Publications

Conference paper

Dipu S, Schwarz M, Ekman AML, Gryspeerdt E, Goren T, Sourdeval O, Mülmenstädt J, Quaas Jet al., 2022,

Exploring satellite-derived relationships between cloud droplet number concentration and liquid water path using large-domain large-eddy simulation

<jats:p>&lt;p&gt;Important aspects of the adjustments to aerosol-cloud interactions can be examined using the relationship between cloud droplet number concentration (N&lt;sub&gt;d&lt;/sub&gt;) and liquid water path (LWP). Specifically, this relation can constrain the role of aerosols in leading to thicker or thinner clouds in response to adjustment mechanisms. This study investigates the satellite retrieved relationship between N&lt;sub&gt;d&lt;/sub&gt; and LWP for a selected case of mid-latitude continental clouds using high-resolution Large-eddy simulations (LES) over a large domain in weather prediction mode. Since the satellite retrieval uses the adiabatic assumption to derive the N&lt;sub&gt;d&lt;/sub&gt; (N&lt;sub&gt;Ad&lt;/sub&gt;), we have also considered N&lt;sub&gt;Ad&lt;/sub&gt; from the LES model for comparison. The joint histogram analysis shows that the N&lt;sub&gt;Ad&lt;/sub&gt;-LWP relationship in the LES model and the satellite is in approximate agreement. In both cases, the peak conditional probability (CP) is confined to lower N&lt;sub&gt;Ad&lt;/sub&gt; and LWP, and the corresponding mean LWP shows a weak relation with N&lt;sub&gt;Ad&lt;/sub&gt;. In contrast, at higher N&lt;sub&gt;Ad&lt;/sub&gt; (&gt; 50 cm&lt;sup&gt;&amp;#8722;3&lt;/sup&gt; ), the CP shows a larger spread; consequently, the mean LWP increases non-monotonically with increasing N&lt;sub&gt;Ad&lt;/sub&gt; in both cases. However, the N&lt;sub&gt;Ad&lt;/sub&gt;-LWP relation lacks, in particular, the negative sensitivity at higher N&lt;sub&gt;Ad&l

Conference paper

Sourdeval O, Gryspeerdt E, Krämer M, Quaas Jet al., 2022,

Assessment of ice clouds - aerosol interactions in global satellite observations

<jats:p>&lt;p&gt;Interactions between aerosols and clouds, as well as their radiative consequences, have been a long-standing problem to understand cloud physics as well as anthropogenic impacts on climate. Satellite-based investigations of the direct and indirect impact of aerosols on liquid clouds have led to significant progress in the understanding during the last decade. This is partly due to the emergence of adapted cloud properties provided by satellites, such as the droplet number concentration. Ice clouds have suffered from such adapted quantity for much longer, but solutions have recently been appearing.&lt;/p&gt;&lt;p&gt;This study investigates aerosol - ice clouds interactions using ice crystal number concentration (Ni) profiles from a lidar-radar dataset (DARDAR-Nice), used cojointly with with collocated aerosol information from the Copernicus Atmospheric Monitoring Service (CAMS) reanalyses. A multitude of cloud regimes, subdivided into seasonal and regional bins, are considered in order to disentangle meteorological effects from the aci signature. First results of joint-histograms between Ni and the aerosol mass show an overall positive sensitivity of Ni to the aerosols load. This response is particularly strong towards to cloud-top and flattens towards cloud-base, consistently with expectations for homogeneous nucleation processes. The response of the ice water content, in terms of adjustment to the initial aerosol perturbation as also quantified.&lt;/p&gt;</jats:p>

Journal article

Franci L, Papini E, Micera A, Matteini L, Stawarz J, Lapenta G, Burgess D, Hellinger P, Landi S, Verdini A, Montagud-Camps Vet al., 2022,

Fully kinetic simulations of the near-Sun solar wind plasma: turbulence, reconnection, and particle heating

<jats:p>&lt;p&gt;We model the development of plasma turbulence in the near-Sun solar wind with high-resolution fully-kinetic particle-in-cell (PIC) simulations, initialised with plasma conditions measured by Parker Solar Probe during its first solar encounter (ion and electron plasma beta &amp;#8804; 1 and a large amplitude of the turbulent fluctuations). The power spectra of the plasma and electromagnetic fluctuations are characterized by multiple power-law intervals, with a transition and a considerable steepening in correspondence of the electron scales. In the same range of scales, the kurtosis of the magnetic fluctuations is observed to further increase, hinting at a higher level of intermittency. We observe a number of electron-only reconnection events, which are responsible for an increase of the electron temperature in the direction parallel to the ambient field. The total electron temperature, however, exhibits only a small increase due to the cooling of electrons in the perpendicular direction, leading to a strong temperature anisotropy. We also analyse the power spectra of the different terms of the electric field in the generalised Ohm&amp;#8217;s law, their linear and nonlinear components, and their alignment, to get a deeper insight on the nature of the turbulent cascade. Finally, we compare our results with those from hybrid simulations with the same parameters, as well as with spacecraft observations.&lt;/p&gt;</jats:p>

