Abrupt Alternation Research Articles

Global drought-flood abrupt alternation: Spatiotemporal patterns, drivers, and projections

<p>The spatiotemporal patterns and driving factors of drought-flood abrupt alternations (DFAA) have been investigated across several regional and watershed scales; however, comprehensive examination at the global scale is lacking. Here, we employed the long period drought-flood abrupt change index (LDFAI), derived from an ensemble of 40 output datasets from eight Coupled Model Intercomparison Project phase 6 (CMIP6) models, to assess the spatiotemporal patterns, drivers, and future projections of global DFAA. The results indicate that DFAA are influenced by various anthropogenic forcings, and greenhouse gas emissions exert the most significant impact. The changes in the intensity of global DFAA (1950–2014), attributed to natural forcing (NAT), anthropogenic aerosols (AER), and greenhouse gas (GHG) forcing, accounted for 5.65%, 14.57%, and 33.55%, respectively. The rates of change of the DFAA intensity under shared socioeconomic pathways (SSPs) from 2014 to <styled-content style-type="number">2100</styled-content> were estimated to be 21.73% (SSP1-2.6), 45.37% (SSP2-4.5), 63.1% (SSP3-7.0), and 69.51% (SSP5-8.5). This means that under high radiative forcing, the regional rivalry and fossil-fuel development models will lead to a significant increase in DFAA. These findings can aid in the development of global adaptive policies related to DFAA.</p>

Exploring the relationship between drought-flood abrupt alternation and soil erosion over Guangdong, China through a convection-permitting model

Climate change has caused a more heterogeneous distribution of extreme precipitation, leading to the deterioration of drought-flood abrupt alternation (DFAA) events and soil erosion. The security and sustainable utilization of water and soil resources are severely threatened. Previous studies have focused separately on these two aspects, failing to comprehensively consider their interrelationship. Furthermore, these studies often rely on climate models with convection parameterization, resulting in substantial uncertainties. We use a 4 km convective permitting model (CPM) to generate reliable outputs for extreme precipitation. By incorporating the long-cycle drought-flood abrupt transition index and the Revised Universal Soil Loss Equation model, we analyze the changes in DFAA events and soil erosion, as well as their interconnectedness. The results show that the CPM outperforms coarse-resolution climate models in reproducing erosive rainfall and simulating the heterogeneous distribution of rainfall by capturing convection processes effectively. Projections indicate an escalation in the occurrence of DFAA events and soil erosion due to the more uneven distribution of precipitation. Specifically, the frequency of flood-to-drought (FTD) events within DFAA is projected to rise from 3.8 to 4.7 per decade. Soil loss is projected to increase 61 t·hm−2·a−1, with 73% of the area experiencing more severe soil erosion intensity. A positive correlation between FTD events and soil erosion is found throughout most of Guangdong. This correlation will be further amplified with an increase in the frequency of FTD events. Consequently, existing soil conservation measures are rendered inadequate, presenting substantial challenges for climate change adaptation and ecological protection in the region.

A novel daily-scale index for detecting drought-flood abrupt alternation events: Proof from Pearl River Basin, China

A novel daily-scale index for detecting drought-flood abrupt alternation events: Proof from Pearl River Basin, China

China is suffering from fewer but more severe drought to flood abrupt alternation events

Drought to flood abrupt alternation (DFAA) events, as a special category of compound extreme events that suddenly shift from drought to flood conditions, have significantly greater impacts than individual drought or flood events. In this paper, we have utilized a multifactorial drought index and flood index to identify daily DFAA events occurring in mainland China and in major impact areas during the period 1961–2022. Based on drought and flood index, we have used entropy weighting method to measure the intensity of DFAA events. Our findings indicate that China's DFAA events primarily occur in the hotspots of Huang-Huai-Hai River Basin, the middle and lower Yangtze River Basin, the southeastern coastal area, and the southwestern part of the country. The most frequent and intense DFAA events occur from June to September, with varying subseasonal patterns in the frequency and intensity of events in each hotspot. The frequency of DFAA events in mainland China shows a significant decreasing trend declining at a rate of 0.25 per year in year-round. While DFAA events occurring in the warm season tend to decrease more significantly compared to the year-round at a rate of 0.26 per year. However, the intensity of DFAA events is increasing with a rate of 0.1 per decade in both the year-round and warm season. The evolution of DFAA events and their direct causes varies non-uniformly across regions and months. Subseasonally, frequency and intensity trends diverged monthly across regions, notably with the Huang-Huai-Hai Basin and southeast coast experiencing a July decline in frequency but a surge in intensity. Our research deepens the understanding of changes in DFAA events and provides practical reference for preventing and mitigating drought-to-flood disasters in mainland China.

