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[Display omitted] • The drought pattern in China is closely related to the basin distribution and multiple teleconnection factors. • The intensity and frequency of drought in China exhibited an increasing trend. • The ENSO-AO had important positive effects in the major basins in China. • Multiple wavelet coherence helps identify the processes controlling drought changes. Due to increasing global warming and the frequent occurrence of severe drought risk in recent decades, many studies have investigated drought in China. However, the spatiotemporal heterogeneities of droughts are complicated, and a comprehensive analysis of the driving forces has not been thoroughly explored. In this paper, we studied the temporal and spatial patterns of drought in China from 1960 to 2018 and disclosed its relationship with multiple teleconnection factors on different time scales. The results show that (1) Drought in China has exhibited a fluctuating increasing trend over the past 59 years, with a standardized precipitation–evapotranspiration index (SPEI) rate of change of –0.12/10 a, and the most severe droughts occurred during 2000–2010. (2) There was a significant abrupt change in China's meteorological droughts induced by climate change around 1997. (3) The trend in China was characterized by drought in spring and autumn and humidification in winter, while the trend in the Southwest River Basin was characterized by drought. (4) A combination of factors can best explain the drought variations from basin to basin, and the El Niño-Southern Oscillation (ENSO)-Arctic Oscillation (AO) was most commonly the best predictor. The use of multiple wavelet coherence helps to identify the dominant drought change processes. [ABSTRACT FROM AUTHOR]

In recent years, studies have found that drought can occur rapidly under anomalous atmospheric circulation patterns and underlying surface conditions. This type of drought is defined as "flash drought". It is more sensitive to global warming compared to traditional drought and may become a common drought phenomenon in the future and require intensive research. But the characteristics and development mechanism of flash drought in northern China has been studied much less than in southern China, and thus deserve further study. Based on the daily station data and GLDAS grid data from 1978 to 2020, this paper identified the flash drought in northern China, analyzed its evolution of temporal-spatial characteristics and explored the meteorological driving factors of flash drought. The main results are as follows: (1)The frequency of flash drought in the year is the highest in WNW (West of Northwest), followed by ENW (East of Northwest), NC (North China) and NE (Northeast China), while the frequency in the plant growing season is the highest in the south of NE and the south of NC, and low in the other regions. (2)The hotspot areas of flash drought showed an obvious eastward trend from WNW to ENW in northern China from the 1980s to 2010s. (3) There is a good relationship between soil moisture and precipitation in WNW and ENW, while the soil moisture is affected by both temperature and precipitation in NC and NE. (4) Flash drought could occur all through the year in WNW and NC, while it mainly occurred in the summer half-year and summer in EWN and NE. The main high occurrence period of flash drought in each region is in late spring and early summer, while a second high occurrence period appears from early September to late October in WNW. (5) From the perspective of the driving of water vapor changes, the flash drought in WNW and ENW is mainly driven by water vapor advection, while that in NC and NE is mainly driven by wind field divergence. • The hotspot areas of flash drought showed an obvious eastward movement from WNW to ENW in northern China. • The main high occurrence period is around early May to early July in northern China, with a second one in WNW. • Flash drought in WNW and ENW (NC and NE) is mainly driven by water vapor advection (wind field divergence). [ABSTRACT FROM AUTHOR]

Drought exerts a significant impact on the sustainable development of social economy. For sustainable water use and rapid drought response, it is very meaningful to explore the correlation between meteorological drought and hydrological drought. This paper investigates the features of drought evolution based on cross wavelet transform (XWT) and mutual entropy. The meteorological drought was measured by the standardized precipitation index (SPI), while the hydrological drought was evaluated by the standardized runoff index (SRI). The research data were collected from hydrological stations and meteorological stations in the Yellow River basin of Henan Province, China. The main conclusions are as follows: (1) Both meteorological drought and hydrological drought had obvious periodicity, especially on the scale of 2–4a. (2) The evolution of meteorological drought varied greatly from place to place; through the study period, Henan province did not suffer any extreme drought, though the drought situation in the western region has an aggravating trend. (3) Hydrological drought has a strong positive correlation with meteorological drought, and generally lagged behind meteorological drought by 1–2 months in the study area. The research results lay a good basis for drought response in the Yellow River basin. [ABSTRACT FROM AUTHOR]

The distribution focuses of water resources, socio-economic development and environmental maintenance are usually mismatched, leading a gap between regional resources and the environment, as well as the disharmony of development. Water resource spatial equilibrium (WRSE) is an important yardstick for guiding regional water resource planning and sustainable utilization. However, research on the spatiotemporal heterogeneity and driving factors of WRSE is extremely lacking, and few existing studies have considered drought and flood disasters as the important reflection of WRSE. Therefore, this paper proposes a systematic integrated model for WRSE including regional evaluation, spatiotemporal heterogeneity and geodetector analysis functions, and constructs the evaluation index system considering droughts and floods. First, the performance of WRSE is quantified using the general deprivation index (GDI) innovatively. Then, combined with the Moran's I , the spatial patterns and regional differences of WRSE are analyzed. Last, the geographical detector models are employed to perform driving analysis of WRSE. The effectiveness of the model is verified in China. Results show that (1) from 2009 to 2021, the national average of WRSEI exhibits a declining trend from 0.879 in 2009 to 0.789 in 2021. (2) The areas with high WRSEI values are mainly distributed in the western provinces, whereas the eastern region has a higher percentage of imbalanced provinces. (3) Water resources per capita, added value of tertiary industry, urbanization rate and GDP per capita are key driving factors of China' WRSE. The study provides a novel insight for WRSE improvement and is greatly helpful for developing differentiated management measures to optimize resource allocation. • A systematically integrated model for water resource spatial equilibrium (WRSE) was established. • First applying the general deprivation index method to analyze WRSE. • The evaluation index system was enriched by adding drought and flood factors. • Differentiated measures can improve the equity of water resources development and utilization process. [ABSTRACT FROM AUTHOR]

[Display omitted] • The proposed MSDI can capture the occurrence of drought. • There was a tendency of aridity with a mutation point of 1983. • The drought severity was the heaviest in the DXJB, with an average MSDI of –0.75. • The most severe drought event occurred from September 1988 to October 1990. • ENSO had the largest influence on the drought variation in the XJB. The reasonable and appropriate drought indicator is a crucial instrument for drought investigation and assessment, which can objectively compare the severity, duration, and frequency of drought events, so as to achieve the purpose of accurately monitoring and evaluating drought. However, a univariate drought index is often difficult to precisely describe the complex drought situation, and it is urgent to establish a multivariate comprehensive drought index to identify and reveal the drought characteristics. Based on Copula models, combined with meteorological factors precipitation and hydrological factors runoff, this paper constructed a Multivariate Standardized Drought Index (MSDI), which can characterize meteorological drought and hydrological drought simultaneously and evaluate the spatial–temporal evolution characteristics of drought over the Xijiang River Basin (XJB) in South China. The results indicated that: (1) the proposed MSDI can capture the occurrence of drought as sensitively as the Standardized Precipitation Index (SPI), and can represent the termination of drought as effectively as the Standardized Runoff Index (SRI), which can comprehensively depict the drought situation in the XJB, China; (2) since the 1980 s, there was a tendency of aridity with a mutation point of 1983 in the downstream of Xijiang River (DXJB), and the worst comprehensive drought occurred in 1989; (3) among the tributaries, the comprehensive drought severity was the heaviest in the DXJB, with an average MSDI value of –0.75; (4) based on the run theory and Copula model, the most serious drought event occurred from September 1988 to October 1990, with a drought severity of 33.36, a drought duration of 27 months, and a drought return period exceeding 50 years; and (5) the drought evolution was significantly influenced by abnormal atmospheric circulation factors, while ENSO had the largest influence on the drought variation in the XJB, followed by sunspot. [ABSTRACT FROM AUTHOR]