Journal article

Adhikari S, Shay MA, Parashar TN, Matthaeus WH, Sharma Pyakurel P, Stawarz JE, Eastwood JPet al., 2022,

Reconnection and Turbulence: A Qualitative Approach to their Relationship

<jats:p>&lt;p&gt;Over the past few decades, the relationship between turbulence and reconnection has emerged as a subject of interest. For example, various properties of reconnection have been studied in different turbulent environments using plasma simulations. In other approaches, reconnection is studied as a subsidiary process occurring in turbulence. Turbulent features are also studied as consequences of instabilities associated with large scale reconnection. Only recently, we have attempted to answer some of the fundamental questions such as: &amp;#8220;What are the turbulent-like features of laminar magnetic reconnection?&amp;#8221;, &quot;Is magnetic reconnection fundamentally an energy cascade?&quot; both related to the interplay between reconnection and turbulence. Using 2.5D particle in cell simulations, we have found that laminar magnetic reconnection in a quasi-steady phase exhibits a Kolmogorov-like power spectrum. Most notably, the energy transfer process in magnetic reconnection is also found to be similar to that of a turbulent system suggesting that reconnection involves an energy cascade. The reconnection rate is correlated to both the magnetic energy spectrum in the ion-scales and the cascade of energy. Further, similarities between reconnection and turbulence in terms of the electric field spectrum, their components, and pressure-strain interaction will be highlighted.&lt;/p&gt;</jats:p>

Journal article

Robertson S, Eastwood J, Stawarz J, Russell C, Giles B, Burch Jet al., 2022,

Survey of EDR-associated Magnetopause Flux Ropes with MMS

<jats:p>&lt;p&gt;Flux ropes are twisted magnetic field structures produced during magnetic reconnection. They are thought to be important for energy transport and particle acceleration and are commonly observed throughout space plasma environments, including at the Earth&amp;#8217;s magnetopause. Flux Transfer Events (FTEs), which typically contain flux ropes, have been observed to grow in size and flux content as they are convected over the magnetopause and into the magnetotail, contributing to flux transport in the Dungey cycle. More recently, small-scale flux ropes have been observed inside the Electron Diffusion Region (EDR) during magnetopause reconnection.&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;br&gt;In this study, we investigate the link between the EDR and flux ropes, presenting a survey of 245 flux ropes observed by the Magnetospheric Multiscale (MMS) mission on days during which the spacecraft also encountered the EDR. MMS measures the thermal electron and ion 3D distributions at 30 msec and 150 msec time resolution, respectively, and at spacecraft separations down to a few kilometres allowing the study of such electron-scale phenomena. We find that flux ropes are more likely to be observed closer to the EDR, and that flux ropes observed closer to the EDR tend to have greater axial magnetic field strength and therefore greater flux content. We suggest that we could be sampling a subset of flux ropes that are recently formed by the EDR and discuss how this impacts current theories for flux rope evolution on the magnetopause.&lt;/p&gt;</jats:p>

Journal article

Kilpua E, Good S, Ala-Lahti M, Osmane A, Fontaine D, Pal S, Räsänen J, Bale S, Zhao L, Hadid L, Janvier M, Yordanova Eet al., 2022,

Magnetic field fluctuations in CME-driven sheath regions

<jats:p>&lt;p&gt;The sheath regions driven by coronal mass ejections (CMEs) are large-scale heliospheric structures where magnetic field fluctuations are observed over various temporal scales. Their internal structure and nature of embedded&amp;#160; fluctuations are currently poorly understood. We report here the key characteristics of&amp;#160; magnetic field fluctuations in CME-driven sheaths, including their spectral index, intermittency, amplitude and compressibility. The results highlight the gradual formation of sheaths over several days as they propagate through interplanetary and the presence of intermittent coherent structures such as strong current sheets. The Jensen-Shannon permutation entropy and complexity analysis suggest that sheath fluctuations are stochastic, but have lower entropy and higher complexity than the preceding wind.&amp;#160; We also show the analysis results during the slow sheath at ~0.5 AU detected by Parker Solar Probe, highlighting that slow CMEs can have prominent sheaths with distinct fluctuation properties.&amp;#160;&lt;/p&gt;</jats:p>

