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1.
The idiom of virtual water feeds a prolific literature now shaping the policies of national administrations and international organizations, including donors. This article explores the manner in which Palestinian agriculture and the concept of virtual water shed light on each other’s coproduction. It opens the black box of virtual water to identify the underlying hypotheses. It invalidates these hypotheses using empirical research. Integrating structuration theory to an STS approach, it explores the manner the coproduction of an interpretive scheme, virtual water, is linked to the construction of a structure of power. Within the idiom of virtual water, flows exist only through the international trade of commodities while states are endowed with an annually renewed stock of water. We focus on the real flow of water from its emergence from the earth to its evapotranspiration by a cultivated plant. We demonstrate that social and political variables within water governance determine the volumes of virtual water flows far more than climatic or agronomic variables. The idiom of virtual water portrays Palestinian smallholders as inefficient water users while ignoring the manner they sustain food security and environmental sustainability. It legitimizes export oriented agribusinesses as their mode of production corresponds to the coproduction of the idea of efficiency underlying the concept of virtual water. These results allow us to reconsider smallholder agriculture as it exists in the Palestinian territories and what sort of policies can support it.  相似文献   

2.
The cognition of thermal comfort plays a pivotal role in human life and activities. Recognizing thermal comfort based on climatic parameters is substantially significant. The main objective of the present study is to map thermal comfort using statistics from 43 meteorological stations, from 1970 to 2013. Initially, according to temperature and relative humidity, annual and seasonal thermal comfort conditions were mapped, and later bioclimatic human thermal comfort conditions in line with spatial factors were zoned based on bioclimatic indexes of Temperature Humidity Index (THI), effective temperature (ET) and Relative Strain Index (RSI). Among geostatistical methods, empirical Bayesian kriging (EBK) method with less RSME is more efficient. The annual distribution of temperature changes according to spatial factors of rugged topography and elevation, and latitude affects relative humidity. Thermal comfort in the northern and western half of Iran is higher than the southern and eastern areas of the country. Spatial factors of latitude and altitude reduce bioclimatic uniformity and create small areas with or without thermal comfort conditions. Bioclimatic indicators based on air temperature and relative humidity range of bioclimatic zones show. The results of ET and THI divide the whole country into six zones, from lack of thermal comfort to having thermal comfort conditions. Areas of southern strip as well as central and southeastern parts of the country do not have any human thermal comfort conditions in most of the year.  相似文献   

3.
晚更新世以来我国北方沙漠地区的气候变化   总被引：44，自引：2，他引：44  
本文通过地层沉积相等资料的分析,讨论了我国北方沙漠地区晚更新世以来的气候变化。  相似文献   

4.
David J. Briggs 《Geoforum》1981,12(1):99-106
Using data on crop yields and soil conditions derived from reports of the Soil Survey of England and Wales, and incorporating a variety of climatic and topographic data, relationships were identified between the yield of spring barley and edaphic and climatic conditions. Yields are highest on fine loamy and silty soils and on freely to imperfectly drained soils. Multiple regression analysis indicated that yields are related to sand contents, drainage conditions and available water capacity of the soil, potential summer soil moisture deficit and annual accumulated temperature.  相似文献   

5.
A study of environmental chloride and groundwater balance has been carried out in order to estimate their relative value for measuring average groundwater recharge under a humid climatic environment with a relatively shallow water table. The hybrid water fluctuation method allowed the split of the hydrologic year into two seasons of recharge (wet season) and no recharge (dry season) to appraise specific yield during the dry season and, second, to estimate recharge from the water table rise during the wet season. This well elaborated and suitable method has then been used as a standard to assess the effectiveness of the chloride method under forest humid climatic environment. Effective specific yield of 0.08 was obtained for the study area. It reflects an effective basin-wide process and is insensitive to local heterogeneities in the aquifer system. The hybrid water fluctuation method gives an average recharge value of 87.14 mm/year at the basin scale, which represents 5.7% of the annual rainfall. Recharge value estimated based on the chloride method varies between 16.24 and 236.95 mm/year with an average value of 108.45 mm/year. It represents 7% of the mean annual precipitation. The discrepancy observed between recharge value estimated by the hybrid water fluctuation and the chloride mass balance methods appears to be very important, which could imply the ineffectiveness of the chloride mass balance method for this present humid environment.  相似文献   