Projecting dry-wet abrupt alternation across China from the perspective of soil moisture

Under a warmer climate, the enhancement of dry-wet abrupt alternation (DWAA) risk poses a great challenge for sustainable development. Here, we introduce a novel framework for DWAA detection based on our proposed soil moisture concentration index. By the end of this century, over humid southern China, the shift of soil moisture time series from anomalously wet to anomalously dry pattern, or the other way around, will be more abrupt. In addition, the proposed framework driven by Coupled Model Intercomparison Project Phase 6 simulations projects more widespread DWAA-affected areas over southwestern China, coastal regions of southeastern China, and the lower reaches of the Yangtze River, especially under a high emission scenario. The framework proposed in this study provides an efficient system for DWAA detection and prediction, and the findings of this study provide a reference for upgrading hydraulic infrastructure and mitigating future DWAA events.

Quantitative characterization, spatiotemporal evolution, and analysis of driving factors of daily dry-wet abrupt alternation: A case study of the Ganjiang River Basin

Study RegionThis study focuses on the Ganjiang River Basin, a major tributary of the Poyang Lake located in southern China. Study FocusWith the growing frequency of extreme weather events driven by climate change, there is increased attention on compound disasters such as Dry-Wet Abrupt Alternation (DWAA). This study aims to quantify and define DWAA in the Ganjiang River Basin by developing and applying a DWAA Index (DWAAI) using a percentile threshold method. The objective is to investigate the spatiotemporal characteristics and patterns of DWAA in the region. Precipitation data from 12 meteorological stations were analyzed to track these events from 1970 to 2019. New Hydrological Insights For the regionThe results of this study provide new insights into DWAA dynamics in the Ganjiang River Basin. Key findings include: (i) The DWAAI effectively captures the extremes of Dry-Wet Abrupt Alternations, especially at the 1st and 99th percentiles; (ii) The basin experienced 37–48 dry-to-wet events (DtWs) during the study period, with higher frequencies observed in the central-eastern, western, and northern mountainous areas, and lower frequencies in the southern regions; (iii) Wet-to-dry events (WtDs) were less common than DtWs and exhibited a distinct spatial and temporal shift from the southern mountains toward the central basin; (iv) Temperature was identified as the dominant factor influencing DWAAI changes, while large-scale atmospheric patterns such as AO, ENSO, PDO, and Sunspot activity showed insignificant correlations. These findings offer critical insights for improving water resource management and climate adaptation efforts in the region.

Effects of Alternative Stress of Drought–Flood on Summer Maize Growth and Yield

The present study aims to assess the responses of growth, development, and yield of summer maize to the effects of drought–flood abrupt alternation through comparative tests under single flood, single-drought, and drought–flood abrupt alternation treatments with varying degrees from the elongation to the tasseling stage during the 2021 and 2022 growing seasons. In addition, a water production function model for summer maize was preliminarily established based on the results obtained under the drought–flood abrupt alternation scenarios. The results indicated that drought–flood abrupt alternation with early moderate drought had a certain restricting effect on summer maize, while early moderate drought followed by waterlogging had a compensation effect on the cultivated summer maize. Furthermore, both mild and severe drought followed by waterlogging exert a significant combined constraint on the normal growth and development of summer maize, leading to a sharp decline in maize yield, necessitating a shorter timeframe for mitigating and reducing the effects of waterlogging. Additionally, the water production function model established through a multiple linear regression equation exhibits a high degree of fit and demonstrates a strong linear relationship. This study provides crucial insights for agricultural practices and water resource management strategies, particularly in the evaluation of the integrated impacts of drought and waterlogging on crop yields and the formulation of effective disaster risk reduction and mitigation measures in response to these impacts.

