地球科学最新文献

As risks from tropical cyclones (TCs) are fueled by climate change escalation, there is an urgent need for transformational solutions to complement traditional approaches. Seeding TCs using aerosols can be a promising method to reduce cyclone intensity, supported by theoretical understanding of the microphysical effects of aerosols on TC clouds. The ideal time to intervene effectively in TCs is likely during their initial stage, before TC wind speeds reach their peak. However, studies exploring potential aerosol effects on TC formation remain scarce. This study investigates how a TC embryo responds to the addition of aerosols of varying sizes using the Weather Research & Forecasting (WRF) model coupled with a spectral-bin microphysics model. We found that aerosols of different sizes and concentrations distinctively affect the pre-TC vortex's microstructure and dynamics. Fine and ultrafine aerosols enhance the latent heat of condensation, freezing, deposition, and riming, initially intensifying the vortex. However, this results in enhancement of the cold pool, thereby reducing inflow and surface fluxes, subsequently weakening the vortex. Coarse aerosols produce the opposite effect to that of fine and ultrafine aerosols. Coarse aerosols lead to a slower initial acceleration owing to enhanced warm rain. However, the resulting weaker cold pool is insufficient to effectively reduce the strength of the vortex at the later stage. This study provides critical insights into how aerosols of varying sizes and concentrations modulate the energy cascade and impact the evolution of a TC embryo, laying the groundwork for further research on TC risk management through aerosol intervention.

The Global-scale Observations of Limb and Disk (GOLD) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instruments were used to investigate the thermospheric composition and temperature responses to the geomagnetic storm on 23–24 April, 2023. Global-scale Observations of Limb and Disk observed a faster recovery of thermospheric column density ratio of O to N₂ (ΣO/N₂) in the southern hemisphere (SH) after the storm ended at 12 Universal time (UT) on 24 April. After 12 UT on 25 April, ΣO/N₂ had mostly recovered in both hemispheres. Global-scale Observations of Limb and Disk also observed an increase of middle thermospheric temperature (140–200 km) (Tdisk) on 24 April with a maximum of 340 K. Within 4–6 hr of the storm ending on 24 April, Tdisk enhancement persisted between 30°N and 60°N, 100°W and 30°W, while Tdisk lower than pre-storm quiet day (17 April) was observed between 45°W and 15°W, 40°S and 50°N. Tdisk recovered between 100°W and 45°W, 30°N and 55°S. On 25 April, Tdisk was lower than on 17 April across the entire GOLD Field-of-Regard (FOR) by ∼50–110 K. Additionally, solar irradiance decreased by 15%–20% from 17 to 25 April, indicating that the lower Tdisk on 25 April resulted from both storm and solar irradiance variations. Latitudinal variations of Tdisk and the SABER observed Nitric Oxide (NO) cooling rate revealed that NO cooling is crucial for the lower Tdisk in the northern hemisphere (NH) mid-high latitudes on 25 April. These results provide direct evidence of decreased thermospheric temperature during storm recovery phase than pre-storm quiet times.

Geophysical surveys and multiproxy analyses of sediment cores have been used to reconstruct the palaeoenvironmental evolution of the Santa Giusta coastal lagoon (SGL), along the western coast of Sardinia. This area served as a natural harbour mainly during the Punic and Roman Republican periods (6th–2nd century bc). The inlet of the SGL is connected to the adjacent mouth of the River Tirso and lies on the incised valley of an ancient tributary that once fed into the Tirso during the last sea-level lowstand. The SGL formed after the sea level rose following the LGM, resulting in the inundation of the incised valleys, which were subsequently filled with estuarine sediments. About 6000 years ago, the area that is now occupied by the mouth of the river and the SGL was protected by a sandy barrier enclosing an open lagoon. About 4500 years ago, the deposition of alluvial sediments marked the beginning of the progradation of the river mouth, leading to the gradual enclosure of the SGL. Before 2100 years ago, the SGL was a suitable location for a sheltered harbour, as evidenced by archaeological indicators, both pottery and wooden structures, found within the lagoon sediments. By this time, the progressive narrowing of the inlet had reduced the accessibility of the site from the sea and the harbour lost its functionality.

Tropical cyclone precipitation (TCP) and associated floods have caused widespread damage globally. Despite growing evidence of significant changes in the activity of tropical cyclones (TCs) in recent decades, the influence of TCs on regional flooding remains poorly understood. Here, we distinguish the role of TCs in fluvial discharge by explicitly simulating discharge with and without observed TCP in the Lancang‒Mekong River Basin, a vulnerable TC hotspot. Our results show that TCs typically contributed approximately 30% of annual maximum discharge during 1967–2015. However, for rare and high-magnitude floods (long return periods), TCs are the dominant driver of extreme discharge events. Moreover, spatial changes in TC-induced discharge are closely related to changes in TCP and TC tracks, showing increasing trends upstream but decreasing trends downstream. This study reveals significant spatiotemporal differences in TC-induced discharges and provides a methodology for quantifying the role of TCs in fluvial discharge.

The mechanical properties of continuous rock fiber (CRF), particularly its elastic modulus and tensile strength, are essential requirements for the ever-increasing applications of this material. Studies on CRF have primarily focused on its application in fiber-reinforced composites, with much less emphasis on the analysis of the fiber structure–property relationship. This review summarizes and discusses the current experimental approaches, theories, models, and parameters in different production stages (geochemistry, rock screening, melting, cooling, and fiber drawing) that would affect the elastic modulus and tensile strength of CRF. For the current research results, the general debate is the trade-off between the network structure and defects in the tensile strength of CRF. The study of elastic modulus functions as the fundamental of tensile strength, as the former can be explored regardless of certain defects, only considering the microstructure of the network, local atom coordination and bonding, whereas the latter can be studied beyond characterizing the defects. The limitations of current methods include theories for crystals and stable substances, which may not be applicable to metastable monofilaments or complex CRF glasses. Experimentally, in situ testing is difficult for fibers in certain procedures that cause permanent damage. Machine learning (ML) and molecular dynamics (MD) can compensate for the lack of experimental data, reduce the effects of operational procedures, provide structure-based information, and reflect the combined effects of multiple input features. An ongoing approach should be based on a solid understanding of conventional models and improvements in standardized experimental and MD datasets incorporated with ML methods.

The Svalbard archipelago region is one of the fastest warming regions in the world. The majority of warming has occurred in wintertime, although the summer season has also been warming approximately linearly since 1980. Nevertheless, in recent years, many monthly and seasonal temperature records have been set in summer, with 2024 breaking its mean summer and August temperature records by the largest margins in the measurement history. In this study, we examine 2024s temperature extremes. The mean August temperature stands out as falling outside of the climatological distribution even after accounting for the warming trend. Our findings suggest that 2024s records are a result of an unprecedented combination of persistent atmospheric patterns and interaction with the warming seas. Given the exceptional nature of these temperature extremes, we recommend further research to the potential increase in the persistence of weather and the consequences of associated temperature extremes.