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Journal articleRovithakis A, Grillakis MG, Seiradakis KD, et al., 2022,
Future climate change impact on wildfire danger over the Mediterranean: the case of Greece
, Environmental Research Letters, Vol: 17, ISSN: 1748-9326Recent studies have shown that temperature and precipitation in the Mediterranean are expected to change, contributing to longer and more intense summer droughts that even extend out of season. In connection to this, the frequency of forest fire occurrence and intensity will likely increase. In the present study, the changes in future fire danger conditions are assessed for the different regions of Greece using the Canadian fire weather index (FWI). Gridded future climate output as estimated from three regional climate models from the Coordinated Regional Downscaling Experiment are utilized. We use three representative concentration pathways (RCPs) consisting of an optimistic emissions scenario where emissions peak and decline beyond 2020 (RCP2.6), a middle-of-the-road scenario (RCP4.5) and a pessimistic scenario, in terms of mitigation where emissions continue to rise throughout the century (RCP8.5). Based on established critical fire FWI threshold values for Greece, the future change in days with critical fire danger were calculated for different areas of Greece domains. The results show that fire danger is expected to progressively increase in the future especially in the high-end climate change scenario with southern and eastern regions of Greece expected to have up to 40 additional days of high fire danger relative to the late 20th century, on average. Crete, the Aegean Islands, the Attica region, as well as parts of Peloponnese are predicted to experience a stronger increase in fire danger.
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Journal articleLotekar AB, Vasko IY, Phan T, et al., 2022,
Kinetic-scale Current Sheets in Near-Sun Solar Wind: Properties, Scale-dependent Features and Reconnection Onset
, ASTROPHYSICAL JOURNAL, Vol: 929, ISSN: 0004-637X- Author Web Link
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- Citations: 5
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Journal articlede Wit TD, Krasnoselskikh VV, Agapitov O, et al., 2022,
First Results From the SCM Search-Coil Magnetometer on Parker Solar Probe
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 127, ISSN: 2169-9380- Author Web Link
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- Citations: 9
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Journal articleMartinovic MM, Dordevic AR, Klein KG, et al., 2022,
Plasma Parameters From Quasi-Thermal Noise Observed by Parker Solar Probe: A New Model for the Antenna Response
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 127, ISSN: 2169-9380- Author Web Link
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- Citations: 2
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Journal articleKoller F, Temmer M, Preisser L, et al., 2022,
Magnetosheath jet occurrence rate in relation to CMEs and SIRs
, Journal of Geophysical Research: Space Physics, Vol: 127, ISSN: 2169-9380Magnetosheath jets constitute a significant coupling effect between the solar wind (SW) and the magnetosphere of the Earth. In order to investigate the effects and forecasting of these jets, we present the first-ever statistical study of the jet production during large-scale SW structures like coronal mass ejections (CMEs), stream interaction regions (SIRs) and high speed streams (HSSs). Magnetosheath data from Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft between January 2008 and December 2020 serve as measurement source for jet detection. Two different jet definitions were used to rule out statistical biases induced by our jet detection method. For the CME and SIR + HSS lists, we used lists provided by literature and expanded on incomplete lists using OMNI data to cover the time range of May 1996 to December 2020. We find that the number and total time of observed jets decrease when CME-sheaths hit the Earth. The number of jets is lower throughout the passing of the CME-magnetic ejecta (ME) and recovers quickly afterward. On the other hand, the number of jets increases during SIR and HSS phases. We discuss a few possibilities to explain these statistical results.
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Journal articleMyhre G, Samset B, Forster PM, et al., 2022,
Scientific data from precipitation driver response model intercomparison project
, Scientific Data, Vol: 9, Pages: 123-123, ISSN: 2052-4463This data descriptor reports the main scientific values from General Circulation Models (GCMs) in the Precipitation Driver and Response Model Intercomparison Project (PDRMIP). The purpose of the GCM simulations has been to enhance the scientific understanding of how changes in greenhouse gases, aerosols, and incoming solar radiation perturb the Earth's radiation balance and its climate response in terms of changes in temperature and precipitation. Here we provide global and annual mean results for a large set of coupled atmospheric-ocean GCM simulations and a description of how to easily extract files from the dataset. The simulations consist of single idealized perturbations to the climate system and have been shown to achieve important insight in complex climate simulations. We therefore expect this data set to be valuable and highly used to understand simulations from complex GCMs and Earth System Models for various phases of the Coupled Model Intercomparison Project.