Response of rice's hydraulic transport and photosynthetic capacity to drought-flood abrupt alternation

Knowledge of the potential interactive effects of drought and flooding on the maximum carboxylation rate at 25°C (Vmax25) and maximum hydraulic conductance (Kmax) is essential for the precise modeling of crop growth, water-carbon cycling, and crop yield formation. However, the lack of data on drought–flood abrupt alternation (DF) experiments and appropriate models to calibrate parameters without the need to specify photosynthetic and hydraulic transport capacity a priori make it difficult to further our understanding of the potential interaction effects on Vmax25 and Kmax. Hence, this study aimed to investigate the potential effects of interactions between the preceding drought and the subsequent flooding on Vmax25 and Kmax. We propose a nested optimization model for calibrating photosynthetic and hydraulic conductance capacity while simultaneously modeling carbon assimilation rate and stomatal conductance. A two-year DF experiment for rice from 2017 to 2018 was conducted to validate the new framework at the Key Laboratory of Water Resources and Hydropower of Anhui Province, Bengbu, China. The results show that reasonable Kmax and Vmax25 from gas exchange data can be extracted with the proposed nested model framework. We find two distinct interactions between the prior drought and the subsequent flooding on Vmax25 and Kmax: (1) the antagonistic effect of the preceding mild drought on the subsequent-flood-induced reduction of hydraulic transport and photosynthetic capacity, and (2) the synergistic effect of the subsequent flooding on the preceding drought-induced reduction in hydraulic transport and photosynthetic capacity. Revealing the interaction of drought and flooding on Kmax and Vmax25 of rice under DF events helps to understand rice’s response to compound water stress on multiple timescales and the stomatal and non-stomatal co-limitations, and these findings can be used as valuable guidelines for accurately predicting the impact of future extreme weather events on agricultural production.

Refined Identification and Spatiotemporal Characteristics of Drought and Flood Abrupt Alternation Events in the Poyang Lake Basin from 1965 to 2023

This paper utilizes actual observation data from 75 precipitation stations in the Poyang Lake Basin (PLB), combined with the daily scale drought and flood abrupt alternation (DFAA) index, to analyze the occurrences of DFAA in the basin from 1965 to 2023. This includes the frequency and spatiotemporal variation of events, as well as the spatial variation in the intensity of DFAA events. The results indicate that there is no apparent temporal pattern in the frequency and intensity of events in the PLB, with spatial concentration mainly in the Fuhe, Xinjiang, and Raohe river basins. The analysis of a typical drought-to-flood event (DTF) in 1994 and a typical flood-to-drought event (FTD) in 2022 shows that the 1994 event progressed from the northeast to the south, and the prolonged drought following the 2022 event exacerbated the losses caused by the DFAA.

Assessing spatiotemporal variation in dry-wet abrupt alternation using an improved process-based approach

Study regionThe Pearl River Basin (PRB), located in the south of China, has a tropical to subtropical climate. Study focusIn this study, we present an improved process-based approach to assess the intensity of the Dry-Wet Abrupt Alternation (DWAA) events, considering both the transition gap (alternation) and the transition rate (urgency) between dry and wet states. Using daily precipitation data from 1961 to 2020 across 75 meteorological stations in the PRB, we analyze the temporal and spatial evolution patterns of DWAA events. New hydrological insights for the regionThe findings reveal that: (1) DWAA events in the western region generally occur less frequently but with higher intensity. (2) Dry-to-wet (D-W) events have an urgency intensity of 1.35, almost twice that of wet-to-dry (W-D) events at 0.69. However, the alternation intensity of W-D is only slightly higher by 0.17 compared to D-W. (3) The alternation and urgency changes in D-W events are asynchronous, with alternation intensity initially decreasing from 9.7 to 9.27, then increasing to 9.58, while urgency decreases continuously from 1.66 to 1.07. (4) The alternation and urgency changes in W-D events are synchronous. The alternation intensity initially decreases from 9.7 to 9.06, then rises to 10.1, while the urgency intensity decreases from 0.68 to 0.58 before subsequently climbing to 0.8.

