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Science, Volume 384, Issue 6701, Page 1155-1155, June 2024.

Science, Volume 384, Issue 6701, Page 1177-1179, June 2024.

Science, Volume 384, Issue 6701, Page 1184-1185, June 2024.

Abstract

Upward-propagating solar tides are responsible for a large part of atmospheric variability in the mesosphere and lower thermosphere (MLT) region, and they are also an important source of ionospheric variability. Tides can be divided into the parts that are symmetric and antisymmetric about the equator. Their distinction is important, as the electrodynamic responses of the ionosphere to symmetric and antisymmetric tides are different. This study examines symmetric and antisymmetric tides using 21 years of temperature measurements by the Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry. The main focus is on the solar migrating semidiurnal tide (SW2), which is one of the dominant tides in the MLT region. It is shown that symmetric and antisymmetric parts of SW2 are comparable in amplitude. However, their spatiotemporal characteristics are different. That is, the symmetric part is strongest during March–June at 30–35° latitude, while the antisymmetric part is most prominent during May–September with the largest amplitude at 15–20° latitude. The symmetric and antisymmetric parts can be well described by the first two symmetric and antisymmetric Hough modes, respectively. Amplification is observed in the antisymmetric part during the major sudden stratospheric warmings (SSWs) in January 2006, 2009, 2013 and 2019. Atmospheric model simulations for the 2009 and 2019 SSWs confirm the amplification in the antisymmetric part of SW2. The enhanced antisymmetric tidal forcing explains the previously-reported asymmetric response of the ionospheric solar-quiet current system to SSWs.

Abstract

Geologic storage of CO2 and H2 are climate-positive techniques for meeting the energy transition. While similar formations could be considered for both gases, the flow dynamics could differ due to differences in their thermophysical properties. We conduct a rigorous pore-scale study of water/CO2 and water/H2 systems at relevant reservoir conditions in a Bentheimer rock sample using the lattice Boltzmann method to quantify the effects of capillary, viscous, inertial, and wetting forces during gas invasion. At similar conditions, H2 invasion is weaker compared to CO2 due to unfavorable viscosity ratios. Increasing flow rate, however, increases the breakthrough saturation for both gas systems in the range of capillary numbers studied. At isolated conditions of flow rate, viscosity ratio, and wettability, local inertial effects are found to be critical and show consistent increase in the invaded gas saturation. The effect of inertial forces persits for both gases across all field conditions tested.

Abstract

Probabilistic projections from the UK Climate Projections 2018 are presented for four global warming levels (GWLs) at 1.5, 2, 3, and 4°C above the 1850–1900 baseline. Our results show how uncertainties associated with climate models and four representative concentration pathways (RCP) emission scenarios translate to UK regional scale changes in maximum temperature and precipitation, with data also available for minimum and mean temperatures, humidity and surface net downward shortwave radiation flux. We compare weighting the likelihood of RCPs based on (hypothetical) policy decisions, against our baseline assumption that each RCP is equally likely. Differences between weighted and unweighted GWL distributions are small, particularly in relation to the full breadth of uncertainties that are incorporated into the probabilistic projections. Finally we quantify the relative importance of scenario, model and internal variability on regional projected GWLs and show that uncertainty associated with an uncertain climate response to forcings dominates at all GWLs.

Abstract

The interaction between sea surface temperatures (SST) and surface heat flux (SHF) is vital for atmospheric and oceanic variabilities. This study investigates SST-SHF relationship in the framework of a coupled oscillatory model, extending beyond previous research that predominantly used AR-1 type simple stochastic climate models. In contrast to the AR-1 type model, we reveal distinct features of SST-SHF relationships in the oscillatory model: sign reversals occur in the imaginary part of SST-SHF coherence and the low-pass SST tendency-SHF correlation. However, these sign reversals are absent in the real part of SST-SHF coherence and in the low-pass SST-SHF correlation. We find these features are robust across both the twentieth Century Reanalysis and GFDL SPEAR model for El Niño-Southern Oscillation (ENSO) variability. Furthermore, we develop a new scheme to assess ENSO's climate forcing magnitude and natural frequency. Our findings thus provide novel insights into understanding ENSO dynamics from the perspective of heat flux.

Abstract

Electron fluxes (20 eV–2 MeV, RBSP-A satellite) show reasonable simple correlation with a variety of parameters (solar wind, IMF, substorms, ultralow frequency (ULF) waves, geomagnetic indices) over L-shells 2–6. Removing correlation-inflating common cycles and trends (using autoregressive and moving average terms in an ARMAX analysis) results in a 10 times reduction in apparent association between drivers and electron flux, although many are still statistically significant (p < 0.05). Corrected influences are highest in the 20 eV–1 keV and 1–2 MeV electrons, more modest in the midrange (2–40 keV). Solar wind velocity and pressure (but not number density), IMF magnitude (with lower influence of B z ), SME (a substorm measure), a ULF wave index, and geomagnetic indices Kp and SymH all show statistically significant associations with electron flux in the corrected individual ARMAX analyses. We postulate that only pressure, ULF waves, and substorms are direct drivers of electron flux and compare their influences in a combined analysis. SME is the strongest influence of these three, mainly in the eV and MeV electrons. ULF is most influential on the MeV electrons. Pressure shows a smaller positive influence and some indication of either magnetopause shadowing or simply compression on the eV electrons. While strictly predictive models may improve forecasting ability by including indirect driver and proxy parameters, and while these models may be made more parsimonious by choosing not to explicitly model time series behavior, our present analyses include time series variables in order to draw valid conclusions about the physical influences of exogenous parameters.

