Results
- Showing results for:
- Reset all filters
Search results
-
Journal articleChen L-J, Gershman D, Burkholder B, et al., 2024, , GEOPHYSICAL RESEARCH LETTERS, Vol: 51, ISSN: 0094-8276
-
Journal articleWang S, Ren T, Yang P, et al., 2024, , Geophysical Research Letters, Vol: 51, ISSN: 0094-8276
A new ice refractive index compilation is reported for a broad spectrum ranging from 0.0443 to 106 饾渿m, focusing on the pronounced temperature-dependence of ice optical properties in the far-infrared (far-IR) segment (15-100 µm). A sensitivity study assuming spherical particles shows that selecting ice refractive indices at 12 temperatures and 215 wavelengths in the far-IR region gives sufficient accuracy in interpolated refractive indices for developing a new ice crystal optical property database. Furthermore, we demonstrate the differences between the bulk single-scattering properties computed for hexagonal ice particles with this new compilation compared to a previous iteration at three far-IR wavelengths where substantial differences are noticed between the two ice refractive index compilations. We suggest that our new ice refractive index dataset will improve downstream light-scattering applications for upcoming far-IR satellite missions and allow robust modeling of outgoing longwave radiation (OLR) under ice cloud conditions.
-
Journal articleGreene SM, Schachat SR, Arita-Merino N, et al., 2024, , ISCIENCE, Vol: 27
-
Journal articleSouthwood D, 2024, , Science, Vol: 385, Pages: 233-233, ISSN: 0036-8075
-
Journal articleXu S, Mitchell DL, Whittlesey P, et al., 2024, , NATURE COMMUNICATIONS, Vol: 15
-
Journal articleMathews JP, Czaja A, Vitart F, et al., 2024, , Geophysical Research Letters, Vol: 51, ISSN: 0094-8276
In this study, we explore the impact of oceanic moisture fluxes on atmospheric blocks using the ECMWF IFS. Artificially suppressing surface latent heat flux over the Gulf Stream (GS) region reduces atmospheric blocking frequency across the Northern Hemisphere by up to 30%. Affected blocks show a shorter lifespan (−6%), smaller spatial extent (−10%), and reduced intensity (−0.4%), with an increased number of individual blocking anticyclones (+17%). These findings are robust across various blocking detection thresholds. Analysis reveals a qualitatively consistent response across all resolutions, with Tco639 (∼18 km) showing the largest statistically significant change across all blocking characteristics, although differences between resolutions are not statistically significant. Exploring the broader Rossby wave pattern, we observe that diminished moisture fluxes favor eastward propagation and higher zonal wavenumbers, while air-sea interactions promote stationary and westward-propagating waves with zonal wavenumber 3. This study underscores the critical role of the GS in modulating atmospheric blocking.
-
Conference paperLewis Z, Stephenson P, Kallio E, et al., 2024,
<jats:p>Comet 67P/Churyumov-Gerasimenko was escorted by the Rosetta spacecraft through a 2 year section of its 6 year orbit around the Sun. This enabled the observation of a large variation in comet outgassing and the resulting evolution of the plasma environment. The diamagnetic cavity, a region of negligible magnetic field arising from the interaction of the unmagnetised cometary plasma with the solar wind, began to be detected sporadically by the Rosetta Plasma Consortium/ Magnetometer (RPC/MAG) in April 2015 at a heliocentric distance of 1.8 au [1]. The last detections were in February 2016 at 2.4 au. Within this cavity, the flow of cometary ions has been shown to be largely radial [2]; the ions are accelerated above the neutral gas speed by an ambipolar electric field, but many newborn ions still undergo multiple ion-neutral chemical reactions before escaping [3,4]. Outside the diamagnetic cavity boundary, which is itself highly variable, the ion flow is considerably more complex, and the ambipolar electric field plays a more minor role compared to the convective electric field of the solar wind [2]. &#160;At large heliocentric distances (>2.5 au), the total plasma density observed from RPC plasma sensors is well explained by a simple flux conservation model that assumes the ions travel radially away from the nucleus at speed close to that of neutrals [5,6]. However, closer to perihelion and once the diamagnetic cavity has formed, such an approach does not hold [7]. We aim to better understand this transition, the driver of ions' acceleration, and the role that the diamagnetic cavity plays.In this study, we explore the varying ion dynamics both in the presence (e.g. during high outgassing activity) and absence (low outgassing activity) of a diamagnetic cavity. Electric and magnetic fields from hybrid simulations of the cometary environment are used to drive a 3D test particle model of the cometary ions for a range of comet activity levels.