Transcriptome analysis of antioxidant system response in Styrax tonkinensis seedlings under flood-drought abrupt alternation

BackgroundStyrax tonkinensis (Pierre) Craib ex Hartwich faces challenges in expanding in the south provinces of Yangtze River region due to climate extremes like flood-drought abrupt alternation (FDAA) caused by global warming. Low tolerance to waterlogging and drought restricts its growth in this area. To study its antioxidant system and molecular response related to the peroxisome pathway under FDAA, we conducted experiments on two-year-old seedlings, measuring growth indexes, reactive oxygen species content, antioxidant enzyme activity, and analyzing transcriptomes under FDAA and drought (DT) conditions.ResultsThe physiological results indicated a reduction in water content in roots, stems, and leaves under FDAA conditions. The most significant water loss, amounting to 15.53% was observed in the leaves. Also, ROS accumulation was predominantly observed in leaves rather than roots. Through transcriptome analysis, we assembled a total of 1,111,088 unigenes (with a total length of 1,111,628,179 bp). Generally, SOD1 and CAT genes in S. tonkinensis seedlings were up-regulated to scavenge ROS. Conversely, the MPV17 gene exhibited contrasting reaction with up-regulation in leaves and down-regulation in roots, leading to increased ROS accumulation in leaves. CHS and F3H were down-regulated, which did not play an essential role in scavenging ROS. Moreover, the down-regulation of PYL, CPK and CALM genes in leaves may not contribute to stomatal closure, thereby causing continuous water loss through transpiration. Whereas, the decreased root vigor during the waterlogging phase and up-regulated CPK and CALM in roots posed obstacles to water absorption by roots. Additionally, the DEGs related to energy metabolism, including LHCA and LHCB, were negatively regulated.ConclusionsThe ROS generation triggered by MPV17 genes was not the main reason for the eventual mortality of the plant. Instead, plant mortality may be attributed to water loss during the waterlogging phase, decreased root water uptake capacity, and continued water loss during the subsequent drought period. This study establishes a scientific foundation for comprehending the morphological, physiological, and molecular facts of S. tonkinensis under FDAA conditions.

A novel multi-scale standardized index analyzing monthly to sub-seasonal drought-flood abrupt alternation events in the Yangtze River basin

Drought-flood abrupt alternation (DFAA) events are often cause severe disasters that affect economic growth and ecological security. Since the current monthly to sub-seasonal drought-flood abrupt alternation index (DFAI) has the limitations of misjudgments, omissions and neglecting alternation speed, this study proposes a novel multi-scale standardized DFAI index (MSDFAI) based on the definition of the misjudgment and omission rates as well as alternation speed. A comparative test and spatial–temporal characterization analysis in the Yangtze River Basin (YRB) are conducted. The results show that the misjudgment rate of DFAI in the YRB varies between 3 %–181 %, and its omission rate varies between 0.5 %–45 %, which is unable to find a suitable point that will satisfy both misjudgment and omission at the same time. The alternation speed has a significant impact on the level of DFAA events, and there are 30 underestimations of DFAA events in the YRB during 1962–2022 when only considering the alternation intensity. The MSDFAI index makes a conditional judgment on whether a drought or flood event occurs based on the standardized precipitation index (SPI) value, which can effectively avoid these misjudgments and omissions. Meanwhile, the MSDFAI index describes the DFAA events in a more comprehensive manner by introducing the speed factor. The DFAA has a spatial pattern with relatively low frequency in the Poyang Lake basin and the middle YRB, and high frequency in the upper YRB, the Han River, and the lower YRB. The inter decadal variability of DFAA events in the YRB is characterized by a turning point in the 1990 s, when DFAA events are increased after the 1990 s. The proposed MSDFAI index can monitor DFAA events much comprehensively and effectively in the YRB, and provide technique support for identification and prevention of DFAA in the changing environment.

