Abstract

Plasma transport and energy conversion during solar wind-magnetosphere interactions under northward, southward, and radial interplanetary magnetic fields (IMFs) are examined using three-dimensional global hybrid simulations. Energy conversion and entry of plasma and energy are weaker when the IMF is northward. After the IMF is southward, the inflow of the electromagnetic energy (the Poynting flux) increases, leading to a loading of magnetic energy. Subsequently, a strong energy conversion occurs from the magnetic field to the plasma, leading to an unloading of the magnetic energy. When the IMF is radial, strong disturbances are formed on the magnetopause, but the total ion flux, energy fluxes, and energy conversion are not pronounced. The corresponding ion enthalpy flux and bulk kinetic energy flux are also examined. These analyses allow precise and quantitative evaluations of various space weather effects.

Abstract

Sequential compound hazards—heatwaves followed by extreme rainfall—can cause greater impacts than their isolated occurrences, yet compounding effects of such hazards on urban flood risk remain unexplored. Using 40-year (1982–2021) hourly rainfall observations in the Chennai Metropolitan Area, we show that the frequency of heatwave-preconditioned rainfall extremes has increased from an average of 1.2 events/year in 1982–1991 to 3.2 events/year in 2012–2021. The tail of the probability distribution of heatwave-preconditioned rainfall intensity decays slower than uncompounded events. Using a state-of-the-art hydrodynamic model and joint exceedance probability of accumulated event rainfall and peak rainfall intensity, we find that the spatial extent of high-hazard zones (1.4–3.5 m inundation depth) is up to ∼6 times larger compared to uncompounded events, while building and population exposure increase by 7 and 11 times, respectively. Flood risk reduction and climate adaptation should consider more frequent heatwave-preconditioned rainfall extremes and their higher flood impacts.

Abstract

Boundaries in the Phanerozoic chronostratigraphic scale are mainly precisely defined and dated, and many correspond to environmental catastrophes induced by the emplacement of LIPs. The pre-Ediacaran geological timescale is currently subdivided by approximate absolute ages. Here we identified a unique four-layer tuff sequence within the Xiamaling Formation black shales, North China Craton, that can be traced over a large area ∼400 km long by ∼100 km wide, and represents a synchronous marker horizon formed by air fall tuffs from distant volcanic eruptions. High-precision U-Pb geochronology shows that the tuff sequence span a short duration of 0.21 Myr at 1380.41 ± 0.99 Ma. The tuff layers match the age of widely distributed ∼1,380 Ma LIPs found on multiple cratons in supercontinent Columbia/Nuna. Based on climate circulation models, the specific inferred source for the tuff sequence is the Mashak LIP in Baltica. We suggest that the four-layer tuff marker horizon represents a unique chronostratigraphic marker for the Calymmian/Ectasian boundary at 1380.41 ± 1.20 Ma.

Abstract

Continental weathering acts as a nexus of global biogeochemical cycles yet its long-term evolution remains unclear. Here we show that continental weathering may not have operated on a massive scale until the early Paleozoic based on a large-number data compilation of mudstone geochemistry. We attribute the long-term evolution of mudstone K/Al to the competing weathering inputs between continents and seafloor. Much of pre-Phanerozoic mudstone is characterized by high K/Al relative to continents, indicating low weathering input of K and Al from continents relative to the hydrothermal input of K from seafloor alteration to the global sedimentary mud reservoir. A quantitative assessment indicates over one order of magnitude increase of weathering partition into continents during the Phanerozoic. The Phanerozoic onset of massive continental weathering reflects a fundamental evolution on the Earth's surface linked to an interactive feedback network consists of mountain building, atmospheric oxygenation, and land plant colonization.

Abstract

The steady-state buoyancy budget of the Atlantic Meridional Overturning Circulation (AMOC) balances water mass transformation with meridional export. Using historical ocean data, Deep Argo observations, and atmospheric reanalysis, we assess the residual of this balance—water mass volume trends—and its role in the transformation budget of the Subpolar North Atlantic and Nordic Seas on interannual to bidecadal timescales. On long timescales, volume trends in deep convective seas can be large but the volume expansion or contraction of the upper and lower AMOC limbs remain minimal, suggesting that water mass transformation and AMOC intensity may be interchangeable. Conversely, interannual trends are larger across all regions and all density ranges. The volume of the AMOC limbs is significantly impacted so relationships with transformation rates can only be established when considering the timescales of the southward export of transformed water masses out of the subpolar domain.