-
Conference paperBeth A, Galand M, Modolo R, et al., 2024,
<jats:p>The Galileo spacecraft flew by Ganymede, down to 0.1 RG from the surface for the closest, six times giving us insight into its plasma environment. Its ionosphere, made of ions born from the ionisation of neutrals present in Ganymede's exosphere, represents the bulk of the plasma near the moon around closest approach. As it has been revealed by Galileo and Juno, near closest approach the ion population is dominated by low-energy ions from the water ion group (O+, HO+, H2O+) and O2+. As we showed in [1] by means of a test particle model, the ion composition during most flybys was a priori dominated by H2+and O2+. However, during Juno's flyby of Ganymede, plasma data revealed the additional presence of H3+ that may only stem from ion neutral reactions between H2 and H2+.&#160;&#160;We have updated our test particle model to account for these ion-neutral collisions of which &#160;H2 + H2+. We show how it modifies the ion composition compared with [1] and assess the role of these collisions in the production of new ion species within Ganymede's exo-ionosphere. This will help to interpret plasma observations made by Juno and in the future by JUICE around Ganymede.&#160;[1] Beth et al., EGU24, https://doi.org/10.5194/egusphere-egu24-11772, 2024</jats:p>
-
Journal articleErvin T, Bale SD, Badman ST, et al., 2024, , ASTROPHYSICAL JOURNAL, Vol: 969, ISSN: 0004-637X
-
Journal articleSchwadron NA, Bale SD, Bonnell J, et al., 2024, , ASTROPHYSICAL JOURNAL, Vol: 970, ISSN: 0004-637X
-
Journal articleMathews J, Czaja A, 2024, , Climate Dynamics, Vol: 62, ISSN: 0930-7575
The connection between atmospheric blocking over the North Atlantic and the diabatic influence of the Gulf Stream is investigated using potential vorticity and moist potential vorticity diagnostics in the ERA5 reanalysis data set during wintertime (1979 - 2020). In line with previous research, the reliance atmospheric blocking has on turbulent heat fluxes over the Gulf Stream and its extension, for induction and maintenance, is shown to be significant. The air-sea heat flux generates negative potential vorticity air masses in the atmospheric boundary layer. These air masses subsequently contribute to the block’s negative potential vorticity anomaly at upper levels through ascending motion in the warm conveyor belt. It is shown that the block’s size and frequency partially depends on oceanic preconditioning via anomalous oceanic heat transport and heat content, prior to the blocking event, both of which allow for stronger turbulent heat fluxes. It is further hypothesized that the block feeds back positively on itself through the advection of cold dry air over the Gulf Stream, sustaining this air-sea interaction. This in turn decreases ocean heat content, eventually halting this air-sea interaction and severing the atmospheric block from its maintenance pathway.
-
Journal articleWilson Kemsley S, Ceppi P, Andersen H, et al., 2024, , Atmospheric Chemistry and Physics, Vol: 24, Pages: 8295-8316, ISSN: 1680-7316
Clouds strongly modulate the top-of-the-atmosphere energy budget and are a major source of uncertainty in climate projections. “Cloud controlling factor” (CCF) analysis derives relationships between large-scale meteorological drivers and cloud radiative anomalies, which can be used to constrain cloud feedback. However, the choice of meteorological CCFs is crucial for a meaningful constraint. While there is rich literature investigating ideal CCF setups for low-level clouds, there is a lack of analogous research explicitly targeting high clouds. Here, we use ridge regression to systematically evaluate the addition of five candidate CCFs to previously established core CCFs within large spatial domains to predict longwave high-cloud radiative anomalies: upper-tropospheric static stability (SUT), sub-cloud moist static energy, convective available potential energy, convective inhibition, and upper-tropospheric wind shear (ΔU300). We identify an optimal configuration for predicting high-cloud radiative anomalies that includes SUT and ΔU300 and show that spatial domain size is more important than the selection of CCFs for predictive skill. We also find an important discrepancy between the optimal domain sizes required for predicting locally and globally aggregated radiative anomalies. Finally, we scientifically interpret the ridge regression coefficients, where we show that SUT captures physical drivers of known high-cloud feedbacks and deduce that the inclusion of SUT into observational constraint frameworks may reduce uncertainty associated with changes in anvil cloud amount as a function of climate change. Therefore, we highlight SUT as an important CCF for high clouds and longwave cloud feedback.
-
Journal articleLester JG, Graven HD, Khatiwala S, et al., 2024, , JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, Vol: 129, ISSN: 2169-9275
-
Journal articleKasoar M, Perkins O, Millington JDA, et al., 2024, , Cell Reports Sustainability, Vol: 1, ISSN: 2949-7906
Fire regimes are intrinsically shaped by humans, but current global fire models do not reflect the diverse objectives humans have for managing fire. With new data sources and collaboration across disciplines, an improved understanding of human influences on fire regimes is increasingly possible and essential to represent.