Journal article

Laker R, Horbury T, Matteini L, Woolley T, Stawarz J, Bale Set al., 2022,

On the Deflections of Switchbacks

<jats:p>&lt;p&gt;Following their presence during Parker Solar Probe&amp;#8217;s (PSP) first encounter, switchbacks have become an active area of research with several proposed mechanisms for their formation. Many of these theories have testable predictions, although it is not trivial to compare simulation results with in-situ data from PSP. For example, there is some debate regarding the deflection direction of switchbacks, with some theories predicting a consistent magnetic deflection in the +T direction in the RTN coordinate system. Such arguments are largely focussed on the first two PSP encounters, as these are the most studied encounters in the literature. We examine the deflection direction of switchbacks for the first eight PSP encounters, with the aim to clear up any ambiguity regarding this property of switchbacks. Much like the earlier results of Horbury et al. 2020 (during the first encounter) we find that switchbacks tend to deflect in the same direction for hours at a time. Although there is some consistency in deflection direction within an individual encounter, crucially we find that there is no preferred deflection direction across all the encounters. We speculate about the cause of these results and what implications they may have for switchback formation theories.&lt;/p&gt;</jats:p>

Journal article

Desai R, Eastwood J, Eggington J, Chittenden J, Horne Ret al., 2022,

Magnetospheric compressions, magnetopause shadowing and the last-closed-drift-shell

<jats:p>&lt;p&gt;Fluxes in the outer radiation belt can vary by orders of magnitude in response to solar wind driving conditions. Magnetopause shadowing, where electron and proton drift paths intersect the magnetopause boundary, is a fundamental loss process which operates on sub-day timescales and can result in rapid loss across the outer radiation belt. Accurate characterisation of this is therefore required to fully account for outer radiation belt dynamics and to avoid unrealistic fluxes impacting long-term forecasts. In this paper we utilise particle simulations of the radiation belts integrated within evolving global MHD simulations, to provide high-resolution high-fidelity simulations of the phenomenon of magnetopause shadowing. We model a variety of magnetopause compression scenarios corresponding to extreme cases of interplanetary shock impacts, and gradual increases in solar wind dynamic pressure. We thus constrain how time-dependent topological variation of the magnetospheric fields results in a complex interplay of open and closed particle drift paths, and examine the role of the electric field in modulating escaping particles trajectories as well as corresponding prompt injections into the inner magnetosphere.&lt;/p&gt;</jats:p>

Journal article

Montagud-Camps V, Hellinger P, Verdini A, Papini E, Franci L, Matteini L, Landi Set al., 2022,

Quantification of the cross-helicity cascade with Karman-Howarth-Monin and Spectral transfer equations

<jats:p>&lt;p&gt;Spectral transfer equations allow to &amp;#160;quantify the value of the energy flux of a turbulent flow across concentric shells in Fourier space. Karman-Howarth-Monin equations serve as a complement to the Spectral Transfer analysis, since they &amp;#160;quantify &amp;#160;as well the energy transfer rate of turbulence across scales via third-order structure functions, but also provide information on the directionality of the flux. We have extended the use of these methods to study the cascade of cross-helicity and compare it to the energy cascade &amp;#160;in 3D compressible MHD simulations. Our results show that the cross-helicity cascade reaches stationarity after the energy cascade, thus indicating a slower turbulence development for this invariant. Once fully developed, the cross-helicity cascade matches the main features of the energy one.&lt;/p&gt;</jats:p>

Journal article

Pisa D, Soucek J, Santolik O, Hanzelka M, Maksimovic M, Vecchio A, Khotyaintsev Y, Chust T, Kretzschmar M, Matteini L, Horbury Tet al., 2022,

Observations of the Time Domain Sampler receiver from the Radio and Plasma Wave instrument during the Solar Orbiter Earth flyby&#160;

<jats:p>&lt;p&gt;On November 27, 2021, Solar Orbiter completed its only flyby of Earth on its way to the following Sun&amp;#8217;s encounter in March 2022. Although this fast flyby was performed primarily to decrease the spacecraft&amp;#8217;s velocity and change orbit to get closer to the Sun, the Radio and Plasma Wave (RPW) instrument had the opportunity to perform high cadence measurements in the Earth&amp;#8217;s magnetosphere. We review the main observation of the Time Domain Sampler (TDS) receiver, a part of the RPW instrument, made during this flyby at frequencies below 200 kHz. The TDS receiver operated in a high cadence mode providing us with the regular waveform snapshot with 62 ms length every ten seconds for two electric components. Besides the regular captures, we have got more than five hundred onboard classified snapshots and the statistical products with a sixteen-second cadence. Before entering the terrestrial magnetosphere around 02:30UT, the spacecraft wandered through the foreshock region, registering intense bursts of Langmuir waves. After the bowshock crossing, Solar Orbiter was for more than two hours in the morning sector of the magnetosphere, recording various plasma wave modes. The closest approach was reached at 04:30UT above North Africa at an altitude of 460 km. Then the spacecraft continued into the Earth&amp;#8217;s tail and entered the magnetosheath around 13:00UT. After 15:00UT, the Solar Orbiter crossed the bowshock, and bursts of Langmuir waves were detected again pointing out to the deep downstream foreshock region. Further from the Earth, intense Auroral Kilometric Radiation (AKR) at frequencies above 100 kHz was also detected.&lt;/p&gt;</jats:p>