Integrating SWAP and SIF anomaly to assess the responses of vegetation to the drought-flood abrupt alternation in the middle and lower reaches of the Yangtze River basin, China

Study regionThe middle and lower reaches of the Yangtze River basin, China. Study focusUnder the background of global warming, drought-flood abrupt alternation (DFAA) events are occurred frequently, with substantial impact on ecosystems and water resources. Therefore, this study calculated the Standard Weighted Average Precipitation (SWAP) based on daily precipitation to verify the applicability of SWAP in the middle and lower reaches of the Yangtze River basin (MLRYRB). The response of Solar-Induced Chlorophyll Fluorescence (SIF) anomaly to DFAA events was determined based on lagged time correlation coefficients. Finally, based on Partial Wavelet Coherence (PWC), the impact of atmospheric circulation factors on the response relationship between DFAA events and vegetation was analyzed. New hydrological insights for the regionThe results indicate that: (1) the evolutionary characteristics of DFAA events determined by SWAP were consistent with historical records. (2) the DFAA events frequency with most regions experiencing 8–11 events during 2001–2019, with intensity of 2–3, and in the northern and southwestern Jiangxi and southeastern Hubei regions were more intensive and frequently. (3) the stronger correlations were mainly in eastern Guizhou and eastern Jiangxi, with SIF anomaly more sensitive to SWAP at 2-month lag time. (4) The El Niño-Southern Oscillation (ENSO) and sunspots have a significant influence on the response relationship between DFAA events and vegetation anomaly. This research can provide a scientific basis for the integrated response to DFAA events and ecological management in the MLRYRB.

Spatial-Temporal Variations of Drought-Flood Abrupt Alternation Events in Southeast China

Under climate change, the frequency of drought-flood abrupt alternation (DFAA) events is increasing in Southeast China. However, there is limited research on the evolution characteristics of DFAA in this region. This study evaluated the effectiveness of the drought and flood indexes including SPI (Standardized Precipitation Index), SPEI (Standardized Precipitation Evapotranspiration Index), and SWAP (Standardized Weighted Average Precipitation Index) in identifying DFAA events under varying days of antecedent precipitation. Additionally, the evolution characteristics of DFAA events in Fujian Province from 1961 to 2021 were explored. The results indicate that (1) SPI-12d had the advantages of high effectiveness, optimal generalization accuracy, and strong generalization ability of identification results, and it can be used as the optimal identification index of DFAA events in Southeast China. (2) There was an overall increase in DFAA events at a rate of 1.8 events/10a. The frequency of DFAA events showed a gradual increase from the northwest to the southeast. (3) DTF events were characterized by moderate drought to flood, particularly in February, July, and August, while FTD events were characterized by light/moderate flood to drought, with more events occurring from June to October. (4) DTF event intensity increased in the northern and western regions from 1961 to 2021. For FTD events, the intensity notably increased in the western region from 1961 to 2001, while a significant increase occurred in all regions except the central region from 2001 to 2021. These findings emphasize the need for precautionary measures to address the increasing frequency and severity of DFAA events in Southeast China.

Responses of the maize rhizosphere soil environment to drought-flood abrupt alternation stress.