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Journal articleHellinger P, Montagud-Camps V, Franci L, et al., 2022,
Ion-scale transition of plasma turbulence: Pressure-strain effect
<jats:p>&lt;p&gt;We investigate properties of solar-wind like plasma turbulence using direct numerical simulations. We analyze the transition from large (magnetohydrodynamic) scales to ion ones using two-dimensional hybrid (fluid electrons, kinetic ions) simulations of decaying turbulence. To quantify turbulence properties we apply spectral transfer and Karman-Howarth-Monin equations for extended compressible Hall MHD to the simulated results. The simulation results indicate that the transition from MHD to ion scales (the so called ion break) results from a combination of an onset of Hall physics and of an effective dissipation owing to the pressure-strain energy-exchange channel and resistivity. We discuss the simulation results in the context of the solar wind.&lt;/p&gt;</jats:p>
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Journal articleMatteini L, Hellinger P, Landi S, et al., 2022,
Kinetic Instabilities from Ion Beams and Differential Streaming in the Close-Sun Solar Wind: Hybrid Expanding Simulations
<jats:p>&lt;p&gt;Parker Solar Probe observations in the inner heliosphere have demonstrated that non-thermal features in solar wind ion distributions are particularly enhanced and dominant in the close-Sun environment. Proton beams and large differential flows of alpha particles are ubiquitously observed, also in slow, though Alfv&amp;#233;nic, streams, qualitatively at odds with typical observations at 1AU, where non-Maxwellian features are usually less apparent in the slow solar wind. All this reinforces the idea, also supported by past Helios and Ulysses explorations, that preferential ion heating and acceleration take place already in the Corona and signatures of the kinetic processes involved are gradually washed out during expansion. To explore further properties of ion differential streaming during expansion, as well as associated kinetic instabilities and their possible role in plasma heating, we perform expanding box hybrid simulations of a multi-species solar wind composed by proton core, beam and alpha particles, focussing on the role of wave-particle interactions in shaping distribution functions and controlling relative drifts. Radial trends and typical distributions found in simulations are then compared with PSP and Solar Orbiter observations in the inner Heliosphere.&lt;/p&gt;</jats:p>
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Conference paperPlaschke F, Koller F, Preisser Renteria LF, et al., 2022,
Magnetosheath jet occurrence in solar wind parameter space
<jats:p>&lt;p&gt;Plasma jets in the magnetosheath are identified as strong local enhancements in dynamic pressure. Being created at the bow shock, they are able to traverse the entire magnetosheath and impact the magnetopause. There, they can severely indent the boundary, set up waves on it, and trigger magnetic reconnection. They are a key yet heavily underexplored element in the solar wind &amp;#8211; magnetosphere coupling. Jets are mostly (but not exclusively) observed downstream of the quasi-parallel shock. Consequently, they have been observed significantly more often under low interplanetary magnetic field cone angle conditions.&lt;/p&gt;&lt;p&gt;In this study, we revisit the occurrence of jets, this time taking into account the whole space of parameters of solar wind input conditions. We answer the question where in this space jet occurrences cluster and how the emerging patterns change when the solar wind input becomes significantly different in nature, e.g., under the influence of coronal mass ejections or stream interaction regions.&lt;/p&gt;</jats:p>
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Conference paperLaMoury A, Hietala H, Eastwood J, et al., 2022,
Magnetosheath jets at the magnetopause: reconnection onset conditions
<jats:p>&lt;p&gt;Magnetosheath jets are localised pulses of high dynamic pressure plasma observed in Earth&amp;#8217;s magnetosheath. They are believed to form from the interaction between the solar wind and ripples in Earth&amp;#8217;s collisionless bow shock, before propagating into the turbulent magnetosheath. Upon impacting the magnetopause, jets can influence magnetospheric dynamics. In particular, previous studies have suggested that, by virtue of their internal magnetic field orientations, jet impacts may be able to trigger local magnetic reconnection at the magnetopause. This is most notable during traditionally unfavourable solar wind conditions, such as intervals of northward interplanetary magnetic field. This idea has been supported by a small number of case studies and simulations. We present a large statistical study into the properties of jets near the magnetopause. We examine the components of the magnetic reconnection onset condition &amp;#8211; the competing effects of magnetic shear angle and plasma beta &amp;#8211; to determine how jets may affect magnetopause reconnection in a statistical sense. We find that, due to their increased beta, jet plasma is typically not favourable to reconnection, often more so than the non-jet magnetosheath. Most jets do contain some reconnection-favourable plasma, however, suggesting that jets may be able to both trigger and suppress magnetopause reconnection. We complement this with new case studies of jets interacting with the magnetopause.&lt;/p&gt;</jats:p>