Journal article

Teixeira J, Burton C, Kelley DI, Folberth G, O'Connor FM, Betts R, Voulgarakis Aet al., 2022,

Representing socio-economic factors in INFERNO using the Human Development Index

<jats:p>&lt;p&gt;INFERNO human fire ignitions and fire suppression functions excluded the representation of socio-economic factors (aside population density) that can affect anthropogenic behaviour regarding fire ignitions. To address this, we implement a socio-economic factor in the fire ignition and suppression parametrisation in INFERNO based on an Human Development Index (HDI) term. The HDI is calculated based on three indicators designed to capture the income, health, and education dimensions of human development. Therefore, we assume this leads to a representation where if there is more effort in improving human development, there is also investment on higher fire suppression by the population. Including this representation of socio-economic factors in INFERNO we were able to reduce large positive biases that were found for the regions of Temperate North America, Central America, Europe and Southern Hemisphere South America without significant impact to other regions, improving the model performance at a regional level and better representing processes that drive fire behaviour in the Earth System.&lt;/p&gt;</jats:p>

Journal article

Myhre G, Stjern C, Samset B, Forster P, Quaas J, Takemura T, Voulgarakis A, Jia H, Jouan C, Sand M, Olivie Det al., 2022,

The timescales of climate responses to carbon dioxide and aerosols

<jats:p>&lt;p&gt;Enhanced emissions of both greenhouse gases and aerosols generate climate responses on a wide range of time scales. An initial radiative response triggers a set of rapid adjustments, which are eventually followed by surface-temperature-driven feedbacks. While a lot happens during the first days and months after a perturbation, the monthly mean data typically used in climate studies are too coarse to show the temporal evolution of responses. In these analyses, we take a closer look at how the climate system responds during the very first hours and days after a sudden increase in carbon dioxide (CO2), in black carbon (BC) or in sulfate (SO4). Five models have performed PDRMIP simulations with hourly output, and we also compare results to monthly PDRMIP and CMIP6 results. We find that the effect of increasing ocean temperatures kicks in after a couple of months. Rapid precipitation reductions are for all three climate perturbations established after just a couple of days, and does for BC not differ much from the full-time response. &amp;#160;For CO2 and SO4, the magnitude of the precipitation response gradually increases with surface warming, and for CO2 the sign of the response changes for negative to positive after two years. Rapid cloud adjustments are typically established within the first 24 hours and while the magnitude of cloud feedbacks for CO2 and SO4 increases over time, the latitude-height pattern of the total cloud changes is clearly present after one year. While previously known that climate responses to BC are dominated by rapid adjustments, this work underlines the swiftness of the processes involved.&lt;/p&gt;</jats:p>

Conference paper

Horner G, Gryspeerdt E, 2022,

Investigating the evolution of tropical cirrus clouds from deep convection

<jats:p>&lt;p&gt;Tropical convective clouds, particularly their large cirrus outflows, play an important role in modulating the energy balance of the Earth&amp;#8217;s atmosphere. Understanding the evolution of these clouds, and how they change in response to anthropogenic emissions is therefore important to understand past and future climate change. Previous work has focused on tracking individual convective cores and their evolution into anvil cirrus and subsequent thin cirrus clouds in satellite data.&lt;/p&gt;&lt;p&gt;In this work we have introduced a novel approach to investigating the evolution of tropical convective clouds by creating a &amp;#8216;Time Since Convection&amp;#8217; (TSC) dataset. Using reanalysis windspeeds, the time since the air at each location last experienced a convective event (as defined by the presence of a deep convective core) is calculated. Used in conjunction with data from the DARDAR and CERES products, we can build a composite picture of the radiative and microphysical properties of the clouds as a function of their time since convection.&lt;/p&gt;&lt;p&gt;As with previous studies, we find that cloud properties are a strong function of time since convection, with decreases in the optical thickness, cloud top height, and cloud fraction over time. These changes in in cloud properties also have a significant radiative impacts, with the longwave and shortwave component of the cloud radiative effect also being a strong function of time since convection. In addition, using the DARDAR product, a combination of CloudSat radar and the CALIPSO lidar measurements, we build composite cross sections of convective clouds, characterising their vertical evolution and how it is influenced by external meteorological and initial conditions flagged in the TSC dataset.&lt;/p&gt;</jats:p>

