Publications

Observations of Uranus in the near-infrared by ground-based telescopes from 1992 to 2018 have shown that the planet's upper atmosphere (thermosphere) steadily cooled from ∼700 to ∼450 K. We explain this cooling as due to the concurrent decline in the power of the solar wind incident on Uranus' magnetic field, which has dropped by ∼50% over the same period due to solar activity trends longer than the 11-year solar cycle. Uranus' thermosphere appears to be more strongly governed by the solar wind than any other planet where we have assessed this coupling so far. Uranus' total auroral power may also have declined, in contrast with the power of the radio aurora that we expect has been predominantly modulated by the solar cycle. In the absence of strong local driving, planets with sufficiently large magnetospheres may also have thermospheres predominantly governed by the stellar wind, rather than stellar radiation.

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Otto F, Clarke B, Barnes C, Kimutai J, Zachariah M, Merz N, Vrkic D, Philip S, Kew S, Pinto I, Vahlberg M, Singh R, Horne Z, Arrighi J, Sparks N, Giguere J, Gilford Det al., 2024,

10 years of rapidly disentangling drivers of extreme weather disasters

, Publisher: Centre for Environmental Policy

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Journal article

Ceppi P, Myers TA, Nowack P, Wall CJ, Zelinka MDet al., 2024,

Implications of a pervasive climate model bias for low-cloud feedback

, Geophysical Research Letters, Vol: 51, ISSN: 0094-8276

How low clouds respond to warming constitutes a key uncertainty for climate projections. Herewe observationally constrain low‐cloud feedback through a controlling factor analysis based on ridgeregression. We find a moderately positive global low‐cloud feedback (0.45 W m− 2 K− 1, 90% range 0.18–0.72 Wm− 2 K− 1), about twice the mean value (0.22 W m− 2 K− 1) of 16 models from the Coupled ModelIntercomparison Project. We link this discrepancy to a pervasive model mean‐state bias: models underestimatethe low‐cloud response to warming because (a) they systematically underestimate present‐day tropical marinelow‐cloud amount, and (b) the low‐cloud sensitivity to warming is proportional to this present‐day low‐cloudamount. Our results hence highlight the importance of reducing model biases in both the mean state of cloudsand their sensitivity to environmental factors for accurate climate change projections

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Journal article

Chakravorty S, Czaja A, Parfitt R, Dewar WKet al., 2024,

Tropospheric response to gulf stream intrinsic variability: a model ensemble approach

, Geophysical Research Letters, Vol: 51, ISSN: 0094-8276

The Gulf Stream's (GS) impact on the marine boundary layer (MBL) is well established, yet the mechanisms and timescales through which it affects the upper-troposphere and contributes to precipitation are debatable. Using a high-resolution regional atmospheric model, we shed light on the impact of ocean intrinsic variability (OIV) along GS on midlatitude-atmosphere. Taking advantage of a 24-member ensemble of ocean model integrations, we devised a novel experimental setup where the same weather system feels different realizations of GS sea surface temperature (SST). We introduce the “Eddy Recharge-Frontal Lift” (ERFL) mechanism, highlighting the joint importance of synoptic variability and boundary layer processes. ERFL mechanism proposes that OIV recharges/discharges MBL with moisture and heat, while convergence associated with passing atmospheric-fronts uplifts these MBL-trapped anomalies to upper-troposphere and imprints on precipitation in surprisingly short periods (a month). The impact of OIV on precipitation depends on the background mean SST.