Abstract: Under the background of climate change, droughts have occurred widely and frequently in North China in recent years. Using tree-ring to study droughts has advantages such as accurate dating, strong continuity and high resolution. This paper uses the Chinese pine ring-width of Xiaowutai Mountain, China, to analyze the correlations between the ring-width and climatic factors. The results show that the standard and residual chronologies of Chinese pine have significant correlations between spring precipitation, 0 cm ground temperature in May, average relative humidity of April and May, hours of sunshine and percentage of sunshine in May, and Z index of spring. The Chinese pine ring-width is fundamentally affected by the precipitation of the study area. 0 cm ground temperature, average relative humidity and hours of sunshine all affect the ring-width by affecting the soil water content indirectly. The years when the Chinese pine ring-width index of Xiaowutai Mountain falls into 0–0.80 could indicate spring drought years. This paper has demonstrated the feasibility of applying tree-rings to study the spatial and temporal development of drought in the study area. [Copyright &y& Elsevier]

• A deep learning algorithm is used to build a comprehensive drought monitoring model. • Multi-source remote sensing data is processed as input data. • The comprehensive drought model has good applicability in the monitoring of meteorological drought and agricultural drought. • The model successfully monitored a drought process in Henan Province, China. • This study provides a new method for the comprehensive assessment of regional drought. Drought is a popular scientific issue in global climate change research. Accurate monitoring of drought has important implications for the sustainable development of regional agriculture in the context of increasingly complex global climate change. Deep learning is a widely used technique in the field of artificial intelligence. However, ongoing on drought monitoring using deep learning is relatively scarce. In this paper, the various hazard factors in drought development were comprehensively considered based on satellite data including Moderate Resolution Imaging Spectroradiometer (MODIS) and tropical rainfall measuring mission (TRMM) as multi-source remote sensing data. By using the deep learning technique, a comprehensive drought monitoring model was constructed and tested in Henan Province of China as an example. The results showed that the comprehensive drought model has good applicability in the monitoring of meteorological drought and agricultural drought. There was a significant positive correlation between the drought indicators of the model output and the comprehensive meteorological drought index (CI) measured at the site scale. The consistency rate of the drought grade of the two models was 85.6% and 79.8% for the training set and the test set, respectively. The correlation coefficient between the drought index of the model and the standard precipitation evapotranspiration index (SPEI) was between 0.772 and 0.910 (P < 0.01), which indicated a strong level of significance. The correlation coefficient between the drought index of the model and the soil relative moisture at a 10 cm depth was greater than 0.550 (P < 0.01), and there was a good correlation between them. This study provides a new method for the comprehensive assessment of regional drought. [ABSTRACT FROM AUTHOR]

Highlights • Few empirical studies investigate the role of forests in agricultural adaptation to climate change. • Whether the presence of forest cover near rice-producing villages can reduce the adverse effects of drought on rice yield is examined. • Natural forests and not planted forests near villages provide protection for rice against drought. • Forest cover enhances the availability of irrigation water in the form of protective role against drought. • Forest ecosystem-based adaptation (EBA) is relevant in coping with climate change and enhancing food security. Abstract Although the importance of forests in climate change mitigation has been widely recognized, there has been a lack of empirical research regarding the role of forests in agricultural adaptation to climate change. This paper uses a careful designed household survey in South China that considers an exogenous shock of drought, to determine whether the presence of natural and planted forests near rice-producing villages can reduce the adverse effects of drought on rice yield. After controlling for local climate and water infrastructure, we find robust evidence that natural forests and not planted forests have significant positive effects on rice yield, due to their influence on the availability of water for irrigation. Although drought hinders farmers' access to irrigation, which negatively affects rice yield, forests near villages provide protection for rice against drought. These findings support the adoption of forest ecosystem-based adaptation (EBA) to cope with climate change and enhance food security. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the relationship between flood/drought change in the Taihu Lake basin (TLB) and ENSO is investigated based on reconstructed flood/drought rank series (FD) and NINO-3.4 SST (DJF) data from 1857 to 2003. With the aid of empirical mode decomposition (EMD) method, the paper reveals that FD series and ENSO both contain strong inter-annual, decadal, multi-decadal and centennial signals, and have quite similar periodicities. The EMD method also obtains a monotonic trend for both series: the trend of FD series is upward, which suggests that flood trend is significant, and the trend of NINO-3.4 SST is also upward showing an increase of El Nino events. Continuous wavelet transform obtains similar oscillations for FD and NINO-3.4 SST series with those of EMD method. The results of cross wavelet and wavelet coherence suggest that there was stable in-phase relation between FD and NINO-3.4 SST from 1857 to 1950s, while this in-phase relation is not clear during recent decades. This conclusion is also verified by χ 2 test. These findings indicate weakening linkage between ENSO and flood/drought disasters in the TLB, which must be taken into account in the prediction of flood and drought disasters in the study area. [Copyright &y& Elsevier]

In this paper, 342 Landsat satellite images were used to study the evolution of the Qingshuigou and Qing8 Lobes during 1976–2016. Sea-level correction and statistical analysis were used to eliminate the effect of sea-level fluctuations on the shoreline positions. The results revealed that the evolution of the two newborn Huanghe Delta lobes was mainly influenced by the river sediment discharges, river channel changes, course shifts, floods, droughts, and marine hydrodynamic forces. During 1976–2016, the total land gain of the two lobes was 377 km 2 according to mean-tide line, and the average epeirogenetic efficiency of river sediment discharge was 0.020 m 2 /ton, which was greatly less than that when the channels were natural. The artificial stabilization of the deltaic channels had negative impact on the land gain. Assuming no artificial adjustment to the deltaic channels, the total land gain would increase 435 km 2 . The land gain of the two lobes was a function of the cumulative sediment discharges, shoreline lengths and Course Shift Bonuses under the circumstance of historical river channel changes. The critical sediment discharge maintaining the area balance of the two lobes was a function of historical shoreline lengths, which increased linearly from 61 M ton in 1976 to an average of 163 M ton during 1996–2016. In the future, there are two ways to increase the land gain under the less Huanghe sediment discharge: reducing artificial disturbance of deltaic channels and letting the river enter the sea through the southwest coast of Qingshuigou Lobe. [ABSTRACT FROM AUTHOR]

Regional precipitation patterns may change in a warmer climate, thereby increasing flood and drought risks. In this paper, annual, annual maximum, intense, heavy, moderate, light, and trace precipitation are employed as indicators to assess changes in precipitation patterns under two scenarios in which the global mean temperature increases by 1.5 °C and 2.0 °C relative to pre-industrial levels using the regional climate model COSMO-CLM (CCLM). The results show that annual precipitation in China will be approximately 2.5% higher under 1.5 °C warming relative to the present-day baseline (1980–2009), although it will decrease by approximately 4.0% under an additional 0.5 °C increase in global mean temperature. This trend is spatially consistent for regions with annual precipitation of 400–800 mm, which has experienced a drying trend during the past half century; thus, limiting global warming to 1.5 °C may mitigate these drying conditions. The annual maximum precipitation continues to increase from present day levels to the 2.0 °C warming scenario. Relative to the baseline period, the frequency of trace and light precipitation days exhibits a negative trend, while that of moderate, heavy, and intense precipitation days has a positive trend under the 1.5 °C warming scenario. For the 2.0 °C warming world, the frequency of days is projected to decrease for all precipitation categories, although the intensity of intense precipitation increases. Spatially, a decrease in the number of precipitation days is expected to continue in central and northern China, where a drying trend has persisted over the past half century. Southeastern China, which already suffers greatly from flooding, is expected to face more heavy and intense precipitation with an additional 0.5 °C increase in global mean temperature. Meanwhile, the intensity of intense precipitation is expected to increase in northern China, and the contribution of light and moderate precipitation to the annual precipitation is expected to decrease in southeastern China. Therefore, flood risk in northern China and drought risk in southern China should draw more attention for a global air temperature increase from 1.5 °C to 2.0 °C. [ABSTRACT FROM AUTHOR]

