Mirror mode structures are born from a plasma instability driven by a large temperature anisotropy and appear downstream of planetary and interplanetary shocks, in their magnetosheath. As magnetic bottles imprisoning dense and hot plasma, they are usually observed downstream of their region of formation, where the anisotropy is large and free energy is available, implying that they are advected with the plasma flow to the detection region. At Earth and other planets, the quasi-perpendicular shock provides the plasma with the necessary heating along the perpendicular direction to the local magnetic field. At Mars, which boasts an extended exosphere, an additional source of temperature anisotropy exists, through unstable ring-beam velocity distributions, that is, through ions locally ionised and subsequently picked up by the local electric fields. We report here for the first time an example of near locally-generated mirror mode structures at Mars using the full plasma instrument suite on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. We present three events in quasi-perpendicular and quasi-parallel shock conditions with a variable exosphere, discuss the locality of the mirror modes excited and show that, in addition to the classic quasi-perpendicular source of anisotropy, another source exists, that is, unstable pickup protons. The existence at Mars of this extra ion anisotropy-generating mechanism is reminiscent of comets.

A document by Daniel Matthiä. Click on the document to view its contents.

Precise knowledge of geocenter motion, i.e., the relative motion between the Earth's center of mass (CM) and the center of figure of the Earth's surface (CF), is crucial to high-stakes geodetic applications such as sea level rise monitoring with satellite altimetry or the establishment of regional and global mass budgets with satellite gravimetry. The computation of the latest release of the International Terrestrial Reference Frame, ITRF2020, involved the estimation of a field of seasonal motions for a global network of geodetic stations, expressed with respect to CM, as sensed by Satellite Laser Ranging, from which the translational part represents seasonal geocenter motion. This paper presents two different methods to isolate seasonal geocenter motion from the field of ITRF2020 seasonal station motions, among which a new method based on a direct weighted average of seasonal station motions, with station-specific weights chosen so as to provide a better approximation of CF than the standard network shift approach. The ITRF2020 annual geocenter motion model thus obtained is then compared with other recent geodetic and geophysical estimates. Although different subgroups of estimates with relatively good internal consistency may be identified, the overall scatter of recent geodetic estimates remains at the level of several mm, i.e., close to the amplitude of annual geocenter motion itself. Efforts toward reconciling seasonal geocenter motion estimates therefore still appear necessary. Meanwhile, it would seem safe to assume that seasonal geocenter motion models, in particular those currently used in satellite altimetry and satellite gravimetry, are still uncertain.

Swells can travel thousands of kilometers. The source of distant-source swells propagated from the North Pacific Ocean into the China Sea area has not yet been clarified. In this study, WAVEWATCH III was used to calculate the wave fields in two domains of the Northwest Pacific Ocean (WNP) and the North Pacific Ocean (NP), respectively. The swell tracking algorithm was improved to determine the source of distant-source swells. Comparative analysis of bulk wave parameters across two computational domains clearly reveals the propagation of distant-source swells into the China Sea during the autumn and winter seasons. Wave spectra at selected points contain information about these far-field swells, and the algorithm identifies that the far-field swells mainly originate from two source locations in the middle and low latitudes of NP. Frequent changes in the wind direction of the storm system at the swell source location are consistent with the shorter duration of the far-field swells. This work provides a basis for future research on coastal swell forecasting and swell warning.

Disentangling latent representations is crucial for improving the interpretability and robustness of AI models, especially in complex scientific datasets where domain scientists often know some generative factors, but many others remain unknown. Our method, the Auxiliary information guided Variational AutoEncoder (Aux-VAE), focuses on disentangling the latent space with respect to the known factors while allowing the remaining latent dimensions to jointly capture the unknown factors. This approach not only maintains data reconstruction accuracy but also enhances the interpretability of latent spaces, providing valuable insights into the underlying mechanisms of data generation.