Conference paper

Jia H, Quaas J, Gryspeerdt E, Böhm C, Sourdeval Oet al., 2022,

Addressing the difficulties in quantifying the Twomey effect for marine warm clouds from multi-sensor satellite observations and reanalysis

<jats:p>&lt;p&gt;Aerosol&amp;#8211;cloud interaction is the most uncertain component of the overall anthropogenic forcing of the climate, in which the Twomey effect plays a fundamental role. Satellite-based estimates of the Twomey effect are especially challenging, mainly due to the difficulty in disentangling aerosol effects on cloud droplet number concentration (&lt;em&gt;N&lt;/em&gt;&lt;sub&gt;d&lt;/sub&gt;) from possible confounders. By combining multiple satellite observations and reanalysis, this study investigates the impacts of a) updraft, b) precipitation, c) retrieval errors, as well as (d) vertical co-location between aerosol and cloud, on the assessment of&amp;#160;&lt;em&gt;N&lt;/em&gt;&lt;sub&gt;d&lt;/sub&gt;-toaerosol sensitivity (&lt;em&gt;S&lt;/em&gt;) in the context of marine warm (liquid) clouds. Our analysis suggests that&amp;#160;&lt;em&gt;S&lt;/em&gt;&amp;#160;increases remarkably with both cloud base height and cloud geometric thickness (proxies for vertical velocity at cloud base), consistent with stronger aerosol-cloud interactions at larger updraft velocity. In turn, introducing the confounding effect of aerosol&amp;#8211;precipitation interaction can artificially amplify&amp;#160;&lt;em&gt;S&lt;/em&gt;&amp;#160;by an estimated 21 %, highlighting the necessity of removing precipitating clouds from analyses on the Twomey effect. It is noted that the retrieval biases in aerosol and cloud appear to underestimate&amp;#160;&lt;em&gt;S&lt;/em&gt;, in which cloud fraction acts as a key modulator, making it practically difficult to balance the accuracies of aerosol&amp;#8211;cloud retrievals at aggregate

Journal article

Woolley T, Matteini L, Horbury TS, Bale SD, Laker R, Woodham LD, Stawarz JEet al., 2022,

Linking In-situ Magnetic and Density Structures in the Low Latitude Slow Solar Wind to Solar Origins

<jats:p>&lt;p&gt;To date, Parker Solar Probe has completed ten solar encounters and measured a wealth of in-situ data down to heliocentric distances of ~13 solar radii. This data provides a novel opportunity to investigate the near-Sun environment and understand the young slow solar wind. Typically, the slow solar wind observed in the inner heliosphere is split into an Alfvenic and a non-Alfvenic component. The Alfvenic slow wind is thought to originate from overexpanded coronal hole field lines, whereas the non-Alfvenic slow wind could originate from active regions, transient events, or reconnection at the tips of helmet streamers. In this work, we find structures associated with non-Alfvenic slow wind in the low latitude wind measured by Parker Solar Probe. We identify at least two distinct types of structure using magnetic field magnitude, electron pitch angle distributions, and electron number density. After statistically analysing these structures, with a focus on their plasma properties, shape, and location with respect to the heliospheric current sheet, we link them to solar origins. We find structures that are consistent with the plasma blobs seen previously in remote sensing observations.&lt;/p&gt;</jats:p>

Journal article

Maffei S, Livermore P, Mound J, Eggington J, Eastwood J, Sanchez S, Freeman Met al., 2022,

The future evolution of the auroral zones

<jats:p>&lt;p&gt;The auroral zones indicate the locations on the Earth&amp;#8217;s surface where, on average, it is most likely to spot aurorae as a consequence of increased solar activity. The shape of the auroral zones and, similarly, the geographical locations most vulnerable to extreme space weather events are modulated by the geomagnetic field of internal origin. As the latter evolves in time, the formers will be subject to variations on the same timescales.&lt;/p&gt;&lt;p&gt;From available geomagnetic field forecasts (which provide an estimate of the future evolution of the geomagnetic field of internal origin) we derive AACGM latitudes and estimate the future evolution of the auroral zones. The novel aspect of this technique is that we make use of all available Gauss coefficients to produce the forecasts, while the majority of present techniques estimate the location of the auroral zones based on the dipolar coefficients only. Our results show that, while the shift of the geomagnetic dipole axis has a first order contribution, higher order Gauss coefficients contribute significantly to the location and shape of the auroral zones.&lt;/p&gt;&lt;p&gt;The same technique is then extended to estimate the future location of the geographical location that would be, on average, most exposed to extreme space weather event. We find that the space-weather related risk will not change significantly for the UK over the next 50 years. For the Canadian provinces of Quebec and Ontario, however, we predict a significant increase in the risk associated to extreme solar activity.&lt;/p&gt;</jats:p>

