to RPC datasets, to find the electric field strength and profile which best recreate the plasma densities measured inside the diamagnetic cavity near perihelion. From this, we also constrain the radial bulk ion speed that is required to explain the observations with the model.</jats:p>
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Conference paperKuhlbrodt T, Swaminathan R, Ceppi P, et al., 2025,
A glimpse into the future: The 2023 temperature extremes in the North Atlantic in the context of longer-term climate change
<jats:p>In the year 2023, we have seen extraordinary extrema in high sea-surface temperature (SST) in the North Atlantic which are outside the 4-sigma envelope of the 1982-2011 daily timeseries. Here we take a first look at the large-scale, longer-term drivers of these extrema. Earth&#8217;s net global energy imbalance (in the 12 months up to September 2023) amounts to +1.9 W/m2 as part of a remarkably large upward trend, ensuring continuous heating of the ocean. However, the regional radiation budget over the North Atlantic does not show signs of a significant step increase from less negative aerosol forcing since 2020 as was suggested elsewhere. While the temperature in the top 100 m of the global ocean has been rising in all basins since about 1980, specifically the Atlantic basin has continued to further heat up since 2016. Similarly, salinity in the top 100 m of the ocean has increased in recent years specifically in the Atlantic basin. Outside the North Atlantic, around 2015 a substantial negative trend for sea-ice extent in the Southern Ocean has begun, leading to record low sea-ice extent in 2023. We suggest analysing the 2023 temperature extremes in the North Atlantic in the context of these recent global-scale ocean changes. Analysing climate and Earth System model simulations of the future, we find that the extreme SST in the North Atlantic and the extreme in Southern Ocean sea-ice extent in 2023 lie at the fringe of the expected mean climate change for a global surface-air temperature warming level (GWL) of 1.5&#176;C, and closer to the average at a 3.0&#176;C GWL. Understanding the regional and global drivers of these extremes is indispensable for assessing frequency and impacts of similar events in the coming years.</jats:p>
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Conference paperMurray-Watson R, Gryspeerdt E, 2025,
Air mass history linked to the development of Arctic mixed-phase clouds
<jats:p>The development of clouds during marine cold-air outbreaks (MCAOs) represent a complex phenomenon, transitioning from stratocumulus decks near ice edges to cumuliform fields downwind. This change cloud morphology changes the radiative properties of the cloud, and therefore is of importance to the surface energy budget. Therefore, it is crucial to understand the factors which may drive transition to a broken cloud field. Previous in situ and modelling studies suggest the formation of ice may enhance precipitation and therefore accelerate break-up. However, little is known about the development of mixed-phase clouds in MCAOs.&#160;This study uses pseudo-Lagrangian trajectories and satellite data to analyze this mixed-phase cloud development. We observe a rapid transition from liquid to ice phases in MCAO clouds, contrasting with similar cloud formations outside MCAO conditions. These mixed-phase clouds initially form at temperatures below -20&#176;C near ice edges but can dominate even at -13&#176;C further into outbreaks. This temperature shift suggests a significant role for biological ice nucleating particles (INPs), which increase in prevalence as air masses age over marine environments. The study also notes the influence of the air mass's history over snow- and ice-covered surfaces, which may be low in INPs, on cloud evolution. This link helps explain seasonal variations in Arctic cloud development, both during and outside of MCAOs. Our findings emphasize the importance of understanding local marine aerosol sources and the broader INP distribution in the Arctic for accurate cloud phase modeling in the region.&#160;</jats:p>
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Journal articleZazzeri G, Wacker L, Haghipour N, et al., 2025,
A new portable sampler of atmospheric methane for radiocarbon measurements
, Atmospheric Measurement Techniques, Vol: 18, Pages: 319-325, ISSN: 1867-1381Radiocarbon (14C) is an optimal tracer of methane emissions, as 14C measurements enable distinguishing between fossil methane and biogenic methane (CH4). However, 14C measurements in atmospheric methane are still rare, mainly because of the technical challenge of collecting enough carbon for 14C analysis from ambient air samples. In this study, we address this challenge by advancing the system in Zazzeri et al. (2021) into a much more compact and portable sampler and by coupling the sampler with the MICADAS (MIni CArbon DAting System) accelerator mass spectrometry (AMS) system at ETH Zurich, using a gas interface.Here, we present the new sampler setup, the assessment of the system contamination and a first inter-laboratory comparison with LARA (Laboratory for the Analysis of Radiocarbon with AMS) at the University of Bern.With our sampling line, we achieved a very low blank, 0.7 µgC compared to 5.5 µgC in Zazzeri et al. (2021), and a sample precision of 0.9 %, comparable with other measurement techniques for 14CH4, while reducing the sample size to 60 L of air. We show that this technique, with further improvements, will enable routine 14CH4 measurements in the field for an improved understanding of CH4 sources.