Using a qualitative social research method at the local administrative level, this paper provides insight into the policy process in China and farmers’ perceptions of the effectiveness of policies implemented to deal with drought. Two villages in rural South-West Yunnan were purposefully selected for the study. The research started with the general assumption that China has a strong top-down hierarchal approach to policy processes and that funding dispersal is prioritised by the central government. However, the study found that funding proposals are prioritised for selection in a bottom-up, participatory manner from the local level. The study also found that farmers’ perceptions of the effectiveness of policy implementation were directly related to their past experience. Among the nine indicators used to measure the effectiveness of policy implementation at the local level, the farmers in the study area perceived access to roads as highly effective; water use efficiency projects, market demand, human mobility for jobs, and government funds as moderately effective; drought knowledge, community participation in planning, and governance structures as least effective; and the role of leadership as not effective. The study found that farmers’ adaptation at the local level is oriented towards short-term market rewards and income diversification. Farmers’ local-level adaptation is guided by government priorities and driven by their perception of tangible benefits. To ensure the effectiveness of policy implementation, long-term adaptation strategies, such as awareness raising, capacity building, watershed management, and source conservation need to be strengthened at the local level. [ABSTRACT FROM AUTHOR]

Basin response to precipitation variability by terrestrial hydrological processes may be manifested at different timescales and vary from one basin to another. A quantitative grasp of natural variability modulation is desirable for characterizing basin tendency or vulnerability on floods and droughts; quantification is not always straightforward, however. Using a macro-scale hydrological model, the Variable Infiltration Capacity (VIC) model, the hydrological time series (runoff, soil moisture, and evapotranspiration) were obtained for the 10 sub-basins over the Pearl River basin in South China for the period 1952–2000. A continuous wavelet transform was used to identify the characteristics of the temporal scales of basin-featured extreme events and related multiple-scale variabilities. By use of wavelet coherence analysis and rank correlation method, the cross correlations of monthly anomalies of hydrological processes were examined. The results showed that the runoff correlated most with, and the evapotranspiration had less response to, the precipitation variability. The analyzed results revealed that the attenuation effect of runoff in response to precipitation variability was mainly within the timescale of 2 yr in the Pearl River basin. The soil moisture variability can extend precipitation variation along with timescales. With understanding of the variability features of the terrestrial hydrological processes, this paper showed one geomorphic index, a basin form factor (FF), can represent the wavelet-based indices for high- and low-frequency responses to precipitation variability. It was found that, for a sub-basin with a higher FF value, precipitation variability can be represented more by runoff variability at less than 2-yr timescales; such a sub-basin is apt to have serious floods. With a lower FF value, a sub-basin has longer memory of soil moisture, leading to severe droughts during dry periods. This finding would be valuable to evaluate the tendency on occurrence of floods and droughts in the Pearl River basin, a humid region, which may be transferable to other basins in the globe. [ABSTRACT FROM AUTHOR]

• The standardized precipitation evapotranspiration index (SPEI) was reconstructed into the Frank copula-based one (SPEI C). • The SPEI C compensated SPEI for the lack of assessment mechanism of the feedback of the water vapor cycle. • The SPEI C 's parameters were calibrated in China, the spatiotemporal distributions of which were analyzed. • The SPEI C was more sensitive in detecting the drought frequency but minor in detecting the drought severity than SPEI. The standardized precipitation evapotranspiration index (SPEI) lacks the assessment mechanism for the coupling relationship between the magnitudes of the precipitation (P), potential evapotranspiration (ET P), and water deficit, making it hard to predict the drought precisely. This paper selected the marginal and joint cumulative distribution functions (CDF) of P and − ET P to present their magnitudes and water deficit, respectively. We formatted the Frank copula-based SPEI (SPEI C) to combine the marginal CDFs at 3, 6, 9, and 12-month scales. It indicated that the two-parameter Gamma distribution was the best-fitted marginal CDFs of the P (CDF P) and − ET P (CDF –ETP). The CDF P exerted a slightly more significant marginal effect on the joint CDF than the CDF –ETP at 6 to 12-month scales, indicated by the steeper slope of the CDF P 's marginal curves vs joint CDF. The verified more significant marginal effect denied the implied assumption of the same marginal effects of the P and − ET P using SPEI. The new-constructed SPEI C temporally fluctuated highly consistent with the SPEI in the whole, energy- and water-limited regions of China, indicated by the higher 3 to 12-month-averaged Nash-Sutcliffe efficiency coefficient ≥ 0.63 and determination coefficient ≥ 0.75. The SPEI C had a more sensitive detectivity of the drought frequency, indicated by more events detected. Besides, it had a minor sensitive detectivity of the drought severity, indicated by the larger SPEI C under the same specified frequencies of the P and − ET P. [ABSTRACT FROM AUTHOR]

Due to the national nutrition crisis and the adjustment of planting structure, millet has once again become a widely planted cash crop in Northern China. However, as the climate warms in recent years, drought has occurred frequently and repeatedly in Northern China, which has seriously threatened millet production safety in this area. Therefore, it is urgent to clarify the hazard of millet drought disaster and provide reference for the formulation of millet disaster prevention and reduction measures. In this paper, combined with the water demand of millet in each growth period, Standardized Precipitation Requirement Index (SPRI) was selected to identify and quantify the drought disaster of millet. Considering the impact of different degrees of drought in different growth periods, a hazard assessment model is constructed to evaluate the hazard of millet drought disaster in Northern China under the background of climate change. The results show that: (1) SPRI can well characterize the drought of millet in Northern China. (2) In the context of climate change, millet drought in Northern China shows a trend of increasing intensity and decreasing frequency, and it is possible that millet drought will be even more severe in the future. (3) Combined with the hazard assessment model, millet drought in Northern China will still be dominated by middle hazard in the future, but the areas with high hazard will gradually increase, mainly distributed in northeast China, central and western Inner Mongolia and northern Gansu. The research results can be of great practical significance for the adjustment of agricultural production structure in the future, especially for the sustainable development of agriculture and the formulation of measures to prevent and resist agricultural disasters. [Display omitted] • We apply SPRI to identify millet drought by considering actual water demand. • Future changes of millet drought evaluated by CMIP6-GCM models. • Hazard assessment model was presented combined with disaster loss coefficient. • The areas with high hazard of millet drought will gradually increase in future. [ABSTRACT FROM AUTHOR]

To effectively meet growing food demands, the global agronomic community will require a better understanding of factors that are currently limiting crop yields and where production can be viably expanded with minimal environmental consequences. Remote sensing can inform these analyses, providing valuable spatiotemporal information about yield-limiting moisture conditions and crop response under current climate conditions. In this paper we study correlations for the period 2003–2013 between yield estimates for major crops grown in Brazil and the Evaporative Stress Index (ESI) – an indicator of agricultural drought that describes anomalies in the actual/reference evapotranspiration (ET) ratio, retrieved using remotely sensed inputs of land surface temperature (LST) and leaf area index (LAI). The strength and timing of peak ESI-yield correlations are compared with results using remotely sensed anomalies in water supply (rainfall from the Tropical Rainfall Mapping Mission; TRMM) and biomass accumulation (LAI from the Moderate Resolution Imaging Spectroradiometer; MODIS). Correlation patterns were generally similar between all indices, both spatially and temporally, with the strongest correlations found in the south and northeast where severe flash droughts have occurred over the past decade, and where yield variability was the highest. Peak correlations tended to occur during sensitive crop growth stages. At the state scale, the ESI provided higher yield correlations for most crops and regions in comparison with TRMM and LAI anomalies. Using finer scale yield estimates reported at the municipality level, ESI correlations with soybean yields peaked higher and earlier by 10 to 25 days in comparison to TRMM and LAI, respectively. In most states, TRMM peak correlations were marginally higher on average with municipality-level annual corn yield estimates, although these estimates do not distinguish between primary and late season harvests. A notable exception occurred in the northeastern state of Bahia, where the ESI better captured effects of rapid cycling of moisture conditions on corn yields during a series of flash drought events. The results demonstrate that for monitoring agricultural drought in Brazil, value is added by combining LAI with LST indicators within a physically based model of crop water use. [ABSTRACT FROM AUTHOR]