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Journal articleKasoar M, Corsaro C, Voulgarakis A, 2022,
Metrics for Regional Climate Responses to Regional Pollutant Emissions
<jats:p>&lt;p&gt;The Absolute Global Temperature change Potential (AGTP) and Absolute Global Precipitation change Potential (AGPP) are widely used climate change indices.&amp;#160; They can be applied quickly and easily to estimate the global mean temperature and precipitation responses to a pulse emission of a long-lived climate pollutant at a given time horizon, making them invaluable policy-relevant metrics.&amp;#160; They can also be extended to short-lived climate pollutants - where a sustained emission is more useful to consider than a pulse emission - by using their time-integrated forms (iAGTP and iAGPP).&lt;/p&gt;&lt;p&gt;However, these metrics are only useful when taking a global-average perspective, and do not allow us to account for the regional nature of either emissions or their climate response.&amp;#160; Although long-lived greenhouse gases induce a relatively homogeneous radiative forcing (RF) which is not sensitive to emission location, nonetheless due to transport of heat there is not a one-to-one correspondence between the RF in a region and the local temperature response.&amp;#160; Moreover when considering short-lived pollutants such as aerosols, the region of emission is potentially critical because the short lifetime of such pollutants results in an inhomogeneous distribution of RF.&amp;#160; Therefore, for both long-lived and short-lived pollutants the AGTP/AGPP (or iAGTP/iAGPP) are not adequate when looking at climate responses on a regional scale, even though this would be the most relevant when evaluating different policy scenarios or climate change impacts.&lt;/p&gt;&lt;p&gt;Here, we combine the results of simulations from the Precipitation Driver Response Model Intercomparison Project (PDRMIP) where emissions (or concentrations) of multiple long- and short-lived climate pollutants were perturbed globally in nine
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Journal articleMisal H, Kountouris I, Voulgarakis A, et al., 2022,
Eliciting public preferences for wildfire management policies in Crete, Greece
<jats:p>&lt;p&gt;Fire regimes form an integral part of terrestrial biomes in the Mediterranean region as they provide essential disturbances which change&amp;#160;the&amp;#160;structure and function of plants that favour Mediterranean type climates. Fire is inextricably linked to such ecosystems and cannot be excluded from them. However, the intensification of human activities in Greece, coupled with increasingly unpredictable wildfires has created huge imbalances and jeopardised the ecological integrity of ecosystems. Expansions into the wildland urban interface, rural abandonment, and the focus on fire suppression are increasing the vulnerability and flammability of the Greek environment. The duality of fire is delicate, both at local and national level, catastrophic wildfires singe deeply on landscapes and economies, social burns can take just as long to heal. In Greece, this is further exacerbated by the burgeoning socio-economic and political complexities that have catalysed the current ineffective and unsustainable fire management strategies. Damages from wildfires affect ecosystem services which can lead to a reduction in human wellbeing. Understanding the interactions between ecosystems and humans through environmental valuation is key to implementing effective policy. This study uses economic valuation methods in the form of a choice experiment to elicit public preference for a wildfire management policy in Crete. A survey was deployed around the island, with respondents asked about their preferences between different management strategies. The policies outlined in the survey are made up of the following attributes: risk of fire, agricultural production, landscape quality and post-wildfire damage mitigation. Results from this study indicate a positive preference by the public for a new proposed policy. The findings from this study can be used for decision making in Crete and other similar southern European environments
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Journal articleStawarz JE, Eastwood JP, Phan T, et al., 2022,
Turbulence-driven magnetic reconnection and the magnetic correlation length in collisionless plasma turbulence