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Journal articleMa B, Chen L, Wu D, et al., 2025,
Type IV-like Solar Radio Burst Consisting of a Series of Short-time Bursts Observed by PSP
, ASTROPHYSICAL JOURNAL, Vol: 979, ISSN: 0004-637X- Cite
- Citations: 1
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Journal articleKaweeyanun N, Masters A, 2025,
Three-dimensional modelling of Ganymede’s Chapman–Ferraro magnetic field and its role in subsurface ocean induction
, Icarus, Vol: 426, ISSN: 0019-1035In April 2023, the Jupiter Icy Moons Explorer (Juice) began its journey to orbit Jupiter’s largest and only magnetic moon, Ganymede. Part of the mission’s objectives aim to verify existence of the moon’s subsurface ocean and determine its structure through its induced response to external excitation by periodically varying magnetic field. Known contributions to the excitation are those from Jupiter’s dipole (at synodic period) and quadrupole (at half-synodic period) variations, and Ganymede’s inclined eccentric orbit around Jupiter (at orbital period). We propose that Ganymede’s magnetopause, where the Chapman–Ferraro (C–F) magnetic field arises from local currents, also contributes to subsurface ocean induction. This article introduces the first three-dimensional model of the C–F field and its outputs at Ganymede’s subsurface ocean and larger magnetosphere. The field is shown to be non-uniform — strongest near upstream Ganymede’s subflow region and gradually weakening away from it. Magnetopause asymmetry due to the Jovian guide field results in largely synodic variation of the C–F field, with exceptions near Ganymede’s equator and subflow meridian where asymmetry effects are minimal and the variations are half-synodic. The C–F field amplitude is of general order ∼50 nT, which is significant relative to excitation from the Jovian field. Comparisons to Galileo data and magnetohydrodynamic simulation results suggest the model is useful, therefore the magnetopause effects must be considered in future induction modeling of Ganymede’s subsurface ocean ahead of the Juice mission.
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Journal articleZhang J, Chen Y-S, Gryspeerdt E, et al., 2025,
Radiative forcing from the 2020 shipping fuel regulation is large but hard to detect
, Communications Earth & Environment, Vol: 6, ISSN: 2662-4435Reduction in aerosol cooling unmasks greenhouse gas warming, exacerbating the rate of future warming. The strict sulfur regulation on shipping fuel implemented in 2020 (IMO2020) presents an opportunity to assess the potential impacts of such emission regulations and the detectability of deliberate aerosol perturbations for climate intervention. Here we employ machine learning to capture cloud natural variability and estimate a radiative forcing of +0.074 ±0.005 W m−2 related to IMO2020 associated with changes in shortwave cloud radiative effect over three low-cloud regions where shipping routes prevail. We find low detectability of the cloud radiative effect of this event, attributed to strong natural variability in cloud albedo and cloud cover. Regionally, detectability is higher for the southeastern Atlantic stratocumulus deck. These results raise concerns that future reductions in aerosol emissions will accelerate warming and that proposed deliberate aerosol perturbations such as marine cloud brightening will need to be substantial in order to overcome the low detectability.
