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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.

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.

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 (

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.

Due to the complex climate types and various meteorological disasters in gansu province, with the background of climate change dominated by warming, the losses caused by meteorological disasters are increasing. The understanding of disaster risk characteristics and its response to climate change need to be solved urgently. In view of this, this study based on the data of the disaster situation of major meteorological stations in gansu province since 1961, constructed the disaster risk index-comprehensive loss rate, and systematically analyzed the space-time variation characteristics of drought, rainstorm and flood, wind and hail and low temperature disasters in gansu province, and discussed the impact of climate change on them. The results show that since 1961, the risk of agricultural drought disaster is the greatest, followed by wind hail and rainstorm flood, and the risk of cold disaster is relatively minimal. Among them, drought disaster, disaster and loss rate (25.2%, 14.1% and 2.2 %) were significantly higher than the national average (15.0%, 8.1 % and 1.7%), and the increase rate (0.16%/10a, 0.15%/10a and 0.05%/10a) was also higher than the national average. The comprehensive loss rates of storm hails, rainstorm and flood disasters and cold and cold disasters also showed an increasing trend, with the increase rates of 0.29%/10a, 0.45%/10 and 0.72%/10a, respectively. The characteristics of inter-decadal disaster risk change have obvious differences, and the drought disaster risk increases uniformly. After climate change, the risk of major meteorological disasters in gansu increased.

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.

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.