A notable increase in the intensity of Persistent Extreme Precipitation (PEP) events over the Eastern Periphery of the Tibetan Plateau (EPTP) is observed after 2000, which is strongly linked to the changes in Southwest Vortices (SWVs). A composited diagnostic of multiple SWVs is carried out in conjunction with the PEP. The Vorticity Vertical Transport (VVT) and Divergence (DIV) terms have a positive impact on the growth of SWVs, whereas the Relative Vorticity Advection (RVA) and Vorticity Tilt (VT) have a negative effect. Although all four terms are related to the variability of SWV intensity, DIV and RVA are the primary contributors to the increased trend in SWVs after 2000, accounting for up to 79.4% of the variation. The changes in meridional wind are thereby the main driver of the upward trend in PEP intensity, since it acts as the primary determinant of the long-term variations in the DIV and RVA.

The upper mesosphere and lower thermosphere (UMLT) is the least explored atmospheric region, with the variability of water vapor, ozone, and temperature remaining poorly understood. This study demonstrates that the UMLT climate during non-summer months is governed by bottom-up processes. Specifically, tropical upwelling drives the transport of H2O, which negatively modulates the secondary ozone layer, while radiative heating of O3 influences temperatures above 90 km (T90). This “upwelling—H2O—O3—T90” link is non-localized, propagating upward and poleward at each step, creating a highly structured climate. Temperatures near 80 km (T80), dominated by adiabatic cooling, serve as an indicator of upwelling. Notably, high-latitude T90 is positively correlated with low-latitude T80 in both hemispheres, and the interannual variability of H2O, O3, and T90 exhibits interhemispheric symmetry. This study challenges the conventional view that UMLT climate is primarily driven by solar and CO2 forcing, highlighting the critical role of atmospheric dynamics.

A document by Emily Graham. Click on the document to view its contents.

Each year, Earth experiences new record-breaking temperatures, highlighting the urgent need to transition to less carbon-intensive energy systems and expand carbon storage operations in the subsurface. Shales and tight formations stand out as a crucial player in large scale storage operations and as a source for low-carbon energy carriers such as methane

The study of icy moons is of great importance to furthering our understanding of the origins of life in the solar system due to their high liquid water content. While missions like JUICE aim to study these bodies through an observational lens, there has yet to be a mission that probes the subsurface of one of these icy moons. This study details our novel mission plan to explore the Saturnian moon Enceladus. This icy world houses a large subsurface ocean filled with important elements for life, alongside potential catalysts for life to form, such as thermal vents. This mission relies on three main components, an orbiter, a lander, and a drill. We detail the designs for every part of the mission and test a simulated thruster system used for landing as well as the water sampling mechanism of the drill. Our testing of the water sampler highlighted the importance of placing the water sampling mechanism above as few mechanical components as possible to prevent the drill from being unable to resurface, and proved that our sampling design is able to collect water efficiently. Similarly, by using drone propellers to simulate thrust from a descent stage and imitate the lack of an atmosphere, we were able to test the lander concept to gain insight on the thrust required to decelerate the lander and negate horizontal velocity for optimal landing on a surface of unknown material composition. We will analyze the water found in the subsurface region of the planet to gauge the habitability of Enceladus and the potential for finding prebiotic lifeforms on the natural satellite. Our mission aims to further study Enceladus and understand more about icy moons through analysis of surface particles and subsurface ocean water. Our mission will help provide key insights into remote sensing, orbiting, landing, and drilling technologies that will be pivotal to exploring other distant icy moons such as Europa or Titan.

A document by Takashi Miyamoto. Click on the document to view its contents.

Recent temperature records have triggered debate about whether global warming is accelerating. Here, we examine for acceleration and explore possible causes for regional differences using gridded surface temperature data. We find that, global and regional warming is accelerating, and on average, regions with low Human Development Index (HDI) experienced much higher accelerated warming in comparison to regions with high HDI. However, regions of low HDI with a large population experienced slow acceleration due to high local aerosol emissions. Since aerosol negative forcing impacts are short-lived and localized, rapid future reduction of aerosol emissions without a concurrent reduction in GHG emissions could have major compounding impacts. Such a pathway, similar to most 21st century scenarios, could expose a large fraction of the world’s most vulnerable people to sudden warming acceleration and heat stress associated impacts. These results call for targeted climate adaptation strategies directing attention to low-socioeconomic aerosol masked regions.