6.
Palaeobotanical studies of the brown coal deposits of the Latrobe Valley have contributed significantly towards an understanding of the age of the deposits, existing climatic conditions and detailed depositional environments. This paper re-assesses some past reconstructions for the Early to Mid Miocene coals using recent information on plant distributions and their bioclimatic significance and on a marine incursion model for coal lithotype formation.The brown coal flora is composed overwhelmingly of rainforest taxa that presently cover a range of different environments within the Australasian region. The application of a bioclimatic prediction model to these taxa allows the construction of consistent and quantitative estimates of climates during coal-forming phases. It is considered that rainfall in the area was more than twice the 850 mm received today, with significant seasonal variation. The mean annual temperature estimate of about 19°C, indicating a mesothermal or subtropical environment, is some 2–5C higher than present and higher than previous estimates. It does, however, correspond with sea-surface temperature estimates for the Southern Ocean at this time.The original model of lithotype formation, which suggests that lithotypes conform to a successional sequence from open water in the lightest coloured lithotypes to raised bog in the darkest lithotypes, is considered to be inconsistent with the evidence for lightening upwards sequences within the coals, a central feature of the proposed marine incursion model of coal formation. The two models are reconciled to some degree by a reinterpretation of the palaeobotanical data and by the postulation of climatic rather than autogenic successional control over lithotype formation.  相似文献   

7.
安国英  郭兆成  叶佩 《现代地质》2022,36(2):406-417
依据1989年至2019年云南大理地区所辖12个气象站点的气候数据和洱海水质监测资料等文献,分析大理地区气候变化特征和洱海富营养化变化趋势,并总结洱海水质综合营养状态指数与降水量、气温的相互关系。结果表明,1989年至2019年期间,大理地区的年平均气温呈波动上升趋势,气候变暖明显,冬季气温升温幅度最大;年降水量总体呈波动下降趋势,秋季降水量减少最为显著。洱海水质的综合营养状态指数及单因子总氮、总磷、高锰酸盐指数等总体呈升高趋势,而水体透明度呈降低趋势;进一步可分成2个阶段,即2003年之前呈快速上升或下降变化趋势;2003年之后呈波动稳定趋势。洱海综合营养状态指数与年平均气温呈正相关,与年降水量呈负相关关系;总氮、水体透明度分别与年平均气温正相关和负相关,与年降水量则呈负相关和正相关;而总磷与冬季平均气温、高锰酸盐指数与夏季或冬季平均气温均呈正相关关系。年内变化上,洱海污染指数、综合营养状态指数在最近的2015—2019年期间呈现6—10月份明显增高,显示非汛期水质明显好于汛期状况。总之,1989—2019年期间,受大理地区气温升高、降水量减少导致入湖水量减少的影响,洱海综合营养状态指数呈升高趋势,湖泊富营养化进程加剧状况没有得到改善,洱海水环境仍然比较脆弱。  相似文献   

8.
Groundwater resource potential is the nation’s primary freshwater reserve and accounts for a large portion of potential future water supply. This study focused on quantifying the groundwater resource potential of the Upper Gilgel Gibe watershed using the water balance method. This study began by defining the project area’s boundary, reviewing previous works, and collecting valuable primary and secondary data. The analysis and interpretation of data were supported by the application of different software like ArcGIS 10.4.1. Soil water characteristics of SPAW (Soil-plant-air-water) computer model, base flow index (BFI+3.0), and the water balance model. Estimation of the areal depth of precipitation and actual evapotranspiration was carried out through the use of the isohyetal method and the water balance model and found to be 1 664.5 mm/a and 911.6 mm/a, respectively. A total water volume of 875 829 800 m3/a is estimated to recharge the aquifer system. The present annual groundwater abstraction is estimated as 10 150 000 m3/a. The estimated specific yield, exploitable groundwater reserve, and safe yield of the catchment are 5.9%, 520 557 000 m3/a, and 522 768 349 m3/a respectively. The total groundwater abstraction is much less than the recharge and the safe yield of the aquifer. The results show that there is a sufficient amount of groundwater in the study area, and the groundwater resources of the area are considered underdeveloped.  相似文献   

