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Agro-pastoral ecotone of northern China is the prominent area for agricultural production, but it is also the most typical ecological fragile area with frequent drought disasters. Taking Yulin City at Shaanxi Province in China as the case area, the paper aims to investigate the spatio-temporal changes of agricultural vulnerability to drought in China's agro-pastoral ecotone in the period 2000 to 2020. The results show that: 1) the agricultural vulnerability to drought in Yulin City has shifted from high vulnerability in the period 2000–2010 to low vulnerability in the period 2011–2020. 2) There exist obvious spatio-temporal differences of the agricultural vulnerability to drought in Yulin City during the research period. 3) Four sensitive events and 14 resilient events were identified in the research and the crops of Yulin had become more resilient to drought. Finally, the paper put forward with policy implications to make adaptive strategies of agriculture to climate change in China's agro-pastoral ecotone in the future, e.g., carrying out agricultural zoning based on agricultural production conditions, intensifying the construction of disaster prevention and relief system, and integrating with modern agricultural technology to develop new type agriculture. [ABSTRACT FROM AUTHOR]

Droughts are increasing in frequency and intensity as the global climate changes. Risk assessment for agricultural drought disasters is an important approach for disaster prevention and mitigation. Based on the formation mechanism of natural disaster risk, the index system model of agricultural drought risk assessment in North China was constructed, and the robustness of the established risk assessment model was tested by using the internal test method. Then based on the characteristics of agricultural drought risk formation in North China, the paper proposes corresponding risk prevention recommendations. The conclusions were as follows: when adjusting the indices and methods in the risk assessment model, the range of changes in the agricultural drought risk ranking for each city was mostly 1-2.5 places, and the model was relatively robust. With the exception of Beijing and Tianjin, which had the highest disaster prevention and mitigation capacity, central and northern China had the highest agricultural drought risk, which was previously linked to the high risk and vulnerability of these regions. The agricultural drought risk in northern Henan and southern Shandong is low, mainly due to the low risk. The 34 cities in North China can be divided into 6 agricultural drought risk clusters, which are not dispersed in space and cross-city distribution, and have good aggregation. Cluster 4, located in the northernmost mountainous areas, has the highest risk of drought, which is associated with high environmental vulnerability and low capacity for disaster prevention and mitigation, so agricultural areas should be reduced and agricultural input should be increased. Clusters 2, 5 and 6, located in the central and southern regions, have higher grain acreage and yields due to drought, so agricultural drought risk can be further reduced by increasing agricultural input and improving irrigation guarantee rate. [ABSTRACT FROM AUTHOR]

The Ningxia Hui Autonomous Region of China (Ningxia), one of main agriculture areas in northwest China, has been severely affected by drought. Based on observed meteorological data, outputs of 20 global climate models and drought disaster data, future climate change and relevant drought hazard in the twenty-first century were projected in Ningxia, with the scenarios of RCP2.6 and RCP4.5; the risks of people, crop, and agriculture economy to drought disasters are quantitatively assessed, with the application of physical vulnerability curve models, probability distribution functions and Monte Carlo simulation method. It is found that the climate in Ningxia is likely to have a warming and wetting tendency in the twenty-first century. The extent of drought hazard is likely to increase. The increase rate is greater under RCP4.5 than that under RCP2.6. In general, the risks of population, crop, and agriculture to drought disasters are likely to increase in Ningxia in the twenty-first century. The magnitude of increase is likely to reach the greatest in the immediate term (2016–2035), followed by the increase in the medium term (2046–2065), and the long term (2081–2100). In comparison with RCP2.6, the drought disaster risks under the scenario of RCP4.5 are likely to increase further in three periods of the twenty-first century. The findings of this work have potential to provide data support for drought disaster risk management and support risk-based decision-making. [ABSTRACT FROM AUTHOR]