Journal article

Tannous SM, Bonnell JW, Pulupa M, Bale SDet al., 2024,

Electron Temperatures in the Venusian Ionosphere From Parker Solar Probe Using Quasi-Thermal Noise Spectroscopy

, GEOPHYSICAL RESEARCH LETTERS, Vol: 51, ISSN: 0094-8276

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Journal article

Auestad H, Spensberger C, Marcheggiani A, Ceppi P, Spengler T, Woollings Tet al., 2024,

Spatio-temporal averaging of jets obscures the reinforcement of baroclinicity by latent heating

, Weather and Climate Dynamics, Vol: 5, Pages: 1269-1286, ISSN: 2698-4016

Latent heating modifies the jet stream by modifying the vertical geostrophic wind shear, thereby altering the potential for baroclinic development. Hence, correctly representing diabatic effects is important for modelling the mid-latitude atmospheric circulation and variability. However, the direct effects of diabatic heating remain poorly understood. For example, there is no consensus on the effect of latent heating on the cross-jet temperature contrast. We show that this disagreement is attributable to the choice of spatio-temporal averaging. Jet representations relying on averaged wind tend to have the strongest latent heating on the cold flank of the jet, thus weakening the cross-jet temperature contrast. In contrast, jet representations reflecting the two-dimensional instantaneous wind field have the strongest latent heating on the warm flank of the jet. Furthermore, we show that latent heating primarily occurs on the warm flank of poleward directed instantaneous jets, which is the case for all storm tracks and seasons.

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Journal article

Mozer FS, Agapitov O, Bale SD, Goetz K, Krasnoselskikh V, Pulupa M, Sauer K, Voshchepynets Aet al., 2024,

Origin of the type III radiation observed near the Sun

, ASTRONOMY & ASTROPHYSICS, Vol: 690, ISSN: 0004-6361

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Clarke B, Barnes C, Sparks N, Toumi R, Yang W, Giguere J, Woods Placky B, Gilford D, Pershing A, Winkley S, Vecchi GA, Arrighi J, Roy M, Poole-Selters L, Van Sant C, Grieco M, Singh R, Vahlberg M, Kew S, Pinto I, Otto F, Hess V, Gorham E, Rodgers S, Philip S, Kimutai Jet al., 2024,

Climate change key driver of catastrophic impacts of Hurricane Helene that devastated both coastal and inland communities

, Publisher: Centre for Environmental Policy

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Journal article

Castrillejo M, Hansman RL, Graven HD, Lester JG, Bollhalder S, Kundig K, Wacker Let al., 2024,

Comparability of radiocarbon measurements in dissolved inorganic carbon of seawater produced at ETH-Zurich

, Radiocarbon: an international journal of cosmogenic isotope research, Vol: 66, Pages: 1054-1063, ISSN: 0033-8222

Radiocarbon observations (Δ14C) in dissolved inorganic carbon (DIC) of seawater provide useful information about ocean carbon cycling and ocean circulation. To deliver high-quality observations, the Laboratory of Ion Beam Physics (LIP) at ETH-Zurich developed a new simplified method allowing the rapid analysis of radiocarbon in DIC of small seawater samples, which is continually assessed by following internal quality controls. However, a comparison with externally produced 14C measurements to better establish an equivalency between methods was still missing. Here, we make the first intercomparison with the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility based on 14 duplicate seawater samples collected in 2020. We also compare with prior deep-water observations from the 1970s to 1990s. The results show a very good agreement in both comparisons. The mean Δ14C of 12 duplicate samples measured by LIP and NOSAMS were statistically identical within one sigma uncertainty while two other duplicate samples agreed within two sigma. Based on this small number of duplicate samples, LIP values appear to be slightly lower than the NOSAMS values, but more measurements will be needed for confirmation. We also comment on storage and preservation techniques used in this study, including the freezing of samples collected in foil bags.

Journal article

Rivera YJ, Badman ST, Stevens ML, Raines JM, Owen CJ, Paulson K, Niembro T, Livi SA, Lepri ST, Landi E, Halekas JS, Ervin T, Dewey RM, Coburn JT, Bale SD, Alterman BLet al., 2024,

Mixed Source Region Signatures inside Magnetic Switchback Patches Inferred by Heavy Ion Diagnostics

, ASTROPHYSICAL JOURNAL, Vol: 974, ISSN: 0004-637X

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Journal article

Cuesta ME, Cummings AT, Livadiotis G, Mccomas DJ, Cohen CMS, Khoo LY, Sharma T, Shen MM, Bandyopadhyay R, Rankin JS, Szalay JR, Farooki HA, Xu Z, Muro GD, Stevens ML, Bale SDet al., 2024,