9.
We reconstructed annual mean temperature (Tann) trends from three radiocarbon-dated Holocene pollen stratigraphies from lake sediments in Estonia, northern Europe. The reconstructions were carried out using a North-European pollen-climate calibration model based on weighted averaging partial least-squares regression. The cross-validated prediction error of the model is 0.89°C and the coefficient of determination between observed modern Tann values and those predicted by the model is 0.88. In the reconstruction, the Holocene thermal maximum (HTM) is distinguishable at 8000-4500 cal yr B.P., with the expansion of thermophilous tree species and Tann on average 2.5°C higher than at present. The pollen-stratigraphical data reflect progressively warmer and drier summers during the HTM. Analogously with the modern decadal-scale climatic variability in North Europe, we interpret this as an indication of increasing climatic continentality due to the intensification of anticyclonic circulation and meridional air flow. Post-HTM cooling started abruptly at around 4500 cal yr B.P. All three reconstructions show a transient (ca. 300 years) cooling of 1.5-2.0°C at 8600-8000 cal yr B.P. We tentatively correlate this cold event with the North-Atlantic “8.2 ka event” at 8400-8000 cal yr B.P. Provided that the 8.2 ka event was caused by freshening of the North-Atlantic surface water, our data provide evidence of the climatic and vegetational responsiveness of the boundary of the temperate and boreal zones to the weakening of the North-Atlantic thermohaline circulation and the zonal energy transport over Europe. No other cold events of comparable magnitude are indicated during the last 8000 years.  相似文献   

10.
海河流域ET0演变规律及灵敏度分析   总被引：10，自引：3，他引：7       下载免费PDF全文
根据国家气象站1956-2000年逐日气象资料,采用Penman-Monteith公式和灵敏指数法,分析了海河流域潜在蒸发蒸腾(ET0)的演变规律及与气象要素的灵敏关系。结果表明:全流域45年ET0呈下降趋势,但年际间呈现4个阶段;逐旬呈倒"V"字型,61.6%集中于4月中旬到8月上旬。在空间上,年和旬值呈现上游小下游大。通过ET0与气象要素演变的比较及灵敏性分析发现,全流域年ET0演变与年均风速、日照时数以及短波辐射相似,与温度相反。旬ET0演变与旬平均温度、实际水汽压、日照时数以及短波辐射相似,但对各要素的灵敏系数以短波辐射最大,其它要素则随时空变化,且彼此的灵敏系数相差较大。分析表明在气象要素的综合作用下,造成全流域ET0降低的主要原因可能在于短波辐射、日照时数的变化。  相似文献   

11.
Riverine sediment load, a reflection of basin erosion and sediment yield, is influenced by both climatic and human factors. Complex interaction between various factors within a basin dampens and counteracts the forces that drive sediment variations. The gross human impact index and the index estimation method have both been proposed to reflect the impacts of human activities on soil erosion and sediment yield. Sediment load and daily rainfall data from 1955 to 2010 in the upper Yangtze basin, and in the Wu, Jialing, Min and Jinsha subbasins, were collected to assess the human versus climatic impacts on sediment yield. From 1955 to 2010, the average annual runoff in the study area was 428.2 billion m3, and the average annual suspended sediment load was approximately 0.43 billion t. There was a critical point in 1984, 1985, 1991, 1993 and 1999 when the sediment load decreased in the Wu, Jialing, upper Yangtze, Min and Jinsha river, respectively. The annual regional rainfall erosivities in the upper Yangtze basin in most years ranged between 2,500 and 3,500 MJ mm hm?2 h?1 year?1 and fluctuated around 3,000 MJ mm hm?2 h?1 year?1 with a small coefficient of variation of 0.11. In the Jinsha subbasin, the index indicated that increasing rainfall erosivity could not account for the reduction in riverine sediment load and that anthropogenic erosion-control measures played a key role. The index values for the Min, Jialing and Wu subbasins ranged from 76 to 97 % and for the upper Yangtze basin is 95 %, demonstrating the joint effects of precipitation and human activities in all basins, with erosion-controlling measures playing a major role in sediment load reduction.  相似文献   