-
Journal articleAcevski M, Masters A, ZomerdijkRussell S, 2024, , Geophysical Research Letters, Vol: 51, ISSN: 0094-8276
Uranus is one of the least explored planets in our solar system, it exhibits a unique magnetic field structure which was observed by NASA's Voyager 2 mission nearly 50 years ago. Notably, Uranus displays extreme magnetic field asymmetry, a feature exclusive to the icy giants. We use the Boris algorithm to investigate how high energy protons behave within this unusual magnetic field, which is motivated by Voyager 2's observation of lower-than-expected high energy proton radiation belt intensities at Uranus. When considering full drift motions of high energy protons around Uranus, the azimuthal drift velocity can vary by as much as 15% around the planet. This results in areas around Uranus where particles will be more depleted (faster drift) and other regions where there is a surplus of particles (slower drift). This could provide a partial explanation for the “weak” proton radiation belts observed by Voyager 2.
-
Journal articleM眉lmenst盲dt J, Gryspeerdt E, Dipu S, et al., 2024, , Atmospheric Chemistry and Physics, Vol: 24, Pages: 7331-7345, ISSN: 1680-7316
General circulation models' (GCMs) estimates of the liquid water path adjustment to anthropogenic aerosol emissions differ in sign from other lines of evidence. This reduces confidence in estimates of the effective radiative forcing of the climate by aerosol–cloud interactions (ERFaci). The discrepancy is thought to stem in part from GCMs' inability to represent the turbulence–microphysics interactions in cloud-top entrainment, a mechanism that leads to a reduction in liquid water in response to an anthropogenic increase in aerosols. In the real atmosphere, enhanced cloud-top entrainment is thought to be the dominant adjustment mechanism for liquid water path, weakening the overall ERFaci. We show that the latest generation of GCMs includes models that produce a negative correlation between the present-day cloud droplet number and liquid water path, a key piece of observational evidence supporting liquid water path reduction by anthropogenic aerosols and one that earlier-generation GCMs could not reproduce. However, even in GCMs with this negative correlation, the increase in anthropogenic aerosols from preindustrial to present-day values still leads to an increase in the simulated liquid water path due to the parameterized precipitation suppression mechanism. This adds to the evidence that correlations in the present-day climate are not necessarily causal. We investigate sources of confounding to explain the noncausal correlation between liquid water path and droplet number. These results are a reminder that assessments of climate parameters based on multiple lines of evidence must carefully consider the complementary strengths of different lines when the lines disagree.
-
Journal articleGraven HD, Warren H, Gibbs HK, et al., 2024, , Science, Vol: 384, Pages: 1335-1339, ISSN: 0036-8075
Vegetation and soils are taking up approximately 30% of anthropogenic carbon dioxide emissions because of small imbalances in large gross carbon exchanges from productivity and turnover that are poorly constrained. We combined a new budget of radiocarbon produced by nuclear bomb testing in the 1960s with model simulations to evaluate carbon cycling in terrestrial vegetation. We found that most state-of-the-art vegetation models used in the Coupled Model Intercomparison Project underestimated the radiocarbon accumulation in vegetation biomass. Our findings, combined with constraints on vegetation carbon stocks and productivity trends, imply that net primary productivity is likely at least 80 petagrams of carbon per year presently, compared with the 43 to 76 petagrams per year predicted by current models. Storage of anthropogenic carbon in terrestrial vegetation is likely more short-lived and vulnerable than previously predicted.