Summary Investigation of drought structure in terms of drought onset, termination, and their transition periods as well as drought duration helps to gain a better understanding of drought regime and to establish a reliable drought early warning system. In this study, a Nonparametric Multivariate Standardized Drought Index (NMSDI) combining the information of precipitation and streamflow was introduced to investigate the spatial and temporal characteristics of drought structure in the Yellow River basin (YRB). Furthermore, the correlations between the El Niño-Southern Oscillation (ENSO) events and NMSDI variations were explored using the cross wavelet technique. The results showed that (1) The variations of NMSDI were consistent with those of 6-month SPI (Standardized Precipitation Index) and SSFI (Standardized Streamflow Index), indicating that the proposed nonparametric multivariate drought index was reliable and effective in characterizing droughts. (2) The preferred seasons of drought onset were spring and summer, and winter was the preferred season of drought recovery in the YRB. The long-term average drought duration in the whole basin was nearly 5.8 months, which was clearly longer than the average drought onset and termination transition periods. (3) Overall, the drought structure in terms of drought duration, onset and termination transition periods in the YRB remained stable, and no appreciable change trend was found. (4) ENSO events exhibited a statistically negative correlation with NMSDI variations, suggesting that they showed strong impacts on drought evolutions in the YRB. Although the YRB was selected as a case study in this paper, the approach/indicator can be applied in other regions as well. [ABSTRACT FROM AUTHOR]

Droughts resulting from global warming severely hamper the healthy development of terrestrial vegetation ecosystems. This paper defines a terrestrial vegetation ecological drought index, i.e., the Standardized Water Supply–Demand Index (SSDI), based on the water balance method using the same calculation model as the SPEI. The theory of run is used to analyze the spatial and temporal distribution of the drought characteristics in the Yangtze River Basin (YRB). The results show that (1) the drought events monitored by the SSDI were in good agreement with historical drought events, and the correlation coefficient between SSDI and NDVI (0.94) was significantly higher than that between SPEI and NDVI (0.88). (2) About 55.4% of the regions in the YRB experienced more than 13 droughts, and about 41.4% of the regions had an average drought duration of more than 3.1 months. In the northern part of the YRB, droughts tend to develop in a short-term high frequency, while in the southern part of the YRB, there is a long-term low-frequency development trend. Nearly 24.5% of the regions have an average drought intensity of more than 1.4, and most of them are located in the lower reaches of the Yangtze River. (3) Over the last 18 years, about 79.5% of the regions in the YRB showed an increasing trend in SSDI, of which 36.8% showed an increasing trend of more than 0.04/yr. In addition, 40.4% of the regions showed a significant upward trend. Precisely analyzing the spatiotemporal variation of drought characteristics in the YRB is critical for drought risk assessment and sustainable development of water resources and could provide a theoretical basis for effective water resource allocation and drought relief. • A new drought monitoring index, i.e., the Standardized Water Supply–Demand Index (SSDI) was defined. • SSDI can effectively monitor drought events. • SSDI is more suitable for monitoring ecological drought. • Drought of vegetation ecosystem in the Yangtze River Basin was assessed and analyzed with the SSDI. • It provides a theoretical basis for drought management and water allocation in the Yangtze River Basin. [ABSTRACT FROM AUTHOR]

• The relationship between the groundwater depth and grassland ecology was analysed; • Groundwater depth affected the composition and diversity of vegetation species; • A reasonable groundwater depth can buffer the impact of climate change on the vegetation to maintain grassland ecological stability; • The control of grassland degradation should include the potential exploitation of groundwater. Grassland degradation in the semiarid area of China is often attributed to overgrazing and expansion of irrigated agriculture without the consideration of groundwater. However, falling groundwater levels in the region have caused many problems for grassland ecology. In this paper,the typical sandy grassland- the Tongliao part of Horqin grassland was selected as the study area to study the spatial distribution of normalized difference vegetation index (NDVI) and the relationship between the NDVI and groundwater depth (GD) of each grassland pixel was studied. The temporal variation of the NDVI and its correlations with precipitation were investigated. The relationship between GD and vegetation species diversity in grassland was analyzed based on the vegetation survey. The results of the relation between GD and NDVI and vegetation species showed that GD can buffer the impact of increase in drought events on the vegetation because GD affected the composition and diversity of vegetation species. As the GD increases, the mean NDVI showed a trend of increasing first and then decreasing, and basically remained unchanged when the GD was greater than 3.5 m. The species diversity of grassland decreased with increasing GD and was not related to GD when GD was greater than 3.5 ∼ 4 m. Falling groundwater levels will cause great changes in the structure of grassland; specifically, azonal vegetation will gradually die and 3.5 m may be the critical GD needed to maintain the incomplete extinction of grassland azonal vegetation in the aeolian sandy soil. Correlation analysis proved that the correlation between NDVI and precipitation was significantly enhanced when GD increased sharply from 3 m to 6 m after 1999. This research indicates that the control of grassland degradation should pay attention to controlling the groundwater exploitation to recover a reasonable groundwater level, which was found to be necessary in the support of diverse and climate resilient of vegetation. [ABSTRACT FROM AUTHOR]

• Precipitation deficit 2020 over southeastern China results from anomalously persistent WPSH and weak cold air intrusion. • Anthropogenic aerosol effects have decreased precipitation and increased drought occurrences. • Anthropogenic impacts on the intensity, duration, and severity of drought are not detectable. Southeastern China experienced a drying trend and the precipitation deficit in 2020 exerts great stress to the water supply and the environment. This paper analyzed the large-scale climate patterns relating to the precipitation deficit in 2020 and attribute the decreasing precipitation and drought over southeastern China based on observations and large GCM ensembles, including HadGEM3-GA6 and CESM LENS single forcing simulations. Results show that the precipitation deficit in 2020 mostly results from the anomalously persistent WPSH over South China and a lack of cold air intrusion to South China, and it is also associated with the La Niña-like Pacific. Detection analyses show that anthropogenic influences have resulted in decreasing precipitation. The aerosol emissions, including industrial aerosols (AER) and biomass burning aerosols (BMB), have substantially decreased precipitation over southeastern China, while the greenhouse gas emissions (GHG) have slightly increased precipitation. Because the AER and BMB effects of decreasing precipitation are larger than the GHG effects of increasing precipitation, precipitation shows a decreasing trend in recent decades. However, as the aerosols emission from industry and biomass burning decreases, the AER and BMB effects of decreasing precipitation will be reduced. Future precipitation over southeastern China is projected to increase due to the GHG effects of increasing precipitation. There were AER and BMB impacts on occurrences of drought over southeastern China, but the anthropogenic GHG impacts on the intensity, duration, and severity of drought are not detectable. [ABSTRACT FROM AUTHOR]

Timely and accurate monitoring of the onset and evolution of drought in China are important to reduce losses from drought. The Integrated Surface Drought Index (ISDI) which originally established in mideast China shows a large potential for real-time regional drought monitoring. However, ISDI is still at the developmental stage, and the applicability of the index requires further examination especially for China with vast area, climatic conditions, complex topography, and land cover. Furthermore, ISDI model depends on the historical training data corresponding to the study area. ISDI application in China must be remodeled using the historical training data over China. In this paper, we remodeled ISDI over China based on previous work and evaluated its capability for near real-time drought monitoring. Using the Palmer Drought Severity Index (PDSI) as a dependent variable, ISDI integrates climate-based drought indices, satellite-based Vegetation Index (VI) and land surface temperature (LST) with other biophysical and elevation data to produce a 1-km regional drought condition map at 16-day intervals. Strong relationships were determined between the calculated ISDI and PDSI for spring, summer and autumn, and all of the correlation coefficients exceeded 0.8. The initial ISDI results demonstrated a good performance for monitoring droughts in southwestern China from 2009 to 2010, high temperatures and droughts in southern China in 2013, and floods in northeastern China in 2013. The higher spatial resolution and near real-time capability of ISDI can provide important inputs for drought management and mitigation in China. [ABSTRACT FROM AUTHOR]