Creep events are millimeter-sized, aseismic movements that produce slip along portions of certain active faults \citep{Tymofyeyeva_2019}. These movements were first observed on the San Andreas through cultural offsets and have been measured with creepmeters since the 1970s. Despite having knowledge of the events for over 40 years, little is known about the mechanisms that produce creep events. There are two popular mechanisms which have been proposed to drive creep events: the ‘kick’ hypothesis (e.g., \citealp*{Kanu_2011}; \citealp*{Helmstetter_2009}) and the self-driven hypothesis (e.g., \citealp{Rubin_2008}; \citealp{Skarbek_2012};\citealp{Wei_2013}). The self-driven hypothesis asserts that creep events are triggered at moderate depths by local frictional weakening patches and then propagate to the surface. In contrast, the ‘kick’ hypothesis suggests that slip events originate very near the surface from perturbations in stress or pore-pressure \citep*{Gittins_2022}, which in turn may be linked to rainfall, atmospheric tides, or other environmental changes. To investigate the ‘kick’ hypothesis, we used a newly generated catalog of creep events synthesized from a global network of creepmeters first established on the central portion of the San Andreas Fault in the 1970s. This catalog of over 5000 creep events spanning over 40 years allows for a more complete analysis compared to earlier work \citep{Roeloffs_2001}. We used this catalog to perform statistical analyses to investigate the relationship between the creep events and rainfall. Our analysis has uncovered that even within the same region, some creepmeters' creep events are more correlated with rain than others. Thus, our results favor the conclusion that creep events are not explained by one of the two theories alone, but instead by a combination of both hypotheses.

The transport and delivery of low-abundance, bioactive trace elements to the surface ocean by aerosol mineral dust is a major planetary control over marine primary production and hence the global carbon cycle. Variations in the concentration of atmospheric dust have established links to global climate over geologic timescales and to regional biogeographic shifts over seasonal timescales. Constraining atmospheric dust variability is thus of high value to understanding oceanographic systems, especially vast, constitutively low-nutrient subtropical gyre ecosystems and high-nutrient/low-chlorophyll ecosystems where availability of the trace element iron is a dominant ecological control. Here we leverage the MERRA-2 reanalysis product to examine over four decades of surface-level atmospheric mineral dust concentrations in a domain of the subtropical North Pacific centered at ocean Station ALOHA. This study region has been sampled regularly since the mid-1980s and was the site of the Hawaii Aerosol Time-Series (HATS) project in 2022-2023. Two unequal semi-annual periods of elevated dust are evident in the long-term data are described and constrained. We look for evidence of shifts in total and seasonal atmospheric dust abundances and in the timing of the onset of the dominant spring/summer dusty period, finding year-to-year variations but little evidence for long-term trends. We observe significant but complex relationships between the Pacific Decadal Oscillation (PDO) index and both dust and precipitation. The data show that 2022 was among the dustiest years for the study domain in the preceding two decades and, by contrast, that 2023 exhibited a significant early-spring lull in dust.

A document by Jack Sheehan. Click on the document to view its contents.

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Prescribed wildland and agricultural fires are common in the eastern United States (U.S.), but their small size and short durations have led polar-orbiting satellite datasets to underestimate their emissions due to omission. The higher temporal resolution of the GOES-16 Advanced Baseline Imager (ABI) improves fire detection, enabling development of a new biomass burning emissions inventory: GOES Eastern U.S. Fire Emissions (GEUFE, pronounced “goofy”). GEUFE is based on geostationary fire radiative power (FRP) observations, incorporates improved crop type classification for agricultural fires, and includes a new emission factor (EF) compilation for 16 land cover types in the eastern U.S., including forest, crop, and grassland types that differ markedly from globally reported EF values. GEUFE provides daily estimates of dry matter (DM) consumption and emissions of CO2, CO, NOx, NH3, SO2, organic carbon (OC), black carbon (BC), and fine particulate matter (PM2.5) at 2 km resolution. An intercomparison of nine biomass burning emissions inventories (GEUFE, GBBEPx, QFED, NEI-2017, FEER, VFEI, GFAS, FINN, GFED) showed that OC estimates in the eastern U.S. during August 2019–July 2020 ranged from 0.05 to 1.32 Tg yr-1, with both EFs and DM consumption driving the large spread in aerosol estimates. GEUFE, at 0.64 Tg yr-1, is at the high end of this range due both to region-specific EFs and continuous GOES-16 monitoring, reducing missed short-lived fires. GEUFE is a process-based inventory that eliminates reliance on empirical scaling factors, such as QFED’s aerosol optical depth-based adjustments, while explaining previously inferred “missing emissions” from small fires.

Flat slab subduction, a unique tectonic phenomenon, is characterized by subhorizontal plate motion extending over hundreds of kilometers. Despite its significance, the mechanisms driving flat slab formation remain debated. This study investigates the dynamic effects of mantle wedge hydration on flat slab subduction through advanced numerical modeling, focusing on the Chilean region. Our models incorporate magmatism, hydration, phase transitions, and dynamic pressure variations, revealing that reduced mantle wedge hydration and increased suction forces are critical for slab flattening. Hydration processes, especially serpentinization, create low-viscosity channels that enhance suction forces, while magmatic heat release influences mantle dynamics. The interplay of gravity and suction torques highlights the limited role of slab buoyancy and emphasizes the dominance of suctiondriven dynamics. The results reproduce key geological features, including flat slab geometry, volcanic gaps, and reduced magmatism, consistent with observations in South America. This study provides a comprehensive framework for understanding the geodynamic evolution of flat slab subduction systems worldwide.