Observations of Kappa Distributions in Solar Energetic Protons and Derived Thermodynamic Properties

, ASTROPHYSICAL JOURNAL, Vol: 973, ISSN: 0004-637X

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Journal article

Quaas J, Andrews T, Bellouin N, Block K, Boucher O, Ceppi P, Dagan G, Doktorowski S, Eichholz HM, Forster P, Goren T, Gryspeerdt E, Hodnebrog Ø, Jia H, Kramer R, Lange C, Maycock AC, Mülmenstädt J, Myhre G, OConnor FM, Pincus R, Samset BH, Senf F, Shine KP, Smith C, Stjern CW, Takemura T, Toll V, Wall CJet al., 2024,

Adjustments to climate perturbations—mechanisms, implications, observational constraints

, AGU Advances, Vol: 5, ISSN: 2576-604X

Since the 5th Assessment Report of the Intergovernmental Panel on Climate Change (AR5) an extended concept of the energetic analysis of climate change including forcings, feedbacks and adjustment processes has become widely adopted. Adjustments are defined as processes that occur in response to the introduction of a climate forcing agent, but that are independent of global-mean surface temperature changes. Most considered are the adjustments that impact the Earth energy budget and strengthen or weaken the instantaneous radiative forcing due to the forcing agent. Some adjustment mechanisms also impact other aspects of climate not related to the Earth radiation budget. Since AR5 and a following description by Sherwood et al. (2015, https://doi.org/10.1175/bams-d-13-00167.1), much research on adjustments has been performed and is reviewed here. We classify the adjustment mechanisms into six main categories, and discuss methods of quantifying these adjustments in terms of their potentials, shortcomings and practicality. We furthermore describe aspects of adjustments that act beyond the energetic framework, and we propose new ideas to observe adjustments or to make use of observations to constrain their representation in models. Altogether, the problem of adjustments is now on a robust scientific footing, and better quantification and observational constraint is possible. This allows for improvements in understanding and quantifying climate change.

Journal article

Waters C, Eastwood J, Fargette N, Newman D, Goldman Met al., 2024,

Classifying magnetic reconnection regions using k-means clustering: applications to energy partition

, JGR: Space Physics, Vol: 129, ISSN: 2169-9402

Magnetic reconnection is a fundamental plasma process which facilitates the conversion of magnetic energy to particle energies. This local process both contributes to and is affected by a larger system, being dependent on plasma conditions and transporting energy around the system, such as Earth's magnetosphere. When studying the reconnection process with in situ spacecraft data, it can be difficult to determine where spacecraft are in relation to the reconnection structure. In this work, we use k-means clustering, an unsupervised machine learning technique, to identify regions in a 2.5-D PIC simulation of symmetric magnetic reconnection with conditions comparable to those observed in Earth’s magnetotail. This allows energy flux densities to be attributed to these regions. The ion enthalpy flux density is the most dominant form of energy flux density in the outflows, agreeing with previous studies. Poynting flux density may be dominant at some points in the outflows and is only half that of the Poynting flux density in the separatrices. The proportion of outflowing particle energy flux decreases as guide field increases. We find that k-means is beneficial for analysing data and comparing between simulations and in situ data. This demonstrates an approach which may be applied to large volumes of data to determine statistically different regions within phenomena in simulations and could be extended to in situ observations, applicable to future multi-point missions.

Journal article

Murray-Watson R, Gryspeerdt E, 2024,

Air mass history linked to the development of Arctic mixed-phase clouds

, Atmospheric Chemistry and Physics, Vol: 24, Pages: 11115-11132, ISSN: 1680-7316