Journal article

Ben-Yami M, Oetjen H, Brindley H, Cossich W, Lajas D, Maestri T, Magurno D, Raspollini P, Sgheri L, Warwick Let al., 2022,

Emissivity retrievals with FORUM's end-to-end simulator: challenges and recommendations

, Atmospheric Measurement Techniques, Vol: 15, Pages: 1755-1777, ISSN: 1867-1381

Spectral emissivity is a key property of the Earth's surface, of which only very few measurements exist so far in the far-infrared (FIR) spectral region, even though recent work has shown that the FIR is important for accurate modelling of the global climate. The European Space Agency's 9th Earth Explorer, FORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) will provide the first global spectrally resolved measurements of the Earth's top-of-the-atmosphere (TOA) spectrum in the FIR. In clear-sky conditions with low water vapour content, these measurements will provide a unique opportunity to retrieve spectrally resolved FIR surface emissivity. In preparation for the FORUM mission with an expected launch in 2027, this study takes the first steps towards the development of an operational emissivity retrieval for FORUM by investigating the sensitivity of the emissivity product of a full spectrum optimal estimation retrieval method to different physical and operational parameters. The tool used for the sensitivity tests is the FORUM mission's end-to-end simulator. These tests show that the spectral emissivity of most surface types can be retrieved for dry scenes in the 350–600 cm−1 region, with an absolute uncertainty ranging from 0.005 to 0.01. In addition, the quality of the retrieval is quantified with respect to the precipitable water vapour content of the scene, and the uncertainty caused by the correlation of emissivity with surface temperature is investigated. Based on these investigations, a road map is recommended for the development of the operational emissivity product.

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Journal article

Saboya E, Zazzeri G, Graven H, Manning AJ, Michel SEet al., 2022,

Continuous CH4 and delta(CH4)-C-13 measurements in London demonstrate under-reported natural gas leakage

, Atmospheric Chemistry and Physics, Vol: 22, Pages: 3595-3613, ISSN: 1680-7316

Top-down greenhouse gas measurements can be used to independently assess the accuracy of bottom-up emission estimates. We report atmospheric methane (CH4) mole fractions and δ13CH4 measurements from Imperial College London from early 2018 onwards using a Picarro G2201-i analyser. Measurements from March 2018 to October 2020 were compared to simulations of CH4 mole fractions and δ13CH4 produced using the NAME (Numerical Atmospheric-dispersion Modelling Environment) dispersion model coupled with the UK National Atmospheric Emissions Inventory, UK NAEI, and a global inventory, the Emissions Database for Global Atmospheric Research (EDGAR), with model spatial resolutions of ∼ 2, ∼ 10, and ∼ 25 km. Simulation–measurement comparisons are used to evaluate London emissions and the source apportionment in the global (EDGAR) and UK national (NAEI) emission inventories. Observed mole fractions were underestimated by 30 %–35 % in the NAEI simulations. In contrast, a good correspondence between observations and EDGAR simulations was seen. There was no correlation between the measured and simulated δ13CH4 values for either NAEI or EDGAR, however, suggesting the inventories' sectoral attributions are incorrect. On average, natural gas sources accounted for 20 %–28 % of the above background CH4 in the NAEI simulations and only 6 %–9 % in the EDGAR simulations. In contrast, nearly 84 % of isotopic source values calculated by Keeling plot analysis (using measurement data from the afternoon) of individual pollution events were higher than −45 ‰, suggesting the primary CH4 sources in London are actually natural gas leaks. The simulation–observation comparison of CH4 mole fractions suggests that total emissions in London are much higher than the NAEI estimate (0.04 Tg CH4 yr−1) but close to, or slightly lo

Journal article

Reville V, Fargette N, Rouillard AP, Lavraud B, Velli M, Strugarek A, Parenti S, Brun AS, Shi C, Kouloumvakos A, Poirier N, Pinto RF, Louarn P, Fedorov A, Owen CJ, Genot V, Horbury TS, Laker R, O'Brien H, Angelini V, Fauchon-Jones E, Kasper JCet al., 2022,