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Journal articleWang JH, Horbury TS, Matteini L, et al., 2025,
Alpha–proton relative drift: implications for the origins and dynamics of the solar wind
, Letters of the Astrophysical Journal, Vol: 978, ISSN: 2041-8205Helium nuclei (alpha particles) strongly influence the momentum and energy balance in the solar wind, comprising up to 20% of the solar wind mass density. In fast Alfvénic wind at heliocentric distances greater than 0.3 au, the alpha particles' bulk flow speed is systematically different to that of the protons. This relative drift speed is of unknown origin and is often close to the local Alfvén wave speed. Novel Parker Solar Probe measurements of the solar wind below 0.3 au show that, closer to the Sun, the alpha–proton drift speed remains on the order of 100–200 km s−1, even where the Alfvén speed is greater than 600 km s−1. This relative speed is quantitatively similar to oxygen–hydrogen drift speeds observed in the transition region by remote sensing, suggesting similar selective acceleration processes in the corona. Due to the relative speed of the Alfvén wave to each particle population close to the Sun, the alphas fluctuate with velocity amplitudes comparable to those of the protons, altering the energy balance of the wave. As a result, alpha particles carry a significant fraction of the total kinetic energy in Alfvénic fluctuations in the near-Sun solar wind. The alpha–proton drift speed is comparable to the proton speed in the near-Sun wind, making the bulk flow of the alpha particles a significant contribution to the kinetic energy flux. These heavy-ion dynamics provide new observational constraints on quantifying the energy budget of the solar wind and the magnetic field evolution through the heliosphere.
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Journal articleLow J, Teoh R, Ponsonby J, et al., 2025,
Ground-based contrail observations: comparisons with reanalysis weather data and contrail model simulations
, Atmospheric Measurement Techniques, Vol: 18, Pages: 37-56, ISSN: 1867-1381Observations of contrails are vital for improving our understanding of the contrail formation and life cycle, informing models, and assessing mitigation strategies. Here, we developed a methodology that utilises ground-based cameras for tracking and analysing young contrails (< 35 min) formed under clear-sky conditions, comparing these observations against reanalysis meteorology and simulations from the contrail cirrus prediction model (CoCiP) with actual flight trajectories. Our observations consist of 14 h of video footage recorded over 5 different days in Central London, capturing 1582 flight waypoints from 281 flights. The simulation correctly predicted contrail formation and absence for around 75 % of these waypoints, with incorrect contrail predictions occurring at warmer temperatures than those with true-positive predictions (7.8 K vs. 12.8 K below the Schmidt–Appleman criterion threshold temperature). When evaluating contrails with observed lifetimes of at least 2 min, the simulation's correct prediction rate for contrail formation increases to over 85 %. Among all waypoints with contrail observations, 78 % of short-lived contrails (observed lifetimes < 2 min) formed under ice-subsaturated conditions, whereas 75 % of persistent contrails (observed lifetimes > 10 min) formed under ice-supersaturated conditions. On average, the simulated contrail geometric width was around 100 m smaller than the observed (visible) width over its observed lifetime, with the mean underestimation reaching up to 280 m within the first 5 min. Discrepancies between the observed and simulated contrail formation, lifetime, and width can be associated with uncertainties in reanalysis meteorology due to known model limitations and sub-grid-scale variabilities, contrail model simplifications, uncertainties in aircraft performance estimates, and observation
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Journal articleMaunder M, Foullon C, Forsyth R, et al., 2025,
Longitudinally Spaced Observations of a Magnetic Cloud-Like Structure Embedded in a Co-rotating Interaction Region
, Annales Geophysicae: atmospheres, hydrospheres and space sciences, ISSN: 0992-7689 -
Journal articleHall RJ, Czaja A, Danabasoglu G, et al., 2025,
A new robust frontal disturbance index of the Oyashio Extension sea surface temperature front
, Journal of Climate, Vol: 38, Pages: 293-307, ISSN: 0894-8755The Oyashio Extension (OE) frontal zone in the northwest Pacific Ocean is associated with strong gradients of sea surface temperature (SST) and salinity. The OE front enhances baroclinicity and anchors the storm tracks; changes in its position and strength may impact atmospheric variability. North–south shifts in the OE front are often defined using the leading principal component for the latitude of the absolute maximum SST gradient in the northwest Pacific (145°–170°E), the so-called Oyashio Extension index (OEI). We show that the OEI is sensitive to the choice of SST dataset used in its construction, and that the significance of regressions of atmospheric fields onto the OEI also depends on the choice of SST datasets, leading to nonrobust results. This sensitivity primarily stems from the longitudinal domain used to define the OEI including a region with parallel or indistinct frontal zones in its central section (155°–164°E), leading to divergent results across datasets. We introduce a new index that considers the extent to which the SST front across this central section departs from climatology, the frontal disturbance index (FDI). For the months considered and over short time lags, the FDI produces more consistent results on air–sea interactions and associated high-frequency storm-track metrics than the conventional OEI, with a southward shift of the storm track for a more positive FDI. The FDI appears to be related to oceanic mesoscale eddy activity in the central OE region. There are significant asymmetric associations between the FDI and storm-track metrics dependent on the sign of the FDI.