<jats:p>&lt;p&gt;&lt;span&gt;Observations of Earth&amp;#8217;s magnetosheath from the Magnetospheric Multiscale (MMS) mission have provided an unprecedented opportunity to examine the detailed structure of the multitude of thin current sheets that are generated by plasma turbulence, revealing that a novel form of magnetic reconnection, which has come to be known as electron-only reconnection, can occur within magnetosheath turbulence. These electron-only reconnection events occur at thin electron-scale current sheets and have super-Alfv&amp;#233;nic electron jets that can approach the electron Alfv&amp;#233;n speed; however, they do not appear to have signatures of ion jets. It is thought that electron-only reconnection can occur when the length of the reconnecting current sheets along the outflow direction is short enough that the ions cannot fully couple to the newly reconnected magnetic field lines before they fully relax. In this work, we examine how the correlation length of the magnetic fluctuations in a turbulent plasma, which constrains the length of the current sheets that can be formed by the turbulence, impacts the nature of turbulence-driven magnetic reconnection. Using observations from MMS, we systematically examine 60 intervals of magnetosheath turbulence &amp;#8211; identifying 256 small-scale reconnection events, both with and without ion jets. We demonstrate that the properties of the reconnection events transition to become more consistent with electron-only reconnection when the magnetic correlation length of the turbulence is below ~20 ion inertial lengths. We further discuss the implications of the results in the context of other turbulent plasmas by considering observations of turbulent fluctuations in the solar wind. &lt;br&gt;&lt;/span&gt;&lt;/p&gt;</jats:p>
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Journal articleRobertson S, Eastwood J, Stawarz J, et 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>
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Journal articleAdhikari S, Shay MA, Parashar TN, et 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>
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Journal articlePyakurel P, Phan T, Shay M, et al., 2022,
On the short-scale spatial variability of electron inflows in electron-only magnetic reconnection in the turbulent magnetosheath observed by MMS
<jats:p>&lt;p&gt;In the Earth&amp;#8217;s turbulent magnetosheath downstream of the quasiparallel bow shock region, magnetic reconnection without ion coupling was observed with bi-directional super-Alfv&amp;#233;nic electron jets. The lack of ion coupling was attributed to the small-scale sizes of the current sheets. In an electron-only reconnection event that occurred on 26 December 2016, we examine the detailed properties of electron inflows observed by all 4 MMS spacecraft. Even though the farthest MMS probe in the outflow direction from the X-line was no more than 8 electron skin depth, the electron inflows have significant asymmetry and highly variable amplitudes. We compare MMS observations with 2D-kinetic PIC simulation and find that the asymmetry in the inflow stems directly from the tilt of the out-of-plane (guide) magnetic field structure in the reconnection plane, with inflow asymmetry enhanced in the downstream region.&lt;/p&gt;</jats:p>
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Journal articleFranci L, Papini E, Micera A, et 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>
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Journal articleGood S, Hatakka L, Ala-Lahti M, et al., 2022,
Cross helicity of interplanetary coronal mass ejections
<jats:p>&lt;p&gt;Like the solar wind in general, interplanetary coronal mass ejections (ICMEs) display magnetic field and velocity fluctuations across a wide range of scales. These fluctuations may be interpreted as Alfv&amp;#233;nic wave packets propagating parallel or anti-parallel to the local magnetic field direction, with cross helicity, &amp;#963;&lt;sub&gt;c&lt;/sub&gt;, quantifying the difference in power between the counter-propagating fluxes. We have determined &amp;#963;&lt;sub&gt;c&lt;/sub&gt; at inertial range frequencies in a large sample of ICME flux ropes and sheaths observed by the Wind spacecraft at 1 au. The mean &amp;#963;&lt;sub&gt;c&lt;/sub&gt; value was low for both the flux ropes and sheaths, with the balance tipped towards the positive, anti-sunward direction. The low values indicate that Alfv&amp;#233;nic fluxes are more balanced in ICMEs than in the solar wind at 1 au, where &amp;#963;&lt;sub&gt;c&lt;/sub&gt; tends to be larger and anti-sunward fluctuations show a greater predominance. Superposed epoch profiles show &amp;#963;&lt;sub&gt;c&lt;/sub&gt; falling sharply in the upstream sheath and being typically close to balance inside the flux rope near the leading edge. More imbalanced, solar wind-like &amp;#963;&lt;sub&gt;c&lt;/sub&gt; values are found towards the trailing edge and further from the rope axis. The presence or absence of an upstream shock also has a significant effect on &amp;#963;&lt;sub&gt;c&lt;/sub&gt;. Coronal and interplanetary origins of low &amp;#963;&lt;sub&gt;c&lt;/sub&gt; in ICMEs are discussed.&lt;/p&gt;</jats:p>
