Search

Understanding the components of water consumption plays a critical role in agricultural management in arid regions. This study aimed to analyze the characteristics of the components of the water consumption of winter wheat on the Loess Plateau in China to investigate their effects on yield and water use efficiency (WUE). Winter wheat observation data were collected from 1981 to 2020 at the Xifeng Agrometeorological Station on the Loess Plateau. The results show that over the past 40 years, the average water consumption of the winter wheat fields was 315 mm, but there were large differences between years. The soil water was first converted from precipitation (P) during the growing season, accounting for 69.4%, and then consumed via soil water storage (ΔW) in the fallow period, accounting for 30.6%. The yield of winter wheat varied from 1057 to 6914 kg·ha−1. The correlation between winter wheat yield and P during the growth period was stronger than the correlation between winter wheat yield and ΔW. The average WUE was 11.0 kg·ha−1·mm−1 from 1981 to 2020, with the highest value of 13.7 kg·ha−1·mm−1 occurring in the 2010s and the lowest value of 9.6 kg·ha−1·mm−1 occurring in the 2000s. The WUE was positively correlated with P (p < 0.01) during the growth period and negatively correlated with ΔW (p < 0.05). Therefore, P can increase yield and WUE more effectively than ΔW. These findings provide a theoretical basis for the efficient utilization of water resources on the Loess Plateau and the sustainable development of dry farming.

Southern China is a major grain-producing area, but has been suffering from increasingly serious droughts caused by global warming. As a result, crop losses have become serious. To provide insights into these losses, we obtained data to support a systematic and comprehensive analysis of how agricultural drought has caused crop losses from 1961 to 2011 and of the relationship between these changes and the climatic factors responsible for the losses. We found an obvious increase in the loss of crops due to agricultural drought in southern China, with the greatest increase in crop loss in the southwest and smaller increases in the south and southeast. Moreover, because each crop growth stage is affected differently by climatic factors and because the values of these factors show an uneven seasonal distribution, the losses were greatest when changes in various climatic factors occurred during key crop developmental periods. The fittings of the relationship between crop loss and various climatic factors was often strongest based on data from key developmental periods rather than based on data for the whole year. In addition, we found improved prediction of losses using multiple regression, and developed a model for assessing crop losses. Our results provide a scientific reference for developing methods to evaluate the losses caused by agricultural drought in southern China.

Extending across three major plateaus, namely the Qinghai-Tibetan Plateau, the Inner Mongolia-Xinjiang Plateau and the Loess Plateau, Northwest China has the complex terrain and spatio-temporal climate variations, and is affected by the interactions among different circulation systems, such as the summer monsoon, the westerlies and the plateau monsoon. The understanding of the climate variability, as well as its characteristics and evolution mechanisms in this area has been limited so far. In this paper, the precipitation characteristics and mechanisms in the eastern and western parts of Northwest China during the flood season are compared and analyzed based on the data from 192 national meteorological observational sites in Northwest China in 1961–2016. The results show that, divided by the northern boundary of the East Asian summer monsoon, there are huge differences in the precipitation variation characteristics between the eastern and western parts. The inter-annual variations, inter-decadal variations and total trends in the two parts all show a significant seesaw phenomenon. Moreover, it is found that the seesaw phenomenon of precipitation variation is closely related to the opposite variation between the East Asian summer monsoon index (MI) and the westerly circulation index (WI). In addition, the inverse variations on different time scales are only related to the contributions of precipitation at specific grades. Besides, in the two matching patterns of precipitation in the seesaw phenomenon, the middle and high latitudes are occupied by the “high-low-high” wave trains in the precipitation increases in the east of Northwest China (ENWC) and decreases in the west of Northwest China (WNWC) pattern, meaning precipitation increases in ENWC and decreases in WNWC. Whereas the opposite “low-high-low” wave trains at 500 hPa height are observed in the middle and high latitudes in the WH-EA pattern at 500 hPa height, meaning precipitation increases in WNWC and decreases in ENWC. Thus, the atmosphere circulation situation with two wave train types can support both the precipitation seesaw phenomenon and the opposite variation between MI and WI. Moreover, the seesaw phenomenon is shown to be related to the separate or joint effects of the South Asian High, ENSO and the plateau heating on the common but opposite effect on the summer monsoon and the westerlies, in which the South Asian High probably plays a more critical role. This study could deepen the scientific understanding of precipitation mechanisms and improve the weather forecast technology in Northwest China during the flood season.

