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Sustainable management of blue and green water resources is vital for the stability and sustainability of watershed ecosystems. Although there has been extensive attention paid to blue water (BW), which is closely related to human beings, the relevance of green water (GW) to ecosystem security is typically disregarded in water resource evaluations. Specifically, comprehensive studies are scarce on the detection and attribution of variations of blue and green water in the Dongjiang River basin (DRB), an important source of regional water supply in the Guangdong–Hong Kong–Macao Greater Bay Area (GBA) of China. Here we assess the variations of BW and GW scarcity and quantify the impacts of climate change and land use change on BW and GW in DRB using the multi-water-flux calibrated Soil and Water Assessment Tool (SWAT). Results show that BW and green water storage (GWS) in DRB increased slowly at rates of 0.14 and 0.015 mm a−1, respectively, while green water flow (GWF) decreased significantly at a rate of -0.21 mm a−1. The degree of BW and GW scarcity in DRB is low, and the per capita water resources in more than 80 % of DRB exceed 1700 m3 per capita per year. Attribution results show that 88.0 %, 88.5 %, and 39.4 % of changes in BW, GWF, and GWS result from climate change. Both climate change and land use change have decreased BW, while climate change (land use change) has decreased (increased) GWF in DRB. These findings can guide the optimization of the allocation of blue and green water resources between upper and lower reach areas in DRB and further improve the understanding of blue and green water evolution patterns in humid regions. [ABSTRACT FROM AUTHOR]

Large‐scale extreme precipitation (LSExP) events, characterized by widespread extent, persistence, and high intensity, can pose devastating threats to millions of people, infrastructure, and ecology in highly urbanized southeastern China. Here we explore the three‐dimensional (spatial and temporal) characteristics and movements of LSExPs and their direct drivers (vertical velocity, water vapor and moisture advection) under six synoptic‐scale circulation patterns in southeastern China. LSExPs are classified as low‐pressure or non‐low types based on circulation anomaly patterns. The low‐pressure LSExPs are associated with anomalous cyclonic low‐pressure systems in the mid‐ and lower‐troposphere, occurring with main coastal precipitation, while the non‐low LSExPs mainly result from cold‐warm air convergence and primarily affect inland areas. Low‐pressure LSExPs exhibit relatively high intensity compared to non‐low types, particularly on days featuring a south‐low and north‐high dipole pattern, which tend to produce more localized and intense precipitation events. Non‐low LSExPs show larger precipitation areas, longer durations, and greater movement distances, and thus impact wider regions, compared to low‐pressure LSExPs. Single high‐pressure or low‐pressure systems are less likely to result in LSExPs, and LSExPs are less severe if occur, compared to other types. All LSExP types move in a direction similar to that of moisture transport, strongly influenced by extreme upward motion of moisture. Low‐pressure LSExPs are more related to the upward motion of the atmosphere at 850 hPa, and they also involve extreme water vapor and moisture transport. Plain Language Summary: Large‐scale extreme precipitation events can be destructive due to their widespread coverage, persistence, and intensity. In southeastern China, the connection between spatiotemporal three‐dimensional large‐scale extreme precipitation (LSExP) events and weather‐scale circulation patterns has not been established. This study assesses the occurrences, spatiotemporal characteristics, and three‐dimensional behaviors of LSExP events under six identified circulation anomalies over southeastern China. Large‐scale extreme precipitation events can be categorized into the low‐pressure types and the non‐low types based on circulation background characteristics. Low‐pressure extreme precipitation events mainly occur along the southeastern coastal areas and show precipitation of high‐intensity, small‐scale precipitation. Non‐low extreme precipitation events are usually triggered by cold‐warm air convergence and typically cover larger areas, last longer, and travel farther, affecting broader regions. All LSExP events move in a direction similar to that of water vapor transport and are associated with extreme upward motions. Low‐pressure LSExP events are additionally associated with higher precipitable water and moisture transport. This three‐dimensional structural perspective enhances insight into the mechanisms and triggers of catastrophic extreme precipitation events, and could potentially improve precipitation forecasting and adaptation. Key Points: Identified the spatiotemporal evolution features of high‐impact, large‐scale extreme precipitation (LSExP) events over southeastern ChinaLinked synoptic circulation patterns with LSExPs, and explored the occurrence, spatiotemporal features and movements of LSExPs under each patternMost LSExP days are accompanied by extreme vertical motion, and low‐pressure LSExP types are also linked to high precipitable water [ABSTRACT FROM AUTHOR]