Abstract

To investigate drying-wetting patterns of precipitation trends in East Asia, we examine the past and future precipitation changes and their underlying control factors using observations and CMIP6 simulations. Over the past seven decades, greenhouse gases enhanced evaporation through enhanced net longwave radiation, raising dryland precipitation, while aerosols suppressed evaporation by reducing net shortwave radiation, lowering humid region precipitation, thereby weakening the dry-wet contrast. Future CMIP6 projections show greater precipitation increases in humid region than in dryland under both intermediate- and high-emission scenarios. Observation-constrained projections indicate a slight decrease in dryland and an increase in humid region, strengthening the dry-wet contrast. This shift stems from aerosol reductions that increased net shortwave radiation, enhancing evaporation in humid region and reversing the historical suppressive effect of aerosols on precipitation. These findings highlight the distinct roles of greenhouse gases and aerosols in modulating regional precipitation, providing insights for climate adaptation strategies in East Asia.

Abstract

The Fengyun-4B (FY-4B) satellite's Geostationary Interferometric Infrared Sounder (GIIRS), featuring thousands of hyperspectral channels and a persistent viewing geometry, induces stronger inter-channel observational error correlations (IOEC). This necessitates, explicit characterization of IOEC to optimize its impact on data assimilation. This study presents the first comprehensive assessment of GIIRS IOECs, demonstrating their potential to improve the assimilation of GIIRS observations for numerical weather prediction (NWP). Results indicate that a more appropriate characterization of GIIRS error covariances enables IOEC to assign more optimal observational weights, leading to improved atmospheric state estimates. Cycling assimilation and forecasting experiments based on the CMA-BJ operational NWP system further demonstrate that IOEC facilitates more accurate temperature and water vapor analysis by adjusting the magnitude and structure of the analysis increments. This, in turn, leads to an improvement of up to 2% in forecast skill for key variables and enhances 24-hr precipitation prediction scores.

Abstract

In this paper we address the question whether variability in the Atlantic Meridional Overturning Circulation (AMOC) and its associated heat transport at mid-latitudes impacts the Arctic Earth system. To that end, we perform coherence analysis on time series of ocean heat transport, AMOC strength, and Arctic climate metrics across a large number of models from the CMIP6 ensemble. We find that, on multidecadal timescales, the majority of CMIP6 models indeed display a statistically significant relationship between AMOC at mid-latitudes (45° ${}^{\circ}$N) and metrics like Arctic surface air temperatures and sea ice. However, our results do not support the narrative that heat transport anomalies at lower latitudes propagate northward toward the Arctic. Instead, our results confirm that variability in meridional ocean heat transport arises in the subpolar North Atlantic and propagates southward and northward.

Abstract

The thermal conductivity of the Earth's core is crucial for assessing the thermal evolution and thermal state of the core. Previous experimental and computational studies have produced widely varying estimates of the core's thermal conductivity. Silicon is likely a significant light element in the Earth's iron-rich core. Here, we utilized the machine learning method to compute the lattice thermal conductivity of hcp Fe-Si alloys at room temperature and high pressure. The lattice thermal conductivity of Fe-Si alloys is significant at room temperature, but it becomes small (3%) and negligible under Earth's core conditions. The comparison between calculations and experimental data at room temperature provides insights into the discrepancies in previous studies. We calculated the total thermal conductivity of solid hcp Fe-8.7wt%Si alloy to be at least 90 W/m/K at the Earth's core-mantle boundary, implying a relatively young inner core if Si were the major light element in the core.

The former Italian PM, well known for a colourful private life, has died at the age of 86.

Aerial images show the partial disintegration caused by an oil tanker fire underneath the I-95 highway.

A court in Japan on Friday paved the way for Shikoku Electric Power Co to restart its only operable nuclear reactor, rejecting a lawsuit from residents to close the unit.

A strong quake with a magnitude of at least 6.4 struck off Greece early on Friday, earthquake monitors said, but there were no initial reports of extensive damage or casualties.

The Australian government proposed on Friday setting up a A$3.9 billion ($2.8 billion) fund for water infrastructure and drought related projects to buffer farming communities from future droughts, as parts of the country endure extreme dry conditions.