The simultaneous occurrence of droughts and floods in neighboring regions amplifies the threats posed by droughts and floods individually. Nonetheless, few studies have been conducted to investigate the simultaneous occurrence of drought and flood events. Here we explore the spatiotemporal characteristics and the shift pattern of droughts and pluvials over Eastern China from a three‐dimensional perspective, using the self‐calibrated Palmer Drought Severity Index and the Climate Research Unit data set as well as four regional climate model simulations. We find that Eastern China experienced droughts and pluvials simultaneously in different locations during boreal summer, and it is projected to simultaneously experience more frequent and more intense droughts and pluvials under a warming climate. Specifically, we investigate the pattern of more pluvials in Southeast China and more droughts in Northeast China for the historical period of 1975–2004. This pattern dynamically evolves under climate warming: the pluvial‐dominated regime shifts from Southeast to Northeast China, while the drought‐dominated regime shifts from Northeast to Southeast China. The weakening strength of the western Pacific subtropical high and a northward displacement of the monsoon rain belt may both contribute to the pattern of more pluvials in Northeast China and more droughts in Southeast China. These findings provide insights into the development of adaptation strategies and emergency response plans for enhancing society's resilience to the spatial co‐occurrence of dry and wet extremes. Plain Language Summary: The spatial co‐occurrence of drought and flood events has been receiving widespread attention in recent years since the superimposed condition of drought and flood has brought unprecedented challenges to disaster prevention, mitigation, and relief work. Eastern China is prone to droughts and floods, but their spatial interconnections are not yet well understood. Thus, we explore the historical evolution and the future change of simultaneous occurrence of droughts and floods over Eastern China under a warming climate. The spatial co‐occurrence of droughts and floods is projected to affect more land areas and become more frequent as climate warms. Eastern China experienced a pattern of more floods in Southeast China and more droughts in Northeast China during 1975–2004. We find that droughts tend to become more intense in Southeast China and the severity of floods is expected to increase in the northern region of East China, resulting in a shift pattern of more droughts in Southeast China and more floods in Northeast China. The shift pattern may be attributed to the weakening of western Pacific subtropical high strength and a northward displacement of the monsoon rain band in a changing climate. Key Points: Eastern China is projected to experience more frequent and more intense droughts and pluvials simultaneouslyThe spatial pattern of more pluvials in Southeast China and more droughts in Northeast China is expected to become an opposite pattern under a warming climateThe weakening strength of the western Pacific subtropical high and a northward displacement of the monsoon rain belt may contribute to the pattern of more pluvials in Northeast China and more droughts in Southeast China [ABSTRACT FROM AUTHOR]

Analyses of the standardized precipitation evaporation index (SPEI), using the season-reliant empirical orthogonal function (S-EOF) method, indicate that the second leading mode of drought over Northeast China features an in-phase variation from spring to summer. Such an in-phase change is closely connected to the persistence of geopotential height anomalies around Lake Baikal. The positive height anomalies around Lake Baikal, with an equivalent barotropic structure in the troposphere, can decrease water vapor transport into Northeast China and induce anomalous descending motion over Northeast China during both seasons, favoring precipitation deficit and high temperature in situ and hence resulting in the synchronous variations of spring and summer droughts. Further investigation reveals that the spring North Atlantic Oscillation (NAO) plays a notable role in the in-phase change of spring–summer droughts over Northeast China. The positive phase of spring NAO could induce spring drought over Northeast China directly through its influence on the above atmospheric circulations via a zonal wave train emanating from the North Atlantic. Meanwhile, it can also increase the soil moisture in central Siberia by enhancing the local snow depth. The wetter soil moisture in the following summer, in turn, increases the meridional temperature gradient between the middle and high latitudes and then forces westerly anomalies around 60°N, consequently yielding positive height anomalies around Lake Baikal that favor the occurrence of summer drought over Northeast China. Therefore, the spring NAO is hypothesized to contribute to the in-phase variations of spring–summer droughts over Northeast China through the combined roles of zonal wave train and central Siberian soil moisture. Significance Statement: Northeast China suffers from frequent droughts severely in recent decades. Thus, it is urgent to understand the physical mechanisms of drought in Northeast China. Using the season-reliant empirical orthogonal function (S-EOF) analysis, this study indicates that the second mode of S-EOF shows an in-phase change of drought from spring to summer over Northeast China, which is associated with the persistence of geopotential height anomalies around Lake Baikal. Our study further reveals that the spring NAO plays a pronounced role in the in-phase change of spring–summer droughts over Northeast China, through the combined roles of zonal wave train and the soil moisture in the central Siberian plateau. These findings are encouraging for better understanding of drought in Northeast China and are also important for disaster prevention and mitigation. [ABSTRACT FROM AUTHOR]

Much attention has recently been devoted to the qualitative relationship between climate factors and drought; however, the influences of climate variability, land-use/cover changes (LUCC), and other human activities on drought have rarely been quantitatively assessed. Based on the Soil and Water Assessment Tool (SWAT) model and the Palmer drought severity index (PDSI), this study presents a framework to quantify drought changes in an attribution study, and quantifies the effects of climate factors, LUCC, and other human activities on drought in a typical basin (Yihe River) in eastern China from 1980 to 2019. (1) The SWAT–PDSI results revealed a slight decreasing trend from 1980 to 2019, indicating that the degree of drought increased—especially in the middle of the basin. (2) The precipitation in the basin exhibited a downward trend (−2.7 mm/10 a), while the temperature exhibited a significant increasing trend (0.13 °C/10 a, p < 0.05). Over the past 40 years, LUCC in the Yihe River Basin was mainly characterized by a reduction in the dryland area (149 km2) and an increase in the built-up area (135 km2), which changed by −1.77% and 18.96%, respectively. (3) Climate fluctuation was the main driving factor of drought change, with a contribution rate ranging from 68 to 84%, and the contribution to drought gradually increased. Among the various factors, the contribution of temperature exceeded that of precipitation from 2010 to 2019, suggesting that temperature has become the most important climate factor affecting drought. The contribution rates of LUCC to drought changes over the periods 1990–1999, 2000–2009, and 2010–2019 were 7.8%, 18%, and 12.6%, respectively. This indicates that the relative contributions of other human activities to drought changes gradually decreased. This study refines the drought attribution framework, which could provide scientific support for the quantitative attribution of drought and the formulation of disaster prevention and reduction strategies. [ABSTRACT FROM AUTHOR]