Abstract

Interplanetary shocks (IPS) can initiate prompt acceleration of relativistic electrons in the Earth's radiation belt, which is related to the generation and propagation of impulsive electric field (IEF). We investigate the effect of IEF on accelerating radiation belt electrons in the 6 September 2017 IPS event. A “surfing” effect of electrons with respect to the electric field, referring to electrons that drift together with the tailward-propagating IEF in the duskside, is investigated in this study. Our results show that the maximum increase of electron differential flux is at 3.4 MeV by a factor of 2.2, corresponding to a drift velocity of 531 km/s, which is more consistent with the IPS propagating speed of 621 km/s rather than the fast-mode speed of 1,074 km/s. We suggest that the effect of IPS propagation is important for radiation belt dynamics, and we highlight the potential importance of the parameter of IPS propagation speed.

Abstract

This paper investigates the formation and segmentation of the tongue of ionization into two consecutive polar cap patches using multi-instrument observations from 27 February 2014. We provide insights into how the interplanetary magnetic field (IMF) variations influence the formation and segmentation of these patches. Our findings reveal that the entry of dayside dense plasma into the polar cap is predominantly driven by the modified convection near the cusp region, which is controlled by the transition of IMF By or the sudden drop of IMF Bz. Furthermore, we observe a rapid north-westward plasma flow within the patch segmentation region, accompanied by equatorward-expanded and enhanced convection near the cusp region. This fast-moving flow, approximately 1.5 km/s, is characterized by low density and high electron temperature and shows a signature of a Subauroral Polarization Stream. This suggests that the fast-westward flow, in conjunction with the expansion and contraction of ionospheric convection, plays a crucial role in the segmentation of polar cap patches from the dayside plasma reservoir. This study provides a comprehensive observation of the evolution of polar cap patches, thereby advancing our understanding of the dynamic mechanisms governing patch formation and segmentation.

Abstract

Magnetosheath jets with enhanced dynamic pressure are common in the Earth's magnetosheath. They can impact the magnetopause, causing deformation of the magnetopause. Here we investigate the 3-D structure of magnetosheath jets using a realistic-scale, 3-D global hybrid simulation. The magnetosheath has an overall honeycomb-like 3-D structure, where the magnetosheath jets with increased dynamic pressure surround the regions of decreased dynamic pressure resembling honeycomb cells. The magnetosheath jets downstream of the bow shock region with θ Bn  ≲ 20° (where θ Bn is the angle between the upstream magnetic field and the shock normal) propagate approximately along the normal direction of the magnetopause, while those downstream of the bow shock region with θ Bn  ≳ 20° propagate almost tangential to the magnetopause. Therefore, some magnetosheath jets formed at the quasi-parallel shock region can propagate to the magnetosheath downstream of the quasi-perpendicular shock region.

Abstract

Magnetosheath high-speed jets (HSJs), localized impulses of dynamic pressure, are attracting growing attention due to their geoeffectiveness. However, how HSJs modulate chorus waves in the magnetosphere still remains unclear. Utilizing combined observations of the Time History of Events and Macroscale Interactions during Substorms satellites A and E, we report, for the first time, the prompt disappearance of the magnetospheric chorus waves caused by a HSJ. Such wave disappearance is directly due to the flux drop of energetic electrons (∼10–100 keV), leading to the cessation of wave generation, which is supported by the linear theoretical analysis. We propose that the flux drop results from the local indentation of magnetopause after the HSJ impact, where two new smaller magnetic mirrors are formed off the equator and part of electrons are then expelled by the mirror force. The HSJs should be an important factor in modulating chorus waves because of their high occurrence rate.

Abstract

The Helmert’s second condensation method is usually used to condense the topographical masses outside the boundary surface in the determination of the geoid and quasi-geoid based on the boundary-value theory. The condensation of topographical masses produces direct and indirect topographical effects. Nowadays, the Remove-Compute-Restore (RCR) technique has been widely utilized in the boundary-value problems. In view of spectral consistency, high-frequency direct and indirect topographical effects should be used in the Hotine-Helmert/Stokes–Helmert integral when the Earth gravitational model serves as the reference model in determining the (quasi-) geoid. Thus, the algorithms for high-frequency topographical effects are investigated in this manuscript. First, the prism methods for near-zone direct and indirect topographical effects are derived to improve the accuracies of near-zone effects compared with the traditional surface integral methods. Second, the Molodenskii spectral methods truncated to power H4 are put forward for far-zone topographical effects. Next, the "prism + Molodenskii spectral-spherical harmonic" combined algorithms for high-frequency topographical effects are further presented. At last, the effectiveness of the combined algorithms for the high-frequency topographical effects are verified in a mountainous test area.