Sustainable management of blue and green water resources is vital for the stability and sustainability of watershed ecosystems. Although there has been extensive attention to blue water (BW) which is closely related to human beings, the relevance of green water (GW) for ecosystem security is typically disregarded in water resource evaluations. Specifically, there is a scarcity of comprehensive study on the detection and attribution of variation of blue and green water in the Dongjiang River Basin (DRB), an important source for regional water supply in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) of China. Here we assess the variations of BW and GW scarcity, quantify the impacts of climate change and land use change on BW and GW in DRB using a multi-water-flux calibrated Soil and Water Assessment Tool (SWAT). Results show that BW and green water storage (GWS) in DRB increased slowly with a rate of 0.14 and 0.015 mm a-1, respectively, while green water flow (GWF) decreased significantly at a rate of -0.21 mm a-1. The degree of BW and GW scarcity in DRB is low, and the per capita water resources in more than 80 % of DRB exceed 1700 m3 capita-1 a-1. Attribution results show that 88.0 %, 88.5 %, and 39.4 % of changes in BW , GWF , and GW S results from climate change, respectively. Both climate change and land use change have decrease BW , while climate change (land use change) decrease (increase) GW F in DRB. These findings can guide to optimize the allocation of blue and green water resources between upper reach and lower reach areas in DRB and further improve the understanding of blue and green water evolution patterns in humid regions. [ABSTRACT FROM AUTHOR]

The unprecedented 2022 Yangtze River Basin (YRB) heatwave is a threat to human society and natural ecology, so the understanding of its underlying drivers is critical to regional climate adaptation and resilience. Here we conducted a multi‐method attribution analysis on the contribution of atmospheric circulation change and anthropogenic impacts to the occurrence probability and intensity of this extreme heatwave. Based on the nonstationary statistical analysis, the 2022 YRB heatwave is a 1‐in‐900‐year event and a 1‐in‐110‐year event with and without considering the 2022 YRB heatwave in the fitting, respectively. The large‐scale meteorological condition analysis shows that the 2022 YRB heatwave is featured with an anomalous high‐pressure system that favors a hot and dry atmospheric column, overlaid by anomalous subsidence and clear skies which leads to warming and greater solar heating. The ensemble constructed circulation analogue analyses show that the circulation anomaly fails to explain the observed 2022 YRB SAT anomalies fully. Specifically, 46% (0.132 ± 0.027°C decade−1) of the observed SAT trend during 1979–2022 (0.290 ± 0.048°C decade−1) is caused by anthropogenic warming and the associated thermodynamic feedback, while the remaining 54% (0.157 ± 0.038°C decade−1) of the trend is caused by changes in the large‐scale atmospheric circulation. Our findings on changes in atmospheric circulation patterns associated with YRB heatwave and anthropogenic contributions to YRB heatwave could provide valuable information for climate adaptation and mitigation strategies in the context of a warming climate. Plain Language Summary: Heatwaves are major climate extremes in the context of global warming, which have inverse effects on human health, food and energy production, and ecosystems. The 2022 heatwave in the Yangtze River Basin (YRB) sets a new record in observational history with its extreme intensity, long duration, and widespread affected areas. The 2022 YRB heatwave is too exceptional to be possible without anthropogenic warming, which is a 1‐in‐900‐year event and a 1‐in‐110‐year event, respectively, with and without considering it in the nonstationary statistical fitting. An anomalous and prolonged high‐pressure system predominated the evolution of the 2022 YRB heatwave, which favors anomalous subsidence and clear skies, leading to hot and dry atmospheric conditions. Next, we applied an ensemble circulation constructed analogue approach to separate the contributions of large‐scale circulation changes and anthropogenic warming in generating the 2022 heatwave. The results reveal that circulation dynamics can only partially explain the 2022 event. When historical changes are taken into account, the changes in large‐scale circulation and anthropogenic warming, respectively, can account for 54% and 46% of the observed summer surface air temperature anomalies in the YRB region. Key Points: The 2022 Yangtze River Basin (YRB) heatwave, linked to anomalous circulation backgrounds, set unprecedented records for surface air temperature (SAT)The atmospheric circulation anomalies alone cannot fully explain the SAT anomalies during the 2022 YRB heatwaveThe variation in atmospheric circulation and anthropogenic warming contributed nearly equally to the historical SAT trend of YRB [ABSTRACT FROM AUTHOR]