Flux rope and dynamics of the heliospheric current sheet Study of the Parker Solar Probe and Solar Orbiter conjunction of June 2020

, Astronomy and Astrophysics: a European journal, Vol: 659, Pages: 1-14, ISSN: 0004-6361

Context. Solar Orbiter and Parker Solar Probe jointly observed the solar wind for the first time in June 2020, capturing data from very different solar wind streams: calm, Alfvénic wind and also highly dynamic large-scale structures.Context. Our aim is to understand the origin and characteristics of the highly dynamic solar wind observed by the two probes, particularly in the vicinity of the heliospheric current sheet (HCS).Methods. We analyzed the plasma data obtained by Parker Solar Probe and Solar Orbiter in situ during the month of June 2020. We used the Alfvén-wave turbulence magnetohydrodynamic solar wind model WindPredict-AW and we performed two 3D simulations based on ADAPT solar magnetograms for this period.Results. We show that the dynamic regions measured by both spacecraft are pervaded by flux ropes close to the HCS. These flux ropes are also present in the simulations, forming at the tip of helmet streamers, that is, at the base of the heliospheric current sheet. The formation mechanism involves a pressure-driven instability followed by a fast tearing reconnection process. We further characterize the 3D spatial structure of helmet streamer born flux ropes, which appears in the simulations to be related to the network of quasi-separatrices.

Journal article

Ukhorskiy AY, Sorathia KA, Merkin VG, Crabtree C, Fletcher AC, Malaspina DM, Schwartz SJet al., 2022,

Cross-scale energy cascade powered by magnetospheric convection

, SCIENTIFIC REPORTS, Vol: 12, ISSN: 2045-2322

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Citations: 2

Journal article

Larosa A, Dudok de Wit T, Krasnoselskikh V, Bale SD, Agapitov O, Bonnell J, Froment C, Goetz K, Harvey P, Halekas J, Kretzschmar M, MacDowall R, Malaspina DM, Moncuquet M, Niehof J, Pulupa M, Revillet Cet al., 2022,

Langmuir-Slow Extraordinary Mode Magnetic Signature Observations with Parker Solar Probe

, ASTROPHYSICAL JOURNAL, Vol: 927, ISSN: 0004-637X

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Citations: 9

Journal article

Sioulas N, Velli M, Chhiber R, Vlahos L, Matthaeus WH, Bandyopadhyay R, Cuesta ME, Shi C, Bowen TA, Qudsi RA, Stevens ML, Bale SDet al., 2022,

Statistical Analysis of Intermittency and its Association with Proton Heating in the Near-Sun Environment

, ASTROPHYSICAL JOURNAL, Vol: 927, ISSN: 0004-637X

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Citations: 16

Journal article

Reville V, Velli M, Panasenco O, Tenerani A, Shi C, Badman ST, Bale SD, Kasper JC, Stevens ML, Korreck KE, Bonnell JW, Case AW, Dudok de Wit T, Goetz K, Harvey PR, Larson DE, Livi R, Malaspina DM, MacDowall RJ, Pulupa M, Whittlesey PLet al., 2022,

The Role of Alfven Wave Dynamics on the Large-scale Properties of the Solar Wind: Comparing an MHD Simulation with <i>Parker Solar Probe</i> E1 data (vol 246. 24, 2020)

, ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, Vol: 259, ISSN: 0067-0049

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Journal article

Mozer FS, Bale SD, Cattell CA, Halekas J, Vasko IY, Verniero JL, Kellogg PJet al., 2022,

Core Electron Heating by Triggered Ion Acoustic Waves in the Solar Wind

, ASTROPHYSICAL JOURNAL LETTERS, Vol: 927, ISSN: 2041-8205

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Citations: 13

Journal article

Desai M, Mitchell DG, McComas DJ, Drake JF, Phan T, Szalay JR, Roelof EC, Giacalone J, Hill ME, Christian ER, Schwadron NA, McNutt RL, Wiedenbeck ME, Joyce C, Cohen CMS, Davis AJ, Krimigis SM, Leske RA, Matthaeus WH, Malandraki O, Mewaldt RA, Labrador A, Stone EC, Bale SD, Verniero J, Rahmati A, Whittlesey P, Livi R, Larson D, Pulupa M, MacDowall RJ, Niehof JT, Kasper JC, Horbury TSet al., 2022,

Suprathermal ion energy spectra and anisotropies near the heliospheric current sheet crossing observed by the Parker Solar Probe during encounter 7

, The Astrophysical Journal: an international review of astronomy and astronomical physics, Vol: 927, Pages: 1-12, ISSN: 0004-637X