Clouds formed during marine cold-air outbreaks (MCAOs) exhibit a distinct transition from stratocumulus decks near the ice edge to broken cumuliform fields further downwind. The mechanisms associated with ice formation are believed to be crucial in driving this transition, yet the factors influencing such formation remain unclear. Through Lagrangian trajectories collocated with satellite data, this study investigates the development of mixed-phase clouds using these outbreaks. Cloud formed in MCAOs are characterized by a swift shift from liquid to ice-containing states, contrasting with non-MCAO clouds also moving off the ice edge. These mixed-phase clouds are predominantly observed at temperatures below −20 °C near the ice edge. However, further into the outbreak, they become dominant at temperatures as high as −13 °C. This shift is consistent with the influence of biological ice-nucleating particles (INPs), which become more prevalent as the air mass ages over the ocean. The evolution of these clouds is closely linked to the history of the air mass, especially the length of time it spends over snow- and ice-covered surfaces – terrains may that be deficient in INPs. This connection also accounts for the observed seasonal variations in the development of Arctic clouds, both within and outside of MCAO events. The findings highlight the importance of understanding both local marine aerosol sources near the ice edge and the overarching INP distribution in the Arctic for modelling of cloud phase in the region.

Journal article

Lee D, Sparrow S, Leach N, Osprey S, Lee J, Allen Met al., 2024,

The Attribution of February Extremes over North America: A Forecast-Based Storyline Study

, JOURNAL OF CLIMATE, Vol: 37, Pages: 5073-5089, ISSN: 0894-8755

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Citations: 1

Journal article

Fargette N, Eastwood JP, Waters CL, Øieroset M, Phan TD, Newman DL, Stawarz JE, Goldman MV, Lapenta Get al., 2024,

Statistical study of energy transport and conversion in electron diffusion regions at earth's dayside magnetopause

, Journal of Geophysical Research: Space Physics, Vol: 129, ISSN: 2169-9380

The electron diffusion region (EDR) is a key region for magnetic reconnection, but the typical energy transport and conversion in EDRs is still not well understood. In this work, we perform a statistical study of 80 previously published near X-line events identified at the dayside magnetopause in Magnetospheric Multiscale data. We find 44 events that clearly present all commonly accepted EDR signatures and use this database to investigate energy flux partition and energy conversion. We find that energy partition is changed inside EDRs, with a 71%–29% allocation of particle energy flux density between electrons and ions respectively. The electron enthalpy flux density is found to dominate locally at all EDRs and is predominantly oriented in the out-of-plane direction, perpendicular to the reconnecting magnetic field. We also examine the transition from electron- to ion-dominated energy flux partition further from the EDR, finding this typically occurs at scales of the order of the ion inertial length, larger than the typical EDR size. We then investigate energy conversion and transport and highlight complex processes, with potential non-steady-state energy accumulation and release near the EDR. We discuss the implications of our results for reconnection energy conversion, and for magnetopause dynamics in general.

Journal article

Trencham NE, Czaja A, Haigh JD, 2024,

The Impact of Oceanic Feedbacks on Stratosphere-Troposphere Coupling in an Idealized Model

, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, Vol: 129, ISSN: 2169-897X

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Grimmich N, Plaschke F, Grison B, Prencipe F, Escoubet CP, Archer MO, Constantinescu OD, Haaland S, Nakamura R, Sibeck DG, Darrouzet F, Hayosh M, Maggiolo Ret al., 2024,

The Cluster spacecrafts' view of the motion of the high-latitude magnetopause

, Annales Geophysicae: atmospheres, hydrospheres and space sciences, Vol: 42, Pages: 371-394, ISSN: 0992-7689

The magnetopause is the boundary between the interplanetary magnetic field and the terrestrial magnetic field. It is influenced by different solar-wind conditions, which lead to a change in the shape and location of the magnetopause. The interaction between the solar wind and the magnetosphere can be studied from in situ spacecraft observations. Many studies focus on the equatorial plane as this is where recent spacecraft constellations such as THEMIS or MMS operate. However, to fully capture the interaction, it is important to study the high-latitude regions as well. Since the Cluster spacecraft operate in a highly elliptical polar orbit, the spacecraft often pass through the magnetopause at high latitudes. This allows us to collect a dataset of high-latitude magnetopause crossings and to study magnetopause motion in this region, as well as deviations from established magnetopause models. We use multi-spacecraft analysis tools to investigate the direction of the magnetopause motion in the high latitudes and to compare the occurrence of crossings at different locations with the result in the equatorial plane. We find that the high-latitude magnetopause motion is generally consistent with previously reported values and seems to be more often associated with a closed magnetopause boundary. We show that, on average, the magnetopause moves faster inwards than outwards. Furthermore, the occurrence of magnetopause positions beyond those predicted by the Shue et al. (1998) model at high latitudes is found to be caused by the solar-wind parameters that are similar to those in the equatorial plane. Finally, we highlight the importance of the dipole tilt angle at high latitudes. Our results may be useful for the interpretation of plasma measurements from the upcoming SMILE mission (Branduardi-Raymont et al., 2018) as this spacecraft will also fly frequently through the high-latitude magnetopause.