-
Journal articleAmtmann C, Pollinger A, Ellmeier M, et al., 2024, , GEOSCIENTIFIC INSTRUMENTATION METHODS AND DATA SYSTEMS, Vol: 13, Pages: 177-191, ISSN: 2193-0856
-
Journal articleKang H, Choi Y-S, Jiang JH, 2024, , Scientific Reports, Vol: 14
<jats:title>Abstract</jats:title> <jats:p>Investigation of the major factors determining tropical upper-level cloud radiative effect (TUCRE) is crucial for understanding cloud feedback mechanisms. We examined the TUCRE inferred from the outputs of historical runs and AMIP runs from CMIP6 models employing a radiative-convective equilibrium (RCE). In this study, we incorporated the RCE model configurations of atmospheric dynamics and thermodynamics from the climate models, while simplifying the intricate systems. Using the RCE model, we adjusted the global mean surface temperature to achieve energy balance, considering variations in tropical cloud fraction, regional reflectivity, and emission temperature corresponding to each climate model. Subsequently, TUCRE was calculated as a unit of K/%, representing the change in global mean surface temperature (K) in response to an increment in the tropical upper-level clouds (%). Our RCE model simulation indicates that the major factors determining the TUCRE are the emission temperatures of tropical moist-cloudy and moist-clear regions, as well as the fraction of tropical upper-level clouds. The higher determination coefficients between TUCRE and both the emission temperature of tropical moist regions and the upper-level cloud fraction are attributable to their contribution to the trapping effect on the outgoing longwave radiations, which predominantly determines TUCRE. Consequently, the results of this study underscore the importance of accurately representing the upper-level cloud fraction and emission temperature in tropical moist regions to enhance the representation of TUCRE in climate models.</jats:p>
-
Journal articleVasko IY, Mozer FS, Bowen T, et al., 2024, , ASTROPHYSICAL JOURNAL LETTERS, Vol: 967, ISSN: 2041-8205
-
Journal articleJebaraj IC, Agapitov O, Krasnoselskikh V, et al., 2024, , ASTROPHYSICAL JOURNAL LETTERS, Vol: 968, ISSN: 2041-8205
-
Journal articleKrupar V, Kruparova O, Szabo A, et al., 2024, , ASTROPHYSICAL JOURNAL LETTERS, Vol: 967, ISSN: 2041-8205
-
Journal articleAgiwal O, Cao H, Hsu H-W, et al., 2024, , PLANETARY SCIENCE JOURNAL, Vol: 5
-
Journal articleHou C, Rouillard AP, He J, et al., 2024, , ASTROPHYSICAL JOURNAL LETTERS, Vol: 968, ISSN: 2041-8205
-
Journal articleEastwood JP, Brown P, Magnes W, et al., 2024, , Space Weather, Vol: 22, ISSN: 1539-4956
Severe space weather has the potential to cause significant socio-economic impact and it is widely accepted that mitigating this risk requires more comprehensive observations of the Sun and heliosphere, enabling more accurate forecasting of significant events with longer lead-times. In this context, it is now recognized that observations from the L5 Sun-Earth Lagrange point (both remote and in situ) would offer considerable improvements in our ability to monitor and forecast space weather. Remote sensing from L5 allows for the observation of solar features earlier than at L1, providing early monitoring of active region development, as well as tracking of interplanetary coronal mass ejections through the inner heliosphere. In situ measurements at L5 characterize the solar wind's geoeffectiveness (particularly stream interaction regions), and can also be ingested into heliospheric models, improving their performance. The Vigil space weather mission is part of the ESA Space Safety Program and will provide a real-time data stream for space weather services from L5 following its anticipated launch in the early 2030s. The interplanetary magnetic field is a key observational parameter, and here we describe the development of the Vigil magnetometer instrument for operational space weather monitoring at the L5 point. We summarize the baseline instrument capabilities, demonstrating how heritage from science missions has been leveraged to develop a low-risk, high-heritage instrument concept.
-
Journal articleFuselier SA, Petrinec SM, Reiff PH, et al., 2024, , Space Science Reviews, Vol: 220, ISSN: 0038-6308
Recent multi-point measurements, in particular from the Magnetospheric Multiscale (MMS)spacecraft, have advanced the understanding of micro-scale aspects of magnetic reconnection. In addition, the MMS mission, as part of the Heliospheric System Observatory, combined with recent advances in global magnetospheric modeling, have furthered the understanding of meso- and global-scale structure and consequences of reconnection. Magneticreconnection at the dayside magnetopause and in the magnetotail are the drivers of the globalDungey cycle, a classical picture of global magnetospheric circulation. Some recent advances in the global structure and consequences of reconnection that are addressed hereinclude a detailed understanding of the location and steadiness of reconnection at the dayside magnetopause, the importance of multiple plasma sources in the global circulation, andreconnection consequences in the magnetotail. These advances notwithstanding, there areimportant questions about global reconnection that remain. These questions focus on howmultiple reconnection and reconnection variability fit into and complicate the Dungey Cyclepicture of global magnetospheric circulation.