Drought is one of the most destructive types of natural disasters, causing great losses of every aspects worldwide. Using a three‐dimensional (longitude, latitude, and time) clustering method based on gridded 3 month standardized precipitation evapotranspiration index data with a resolution of 0.25° collected for East China between 1960 and 2017, we identified and analysed five characteristics of drought events via the Mann–Kendall (MK) test. The results revealed that this method could capture drought events on the basis of their spatiotemporal characteristics. Drought development processes could be visualized via the spatial expansion of drought patches and the transferring path (reconstructed from the centroids of drought patches observed each month). By applying this identification method to the territory of East China, the occurrence of 174 droughts in the last six decades could be determined; furthermore, their objective existence in the spatiotemporal scale was confirmed by comparing the results with historical records and soil moisture data. The increasing moving speed of the centroids and the non‐repetitive rate of the impacted areas suggests that an increasing number of regions have likely been affected over time by large‐scale drought events. The drought patches associated with all of the events identified in the present study tended to move westward in South China and eastward in southwestern China. The remaining four characteristics (i.e., duration, severity, affected area, and intensity), were used to quantify the degree of drought, along with its development, where significant decreasing trends were found among the first three characteristics. In southwestern China, drought events decreased in frequency, but increased spatially, whereas drought events in southeastern China showed an opposite change. Drought events with a small spatial scale occurred more frequently in coastal regions. The majority of drought events mainly occurred in central and North China and moved northward. [ABSTRACT FROM AUTHOR]

Crop reference evapotranspiration (ET0), which connects the energy and water balance, is an important indicator used in water resource management and agricultural production. On the basis of daily meteorological data from 479 observation stations, we investigate changes in ET0 and associated climate factors across the main grain‐producing area (MGPA) of China from 1960 to 2015. The Mann–Kendall test and Sen's slope estimator were applied to detect trends in ET0, and regression analyses and composite analyses were used to evaluate the contributions of climatic variables and large‐scale anomalies that may affect ET0. The results of this study show that ET0 in the MGPA decreased (−2.67 mm/decade) during summer throughout the past 56 years, and that this change is largely attributable to decreased sunshine duration and wind speed (WS). Furthermore, decreased WSs in the 850‐hpa geostrophic wind field, are responsible for decreases in ET0 in Northeast China Region (−1.85 mm/decade), which affect ET0 by significantly weakening the observed surface WS. Meanwhile, significant low cloud cover variations accounted for the decrease in ET0 in the Huang‐Huai‐Hai Region (−7.85 mm/decade), Loess Plateau Region (−2.91 mm/decade), Yangtze River Region (−3.96 mm/decade), and Southwest China Region (−2.71 mm/decade). However, decreases in the integrated atmospheric water vapour content (IWVC), which act to weaken the surface relative humidity, are hypothesised to increase ET0 in the South China Region (1.25 mm/decade). Topographic map of China with 479 meteorological stations across main grain‐producing area (MGPA). [ABSTRACT FROM AUTHOR]

• Responses of streamflow to changes in vegetation composition and climate variability were investigated considering changes in the terrestrial water storage. • The Budyko parameter is significantly related to vegetation composition and climate variability. • Streamflow changes were more (less) sensitive to tree coverage than non-tree coverage in humid (arid) regions. Vegetation and climate play critical roles in the hydrological cycle as vital components of the earth system. Understanding the impacts of changes in vegetation composition and climate on hydrological processes is essential for water balance and sustainable water resource management. We analyzed the effects of changes in vegetation composition and climate variability on streamflow changes in 3434 global watersheds from 2003 to 2016 using the Budyko framework. We found that ignoring changes in terrestrial water storage would result in large errors in the influence of landscape changes on streamflow changes. The sensitivity of streamflow changes to climate seasonality index (CSI), precipitation seasonality index (PSI), total vegetation coverage (M), tree coverage (MT), and non-tree coverage (MNT) varied in different regions. Effective precipitation (Pe), potential evapotranspiration (PET), CSI , PSI , M , MT , and MNT changes were the dominant factor in streamflow changes for 64.8%, 3.0%, 5.1%, 4.1%, 9.8%, 7.7%, 5.6% of global watersheds, respectively. Attributing streamflow changes showed that the effects of MT and MNT on streamflow changes were mutually reinforcing in most basins. The influence of vegetation composition on streamflow changes was greater in semi-humid and arid regions than in humid regions. This research quantified the impacts of vegetation composition changes and climate change on streamflow changes worldwide and could clarify the hydrological responses to changing environments. [ABSTRACT FROM AUTHOR]