Southern China is the nation’s major grain-producing areas. In recent years, under the background of global climate change, regional drought disasters have been increased, and caused serious agricultural drought loss and obvious anomaly characteristics. However, the variation characteristics of agricultural drought loss and drought hazard mechanism are still unclear in south China, which seriously affects the in-depth understanding of southern agriculture drought and its assessments. Therefore, based on agricultural drought disaster conditions, crop acreage, meteorological drought monitoring index and conventional meteorological factors and other related data, systematical and comprehensive agricultural drought loss rate variation and its relationship with climate-formative factors have been analyzed in recent 50 years. Agricultural drought comprehensive loss rate is used as an agricultural drought disaster or risk characteristics loss severity index. Agricultural drought comprehensive loss rate is an integrated index that can reflect severity of loss caused by agricultural drought disaster and established by drought-affected crop planting area at different levels and planting area. The results showed that comprehensive agricultural drought loss rate increased obviously and with a rate of about 2.5%, the relative increased rate reached to as high as 80%. Agricultural drought disasters loss has been increased seriously and doughty disasters risk also has been increased more higher than before, southwest is more apparently than south and southeast. With respect to spatial distribution, probability of climate tendency rate for comprehensive loss rate in south China ranges from 0.1%/10 a to 1.8%/ 10 a. In addition, increase in climate tendency rate in the southwest is more obvious than that in the south and southeast. And, as a result of crop growth stages on the climate elements in dependence on different season and climate factors of non-uniform distribution characteristics, agricultural drought loss rate is mainly affected by key period meteorological drought and the effects of climate change, mainly precipitation and temperature. As for precipitation, 6 months including April, May, June, July, August and October serve as key impacting periods. As for temperature, 5 months including January, June, July, August and October serve as key impacting periods. As for MCI, only two months including July and August serve as key impacting periods. But other climatic factors change is not obvious influence on agricultural drought loss rate. In south China, key impacting periods of MCI coincide with key growth phases of most crops; common key impacting periods of temperature and precipitation coincide with major growth phases of most crops in south China; key impacting periods of precipitation coincide with major or key growth phases of some crops; while key impacting periods of temperature coincide with key periods for overwintering of winter wheat. As a result, the fitting relationship between the south agricultural drought loss rate and the critical period climate factor is much better than its relationship with throughout annual climate, and more key climate factors has more obvious advantages in fitting relationship compared with single factor. Such multi-factor relationship can not only describe the disaster-causing effect of meteorological drought, but also reflect the roles played by severe evapotranspiration and soaking rain processes on drought disaster-causing process. Meanwhile, the agricultural drought loss assessment model with multiple factor relationship had been done for cross validation method, correlation, error level and reliability are the relevance of the ideal, which indicated that the model is an optional reliable and objective model for evaluating the impact of drought disasters on agricultural yield in south China or estimation on risks of agricultural drought disasters in future climate scenarios. The study results have important scientific reference significance for the development of south China agriculture dry drought damage assessment method.

Increasing global temperatures and frequency of low precipitation have made drought a major natural disaster around the world. Drought is a major threat to China's food security. Thus, the recent abnormal characteristics of Chinese droughts warrant further study. We therefore examined daily air temperature and precipitation from 1961 to 2014 at 572 Chinese meteorological stations. We used an improved version of Meteorological Drought Composite Index (MCI) as a drought indicator to analyze the spatial variation and temporal changes of the drought severity, frequency, duration, and location. China's drought-affected area has expanded, and the severity and frequency have increased due to climate warming. The drought-affected areas are also changing, with drought intensifying in the north but increasing even more in the south, especially for severe drought. Drought was most widespread and sustained in the late 1990s and early 2000s, primarily in the southern Yellow River Basin and the northern Yangtze River Basin. Frequency analysis revealed >30% drought frequency (% of total years) in the western and eastern parts of northwestern China and in eastern, northern, and southwestern China. Drought frequency was higher in the Yangtze River and Yellow River basins. China's drought intensity, duration, and frequency were generally higher in the north and east than in the south and west; however, these parameters increased more rapidly in the south. Droughts occurred year-round in China, but the occurrence, range, duration, and frequency differed among years and regions. Our results offer insights into the development of drought in China and provide support for disaster risk assessment and response planning.