The forward simulation of radar reflectivity requires details of clouds and precipitation from general circulation models (GCMs). But such details are represented as sub-grid processes that involve parameterizations and assumptions about the spatial coverage and thus depend on the GCM. In this research, we propose the use of a statistical method to generate sub-grid precipitation for generic use. In addition, the proposed method can be used to provide uncertainty estimates on the signals. The sub-grid variability is obtained from simulation with a global storm-resolving model called NICAM (non-hydrostatic icosahedral atmospheric model). The proposed method first generates precipitation probabilities for the possible scenarios and then sub-grid precipitation rates are generated from the generalized gamma distribution for the given cloud fraction and grid-scale precipitation rates. Compared to the standard method (which neglects the probabilities) that overestimates the precipitation fraction, our method well reproduces the NICAM dataset profiles of both the precipitation fraction and the radar-based cloud fraction. The in-cloud signal frequencies are also reproduced, although less accurately over a tropical region. Inclusion of sub-grid variability in precipitation rates was particularly important for the tropical region to obtain agreement of the precipitation fraction. Application of the two methods to a GCM shows it to have a robust bias for low-level liquid clouds. The proposed method can be used to identify uncertainty in the signals associated with sub-grid variability in the precipitation processes, indicating an effective way to use a global storm-resolving model to evaluate conventional GCMs.

As society moves towards greater dependence on technology, understanding and predicting extreme Space Weather becomes increasingly important. Indeed, the complex, simultaneous interplay between multiple phenomena can unpack further insight into Space Weather effects. Thanks to decades of in-situ and ground observations, long archives of Space Weather measurements are ripe for exploitation by more complex, data intensive techniques. In this study, three decades of in-situ and ground observations of Earth’s Space environment are leveraged to model the joint extremal behaviour of solar wind driving and internal geomagnetic responses, using Bivariate Extreme Value Analysis. While often utilised in other fields with more long-term and/or higher spatial resolution datasets (such as meteorology), this is the first application of this technique in more than one dimension in the field of space plasma physics. An initial result is that upstream and internal variables exhibit weaker extremal dependence on minute timescales than on hourly timescales, in line with characteristic magnetospheric coupling timescales. Specifically, the joint extremal behaviour of a solar wind coupling function with the auroral electrojet index AE is explored and predicted. This modelling enables estimation of a 75-year return period for the 2003 Halloween geomagnetic storm.

While the service industry is generally considered a low-carbon sector, it contributes significantly to global carbon emissions. However, such emissions have typically relied on production-based evaluations without accounting for emissions embodied in international trade. Here, this paper estimates the consumption-based emissions (CBE) of the service industry and investigates the flows of embodied emissions globally using a Multi-regional Input-output model. Structural path analysis (SPA) and decomposition (SPD) methods are used to explore emission reduction paths and the driving factors. Our results show that the CBE of the global service industry not only increased by 63% but now comprised approximately over 30% of global total emissions, with the public and welfare services, health services sectors contributing the most to emissions growth. The consumption-based carbon intensity of the global service industry declined markedly, or nearly one-quarter of global carbon intensity. Advanced countries such as Japan, the UK, and the USA, were identified as the leading net importers of embodied service industry emissions, with air transport and water transport being the primary sources of carbon inflow. Russia was the principal net exporter of emissions. China altered from a net exporter of emissions to a net importer. The results reveal that the second layer had a more pronounced influence on the emissions than other layers, although the contribution of higher layers to emissions steadily increased. Emission intensity effect promoted emissions declines, while the increasing consumption level restrained such decreases. This study aims to provide valuable insights into reducing the emissions of the global service industry.

Here, the use of an hybrid methodology, VarDyn, combining minimal physically-based constraints with a variational scheme, is demonstrated to improve mapping capabilities of sea surface height (SSH) and temperature (SST). Synthesizing multi-modal satellite observations, VarDyn improves the accuracy of SSH and SST maps compared to operational products, both in terms of RMSE and effective spatial resolution. Expected, most improvements occur in high energetic ocean regions. Still, the accuracy of SSH maps also slightly improves in low energetic regions, which is a clear improvement compared to other methods. VarDyn SSH fields and associated geostrophic velocities further reveal strong agreements with newly available high-resolution instantaneous SWOT estimates. Remarkably, the assimilation of SST especially benefits SSH reconstruction when only 2 altimeters are available. The VarDyn method thus opens robust means to refine climate SSH records, jointly assimilating SSH from 2 altimeters and SST from microwave sensors.