We present observations of ≳10–100 keV nucleon−1 suprathermal (ST) H, He, O, and Fe ions associated with crossings of the heliospheric current sheet (HCS) at radial distances of <0.1 au from the Sun. Our key findings are as follows: (1) very few heavy ions are detected during the first full crossing, the heavy-ion intensities are reduced during the second partial crossing and peak just after the second crossing; (2) ion arrival times exhibit no velocity dispersion; (3) He pitch-angle distributions track the magnetic field polarity reversal and show up to ∼10:1 anti-sunward, field-aligned flows and beams closer to the HCS that become nearly isotropic farther from the HCS; (4) the He spectrum steepens either side of the HCS, and the He, O, and Fe spectra exhibit power laws of the form ∼E−4–E6; and (5) maximum energies EX increase with the ion's charge-to-mass (Q/M) ratio as ${E}_{X}/{E}_{H}\propto {({Q}_{X}/{M}_{X})}^{\delta }$, where δ ∼ 0.65–0.76, assuming that the average Q states are similar to those measured in gradual and impulsive solar energetic particle events at 1 au. The absence of velocity dispersion in combination with strong field-aligned anisotropies closer to the HCS appears to rule out solar flares and near-Sun coronal-mass-ejection-driven shocks. These new observations present challenges not only for mechanisms that employ direct parallel electric fields and organize maximum energies according to E/Q but also for local diffusive and magnetic-reconnection-driven acceleration models. Reevaluation of our current understanding of the production and transport of energetic ions is necessary to understand this near-solar, current-sheet-associated population of ST ions.

Journal article

Wang S, Toumi R, 2022,

On the intensity decay of tropical cyclones before landfall

, Scientific Reports, Vol: 12, ISSN: 2045-2322

It remains unclear how tropical cyclones (TCs) decay from their ocean lifetime maximum intensity (LMI) to landfall intensity (LI), yet this stage is of fundamental importance governing the socio-economic impact of TCs. Here we show that TCs decay on average by 25% from LMI to LI. A logistic decay model of energy production by ocean enthalpy input and surface dissipation by frictional drag, can physically connect the LMI to LI. The logistic model fits the observed intensity decay as well as an empirically exponential decay does, but with a clear physical foundation. The distance between locations of LMI and TC landfall is found to dominate the variability of the decay from the LMI to LI, whereas environmental conditions are generally less important. A major TC at landfall typically has a very large LMI close to land. The LMI depends on the heating by ocean warming, but the LMI location is also important to future landfall TC intensity changes which are of socio-economic importance.

Journal article

Trofimov H, Post P, Gryspeerdt E, Toll Vet al., 2022,

Meteorological conditions favorable for strong anthropogenic aerosol impacts on clouds

, Journal of Geophysical Research: Atmospheres, Vol: 127, ISSN: 2169-897X

Ship-track-like polluted cloud tracks provide a direct way to study aerosol-cloud interactions. Here, we study environmental conditions favorable for pollution tracks' formation. We study polluted cloud tracks forming downwind of localized anthropogenic air pollution hot spots of Norilsk and Cherepovets in Russia and Thompson in Canada. Polluted cloud tracks form on 20%–37% of days with liquid-phase clouds. The large-scale atmospheric circulation largely determines the occurrence of track-favoring conditions. Tracks tend to form in clean and thin clouds under stable and dry conditions that are more often associated with anticyclonic large-scale flow in the studied locations.

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Journal article

Li D, Feng J, Zhu Y, Staneva J, Qi J, Behrens A, Lee D, Min S-K, Yin Bet al., 2022,

Dynamical Projections of the Mean and Extreme Wave Climate in the Bohai Sea, Yellow Sea and East China Sea

, FRONTIERS IN MARINE SCIENCE, Vol: 9

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Journal article

Chen L-J, Halekas J, Wang S, DiBraccio GA, Romanelli N, Ng J, Russell CT, Schwartz SJ, Sibeck DG, Farrell W, Pollock C, Gershman D, Giles B, Collado-Vega YMet al., 2022,

Solitary Magnetic Structures Developed From Gyro-Resonance With Solar Wind Ions at Mars and Earth

, GEOPHYSICAL RESEARCH LETTERS, Vol: 49, ISSN: 0094-8276

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Citations: 9

Journal article

Mozer FS, Bale SD, Kellogg PJ, Larson D, Livi R, Romeo Oet al., 2022,

An Improved Technique for Measuring Plasma Density to High Frequencies on the Parker Solar Probe

, ASTROPHYSICAL JOURNAL, Vol: 926, ISSN: 0004-637X

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Citations: 5

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On the intensity decay of tropical cyclones before landfall

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