• Optimal GAMLSS models were selected by meteorological and anthropogenic covariates. • A nonstationary SRI was proposed for a coupled human-water system. • NSRI excels in accuracy and recall, showing an advantage in drought recognition. Significant nonstationarity of hydrological sequences, driven by the coupled influence of climate change and anthropogenic activities, has challenged traditional hydrological drought analysis under the stationarity assumption in some regions, and has questioned regional hydrological drought analysis under the changing environment. To evaluate hydrological drought characteristics, the novelty of this paper is the proposition of a GAMLSS (Generalized Additive Models for Location, Scale, and Shape)-based nonstationary standardized runoff index (NSRI), considering climate change and anthropogenic influence, for investigating the hydrological drought regime in the Wuding River basin. To that end, nonstationary test methods were performed on hydrological sequences, and data was segmented into three parts according to the results of the Pettitt test. A nonstationary probability distribution was fitted to runoff data with meteorological covariates (precipitation, temperature) and anthropogenic covariates (water consumption for social development demand, and water consumption triggered by water impounding by check dams). After selecting an optimal combination of covariates, the NSRI was calculated utilizing the GAMLSS model. A newly constructed evaluation threshold was proposed, based on the traditional SRI threshold. The performance of SRI and NSRI were compared at the Dingjiagou station in the Wuding River basin. Results of comparison between index identification and recorded drought events demonstrated that the NSRI better performed in drought event identification. Moreover, the NSRI identified more frequent severe droughts and extreme droughts. Therefore, the proposed NSRI provided a more accurate basis for the identification of drought events, which can offer valuable information for drought planning, preparedness, and mitigation. [ABSTRACT FROM AUTHOR]

Abstract: This paper quantifies the contribution of climatic factors to potential evapotranspiration (ET0) under different drought periods by making use of the FAO Penman–Monteith method, linear regression analysis, Mann–Kendall test, and the drought classification derived from the Standardized Precipitation Index (SPI). ET0 and meteorological data from 93 North China weather stations from 1961 to 2010 located in a semi-arid climate zone were analyzed. The annual ET0 values showed a significantly increasing trend with the aggravation of drought. Results indicated that in drought periods, temperature and sunshine hours had positive effects on the variation of ET0, while other key climatic factors (i.e. effective precipitation, vapor pressure, wind speed, relative humidity) had negative effects on ET0. ET0 was most sensitive to effective precipitation and mean daily temperature, with sensitivity rates of −4.163 and 1.368 respectively. The sensitivities of ET0 decreased over time in the drought period, which was caused by the joint effects of the climatic factors. The decreasing sensitivity of wind speed and relative humidity increased the ET0, and the increase of daily temperature produced the majority of rise in ET0 rates. The decrease of wind speed and relative humidity resulted in positive contributions to ET0. The increase in the sensitivity of precipitation and vapor pressure resulted in strongly decreased ET0, and the decrease of sunshine hours resulted in little change in ET0 rates. [Copyright &y& Elsevier]

Abstract: Crop models often simulate drought impacts with full and no irrigation scenarios, while planners are more interested in whether the current available irrigation water can cope with the future more serious droughts. This paper addresses a key constraint common to modeling studies: the limited representation of actual irrigation water supply. We present a data-driven approach to identify a benchmark for agronomic drought risk levels as defined by water availability thresholds at the baseline climate (1980–2008) using reported crop yields, climate and irrigation statistics. Then, holding the current irrigation supplies, we adopted Bayesian formula to estimate magnitude of the future water availability and the associated probability of crops yields being decreased to rainfall-deficiency under climate conditions in 2030s (2020–2040) based on the RegCM3 climate model output driven by IPCC SRES A1B scenario. Results reveal that future drought stress would overwhelm the irrigation capacity of current supplies in northern and western China, while drought remains at baseline climate levels in the central, eastern and southern regions. The largest increases in the probability of projected drought risk were in northeast and southwest, ranging from 14% to 28% above baseline climate. Regional drought impacts for grain self sufficiency are discussed. [Copyright &y& Elsevier]

Accurately monitoring the temporal, spatial distribution and severity of agricultural drought is an effective means to reduce the farmers’ losses. Based on the concept of the new drought index called VegDRI, this paper established a new method, named the Integrated Surface Drought Index (ISDI). In this method, the Palmer Drought Severity Index (PDSI) was selected as the dependent variable; for the independent variables, 12 different combinations of 14 factors were examined, including the traditional climate-based drought indicators, satellite-derived vegetation indices, and other biophysical variables. The final model was established by fully describing drought properties with the smaller average error (relative error) and larger correlation coefficients. The ISDI can be used not only to monitor the main drought features, including precipitation anomalies and vegetation growth conditions but also to indicate the earth surface thermal and water content properties by incorporating temperature information. Then, the ISDI was used for drought monitoring from 2000 to 2009 in mid-eastern China. The results for 2006 (a typical dry year) demonstrate the effectiveness and capability of the ISDI for monitoring drought on both the large and the local scales. Additionally, the multiyear ISDI monitoring results were compared with the actual drought intensity using the agro-meteorological disaster data recorded at the agro-meteorological sites. The investigation results indicated that the ISDI confers advantages in the accuracy and spatial resolution for monitoring drought and has significant potential for drought identification in China. [ABSTRACT FROM AUTHOR]

Drought is a complex hazard caused by the breaking of water balance and it has always an impact on agricultural, ecological and socio-economic spheres. Although the drought indices deriving from remote sensing data have been used to monitor meteorological or agricultural drought, there are no indices that can suitably reflect the comprehensive information of drought from meteorological to agricultural aspects. In this paper, the synthesized drought index (SDI) is defined as a principal component of vegetation condition index (VCI), temperature condition index (TCI) and precipitation condition index (PCI). SDI integrates multi-source remote sensing data from moderate resolution imaging spectroradiometer (MODIS) and tropical rainfall measuring mission (TRMM) and it synthesizes precipitation deficits, soil thermal stress and vegetation growth status in drought process. Therefore, this method is favorable to monitor the comprehensive drought. In our research, a heavy drought process was accurately explored using SDI in Shandong province, China from 2010 to 2011. Finally, a validation was implemented and its results show that SDI is not only strongly correlated with 3-month scales standardized precipitation index (SPI3), but also with variation of crop yield and drought-affected crop areas. It was proved that this index is a comprehensive drought monitoring indicator and it can contain not only the meteorological drought information but also it can reflect the drought influence on agriculture. [ABSTRACT FROM AUTHOR]

Abstract: Water disaster is always one of the most serious natural disasters in China. The greatest social losses and threat is from water disasters, especially floods and droughts. In this background, this paper does a literature research, which aims to give a whole research status at abroad and home. Finally, it will do literature evaluation about the literature review. [Copyright &y& Elsevier]

Abstract: Based on the tree rings of Qilian juniper (Juniperus przewalskii), this paper presents a Palmer Drought Severity Index (PDSI) reconstruction (r = 0.578, p < 0.01) since AD 1411 for the northeastern Tibetan Plateau (TP). Regional extreme dry years (<2SD) were found in 1451, 1455, 1480, 1488, 1490, 1591, 1649, 1770, 1776, 1824, 1831, 1879, 1922, 1927 and 1992, while extreme wet years (≥2SD) were not observed. Persistent decadal dry intervals were observed in the 1450s, 1480s, 1510s, 1580s–90s, 1680s–1720s, 1820s–40s, 1920s–30s and after 1990s, and decadal wet intervals in the 1410s, 1500s, 1540s–50s, 1610s–70s, 1750s–60s, 1790s–1800s, 1880s–1910s, 1960s–80s. Regional droughts evident in the reconstruction appear to be relatively consistent with the drought history of the entire arid northeastern TP to the north indicated by previous studies. Spectral peaks of 2.1–5.9 years may be indicative of ENSO and IOD activity, as also suggested by negative correlations with SSTs in the eastern equatorial and southeastern Pacific Ocean and the northern Indian Ocean. Significant multi-decadal spectral peaks of 31.1–36.6 years and 41–53.8 years were identified and indicated that the decadal-scale variability may be linked to SST variations in the northern Pacific and Atlantic Oceans. [Copyright &y& Elsevier]