Abstract All earthquakes over 5th magnitude since 1962 were recorded on Sumatra and surroundings, marking their depths and distinguished whether they were triggered by maximum westward or north-southward tidal torques. Greatest differences were found in period 2003-2009 where earthquakes triggered by north-southward torque were situated on rim of Sumatra continental area on Mentawai Fault. Period 2009-2023 is characteristic by large number of westward tidally triggered earthquakes, situated westward from Sumatra coast reaching sometimes as far as into oceanic lithosphere. As far as the great earthquake M 9.1, 26.12.2004 was triggered by the beat of close tidal frequencies: 19 years Metonic cycle and Moon’s nodal 18.61 years variations and if the beat were symmetric with maximum amplitude 26.12.2004, then because Full Moon will be 27.12.2023 and New Moon 11.1.2024, (Moon’ declinations large +28.1º and -27.6º respectively), the earthquake will occur of 6.5 5th magnitude as similar earthquake 27.12.1985. This prediction has not been fulfilled because the beat has not been symmetric, but asymmetrically shifted by westward tidal torque as proved by absolutely missing earthquakes 25. and 26.12. 2023, documented by very sensitive earthquakes detection up to 2.5 magnitude.

Vegetation is crucial for stabilizing and developing coastal dunes. Different plant species exhibit different spatial distributions which reflect their environmental role and adaptation strategy. This study aims to provide a fine-scale species-by-species analysis of vegetation spatial patterns on coastal dunes within the San Rossore – Migliarino – Massacciuccoli Regional Park (Tuscany, Italy). A comprehensive vegetation dataset generated by an Object-Based Image Analysis (OBIA) algorithm applied to high-resolution ortho-images has been utilized. A Digital Terrain Model (DTM) of the study area was created to assess the impact of dune morphology on plant distribution. Moreover, a wave runup analysis was also conducted to understand the interaction between vegetation and hydrodynamic forces. The research highlights how the vegetation threshold distance from the coastline, L_veg, is superimposed by the reaching distance of wave runup during extreme events. Terrain morphology significantly affects the vegetation zonation: on taller and undisturbed dunefields, species zonation is clearer and more defined, whereas, on flatter and disturbed ones, spatial distribution is significantly fuzzier. A positive correlation emerges between the abundance of a species and its degree of spatial clustering, indicating that less abundant species show more tightly clustered spatial patterns. Modified Ripley’s L-function analysis revealed a multi-scale clustered pattern for most species under examination. The present results may provide a solid benchmark in coastal ecology research for supporting natural-based conservation plans and eco-morphodynamic modeling.

Lagrangian simulations based on 18 years (2002-2019) of high-resolution eddy-resolving thermohaline and three-dimensional velocity fields allow to revisit the fate and thermohaline changes of the upper-ocean Antarctic Circumpolar Current (ACC) waters that enter directly the South Atlantic Ocean basin. An advection-diffusion scheme applied to the climatological annual-mean and daily-mean fields allows accurate estimations of the mean pathways and seasonal variability, as well as the recirculation volume transports, times and depths in the South Atlantic Subtropical Gyre (SASG). On average, 94.8 Sv of the upper-ocean waters (up to the 28.00 kg m-3) that cross the Drake Passage remain in the ACC, while 15.1 Sv join the SASG. Among those entering the SASG, 10.3 Sv reach the North Brazil Current and contribute to the Atlantic Meridional Overturning Circulation returning limb, this contribution being substantially higher than previously stated. All these Drake Passage upper-ocean waters undergo substantial water mass transformations as they reach the eastern SASG, from intermediate-deep to surface layers (6.7 Sv) and increase their heat transport in 0.46 PW and their salt transport in 8.5 × 106 kg s-1, but remain largely unchanged in their westward drift to the western boundary at 21°S. Most waters within the SASG (78.1%) recirculate one single loop, taking an average of 25.2 ± 14.3 years, although some of them complete as many as three loops before exiting. Regarding seasonality, the transit times and transport fraction of the upper-ocean Drake waters, into the SASG show higher variability than those remaining in the ACC path.

In this paper, dayside magnetopause energy transport (energy transport across the separatrix surface to the magnetopause boundary layer and energy transport inside the magnetopause boundary layer) and its dependence on the magnetopause dynamic evolution under purely southward interplanetary magnetic field (IMF) conditions are studied via a 3-D global hybrid simulation. By investigating the energy transport across the separatrix surface, current layer surface, and magnetopause surface, we find that the energy transport from the magnetosheath to the magnetopause boundary layer is mainly in the form of electromagnetic energy, while the energy transport directly across the magnetopause surface to the magnetosphere is mainly in the form of plasma energy. The energy transport across the magnetopause surface exhibits temporal variability, driven by the dynamic evolution of reconnection and flux rope. During the development of multiple X-lines reconnection and flux rope, a substantial portion of solar wind energy does not directly penetrate the dayside magnetopause to the magnetosphere. Instead, it is transported with the reconnection outflow and flux rope from low latitude to high latitude, and with the drifting flow from the subsolar region to the tail magnetopause within the magnetopause current layer. These results significantly improve our understanding of solar wind-magnetosphere coupling at the dayside magnetopause.