Gobis (gravel deserts) cover large areas in northwestern China and other parts of the world, but sediment transport above gobi surfaces has not been widely investigated; thus, there is insufficient empirical data to support dust source identification. In the present study, we used the LDDSEG vertically segmented sediment sampler to collect sediment transport data above a gobi surface. The results demonstrated that the sediment transport rate above the gobi surface was larger than that above a sandy surface, with rates as high as 9.7 kg m-1h−1. The transport flux can be expressed as a Gaussian peak function, with the maximum sediment transport at 0.05 to 0.09 m above the surface. Principal-components analysis (PCA) indicated that the mean grain size of the transported sediment was controlled mainly by the content of silt and clay (

Agro-drought risk analysis is helpful for improving the ability of regional disaster management and reducing potential drought risk under climate change. In this paper, we use daily meteorological observations from 60 stations and maize yield data in Southwest China during the period from 1961 to 2012. Based on natural disaster risk theory, maize drought risk assessment model is established from four factors: hazard, exposure, vulnerability, drought prevention and mitigation, and maize drought risk is zoned and analyzed in Southwest China under climate change. The results show that under climate warming, the high and sub high risk zones are decreased in Yunnan Province and emerged in central and northwest Sichuan Province, the low and sub low risk zones are largely reduced in Sichuan Province, Guizhou Province and Chongqing City, and the other increasing zones are mainly moderate risk zones. In summary, maize drought risk mainly depends on the maize drought hazard; the maize drought risk increases in the north and decreases in most of south under climate warming in Southwest China. Enhancing maize drought risk management helps to reduce the potential risk to agricultural production in southwest China under climate change.

Drought disaster risk occurrence frequency is one of most high, and its affection is most severe in the worldwide, which is more serious in China and had threatened our food security. With the climate change, drought disaster had serious impacts on agricultural production and increasing risks of agricultural disasters. Therefore, the agricultural drought risk characteristics and management problem are particularly important under climate warming conditions. Drought disaster risk was effected by the spatial and temporal pattern of drought risk hazard factors such as the frequency and intensity of precipitation, environmental vulnerability, sensitivity and exposure. These three factors are both independent and connected each other. In view of this, based on the crops drought threshold and the risk mechanism, firstly, we analyzed the drought disaster risk research progress domestic and overseas in recent, which can provide information to the future studies. Secondly, the agriculture drought risk assessment must be established based on detailed agricultural drought dynamic monitoring and assessment methods, and the main technological process included building the assessed database using the meteorological observation data, drought disaster data, integration of data and remote sensing, a long sequence of yield and climate and drought disaster loss data (including agricultural drought of drought-induced areas, drought-occurred areas and no harvest areas), based on remote sensing inversion, field investigation, mathematical statistics and so on, comparing the adaptability of the drought monitoring index, identifying the drought disaster hazard index. Thirdly, based on the long term drought disaster and production data, selecting the occurring drought samples in the crop growth period and calculating reduction rate, building the relationship between production and drought disaster index, based on the reduction rate to quantify the hazard index critical value and grading, quantify the contribution degree of the drought in different growth period to production, confirming the different agriculture drought intensity threshold values and its classifications. And then, based on the theory of coupled risk simulation, combined the drought disaster hazard factor, environmental vulnerability, sensitivity and exposure theory to build the agriculture key growth period disaster risk assessment models. Based on the built models, the different grades drought threshold values, the drought risk development characteristics and drought regional difference can be identified. Lastly, revealed the contribution of key physical factor to risk and it physical mechanism to happen. These can provide some information on the agriculture key growth period drought risk physical mechanism and improving risk management levels.