Droughts and heatwaves are the most detrimental climatic threats to global wheat production, their spatiotemporal coexistence (compound drought and heatwave events [CDHEs]) can cause synergistic and amplified impacts on wheat yield, which call for an improved understating of their characteristics and variations that related to wheat growth. Past decade has witnessed a surge in the study of CDHEs in terms of their causative mechanisms, variabilities and impacts; however, changes in CDHEs occurring within crops' growing seasons are barely discussed, especially on global scale. In this study, we proposed a novel approach to identify and summarize CDHEs by taking "crop growing season" as accumulated period, and investigated the spatiotemporal changes of CDHEs occurring within wheat growing seasons over global wheat‐producing areas during 1981–2020, including their spatial extent, frequency and duration. Results show that the spatial extent of CDHEs experienced rapid expansion during wheat growing seasons of 1981–2020, meanwhile, droughts and heatwaves increasingly tended to occur simultaneously. More than 92% of wheat‐producing areas experienced at least one CDHE in each wheat growing season, the frequency of CDHEs increased significantly in 28.2% of wheat‐producing areas, and the total duration of CDHEs increased significantly in 33.2% of wheat‐producing areas. Europe, eastern China, western US and northern Argentina are the hotspot regions with the biggest contradiction between fast‐increasing CDHEs and wheat production, pointing to the urgency of marking spatially targeted adaptation measures for disaster reduction and risk management. [ABSTRACT FROM AUTHOR]

The start and duration of a drought are often not easy to define. The advance and onset are usually slow and the social and economic impacts can then extend over a long period. In this study, the Standardized Precipitation Index (SPI) was used to describe and compare droughts in different periods and regions under different climatic conditions. The importance of the index lies in its simplicity and in its ability to identify the beginning and end of a drought event. Thus it may be a useful tool for drought contingency planning. This paper examines the SPI by evaluating its application using historical precipitation data from nine weather stations in China. Different time series data covering the period 1980 to 2011 and for differing timescales of 3, 9 and 24 months were used. The results underline the potential of the SPI to inform drought alerts and forecasting efforts as part of a drought contingency planning strategy. [ABSTRACT FROM AUTHOR]

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Debris-flow disasters occurred frequently after the Mw 8.0 Wenchuan earthquake on 12 May 2008 in Sichuan Province, China. Based on historical accounts of debris-flow disaster events, it found that debris flow occurrence is closely related to the impact of earthquakes and droughts, because earthquake-drought activities can increase the loose solid materials, which can transform into debris flows under the effect of rainstorms. Based on the analysis of historical earthquake activity (frequency, magnitude and location), drought indexes and the trend of climate change (amount of rainfall), a prediction method was established, and the regional debris flow susceptibility was predicted. Furthermore, in a debris flow-susceptible site, effective warning and monitoring are essential not only from an economic point of view but are also considered as a frontline approach to alleviate hazards. The advantages of the prediction and early monitoring include (1) the acquired results being sent to the central government for policy making; (2) lives and property in mountainous areas can be protected, such as the 570 residents in the Aizi valley, who evacuated successfully before debris flows in 2012; (3) guiding the government to identify the areas of disasters and the preparation for disaster prevention and mitigation, such as predicting disasters in high-risk areas in the period 2012–2017, helping the government to recognize the development trend of disasters; (4) the quantitative prediction of regional debris-flow susceptibility, such as after the Wenchuan earthquake, can promote scientific and sustainable development and socioeconomic planning in earthquake-struck areas. [ABSTRACT FROM AUTHOR]

Understanding the spatiotemporal characteristics of regional drought is of great significance in decision-making processes such as water resources and agricultural systems management. The North China Plain is an important grain production base in China and the most drought-prone region in the country. In this study, the monthly standardized precipitation evapotranspiration index (SPEI) was used to monitor the spatiotemporal variation of agricultural drought in the North China Plain from 1960 to 2017. Seven spatial patterns of drought variability were identified in the North China Plain, such as Huang-Huai Plain, Lower Yangtze River Plain, Haihe Plain, Shandong Hills, Qinling Mountains Margin area, Huangshan Mountain surroundings, and Yanshan Mountain margin area. The spatial models showed different trends in different time stages, indicating that the drought conditions in the North China Plain were complex and changeable in the past 58 years. As an important agricultural area, the North China Plain needs more attention since this region shows a remarkable trend of drought and, as such, will definitely increase the water demand for agricultural irrigation. The strong correlation between these spatial distribution patterns indicates that the climate and weather conditions leading to drought are consistent and that drought conditions are independent for regions that are not correlated. If this trend continues, the characteristics of drought variability in the North China Plain will become more complex, and a more detailed water management strategy will be needed to address the effects of drought on agro-ecosystems. Recognizing the drought variability in the North China Plain can provide a basis for agricultural disaster reduction planning and water resources allocation. [ABSTRACT FROM AUTHOR]