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Journal articleSparks N, Toumi R, 2025,
Climate change attribution of Typhoon Haiyan with the Imperial College Storm Model
, Atmospheric Science Letters, Vol: 26, ISSN: 1530-261XIt is difficult to model changes in the likelihood of tropical cyclones under climate change to date. We do this, for the first time, by a applying a stochastic tropical cyclone event set generated by the Imperial College Storm Model to attribute the contribution of climate change to the case of Typhoon Haiyan in 2013. Compared to a pre-industrial baseline, we estimate that a typhoon with a landfall maximum wind speed like Haiyan was larger by +3.5 m/s. This is in good agreement with previous full physics numerical model estimates. A Haiyan type of event has a current return period of 850 years, and the fractional attributable risk due to climate change is 98%. Without climate change, this event was very unlikely. The type of information available from the IRIS model could inform subsidizing of catastrophe bond yield in the context of the loss and damage fund.
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Conference paperDewitte S, Mauritsen T, Meyssignac B, et al., 2025,
The Earth Climate Observatory space mission concept for the monitoring of the Earth Energy Imbalance
, ISSN: 1755-1307We present the Earth Climate Observatory space mission concept - currently studied in Phase 0 as a European Space Agency Earth Explorer 12 candidate - for the measurement of the Earth Energy Imbalance and the Earth Radiation Budget. Key innovations are 1) the differential Sun-Earth observation with identically constructed wide field of view radiometers, 2) an adequate sampling of the seasonal diurnal cycle with a constellation of polar precessing orbits, 3) complementary full angular coverage at high spatial resolution using wide field of view multispectral cameras.
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Journal articleMauel M, Bale SD, Fox NJ, et al., 2025,
Preface to special topic: Plasma physics of the Sun in honor of Eugene Parker
, PHYSICS OF PLASMAS, Vol: 32, ISSN: 1070-664X- Cite
- Citations: 1
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Journal articleLai T, Toumi R, 2025,
Sensitivity of the energy conversion efficiency of tropical cyclones during intensification to sea surface temperature and static stability
, Quarterly Journal of the Royal Meteorological Society, Vol: 151, ISSN: 0035-9009It is projected that the sea surface temperature (SST) increases under climate change and enhances tropical cyclone (TC) intensification directly. An opposing expected feature of climate change is the strengthening atmospheric static stability, which may suppress intensification. The intensity and diabatic heating are closely related through the secondary circulation, but it has been unclear whether both will change at the same rate. Here we show that they respond differently to stability changes. The efficiency of converting diabatic heating to kinetic energy (KE) of TCs to SST and static stability during the intensification stage is examined. In a set of idealised simulations, the efficiency does not have a significant relation with the SST. However the efficiency is found to decrease with increasing static stability at a rate of about -5 % ⋅K‾¹. It is shown that the KE increment declines, while the diabatic heating in the eyewall remains unchanged with larger static stability. The decrease in KE gain at the eyewall is associated with an enhanced outward advection of absolute angular momentum. The combined effect of enhanced water‐vapour supply and the slightly reduced updraft at the eyewall keeps the diabatic heating steady with varying static stability. This study demonstrates the complex effects of enhanced static stability, which is expected to accompany surface warming, on tropical cyclones.
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