Journal article

Huang Z, Shi C, Velli M, Sioulas N, Panasenco O, Bowen T, Matteini L, Xia M, Shi X, Huang S, Huang J, Casillas Let al., 2024,

Solar Wind Structures from the Gaussianity of Magnetic Magnitude

, ASTROPHYSICAL JOURNAL LETTERS, Vol: 973, ISSN: 2041-8205

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Ervin T, Bale SD, Badman ST, Bowen TA, Riley P, Paulson K, Rivera YJ, Romeo O, Sioulas N, Larson D, Verniero JL, Dewey RM, Huang Jet al., 2024,

Near Subsonic Solar Wind Outflow from an Active Region

, ASTROPHYSICAL JOURNAL, Vol: 972, ISSN: 0004-637X

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Journal article

Davies EE, Ruedisser HT, Amerstorfer UV, Moestl C, Bauer M, Weiler E, Amerstorfer T, Majumdar S, Hess P, Weiss AJ, Reiss MA, Green LM, Long DM, Nieves-Chinchilla T, Trotta D, Horbury TS, O'Brien H, Fauchon-Jones E, Morris J, Owen CJ, Bale SD, Kasper JCet al., 2024,

Flux Rope Modeling of the 2022 September 5 Coronal Mass Ejection Observed by Parker Solar Probe and Solar Orbiter from 0.07 to 0.69 au

, ASTROPHYSICAL JOURNAL, Vol: 973, ISSN: 0004-637X

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Bowen TA, Vasko IY, Bale SD, Chandran BDG, Chasapis A, de Wit TD, Mallet A, McManus M, Meyrand R, Pulupa M, Squire Jet al., 2024,

Extended Cyclotron Resonant Heating of the Turbulent Solar Wind

, ASTROPHYSICAL JOURNAL LETTERS, Vol: 972, ISSN: 2041-8205

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Journal article

Russell J, Bantges R, Brindley H, Bodas-Salcedo Aet al., 2024,

The GERB Obs4MIPs: a dataset for evaluating diurnal and monthly variation in top of atmosphere radiative fluxes in climate models

, Earth System Science Data, Vol: 16, Pages: 4243-4266, ISSN: 1866-3508

A newly available radiative flux dataset specifically designed to enable the evaluation of the diurnal cycle in top-of-atmosphere (TOA) fluxes as captured by climate and Earth system models is presented. Observations over the period 2007–2012 made by the Geostationary Earth Radiation Budget (GERB) instrument are used to derive monthly hourly mean outgoing longwave radiation (OLR) and reflected shortwave (RSW) fluxes on a regular 1° latitude–longitude grid covering approximately 60° N–60° S and 60° E–60° W. The impact of missing data is evaluated in detail, and a data-filling solution is implemented using estimates of broadband fluxes from the Spinning Enhanced Visible and Infrared Imager flying on the same Meteosat platform, scaled to the GERB observations. This relatively simple approach is shown to deliver an approximate improvement by a factor of 10 in both the bias caused by missing data and the associated variability in the error. To demonstrate the utility of this V1.1 filled GERB Observations for Climate Model Intercomparison Projects (Obs4MIPs) dataset, comparisons are made to radiative fluxes from two climate configurations of the Hadley Centre's Global Environmental Model: HadGEM3-GC3.1 and HadGEM3-GC5.0. Focusing on marine stratocumulus and deep convective cloud regimes, diurnally resolved comparisons between the models and observations highlight discrepancies between the model configurations in terms of their ability to capture the diurnal amplitude and the phase in TOA fluxes, details that cannot be diagnosed by comparisons at lower temporal resolutions. For these cloud regimes the GC5.0 configuration shows improved fidelity to the observations relative to GC3.1, although notable differences remain. The V1.1 filled GERB Obs4MIPs monthly hourly TOA fluxes are available from the Centre for Environmental Data Analysis, with the OLR fluxes accessible at https://doi.org/10.5285/90148d9b1