Changes in the soil environment in the root zone will affect the growth, development and resistance of plants. The mechanism underlying the effect of drought and flood stress on rhizosphere bacterial diversity, soil metabolites and soil enzyme activity is not clear and needs further study. To analyze the dynamic changes in bacteria, metabolites and enzyme activities in the rhizosphere soil of maize under different drought-flood abrupt alternation (DFAA) stresses, the barrel test method was used to set up the 'sporadic light rain' to flooding (referring to trace rainfall to heavy rain) (DFAA1) group, 'continuous drought' to flooding (DFAA2) group and normal irrigation (CK) group from the jointing to the tassel flowering stage of maize. The results showed that Actinobacteria was the most dominant phylum in the two DFAA groups during the drought period and the rewatering period, and Proteobacteria was the most dominant phylum during the flooding period and the harvest period. The alpha diversity index of rhizosphere bacteria in the DFAA2 group during the flooding period was significantly lower than that in other stages, and the relative abundance of Chloroflexi was higher. The correlation analysis between the differential genera and soil metabolites of the two DFAA groups showed that the relative abundance of Paenibacillus in the DFAA1 group was higher during the drought period, and it was significantly positively correlated with the bioactive lipid metabolites. The differential SJA-15 bacterium was enriched in the DFAA2 group during the flooding period and were strongly correlated with biogenic amine metabolites. The relative abundances of Arthrobacter, Alphaproteobacteria and Brevibacillus in the DFAA2 group were higher compared with DFAA1 group from rewatering to harvest and were significantly positively correlated with hydrocarbon compounds and steroid hormone metabolites. The acid phosphatase activity of the DFAA1 group was significantly higher than that of the DFAA2 group during the flooding period. The study suggests that there is a yield compensation phenomenon in the conversion of 'continuous drought' to flooding compared with 'sporadic light rain', which is related to the improvement in the flooding tolerance of maize by the dominant bacteria Chloroflexi, bacterium SJA-15 and biogenic amine metabolites. These rhizosphere bacteria and soil metabolites may have the potential function of helping plants adapt to the DFAA environment. The study revealed the response of the maize rhizosphere soil environment to DFAA stress and provided new ideas for exploring the potential mechanism of crop yield compensation under DFAA.

The Interaction Effects of Drought–Flood Abrupt Alternation on Rice Yield and Dry Matter Partitioning

The frequent occurrence of drought–flood abrupt alternation (DFAA) seriously affects crop yield. It is particularly important to explore the dynamics of material accumulation and distribution under DFAA stress to analyze the mechanism of yield formation. In this study, a bucket experiment with DFAA stress groups, drought control (DC) groups, flood control (FC) groups, and normal irrigation (CK) groups was set up from the jointing to the heading stage of rice to analyze the interaction effects of DFAA stress on rice yield and dry matter partitioning. The results showed that compared with the CK group, the average yield reduction rate of rice in the DFAA groups was 23.03%, and the number of grains per panicle, total grain number, thousand-seed mass, and seed setting rate decreased. Compared with the DC groups, the DFAA groups had a significant reduction in yield and its components during the flooding period. Compared with the FC groups, the DFAA groups showed a compensation phenomenon in the yield and its components during the drought period. From the end of DFAA stress to the harvest period, the root partitioning index (PI) of the DFAA groups decreased, the stem PI increased first and then decreased, the leaf PI decreased, and the panicle PI increased. The results showed that the rice leaves increased and thickened, and the stems thickened under DFAA conditions to enhance the ability to resist drought and flooding stress, but the panicle rate was reduced, the growth period of rice was delayed, and the redundant growth of stems and leaves was increased. It is suggested that the depth and duration of stagnant water storage during the flood period of DFAA should be controlled, and the transfer and supply of photosynthetic products to grains should be increased to avoid serious yield reductions. The research results provide a theoretical basis for the rational development of farmland DFAA mitigation measures.

Monitoring and Evaluating the Severity of Drought-flood Abrupt Alternation Events Using Daily Standardized Precipitation Index

A drought-flood abrupt alternation (DFAA) event is an extreme combination of an overlapping drought and flood resulting in adverse impacts on ecosystems and human society. As precipitation variability increases due to climate change, the occurrence and magnitude of DFAA events are expected to increase. Using daily precipitation data for 1966–2018, we calculated the daily standardized precipitation index for middle-sized watersheds and evaluated the severity of DFAA events in South Korea. The severity of DFAA events was evaluated in two ways: the severity of whole period (SWP) represents the total magnitude of DFAA event, and the severity of transition period (STP) indicates the instantaneous severity of DFAA event during the transition from drought to flood. The severities were also graded by the quantiles to identify risk regions, and we used precipitation concentration degree (PCD) and precipitation concentration period (PCP) to analyze the relationship between DFAA events and precipitation trends in South Korea. The results showed that the STP in the Yeongsan River basin and SWP in the Han River and the Nakdong River basin were higher than in the other basins. In addition, considering patterns and trends of the PCF and PCP in South Korea, this study found that the frequency and severity of DFAA events were high during flood seasons when precipitation was concentrated.