SummaryThis study analyzed seismicity in southwestern China (1 January 2008 to 30 June 2021) using the earthquake catalog compiled by the China Earthquake Network Center and four different space–time Epidemic-Type Aftershock Sequence models: the 2D point-source (PS) model, the 2D finite-source (FS) model, the 3D PS model, and the 3D FS model. Our objective was to understand the features of the background seismicity and the patterns of earthquake clusters to better evaluate the regional seismic hazard. We carefully investigated the aftershock sequences that followed 7 of the 10 MS≥6.0 earthquakes that have struck this region since the occurrence of the 2008 Wenchuan MS8.0 earthquake (i.e., the Panzhihua (31 August 2008; MS6.0), Yaoan (9 July 2009; MS6.0), Lushan (20 April 2013; MS7.0), Ludian (3 August 2014; MS6.5), Jinggu (7 October 2014; MS6.6), Kangding (11 November 2014; MS6.3), and Yangbi (21 May 2021; MS6.4) earthquakes). Our results revealed the following. (1) The background seismicity level for natural earthquakes is usually stable but can experience sudden change due to major events, such as the 2014 Ludian MS6.5, and the 2014 Jinggu MS6.6 events. Such changes in the background rate can reach 50%. (2) Reservoir-induced earthquakes substantially increase the level of regional seismicity, indicating that they cannot be ignored when analyzing natural seismicity and evaluating regional earthquake hazards. (3) Events triggered directly by the mainshock occur mostly in regions adjacent to areas with large coseismic slip, showing a pattern complementary to the mainshock ruptures.

SummaryThe Pohang Basin sustained the most extensive seismic damage in the history of instrumental recording in Korea due to the 2017 MW 5.5 earthquake. The pattern of damage shows marked differences from a radial distribution, suggesting important contributions by local site effects. Our understanding of these site effects and their role in generating seismic damage within the study area remains incomplete, which indicates the need for a thorough exploration of subsurface information, including the thickness of soil to bedrock and basin geometry, in the Pohang Basin. We measured the depth to bedrock in the Pohang Basin using dense ambient noise measurements conducted at 698 sites. We propose a model of basin geometry based on depths and dominant frequencies derived from the horizontal-to-vertical spectral ratio (HVSR) of microtremor at 698 sites. Most microseismic measurements exhibit one or more clear HVSR peak(s), implying one or more strong impedance contrast(s), which are presumed to represent the interface between the basement and overlying basin-fill sediments at each measurement site. The ambient seismic noise induces resonance at frequencies as low as 0.32 Hz. The relationship between resonance frequency and bedrock depth was derived using data from 27 boreholes to convert the dominant frequencies measured at stations adjacent to the boreholes into corresponding depths to the strong impedance contrast. The relationship was then applied to the dominant frequencies to estimate the depth to bedrock over the whole study area. Maps of resonance frequency and the corresponding depth to bedrock for the study area show that the greatest depths to bedrock are in the coastal area. The maps also reveal lower fundamental frequencies in the area west of the Gokgang Fault. The results indicate a more complex basin structure than previously proposed based on a limited number of direct borehole observations and surface geology. The maps and associated profiles across different parts of the study area show pronounced changes in bedrock depth near inferred blind faults proposed in previous studies, suggesting that maps of bedrock depth based on the HVSR method can be used to infer previously unknown features, including concealed or blind faults that are not observed at the surface.

Earthquakes may betray their impending presence much earlier than previously thought through a variety of anomalies present in the ground, atmosphere and ionosphere that can be detected using satellites, a recent study in the Journal of Applied Geodesy suggests.

Edinburgh, no stranger to an occasional haze, experienced an unprecedented atmospheric event on 31 May, unlike any seen over the past 30 years. While sea haar from the North Sea often blankets Scotland's capital, the haze observed that Friday felt distinctively different. UKCEH researchers are currently investigating if this haze can be attributed to a volcanic plume that transited the UK following an eruption in Iceland.

The Western U.S. is heavily reliant on mountain snowpacks and their gradual melt for water storage and supply, and climate change is expected to upend the reliability of this natural process. Many agricultural communities in this part of the country are examining ways to adapt to a future with less water, and new research shows that a focus on supplementing water supply by expanding reservoir capacity won't be enough to avert future water crises.

University of Southern California scientists have proven that the Earth's inner core is backtracking—slowing down—in relation to the planet's surface, as shown in new research published in Nature.

Synergistic approach of frozen hydrometeor retrievals: considerations on radiative transfer and model uncertainties in a simulated framework
Ethel Villeneuve, Philippe Chambon, and Nadia Fourrié
Atmos. Meas. Tech., 17, 3567–3582, https://doi.org/10.5194/amt-17-3567-2024, 2024
In cloudy situations, infrared and microwave observations are complementary, with infrared being sensitive to cloud tops and microwave sensitive to precipitation. However, infrared satellite observations are underused. This study aims to quantify if the inconsistencies in the modelling of clouds prevent the use of cloudy infrared observations in the process of weather forecasting. It shows that the synergistic use of infrared and microwave observations is beneficial, despite inconsistencies.