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Journal articleSoljento J, Good S, Osmane A, et al., 2022,
Turbulence modified by velocity shear in coronal mass ejection sheaths
<jats:p>&lt;p&gt;Fast coronal mass ejections (CMEs) drive shock waves ahead of them. The turbulent sheath region between the shock and the CME itself contains magnetic field and velocity fluctuations on a broad spectrum of frequencies. In this work we aim to characterise the direction and source of solar wind fluctuations at MHD fluid scales in CME-driven sheaths near Earth. One possible source for these fluctuations is velocity shear, which are common occurrences in CME-driven sheaths. Here we first identify velocity shear as it occurs and then relate that to signatures of new fluctuations being created locally in the sheath. Turbulence parameters such as cross helicity, residual energy, Elsasser ratio, and Alfv&amp;#233;n ratio are calculated, and they are correlated against large-scale signatures of velocity shear. Findings indicate a clear association between velocity shear and locally generated fluctuations, as well as a balance in the directionality of these new fluctuations, i.e., they tend to propagate equally towards and away from the Sun. In contrast, most solar wind is typically dominated by anti-sunward fluctuations.&lt;/p&gt;</jats:p>
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Conference paperSourdeval O, Gryspeerdt E, Krämer M, et 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>
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Conference paperDipu S, Schwarz M, Ekman AML, et 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
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Conference paperGoren T, Feingold G, Gryspeerdt E, et al., 2022,
Exploring the Effect of Aerosol on Marine Cloud Cover Using a Counterfactual Approach
<jats:p>&lt;p&gt;Aerosol&amp;#8211;cloud interactions in marine stratocumulus clouds (Sc) are among the most challenging frontiers in cloud&amp;#8211;climate research.&amp;#160;In particular, the cloud cover susceptibility to droplet concentration remained under-represented in the literature.&amp;#160;We developed methodologies to estimate what&amp;#160;would have been the cloud cover and&amp;#160;the associated&amp;#160;radiative&amp;#160;&lt;span&gt;effect&lt;/span&gt; of currently observed Sc, but in a hypothetical cleaner world. The first methodology uses a realistic Lagrangian large eddy simulation coupled with satellite observations and provides a process-oriented analysis. The other uses a &lt;span&gt;simple&lt;/span&gt; model and provides a global estimate of the radiative impact. We found that overcast Sc decks would have broken up sooner had they not been influenced by anthropogenic aerosol, thereby causing a significant effective radiative forcing.&lt;/p&gt;</jats:p>
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Journal articleArcher M, Waters C, Dewan S, et al., 2022,
Developing a new space sector careers resource based on educational research recommendations
<jats:p>&lt;p&gt;Educational research shows participation issues across Science Technology Engineering and Mathematics (STEM) are due to whether students see these fields and their potential career opportunities as for &amp;#8220;people like me&amp;#8221;. These perceptions form early and remain relatively stable with age, which has led to recommendations for increased provision and quality of careers education/engagement at both primary and secondary levels. Space-related roles should be rife for inclusion in careers education resources. However, we find that current UK careers resources concerning the space sector do not perhaps best reflect the diversity of roles present and may in fact perpetuate misconceptions about the usefulness of science. We present the development process of a new space careers resource, detailing how we have attempted to improve the diversity of space-related careers highlighted as well as addressing the key issues and recommendations raised by recent educational research.&lt;/p&gt;</jats:p>
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Journal articleWang S, Toumi R, 2022,
More tropical cyclones are striking coasts with major intensities at landfall
, Scientific Reports, Vol: 12, ISSN: 2045-2322In this study we show that the number of annual global tropical cyclone (TC) landfalls with major landfall intensity (LI≥50 m s-1) has nearly doubled from 1982 to 2020. The lifetime maximum intensity (LMI) of global major landfalling TCs has been increasing by 0.8 m s-1 per decade (p<0.05), but this significance of intensity change disappears at landfall (0.3 m s-1 per decade, p=0.69). The lack of a significant LI trend is caused by the much larger variance of LI than that of LMI in all basins and explains why a significant count change of TCs with major intensity at landfall has only now emerged. Basin-wide TC trends of intensity and spatial distribution have been reported, but this long-term major TC landfall count change may be the most socio-economic significant.