Abstract: This paper presents a drought reconstruction for the eastern Qilian Mountains based on a tree-ring width chronology developed from three sites of the Qinghai spruce (Picea crassifolia Kom.). The drought reconstruction, spanning the years 1856–2009, was developed by calibrating tree-ring data with the regional averaged Palmer Drought Severity Index (PDSI). The reconstruction explains 49.9% of the actual PDSI variance during the calibration period from 1951 to 2005. The reconstruction shows droughts occurred in the 1900s, the 1920s and early 1930s, and at the turn of the 21st century. Multi-taper method spectral analysis indicates the existence of some significant peaks at 2.6, 4.2 and 56.9 years. Drought variations in the study area are significantly correlated with sea surface temperatures in eastern equatorial Pacific Ocean, northern Indian Ocean, eastern China Sea and the Atlantic Ocean, suggesting a possible connection with the El Niño-Southern Oscillation, the Asian monsoon and the Westerlies. [Copyright &y& Elsevier]

Abstract: Drought is a recurring phenomenon in north-central China. Long-term information about the history of drought is still limited because the instrumental records for many areas in north-central China go back only a few decades at best. This paper presents an earlywood width (EWW) chronology of Chinese pine (Pinus tabulaeformis) in the Shimen Mountains, Tianshui, eastern Gansu, north-central China. The climate-response analysis shows that April–July precipitation is the main factor limiting the earlywood growth of Chinese pines in the Shimen Mountains, Tianshui. Based on the EWW chronology, an April–July precipitation reconstruction for the period A.D. 1629–2008 was developed for Tianshui. The climate/tree-growth model accounts for 41.6% of the observed precipitation variance during the period 1953–2008. Spatial analysis shows that the precipitation reconstruction contains a strong common drought signal for north-central China. Reconstructed drought events are compared to a precipitation reconstruction of Huashan and historical archives for north-central China. The results reveal common climatic extremes over much of north-central China. Moreover, some dry periods coincided with solar minima or volcanic eruptions over the past several hundred years. Multi-taper spectral analysis reveals the existence of significant 3.8-year (90%), 3.1-year (95%), 2.7-year (99%), 2.4-year (99%) and 2.0-year (99%) periods of variability. The linkages to the Asian-Pacific Oscillation Index suggest regional precipitation variations may be linked to the East Asian summer monsoon circulations. [Copyright &y& Elsevier]

Abstract: MODIS sensor has a high temporal resolution, spectral resolution, and moderate spatial resolution. The data products are widely used in Large-scale and long period dynamic monitoring of drought. This paper focuses on characters of farming rice dominated in Jiangxi province, and analysis on remote sensing monitoring model and drought monitoring indicators which selection the MODIS data products and drought information related from 2000-2008. Established standard for classification of drought in Jiangxi province, and verified instances of 2003 drought in Jiangxi. This study may have a certain significance to agricultural drought monitoring based on rice planting in southern China, because the correspondencematch between the selected TD indices and cloud cover with precipitation and daily maximum temperature evolution curve. [Copyright &y& Elsevier]

Abstract: Desiccation of the Tarim River is increasingly severe, as shown by the increases in length affected and time of desiccation. If the tendency is not constrained, the difficulty in water transfer to the lower reach of the Tarim River will be greatly increased, and the ecological security in the river basin and the downstream “Green Corridor” protection will be severely impacted. This paper analyses the desiccation tendency and hydrological regime of the Tarim River, discusses the causes of this condition, the point of zero flow movement, and the influence on the ecological security in the Tarim River basin that may be caused by the further development of desiccation. The relationship between soil and water resource management and hydrological regime change in the Tarim River basin and river desiccation is analyzed. The main causes of the river desiccation were the increase in irrigated area of the headstream section in the upstream region, the rise in water consumption in the upper and middle reaches, and the construction of reservoirs in the mountain areas. Accordingly, possible countermeasures and ideas for mitigating the desiccation tendency are suggested, so as to provide decision-making references for water resource management and sustainable and healthy social, ecological and economic development in the Tarim River basin. [Copyright &y& Elsevier]

Abstract: Designing scientifically drought vulnerability evaluation index system has great meaning to the quantitative analysis of drought vulnerability, vulnerability zoning of drought and drought risk management. This article takes seven counties of Xiaogan city in Hubei Province as the case study area, screens out 17 factors which closely related to drought vulnerability as evaluation index mainly from a socio-economic perspective, applies AHP to determine the weights of various relevant factors in the evaluation index, and then uses the fuzzy comprehensive evaluation method to achieve a drought vulnerability assessment. The results show that the overall level of drought vulnerability degree in Xiaogan City is high, in which Dawu County and Xiaochang County have the highest level of vulnerability. Accordingly, the paper brings forward the policy recommendations, including: diversifying peasants’ income channels, increasing non-agricultural income and reducing the dependence on agriculture; improving government''s risk management capacity and establishing drought emergency management programs; developing rural micro-credit capital markets and a variety of intermediary organizations. This article aims to make references to the study and practice of drought vulnerability evaluation. [Copyright &y& Elsevier]

• An observation-based natural and human-impacted catchment comparison method is proposed. • Human influence are quantified based on gridded socio-economic and land use data. • Climatic and anthropogenic influences on drought propagation are investigated. • Climate change accelerates the response of hydrological drought to meteorological drought. • Human activities delay the propagation from meteorological to hydrological drought. It is crucial to investigate how a precipitation deficit is transformed into hydrological drought and how climate change and human activities affect this transformation process, which is helpful to gain a deep understanding of drought propagation process in this changing environment. This study proposed an observation-based natural and human-impacted catchment comparison method to assess the impacts of climate change and human activities on propagation from meteorological drought to hydrological drought. The method mainly consists of the following three steps: (1) selection of natural catchments through analysis of trends and change points of hydro-meteorological data, as well as statistics analysis of human influence based on land use and socio-economic indicators data sets; (2) calculation of drought propagation characteristics (e.g., drought severity, duration, and propagation time) based on run theory and the Pearson correlation coefficient; and (3) comparison of drought propagation characteristics of natural catchments between undisturbed and disturbed periods to identify the impacts of climate change on drought propagation, and comparison of the propagation characteristics between natural and human-impacted catchments during the disturbed period to investigate human influence on drought propagation. The Laohahe basin (with eleven sub-catchments), located in northern China, was evaluated via the proposed procedure, and standardized precipitation index (SPI) and standardized runoff index (SRI) were used to characterize meteorological and hydrological droughts, respectively. The results demonstrate that the proposed method is suitable tool for distinguishing natural and human-impacted catchments, and separating the impacts of climate change and human activities on drought propagation. Furthermore, the comparison results of different schemes show that climate change accelerates the propagation from meteorological drought to hydrological drought in the Laohahe basin, shortening it by approximately 3 months. Human activities, however, disturb and then delay the natural propagation from meteorological drought to hydrological drought, retarding it by 11–12 months. Although the Laohahe basin was selected as a case study in this paper, the proposed method can be applied in other regions as well to improve drought prediction and water resources management. [ABSTRACT FROM AUTHOR]