-
Journal articleChoi H, Choi Y-S, Song H-J, et al., 2024, , Asia-Pacific Journal of Atmospheric Sciences, Vol: 60, Pages: 245-253, ISSN: 1976-7633
<jats:title>Abstract</jats:title><jats:p>In this study, we propose a new approach to improve the accuracy of the horizontal atmospheric motion vector (AMV) in cloud-free skies and its forecasting. We adapted the optical flow of the convolutional neural network (CNN) framework model using two 10-min interval infrared images at water vapor channels (centered at 6.3, 7.0, and 7.3 <jats:inline-formula><jats:alternatives><jats:tex-math>$$\mu m$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>m</mml:mi> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>) from the Korean geostationary satellite GEO-KOMPSAT-2A (GK2A). Since all pixels had seamless AMVs calculated by CNN (CNN AMVs), we could also predict AMVs using the linear regression method. The tracking performance of the CNN-based algorithm was validated using AMVs retrieved from GK2A (GK2A AMVs) by estimating the difference between those values and the ECMWF (European Centre for Medium-Range Weather Forecasts) Reanalysis v5 (ERA5) wind data over Korea in 2022. CNN AMVs showed similar or better root-mean-square vector differences (RMSVDs) than GK2A AMVs (12.33–12.86 vs. 15.89–19.96 m/s). The RMSVDs of the forecasted AMVs were 2.74, 2.95, 3.41, and 4.79 m/s at lead times of 10, 20, 30, and 60 min, respectively. Consequently, our method showed higher accuracy for tracking motion in the production of AMVs and succeeded in forecasting AMVs. We expect that such potential improvements in computational accuracy for operational GK2A AMVs will contribute to increased accuracy when forecasting meteorological phenomena related to wind.</jats:p>
-
Journal articleArcher M, Pilipenko V, Li B, et al., 2024, , Frontiers in Astronomy and Space Sciences, Vol: 11, ISSN: 2296-987X
Sharp boundaries are a key feature of space plasma environments universally, with their wave-like motion (driven by pressure variations or flow shears) playing a key role in mass, momentum, and energy transfer. This review summarises magnetohydrodynamic surface wave theory with particular reference to Earth’s magnetopause, due to its mediation of the solar-terrestrial interaction. Basic analytic theory of propagating and standing surface waves within simple models are presented, highlighting many of the typically-used assumptions. We raise several conceptual challenges to understanding the nature of surface waves within a complex environment such as a magnetosphere, including the effects of magnetic topology and curvilinear geometry, plasma inhomogeneity, finite boundary width, the presence of multiple boundaries, turbulent driving, and wave nonlinearity. Approaches to gain physical insight into these challenges are suggested. We also discuss how global simulations have proven a fruitful tool in studying surface waves in more representative environments than analytic theory allows. Finally, we highlight strong interdisciplinary links with solar physics which might help the magnetospheric community. Ultimately several upcoming missions provide motivation for advancing magnetopause surface wave theory towards understanding their global role in filtering, accumulating, and guiding turbulent solar wind driving.
-
Journal articleAgarwal P, Stevenson DS, Heal MR, 2024, , Environmental Science Atmospheres, Vol: 4, Pages: 655-669
Intense episodes of fine particulate matter (PM<inf>2.5</inf>) pollution often overwhelm large areas of the Indo-Gangetic Plain (IGP) in northern India during the post-monsoon season, a time when crop residue burning is at its peak. We conduct idealised emission sensitivity experiments using the WRF-Chem model to investigate the leading causes and spatiotemporal extent of one such extreme episode from 31 Oct to 8 Nov 2016, when hourly PM<inf>2.5</inf> levels exceeded 500 μg m<sup>−3</sup> across much of the IGP on several days. We utilise the anthropogenic emissions from EDGARv5.0 and the latest FINNv2.5 for fire emissions and evaluate modelled and observed ambient PM<inf>2.5</inf> and black carbon (BC) concentrations across the IGP. The model captured the PM<inf>2.5</inf> and BC peaks during the latter half of the episode and underestimated on other days. We find that biomass burning (BB) emissions during this episode have the strongest effect across the source regions in the upper (NW) IGP, followed by Delhi (middle IGP), where it contributes 50-80% to 24 h mean PM<inf>2.5</inf>. Complete elimination of BB emissions decreases PM<inf>2.5</inf> concentrations by 400 μg m<sup>−3</sup> (80-90%) in the upper IGP and by 280 μg m<sup>−3</sup> (40-80%) across the middle IGP during this episode. Contributions from the BB source to daily varying BC concentrations are 80-90%, 40-85% and 10-60% across upper, middle and lower IGP, respectively. BB emissions dominantly contribute to daily mean secondary organic aerosols (80%), primary organic aerosols (90%), dust (60%), and nitrate (50%) components of PM<inf>2.5</inf> across the upper and middle IGP. In comparison, the anthropogenic share of these compounds was nearly one-third everywhere except across the lower IGP. The buildup of the episode across the middle IGP was facilitated by
-
Journal articleP枚ppelwerth A, Koller F, Grimmich N, et al., 2024, , Frontiers in Astronomy and Space Sciences, Vol: 11
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.