Drought-flood abrupt alternation (DFAA) events, characterized by their complex compound nature and profound impacts on ecosystems and human societies, have emerged as critical hydrometeorological risks in the middle and lower reaches of the Yangtze River basin (MLYRB), China. The concentrated and unstable characteristics of precipitation during the mei-yu season provide a typical climatic background for DFAA events. By using satellite precipitation data from 2001 to 2023, this study analyzes the spatiotemporal characteristics of DFAA occurrences and investigates how rain belt migration and mei-yu anomalies influence DFAA formation and regional differentiation. Results show that over 40% of annual DFAA events are concentrated in summer, mainly in eastern subregions with high precipitation variability. During the meiyu season, northward migration of the rain belt reshapes the precipitation distribution and produces a distinct north-south opposition, with flood-to-drought (FTD) transitions prevailing in the south and drought-to-flood (DTF) events dominating the north. The average DFAA-affected area reaches 19.5% of the basin, with nearly equal shares of the two alternation types. Mechanistically, DFAA events are generally found to follow a chain-driven process initiated by anomalies of the western Pacific subtropical high (WPSH), which restructure moisture transport pathways and rain belt position, then lead to regional drought and flood anomalies, and finally trigger DFAA events. Meanwhile, a weakened South China Sea summer monsoon (SCSM) further enhances the north-south opposition. This study highlights the critical role of the rain belt movement and mei-yu variability in shaping DFAA patterns and provides insight into their physical drivers and regional differentiation. SIGNIFICANCE STATEMENT: Drought-flood abrupt alternation (DFAA) events in the middle and lower Yangtze River basin pose significant challenges for regional water management and disaster preparedness. This study clarifies the spatiotemporal distribution of these events and examines how monsoons, moisture transport, and the western Pacific subtropical high (WPSH) interact during the mei-yu season to shift the rain belt and lead to sudden hydroclimatic extremes. By uncovering how these factors combine to drive severe DFAA events, this work enhances understanding of compound hydrometeorological hazards and provides insights to support early warning systems and climate resilience planning across East Asia and other monsoon-affected regions worldwide.
Atmospheric dust transport is a complex multidisciplinary problem that has substantial impacts on weather and climate. Here, we used the Weather Research and Forecasting with Chemistry (WRF-Chem) model to investigate the role that springtime snow, frozen soil, and soil moisture might have played on a historic dust storm that occurred across East Asia in March 2021. We used the Land Information System to generate several different initial surface conditions representative of the 7-yr period spanning 2016-22. The 2021 dust storm is then simulated with WRF-Chem initialized using each different initial condition. The results showed that antecedent surface conditions likely contributed to the magnitude of the observed storm and its human impact with a nearly 2.53 increase in the areal extent of hazardous air quality compared to the wettest initial state. In simulations with anomalously high snow extent, dust emission was restricted by snow in the northern Gobi Desert during the initial phase of the storm. This led to weaker and less expansive atmospheric dust loading even as the storm progressed south over snow-free regions. The impacts of frozen soil and soil moisture appear to be secondary but were not negligible, particularly in the snow-free southern Gobi Desert. The results of this study indicate that accurately characterizing snow and soil moisture is critical for forecasting springtime dust storms over East Asia. Finally, these results suggest that as the climate warms and snow melts earlier in the spring season, springtime dust storms in the Gobi Desert may occur earlier and become more severe in the future. SIGNIFICANCE STATEMENT: Dynamic soil conditions constrain soil erodibility during high wind events and can influence dust storms. The purpose of this study was to examine how interannual variability in snow cover and soil moisture affects dust storm severity in the Gobi Desert region of East Asia. The results of this study show that dust storms in this region can be more than 23 as severe in dry, snow-free years than in snowy wet years. This suggests that more accurately characterizing the land surface in this region can improve dust storm prediction.
The sequestration of CO2 into coal-based media via the hydrate method contributes to achieving carbon neutrality; however, at the molecular scale, the mechanism underlying the influence of coal-based media on CO2 hydrate nucleation remains to be investigated. In this study, coal-based media were characterized using bilayer graphene. Taking the lattice size of sI-type CO2 hydrate as the basic unit of the simulation domain, two sets of models were constructed: the first set consists of five models with different lattice spacings in the z-direction, and the second set comprises three models with 10%, 20%, and 30% hydroxyl concentrations. By analyzing the synthesis trajectory, structural parameters, potential energy, and density of CO2 hydrates, the response characteristics of the size effect and hydrophilicity to CO2 hydrate nucleation were investigated. The results showed that the simulation domain formed a "CO2 adsorption layer-CO2 aqueous solution region-CO2 adsorption layer" structure, and hydrates (predominantly sI-type) only nucleated in the CO2 aqueous solution region. Under the coupled effect of temperature and pressure, a relatively low potential energy environment reduces the intensity of the violent motion of molecules within the system. CO2 bubbles dissolve in the aqueous phase, forming local low-potential energy regions, which in turn induce the regular arrangement of high-density water molecules to form initial cage-like structures. Nucleation is a cyclic process involving the formation and decomposition of cage-like structures, where water molecules continuously arrange themselves in an ordered manner around initial water cages, facilitating the formation of hydrate clusters and their gradual growth to the critical nucleus size. The z-direction spacing of the five CO2 hydrate unit cells was the critical size threshold, and a narrower spacing increased the system potential energy, thus inhibiting CO2 dissolution and nucleation. The hydroxyl groups on graphene form hydrogen bonds with water, reducing the free water and dissolved CO2 concentrations, thereby suppressing hydrate synthesis. This work provides molecular-level insights for optimizing coal-based CO2 hydrate storage via carbon capture and storage (CCS) technologies.
Dynamic cross-linked polymers have garnered attention due to their recyclable nature. Research on constructing dynamic cross-linked polymers with various dynamic chemical bonds has achieved numerous outstanding outcomes. Nevertheless, studies on mechanisms such as polymer chains' movement, energy transformation, and dissipation within the dynamic cross-linked network have been relatively scarce, which is the essential determinant for the ambient-temperature usage and high-temperature recycling characteristics of dynamic cross-linked polymers. This research uses the widely studied dynamic imine bonds as a representative to investigate dynamic cross-linked polymers. Through the utilization of rheological tests, the dynamic and static properties were tested and analyzed at the polymer chain level, explaining the mechanical property stability of dynamic cross-linked polymers during ambient-temperature service and the influence of dynamic performance on the energy dissipation mechanism, further clarifying the potential application mechanism in materials such as shock absorption. Simultaneously, it also demonstrated the polymer chain structure basis for their recycling.
Owing to the highly efficient activation ability of frustrated Lewis-pair (FLP) sites for small molecules, the development of FLP-based materials is a fascinating route to convert CO2 to value-added chemicals using solar energy. Herein, rhenium (Re) single atoms are introduced into the frame of graphitic carbon nitride (Re-1/gCN) to construct unique N center dot center dot center dot Re-1 FLP sites, where Re single atoms and neighboring N atoms serve as acidic and basic sites, respectively. The N center dot center dot center dot Re-1 FLP sites can interact with CO2 molecules to form a Re-O-C-N structure (acid site-basic site-acid site-basic site) via the dramatic d-p orbital interactions, thus inducing an unusual push-push electronic effect to effectively break the C=O bond for CO2 activation and conversion. As a result, Re-1/gCN achieves a high photocatalytic CO2-to-CO generation rate of 123.4 mu mol g(-1) h(-1) (a CO selectivity of 95.6%) without any sacrificial agents, exceeding the majority of state-of-the-art catalysts under similar test conditions.