• China's drought risk, the severity and frequency have increased due to climate warming. • Droughts occurred year-round in China, but differed among years and regions. • Clarify the regional differences of drought disaster risk over the mainland of China. Drought is complex geographical elements, which endangers China's food security, with coexistence of spatial and temporal heterogeneity and similarity. Thus, the recent abnormal characteristics of Chinese droughts warrant further study. This paper proposes a three-step framework to identify the spatiotemporal evolution characteristics of drought events in China Mainland, using the standardized precipitation evapotranspiration index (SPEI) at different time scales (1, 6 and 12 months). And then the drought characteristics are separated using the run theory. Finally, the spatiotemporal evolution patterns of meteorological, agricultural and hydrological drought risk in distance are investigated based on the geographic statistics analysis method (i.e., global and local Moran's index). Results show that the drought trend is gradually increasing in some basins, especially the Yellow River Basin, the Hai River Basin and the Southwest River Basins. The multi-variate attributes of drought characteristics in spatiotemporal evolution patterns at different time scales have the characteristics of regularity and mutation, for example, the drought frequency in northwestern China shows a low values in a low value neighbourhood, but the drought duration and intensity shows a high values in a high value neighbourhood. This indicates that the hydrological drought disaster in the region is extremely prominent. In addition, the risk of drought in inland River basins is the highest, followed by the Hai River basin and the Yellow River basin; the Pearl River basin has the lowest. Our results offer insights into the development of drought in China and provide support for disaster risk assessment and response planning. [ABSTRACT FROM AUTHOR]

Abstract: The institutional evolution is often induced by some factors. This paper intends to analyze the affecting factors in integrated urban and rural water affairs management reform in China. The integrated urban and rural water affairs management reform is to restructure the governmental organizational setting in water management by forms of water affair bureau or re-designing functions of current water resources bureau to incorporate part or all functions of resources management, service regulation and environment management in water sector. The analyses selected some natural and socio-economic factors. The results point out that the integrated urban and rural water affairs management reform is a factor-induced institutional evolution. The factors promoting this reform include occasional drought events, higher central water investment percentage; but the data from the urban sector do not provide the support to the reform. [Copyright &y& Elsevier]

• Sustainability index based on the RRV concept was adopted to evaluate drought. • CA-Markov was adopted to predict future drought. • The spatio-temporal variability and trends of drought in China was studied. Drought threatens both social and economic development, and it is necessary to develop a comprehensive drought index and a method of predicting future drought occurrence to enable effective associated management and warnings. However, barring a few, current drought indexes are not comprehensive; for example, they ignore the ability to recover from drought, and drought prediction does not consider spatial and temporal characteristics. In this study, the Sustainability Index (SI), which considers reliability, resilience, and vulnerability, was used to identify agricultural drought, and the Cellular Automata-Markov (CA-Markov) was used in drought prediction. In order to reflect the characteristics of crop water deficit in agricultural drought, this paper uses the Permanent Wilting Point (PWP) as the threshold; droughts are defined as soil moisture < PWP. The results of SI from 1951 to 2015 in China showed that the drought was most severe in the western Northwest (WNW) region; the drought was mild in the South (S), Southwest (SW), and Tibet regions; and the drought was relatively severe in the North (N), eastern Northwest (ENW), and Northeast (NE) regions. The Mann-Kendall test was used to characterize SI trends over the past 65 years. Drought in the northern WNW and Tibet regions significantly improved, whereas that in the southern SW, N, and eastern NE regions intensified. The prediction of drought occurrence for 2016–2020 and 2021–2025 using the CA-Markov showed that overall drought in China will be alleviated. The SI and CA-Markov adopted in this study could be used in the identification and prediction of agricultural drought or other drought categories, and could be used in local drought management. [ABSTRACT FROM AUTHOR]

In the context of global climate change, droughts pose a serious threat to agricultural development and food security. Assessing the vulnerability and risk of regions to drought is important for its prevention. In this paper, to understand the vulnerability of maize to drought in different regions of China and quantify its risk, 241 prefecture-level administrative regions (including prefecture-level cities, autonomous prefectures, prefectures, and leagues) in the five main maize-growing regions of China are used as study area. By using a method of global sensitivity analysis, the extended Fourier amplitude sensitivity test (EFAST), we chose two parameters that are most sensitive to maize yield to calibrate the AquaCrop model. We then used it to simulate the water stress of maize in the study area under different irrigation scenarios as well as the corresponding production. We defined the drought hazard index (DHI) as the daily average of the crop water stress indicator during the growing season, and used it to describe the intensity of droughts. Vulnerability curves (the function of the DHI and rate of yield loss) of the entire growth season and various stages of growth were also formulated. These were used to determine the loss of maize yield under four levels of risk (return periods of 5, 10, 20, and 50 years). The results showed the following: 1) the vulnerability curve of maize for the entire growing season was consistent with logistic function, and the coefficient of determination of the equation of regression was R 2 = 0.93. The rate of yield loss began increasing rapidly once the DHI had reached 0.2 and approached its maximum value when the DHI was 0.6. 2) The coefficients of determination of the results of regression in 14 scenarios, in which drought had occurred in different stages of growth, were between 0.28 and 0.92. Drought from the tasseling stage to the milk stage had the most significant negative effect on the maize yield, followed by the seventh leaf stage to the tasseling stage and the sowing stage to the seventh leaf stage. Drought from the milk stage to physiological maturity had the least negative effect on the maize yield. 3) Under all four risk levels, the DHI and the yield loss rate of maize in China decreased from the northwest to the southeast. The Northwest Irrigated Maize Region had the highest drought risk among the five maize-growing regions, followed by the North Spring Maize Region, the Huang-Huai-Hai Summer Maize Region, the South Hilly Maize Region, and the Southwest Mountain Maize Region. 4) The DHI calculated by the average method was more representative than that calculated using the accumulative method. Unlabelled Image • A new drought hazard index was proposed for building drought loss curves. • Drought vulnerability curves were built for five main maize-growing regions in China. • Yield loss curves of maize were built for droughts occurred in various growth stages. • Risk of maize yield loss for return periods of 5, 10, 20, and 50 years were assessed. • The drought risk of maize in China decreases from northwest to southeast. [ABSTRACT FROM AUTHOR]

In this paper, future drought characteristics (frequency, duration and intensity) over China are analysed by using four climate models from CMIP6 under the seven SSP-RCP (shared socioeconomic pathway-representative concentration pathway) scenarios (SSP119, SSP126, SSP434, SSP245, SSP460, SSP370, and SSP585) for three defined periods of 2021–2040 (near-term), 2041–2060 (mid-term) and 2081–2100 (long-term). The corresponding four climate models output from CMIP5 are also used to conduct a comparison analysis between CMIP5 and CMIP6 to address the improvements added to CMIP6 in terms of drought identification. The drought characteristics are identified by applying the standardized precipitation-evapotranspiration index (SPEI) at a 12-month timescale and run theory. The results show that CMIP6 has a robust capability to capture historical (1986–2005) drought characteristics. For the future period of 2021–2040, the decrease in precipitation and increase in potential evapotranspiration will lead to continuous dry conditions in the upper and middle Yangtze River basin and eastern Pearl River basin. Relative to the reference period, drought events will be more frequent and severe with longer durations in the Northwest River basins and middle Yangtze River basin. Furthermore, higher emissions signify a greater increase in drought frequency and intensity in the long-term period. Except for the SSP585 scenario, the lower emission scenario corresponds to the higher drought duration soon and in the mid-21st century (2021–2060). This finding is regarded as a "strange phenomenon", which cannot be detected by the previous CMIP5-based emission scenarios (RCP2.6, RCP4.5 and the unlikely pathway RCP8.5). Therefore, additional "possible future"-based scenarios (SSP119, SSP126, SSP434, SSP245, SSP460, and SSP370) should be included in extreme climate studies, especially for the near future and mid-21st century. Notably, compared with CMIP5, the reduced biases in drought characteristics are more likely associated with improvements in the representation of physical processes in climate models from CMIP6. The results of this study could provide a basis for the development of drought adaptation measures over China. • Latest CMIP6 climate models and seven SSP-RCP scenarios are used to analyze the possible changes in droughts over China. • More robust projections will be presented by CMIP6 than CMIP5, due to the better representations in physical processes. • The higher emission signifies shorter drought duration, lower precipitation and PET in mid-21st century over China. [ABSTRACT FROM AUTHOR]