Journal article

Rivera YJ, Badman ST, Stevens ML, Verniero JL, Stawarz JE, Shi C, Raines JM, Paulson KW, Owen CJ, Niembro T, Louarn P, Livi SA, Lepri ST, Kasper JC, Horbury TS, Halekas JS, Dewey RM, De Marco R, Bale SDet al., 2024,

In situ observations of large-amplitude Alfvén waves heating and accelerating the solar wind

, SCIENCE, Vol: 385, Pages: 962-966, ISSN: 0036-8075

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Clarke B, Zachariah M, Barnes C, Sparks N, Toumi R, Yang W, Vahlberg M, Lagmay AM, Ybañez R, Delmendo PA, Malaiba C, Vrkic D, Otto F, Basconcillo J, Kimutai J, Philip S, Blomendaal N, Singh R, Arrighi J, Rodriguez LC, Rances Aet al., 2024,

Climate change increased Typhoon Gaemi's wind speeds and rainfall, with devastating impacts across the western Pacific region

, Publisher: Centre for Environmental Policy

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Journal article

Kelly H, Archer M, Ma X, Nykyri K, Eastwood J, Southwood Det al., 2024,

Identification of Kelvin-Helmholtz generated vortices in magnetised fluids

, Frontiers in Astronomy and Space Sciences, Vol: 11, ISSN: 2296-987X

The Kelvin-Helmholtz Instability (KHI), arising from velocity shear across the magnetopause, plays a significant role in the viscous-like transfer of mass, momentum, and energy from the shocked solar wind into the magnetosphere. While the KHI leads to growth of surface waves and vortices, suitable detection methods for these applicable to magnetohydrodynamics (MHD) are currently lacking. A novel method is derived based on the well-established λ-family of hydrodynamic vortex identification techniques, which define a vortex as a local minimum in an adapted pressure field. The J × B Lorentz force is incorporated into this method by using an effective total pressure in MHD, including both magnetic pressure and a pressure-like part of the magnetic tension derived from a Helmholtz decomposition. The λMHD method is shown to comprise of four physical effects: vortical momentum, density gradients, fluid compressibility, and the rotational part of the magnetic tension. A local three-dimensional MHD simulation representative of near-flank magnetopause conditions (plasma β’s 0.5–5 and convective Mach numbers Mf ∼ 0.4) under northward interplanetary magnetic field (IMF) is used to validate λMHD. Analysis shows it correlates well with hydrodynamic vortex definitions, though the level of correlation decreases with vortex evolution. Overall, vortical momentum dominates λMHD at all times. During the linear growth phase, density gradients act to oppose vortex formation. By the highly nonlinear stage, the formation of small-scale structures leads to a rising importance of the magnetic tension. Compressibility was found to be insignificant throughout. Finally, a demonstration of this method adapted to tetrahedral spacecraft observations is performed.

Journal article

Cheng S, Chassagnon H, Kasoar M, Guo Y, Arcucci Ret al., 2025,

Deep Learning Surrogate Models of JULES-INFERNO for Wildfire Prediction on a Global Scale

, IEEE TRANSACTIONS ON EMERGING TOPICS IN COMPUTATIONAL INTELLIGENCE, ISSN: 2471-285X

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10 years of rapidly disentangling drivers of extreme weather disasters

Climate change key driver of catastrophic impacts of Hurricane Helene that devastated both coastal and inland communities

Climate change increased Typhoon Gaemi's wind speeds and rainfall, with devastating impacts across the western Pacific region

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