Drought is a serious ecological problem around the world, and its impact on crops and water availability for humans can jeopardize human life. Although drought has always been common, the drought risk has become increasingly prominent because of the climatic warming that has occurred during the past century. However, it still does not comprehensively understand the mechanisms that determine the occurrence of the drought risk it poses to humans, particularly in the context of global climate change. In this paper, we summarize the progress of research on drought and the associated risk, introduce the principle of a drought “transition” from one stage to another, synthesize the characteristics of key factors and their interactions, discuss the potential effect of climatic warming on drought risk, and use this discussion to define the basic requirements for a drought risk management system. We also discuss the main measures that can be used to prevent or mitigate droughts in the context of a risk management strategy.

Drought is a serious problem in southwestern China, where drought risk exceeds the national average. Climate change is likely to exacerbate the problem, thereby endangering China’s food security. In this paper, we used the analytic hierarchy process and meteorological, geographic, soil, and remote-sensing data to develop a drought risk assessment model based on the drought hazard, environmental vulnerability, sensitivity and exposure of the values at risk, and capacity to prevent or mitigate the problem. Using the model, we assessed the drought risk (defined using a comprehensive drought risk index, R) and its spatial distribution in southwestern China and revealed complex zonality. The eastern part of the study area had an extremely high risk, and risk was generally greater in the north than in the south, and increased from southwest to northeast. The comprehensive risk (R) was lowest in Yunnan province. It was highest in Sichuan Province and Chongqing Municipality. The contribution of the risk factors to R was highest for the capacity for prevention and mitigation, followed by the drought hazard, sensitivity and exposure, and environmental vulnerability.

Dust storm events, especially those associated with strong winds, are immediately dangerous, and have long-term harmful effects. During a dust storm event, dust in the near-surface atmospheric layer decreases visibility, and changes local meteorological parameters. In this paper, we analyzed levels of near-surface turbulence during and outside a dust storm event and found differences in the degree of turbulence, with wind speed increasing and amounts of windblown sand greatly increasing air turbulence during the dust storms compared with the corresponding values on a sunny day. In addition, the wind profile during the dust storm deviated from the normal profile and became more complex. In the near-surface atmospheric layer, sand and dust flux during the dust storm also differed from those on a sunny day.

[Han, Lanying] Lanzhou Univ, Coll Atmospher Sci, Northwest Reg Climate Ctr, Lanzhou 730000, Peoples R China

Snow coverage plays a significant role in the Earth's water cycle and is sensitive and informative indicators of climate change. Recently, snow coverage in the Qilian Mountain great changed and caused great changes of the ecological environment in the Shiyang River. In this paper, remote sensing imagines were used to calculate the snow coverage, vegetation coverage and water resource. The result indicated that the entire area of the glacier snow was fluctuated on the Qilian Mountains region, having linear and increasing trend from 1997 to 2006. In the eastern and middle of Qilian Mountains, the snow coverage tends to decrease, but in the western, snow coverage tends to increase. As a whole, vegetation coverage is decreasing in Shiyang River Basin. Sparse vegetation and density vegetation were the worst degradation. Water resource in the downriver of Shiyang River (Hongya Mountain Reservoir) decreased.

In Shiyang River Basin, the average temperature since 1951 was sustained upward trend. Which, 1992 is a significant warming of the year, with significant warming ago, the temperature rose by 0.85°C, higher than the national 0.79°C warming of nearly 97 years, but lower than the nearly 51 1.1°C increase in the level. East Qilian Mountains of snow in the area overall decrease, in the basin precipitation generally increasing, runoff from mountain pass is reducing, the groundwater level rapidly declined in Minqin oasis. After temperatures notable warming, annual precipitation increased by 18.2 mm, an increase of 5.8%. runoff reduce 410 million m 3 , Groundwater dropped by 1-2 times in Minqin oasis. The analysis of water resources changing reasons showed that runoff from mountain pass reducing because of mountain precipitation decrease and Hongyashan Reservoir Inflow to the sustained, rapid decrease is one of reasons which leading to a rapid decline of groundwater in Minqin Oasis. Subject to the effects of climate change, the Shiyang River basin runoff from a mountain pass in advance of the peak, Human activities are seriously affected the middle reaches of the Shiyang River basin runoff and downstream utilization of available volume ratio. Climate change and human activities affect the common, Reducing of vegetation area and the patches number in Shiyang River Basin shows not only changes in vegetation types, there are also sparse vegetation to the bare land into the trend, which is the deterioration of ecological environment tends to the obvious signs.