In this paper, we comprehensively evaluated the utility of integrated long-term satellite-based precipitation and evapotranspiration products for drought monitoring over mainland China. The latest Integrated Multi-satelliteE Retrievals for Global Precipitation Measurement V06 three Runs precipitation products, i.e., the near real-time Early Run (IMERG-E) and Late Run (IMERG-L) and the post-real time Final Run (IMERG-F), and the Global Land Evaporation Amsterdam Model V3.3a (GLEAM) potential evapotranspiration (PET) products from 2001 to 2017 were considered. The accuracy of IMERG precipitation and GLEAM PET products was first evaluated against observed precipitation and Penman-Monteith method estimated PET, respectively, based on dense meteorological station network. The Standard Precipitation Evapotranspiration Index (SPEI) calculated based on IMERG precipitation and GLEAM PET products (SPEIs, including SPEI E , SPEI L and SPEI F corresponding to IMERG-E, IMERG-L and IMERG-F, respectively) were then validated by using SPEI calculated based on meteorological data (SPEIm) at multiple temporal-spatial scales. Finally, four typical drought events were selected to analyse the ability of SPEIs to characterize the temporal-spatial evolution of drought situations. The results showed that the IMERG-F presents much better performance than IMERG-E and IMERG-L in terms of higher CC and smaller BIAS and RMSE values over mainland China. The GLEAM PET well simulated the change trend of reference PET, but generally underestimated reference PET in Northwest China (NW), Xinjiang (XJ) and Qinghai–Tibet plateau (TP). In general, the performances of SPEIs over eastern China and Southwest China (SW) were significantly superior to their performances in the NW, XJ, and TP regions. Even though the SPEI F performed the best, the SPEI E and SPEI L also performed reasonably well in some specific regions. SPEIs can well capture the temporal process and reasonably reflect the spatial characteristics for four typical drought events. It is thus highlighted that the latest IMERG precipitation (especially for IMERG-F) and GLEAM PET products could be used as alternative data sources for comprehensive drought monitoring, on account of the water balance principle over mainland China, particularly in eastern China and SW China. The outcomes of this study will provide valuable references for drought monitoring by integration of multi-source remote-sensing datasets in the GPM era. • The utility of integrated IMERG precipitation and GLEAM PET for drought monitoring was evaluated over mainland China. • SPEIs based on IMERG precipitation and GLEAM PET were validated at multiple spatial and temporal scales over mainland China. • IMERG precipitation and GLEAM PET show great potential for drought monitoring over eastern China and Southwest China. • SPEIs can well capture the temporal process and reasonably reflect the spatial characteristics for typical drought events. [ABSTRACT FROM AUTHOR]

• A long series of highly accurate soil moisture data was combined. • SWDI was improved and extended to the monthly scaled drought index. • Temporal features of SWDI were characterized in four geographical regions. • The relationship among drought indexes (SPI, SWDI and VCI) was explored. Drought monitoring and assessment are of great importance due to the costly damage caused by drought. Datasets, drought indexes and drought relationships are three critical areas of drought research. Satellite-retrieved soil moisture (SM) products derived from the European Space Agency Climate Change Initiative (ESA CCI) show application potential in drought monitoring. However, the products are missing certain data in some areas. The model-assimilated SM product derived from the Global Land Data Assimilation System (GLDAS) was used to supplement these missing data. The main goals of this paper are to characterize agricultural drought after the utility and applicability of the combined SM product and the monthly scaled soil water deficit index (SWDI) have been evaluated and to investigate the relationships among meteorological, agricultural and vegetation droughts. First, we provided a long series of highly accurate SM products through simple calculations. The drought index, SWDI, was extended to a monthly scale for long-term drought analysis by using the combined SM product. The probability of detection (POD) between the SWDI and in situ drought records performed fairly well. Half of the 566 stations had PODs higher than 0.9, and one-third of these stations had POD values equal to 1. Through correlation analysis and grey incidence analysis (GIA) between the standardized precipitation index (SPI) and SWDI, we found that the propagation time from meteorological drought to agricultural drought was shorter under drier conditions than wetter conditions, and at the regional scale, the response time ranged from 1 month to 2.5 months. Correlation analysis between the SWDI and vegetation condition index (VCI) indicated that there was no delay effect from agricultural to vegetation drought on a monthly scale in most parts of China except in several provinces distributed in the South; additionally, there was a significant time lag in forests, while grassland and agriculture were more inclined to have no time lag or the response time was less than 1 month. [ABSTRACT FROM AUTHOR]

Unanticipated environmental shocks impact the livelihoods of many resource users around the world. These shocks are likely to be more unpredictable as the effects of climate change continue to mount. Yet how households adapt to these changing climatic conditions especially in the context of rapidly changing market conditions in most areas of the world, is poorly understood. These interactions have wide implications for both smallholder livelihoods and sustainable use of natural resources. In this paper, we examine the relationship between environmental shocks and stocking rates in livestock herds in the Inner Mongolian grasslands of northern China. We uniquely examine three types of shocks and how households adapt livestock production strategies in response to each. Separately and in aggregate, we look at three common shocks in Inner Mongolia: droughts, snowstorms, and locust outbreaks. We use a difference-in-differences approach to estimate changes in stocking rates among households that experience shocks versus those that do not with a panel dataset from 2009 to 2014 of 597 households. While we find no clear impact from locusts, our results suggest droughts and snowstorms have opposite effects: droughts are associated with increases in herd sizes, but snowstorms result in decreased herds. We suggest these differences are due to interactions between shocks, emerging options to borrow on credit, and livestock markets. Household adaptation to climate change will be strategic and take advantage of both available resources as well as market conditions. • Climate change is causing stronger and more unpredictable environmental shocks. • We use a difference-in-differences model to estimate the impact of shocks on stocking rate. • Drought relates to bigger herds; snowstorms relate to smaller herds. • Households adapt to shocks taking advantage of both available resources and market conditions. • Shaping well-functioning market may reduce opportunistic resource exploitation. [ABSTRACT FROM AUTHOR]

• A quantitative drought monitoring framework at field scales using ESTARFM between MODIS and Sentinel-2 has been developed. • The fused VTCI are better correlated with cumulative precipitation in winter wheat planting area in China. • The study shows that drought levels of winter wheat, woodland and bare land can be clearly separated and quantified. Time-series high spatial resolution drought monitoring is essential for effective agricultural management. For more than a decade, the multiyear vegetation temperature condition index (VTCI) based on the Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS) has been applied to regional drought monitoring. However, the spatial resolutions of AVHRR and MODIS (1 km) often represent mixtures of built-up areas and different vegetation or crop types. In this paper, a framework is proposed to obtain a ten-day interval multiyear VTCI at field scales, which is fused from Sentinel-2 data with a fine spatial resolution (20 m) and ten-day interval Terra MODIS data with a coarse spatial resolution using the Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model (ESTARFM). This framework includes the disaggregation of the Terra MODIS land surface temperature (LST) using Sentinel-2 data and digital elevation model (DEM) data, the spatiotemporal fusion of normalized difference vegetation index (NDVI) and LST, and drought monitoring by the fused VTCI. The accuracy of this framework for regional drought monitoring was tested in the Guanzhong Plain of China. The results indicate that 1) the Sentinel-2 biophysical products combined with DEM data based on support vector regression can accurately disaggregate the Terra MODIS LST; 2) the ESTARFM has good capability to fuse the NDVI and LST derived from Sentinel-2 and Terra MODIS; 3) the multiyear spatiotemporally fused VTCI, a quantitative drought monitoring index at field scales, can be calculated by using the linear regression between the single-year fused VTCI based on the data in 2018 and the multiyear Terra MODIS VTCI based on an 18-year data record; and 4) the spatiotemporal fusion of the multiyear VTCI can significantly improve the drought monitoring accuracy in the winter wheat and woodland area of the Guanzhong Plain. From mid-March to early May, the multiyear spatiotemporally fused VTCIs have better correlation with the cumulative precipitation over the past 20 days (R2 is 0.83 in the entire study area) than the multiyear Terra MODIS VTCIs (R2 is 0.80 in the entire study area). The results of this study demonstrate the potential of using the spatiotemporal fusion algorithm to obtain the multiyear VTCI at field scales and provide an effective method for improving the accuracy of drought monitoring. [ABSTRACT FROM AUTHOR]