We investigate details of the interaction of subaqueous barchans with dune-size obstacles by carrying out numerical simulations where the fluid is solved at the grain scale and the motions of individual grains are computed at all time steps. With the outputs, we analyze the disturbances of the fluid flow, the trajectories of grains, and the resultant force on each grain, the latter being unfeasible from experiments and field measurements. We show that in some cases particles pass over the obstacle, while in others they completely circumvent it (without touching it), or are even blocked. For the circumvention and blocking cases, which we call bypass and trapped, respectively, we show the existence of a strong vortex between the lee face of the dune and the obstacle. This vortex results from the interactions of recirculation regions and horseshoe vortices, and has enough strength to deviate the main flow and carry grains around the obstacle in those cases. Our results shed light on the reasons for passing over, circumventing, and blocking, and contribute to our understanding of dunes in the presence of large obstacles such as hills, crater rims, and human constructions.

Terrestrial ecosystem water balance refers to the state between inputs from precipitation, and outputs including evapotranspiration, groundwater recharge and runoff. The Three River Source Region (TRSR) is known as the “water tower of Asia” and is an important water source region for much of southeast Asia. Spatial and temporal distributions of water balance have changed within the TRSR under recent changing climatic conditions. However, the status and variation of water balance under the influence of environmental factors remain unclear. We used a daily time step ecosystem water model (SOILWAT2) and 35 years data for 29 meteorological stations to describe water balance across the TRSR and found that 15 of the sites represented a net water source (precipitation > actual evapotranspiration) between 1981 and 2015. Stations at intermediate elevations (3400 to 4100 m) and low latitudes (< 34°N) were net water sources; stations at lower and higher elevations as well as higher latitudes were not sources because of moisture limitations by a dry climate. In contrast to a strong spatial pattern, we found no obvious temporal trend of the net water source. The interannual and seasonal variability of the net water source is dependent on the temporal fluctuations in potential evapotranspiration and precipitation. We therefore suggest that there is an elevation and latitude dominated spatial pattern of the water balance on the TRSR, with important implications for the availability of water resources.

A document by Pushkar Nalawade. Click on the document to view its contents.

Solar eruptive phenomena result in irregular processes in solar wind plasma and interplanetary magnetic field. Most high-speed streams, interplanetary shock waves, and other irregularities propagate to the heliosphere's edge non-independently from each other. One such mutual impact is the effective acceleration of charged particles at fronts of shock waves driven by the Coronal Mass Ejections (CMEs). In our study, we review a few fast-forward shock waves that affected differently the spectra, intensities, and species of energetic particles in the interplanetary space from January to May 2023. IP shocks were identified based on data from the Proton Alpha Sensor (PAS) of the Solar WindAnalyzer (SWA) and the Magnetometer (MAG). Simultaneously, we analyze some specific features in the effectivity of the charged particle acceleration for some selected phenomena mentioned using data and spectrograms of energetic particles observed by the Electron Proton Telescope (EPT), the SupraThermal Electrons and Protons (STEP), and the SupraThermal IonSpectrograph (SIS), of the EPD suite. We demonstrate that shock waves are not the only objects that influence the peculiarities in parameters of energetic particles in the heliosphere. The magnetic flux ropes, wave foreshocks, short- and long-duration magnetic holes, and other plasma structures should be considered from the point of view of affecting the spectral, temporal, and spatial parameters of energetic particles.This work is supported by the “Long-term program of support of the Ukrainian research teams at the Polish Academy of Sciences carried out in collaboration with the U.S. National Academy of Sciences with the financial support of external partners”.

The geomagnetic field, electric currents, and storm-time plasma pressure are reconstructed for extreme storms before 1995: the July 1982 superstorm and the March 1989 Hydro-Québec grid collapse event. The reconstructions are based on an improved magnetic field data mining method that fills gaps in the solar wind data using a recently published machine learning algorithm. The data mining reconstructions are rescaled using statistics of the nearest neighbor bins to eliminate the bias toward weaker storms. A concurrent reconstruction method provides the combined description of storms and substorms: storm and substorm features are first reconstructed independently for the inner and tail magnetosphere, respectively, and then the data fitting is reiterated using synthetic data generated using the first round of reconstructions. The data fitting procedure is further tuned to better resolve the location of the field-aligned currents. Testing the updated methods for the November 2003 and 1982 superstorms significantly improves the validation results for in-situ observations. The effect of rescaling doubles the peak ring current density (from 81 to 168 nA/m2 for the November 2003 storm) while the tuned fitting procedure shifts the Region-2 field-aligned currents equatorward to magnetic latitudes as low as 50°. Rescaling also intensifies the equatorial currents such that X-line arcs and even an X-loop are formed within geosynchronous orbit, where reconnection may approach a relativistic regime. Such a change in the field topology limits the peak plasma pressure obtained from the quasi-static force balance equation.