A document by Chao Song. Click on the document to view its contents.

Clouds significantly influence radiative transfer in the atmosphere by creating large deviations from clear-sky fluxes. Over the past two decades, the radiative signatures of clouds on their surrounding have been extensively studied, highlighting the challenges of adequately defining clouds and distinguishing them from aerosols. These distinctions are important for accurately quantifying cloud and aerosol radiative effects and for remote sensing under clear-sky conditions of both the surface and atmosphere. In this study, we take a step further by analyzing high-resolution multi-spectral images of cloud fields co-located with broadband top-of-the-atmosphere radiative fluxes. By adjusting the equation for radiative fluxes at the top of the atmosphere to explicitly include cloud effects in the  ''clear sky '' term, we can make use of CERES measurements together with MODIS high-resolution spectral data to quantify, for the first time, the net radiative effect of clouds within the inter-cloud zone. We find that the local radiative effect of this zone over the Ocean at noon is -7 to -10 W m^(-2) in the solar and +1–1.5 W m^(-2) in the longwave infrared.These results indicate that a significant portion of the shortwave aerosol direct radiative effect is induced by clouds and show that the near-cloud radiative effect in the longwave infrared is equivalent to a substantial increase in greenhouse gases. We highlight the benefits that can be gained by categorizing the sky into three regimes — cloudy, cloud-influenced, and pure clear, and suggest new directions that can move beyond a discrete definition of the cloudy sky.  

We describe CATKE, a parameterization for fluxes associated with small-scale or “microscale’ ocean turbulent mixing on scales between 1 and 100 meters. CATKE uses a downgradient formulation that depends on a prognostic turbulent kinetic energy (TKE) variable and a diagnostic mixing length scale that includes a dynamic convective adjustment (CA) component. With its dynamic convective mixing length, CATKE predicts not just the depth spanned by convective plumes but also the characteristic convective mixing timescale, an important aspect of turbulent convection not captured by simpler static convective adjustment schemes. As a result, CATKE can describe the competition between convection and other processes such as shear-driven mixing and baroclinic restratification. To calibrate CATKE, we use Ensemble Kalman Inversion to minimize the error between 21~large eddy simulations (LES) and predictions of the LES data by CATKE-parameterized single column simulations at three different vertical resolutions. We find that CATKE makes accurate predictions of both idealized and realistic LES compared to microscale turbulence parameterizations commonly used in climate models.

Predicting solid particle transport in the lowest parts of the atmosphere is a major issue for man-made obstacles in semi-arid regions. Here, we investigate the effects on solid particle saltation, of rectangular obstacles on the ground with different spacings. The aerodynamic field is determined by large eddy simulations coupled with an immersed boundary method for the obstacles. Solid particles are tracked by a Lagrangian approach. Take-off and rebound models are introduced for the interaction of particles with the wall. Without particles, fluid velocity profiles are first compared with experiments showing good agreement. Special focus is put on the recirculation zone that plays an important role in solid particle entrapment. Particle concentration fields are presented. Accumulation zones are studied regarding the different obstacle spacings as an extension of the aerodynamic scheme by Oke (1988) to solid particle transport. A deposition peak appears before the first obstacle. When the spacing between the two obstacles is large enough, some particles are trapped within the recirculation and a second deposition peak arises. The streamwise evolution of the horizontal saltation flux shows that the lowest flux downstream of the obstacles is obtained for the highest separation. The deposition rate or the streamwise saltation flux are estimated globally as a function of obstacle spacing. These results illustrate how the numerical tool developed here can be used for assessing air quality in terms of solid particle concentration.

Thomas C. Harmon1,2,3, Humberto Flores3, Lorenzo Booth4, Emily R. Waring2,Emily Gomez1, and Stefano Carpin4,51Department of Civil & Environmental Engineering, University of California Merced2Sierra Nevada Research Institute, University of California Merced3Enivronmental Systems Graduate Program4Electrical Engineering & Computer Science Graduate Program, University of California Merced5Department of Computer Science, University of California MercedPoster presentation GC51P-0859 at the Fall 2023 Meeting of the American Geophysical Union, San Francisco, CA, December 12-16, 2023