Exploring two-decadal risk variability of drought-flood abrupt alternation in a high-plateau basin

The escalating intensity and frequency of drought-flood abrupt alternation (DFAA) events, intensified by climate change, pose a significant threat to both the eco-environment and human life. Despite their evident impacts, the risk associated with DFAA events has received limited attention. In this study, we present a comprehensive risk assessment model incorporating multifold natural and anthropogenic indicators to analyze the spatiotemporal variations of DFAA risk. Utilizing a DFAA index (DFAAI) based on river flow data from seven monitoring stations spanning 1999 to 2019, we investigate DFAA events in the Dianchi Basin, the largest lake in the Yunnan-Guizhou Plateau, China. Our analysis reveals that 56% of total DFAA events occurred between June and August, with drought-to-flood (DTF) events accounting for 62.5% of DFAA occurrences in the Dianchi Basin. Notably, the intensity and frequency of DFAA events exhibit significant spatial variations across the basin. The hazard, vulnerability, exposure, and disaster defense indices further exhibit substantial spatial discrepancies, with hazard indicators being the most influential, notably the DFAA rate accounting for 72.4% of the overall impact. Spatial correlations in DFAA risk among monitoring stations were found to be low, primarily influenced by variations in meteorological conditions, underlying surface characteristics, and human activities. The findings of this study can offer valuable insights for effective water resource management in an ever-changing environment.

Growing Threats From Swings Between Hot and Wet Extremes in a Warmer World

AbstractThe abrupt alternation between hot and wet extremes can lead to more severe societal impacts than isolated extremes. However, despite an understanding of hot and wet extremes separately, their temporally compounding characteristics are not well examined yet. Our study presents a comprehensive assessment of successive heat‐pluvial and pluvial‐heat events globally. We find that these successive extremes within a week occur every 6–7 years on average within warm seasons during 1956–2015, about 15% more often than would be expected by chance, and that they have a significant increase in frequency of about 22% per decade due to warming. We further investigate the role of vapor pressure deficit (VPD) and find that heat‐pluvial (pluvial‐heat) events are linked to negative (positive) VPD anomalies. Our results are statistically significant based on moving‐blocks bootstrap resampling and field significance tests, highlighting these methods' importance in robustly identifying compound events under autocorrelation and multiple‐testing conditions.

Projection of drought-flood abrupt alternation in a humid subtropical region under changing climate

Drought-flood abrupt alternation events (DFAAEs) bring about detrimental impacts on economics and environment. Projection of the future change in the DFAAEs is a challenging issue. Incorporated with the datasets of the Coupled Model Intercomparison Project Phase 5 under two Representative Concentration Pathway scenarios (RCP4.5 and RCP8.5), we applied the Soil and Water Assessment Tool model and the drought-flood abrupt alternation index (DFAAI) to detect climate change impacts on the DFAAEs in the Poyang Lake Basin for the period from 2020 to 2099. Our results demonstrated that the projected DFAAEs would become more frequent and be mainly distributed from January to October. Among them, the drought-to-flood events mainly occur from January to July, while the flood-to-drought events mainly occur from July to October. The occurrence of the DFAAEs is more frequent, and the occurrence frequency of DFAAEs under RCP4.5 is 75. The mild DFAAEs would be the dominated events in the Poyang Lake Basin, while the moderate and extreme DFAAEs are spatially unevenly distributed. The annual maximum and minimum of DFAAI would increase, and the frequency and intensity of the DFAAEs tend to increase. The projected runoff tends to increase but spatially homogenous. The projected peak flow would delay leading to a change in the transition time of the DFAAEs' type. This study provides a future projection on DFAAEs, valuable for policy makers to mitigate flood disasters at a basin scale.