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Conference paperGryspeerdt E, Louro Coelho M, Smith T, et al., 2022,
Measuring cloud sensitivity to aerosols at a global scale using isolated aerosol sources
<jats:p>&lt;p&gt;The sensitivity of clouds to anthropogenic aerosol perturbations remains one of the largest uncertainties in the human forcing of the climate system. A key difficulty is in isolating the impact of aerosols from large-scale covariability of aerosol and cloud properties. Natural experiments, where aerosol is produced independently of the cloud and meteorological properties, provide a pathway to address this issue. These aerosol sources often modify cloud properties, leaving linear cloud features known as shiptracks (when formed by a ship) or pollution tracks (more generally).&lt;/p&gt;&lt;p&gt;In this work, we use a database of point sources of aerosol over both land and ocean to identify clouds that are sensitive to aerosol and to measure their response. Using a neural network to identify when a point source is modifying the cloud, we are able to measure the sensitivity of individual clouds to aerosol at a global scale, looking at over 400 million cases.&lt;/p&gt;&lt;p&gt;We find the probability of track formation is strongly dependent on the background cloud and meteorological state, similar to previous regional studies. With our global database, we identify regions that are strongly susceptible to aerosol perturbations, even where aerosol sources are rare. We find that there are several regions that are highly susceptible to aerosol, but that have been previously overlooked due to a low frequency of pollution tracks. &amp;#160; &amp;#160;&lt;/p&gt;</jats:p>
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Journal articleKilpua E, Good S, Ala-Lahti M, et 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>
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Journal articleMontagud-Camps V, Hellinger P, Verdini A, et 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>
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Journal articleBlasl KA, Nakamura T, Plaschke F, et al., 2022,
Multi-scale observations and evolution of the magnetopause Kelvin-Helmholtz waves during southward IMF
<jats:p>&lt;p&gt;The mass and energy transfer across Earth&amp;#8217;s magnetopause is caused by a variety of different plasma processes. One of these processes is the Kelvin-Helmholtz instability (KHI), excited by the velocity shear between the fast-flowing magnetosheath plasma and the relatively stagnant magnetosphere. It has been frequently observed during periods of northward interplanetary magnetic field (IMF), however much less is known about its behaviour during southward IMF conditions.&lt;/p&gt;&lt;p&gt;We present the first Magnetospheric Multiscale (MMS) observations of KH waves and vortices at the dusk-flank magnetopause during southward IMF conditions on September 23, 2017. The instability criterion for the KHI was fulfilled during this event. The boundary normal vectors, obtained by using multi-point methods, are consistent with the predicted structures of the KH waves. We further performed a series of realistic 2D and 3D fully kinetic PIC simulations based on the plasma parameters observed during this MMS event. A comparison to results from these simulations demonstrated quantitative consistencies with the MMS data in many aspects such as the flow and total pressure variations in the KH waves, and the signatures of the non-linearly rolled up KH vortices including the Low Density Faster Than Sheath (LDFTS) plasma.&lt;/p&gt;&lt;p&gt;The simulations further showed that secondary instabilities are excited at the edges of the primary KHI. The Rayleigh-Taylor instability (RTI) can lead to the penetration of high-density arms into the magnetospheric side and disturb the structures of the vortex layer, leading to irregular variations of the surface waves. This can be an important factor in explaining the lower observational probability of KH waves during southward IMF than northward IMF. In the non-linear growth stage of the primary KHI, the lower-hybrid drift instabi
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Conference paperJia H, Quaas J, Gryspeerdt E, et 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
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Journal articleMyhre G, Stjern C, Samset B, et 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>
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