12.
Ji  Yuhe  Zhou  Guangsheng  Wang  Lixia  Wang  Shudong  Li  Zongshan 《Natural Hazards》2019,96(3):1213-1222

A long time series in crop yield is usually expressed as a long-term trend and a short-term fluctuation due to agricultural technological advance and climatic anomaly. The real climate risk is related to the short-term fluctuation in crop yield. In the paper, the climate risk of maize yield response to long-term climate variables is tested with the long time series (1961–2015) by a trend base line method. The long time series of maize yield is divided into short-term fluctuating meteorological yield and long-term trend yield. The long time series of climate variables are also divided into fluctuating variables and trend variables. After that, Pearson correlation analysis between fluctuating maize yield and fluctuating climate variables is used to identify risk factor causing maize yield fluctuation. Our results reveal that the main risk factors are night-time precipitation and extreme high temperature in growing season. Comparing climate risks in maize-producing provinces, much more climate risks are identified in some regions such as Liaoning province. The results provide useful information for reducing maize yield loss under climatic change.

  相似文献   

13.
A unique 800-yr-long record of annual temperatures and precipitation over the south of western Siberia has been reconstructed from the bottom sediments of Teletskoye Lake, Altai Mountains using an X-ray fluorescence scanner (XRF) providing 0.1-mm resolution timeseries of elemental composition and X-ray density (XRD). Br content appears to be broadly correlative with mean annual temperature variations because of changes in catchment vegetation productivity. Sr/Rb ratio reflects the proportion of the unweathered terrestrial fraction. XRD appears to reflect water yield regime and sediment flux. Sedimentation is rather continuous because annual clastic supply and deposited mass are the same. The artificial neural networks method was applied to convert annual sedimentary time-series of XRD, Br content, and Sr/Rb ratio to annual records of temperature and precipitation using a transfer function. Comparison of these reconstructed Siberian records with the annual record of air temperature for the Northern Hemisphere shows similar trends in climatic variability over the past 800 yr. Estimated harmonic oscillations of temperature and precipitation values for both historical and reconstructed periods reveal subdecadal cyclicity.  相似文献   

14.
蒸散发是水循环过程中的重要环节,研究蒸散发时空变化影响因素,有利于认识区域水资源的时空分异规律。黄河流域地处干旱半干旱地区,水资源短缺且时空分布不均,水问题突出。在黄河流域分析蒸散发对变化环境的响应,揭示气候变化、植被季节性和物候变化的水文水资源效应,对地区水资源可持续发展和规划管理等具有重要的理论意义和现实意义。基于多元自适应回归样条(MARS)非参数模型,采用黄河流域内30个子流域的全球监测与模型研究组(GIMMS)制作的第三代归一化植被指数(NDVI3g)数据集、气象数据、土壤数据、土地利用/覆盖数据以及地形地貌数据,在Budyko框架下分析了水热耦合控制参数■与环境变量因子的关联性,探讨了变化环境对流域蒸散发的影响机制。结果表明：(1)流域水平衡关系的空间变异与流域水热耦合季节性、地形地貌空间变异性、降水的季节性特征(平均暴雨深度和降水变异系数)显著相关。(2)年际尺度上：流域水热的不同步性是影响流域水平衡年际分异最重要的气候季节性指数,水热的不同步性增大,流域的蒸散比减小,产流增加;降水越集中、年内变异程度越高、降水的季节性越明显,流域蒸散比越小;植被的...  相似文献   

15.
The objective of this study was to analyze climate change impacts on irrigation water demand and availability in the Jaguaribe River basin, Brazil. For northeastern Brazil, five global circulation models were selected using a rainfall seasonal evaluation screening technique from the Intergovernmental Panel on Climate Change named Coupled Model Intercomparison Project Phase 5. The climate variables were generated for the base period of 1971–2000, as were projections for the 2025–2055 future time slice. Removal of maximum and minimum temperature and rainfall output bias was used to estimate reference evapotranspiration, irrigation water needs, and river flow using the rainfall—river flow hydrological model Soil Moisture Accounting Procedure for the baseline and future climate (Representative Concentration Pathways 4.5 and 8.5 scenarios). In addition, by applying improved irrigation efficiency, a scenario was evaluated in comparison with field observed performance. The water-deficit index was used as a water availability performance indicator. Future climate projections by all five models resulted in increases in future reference evapotranspiration (2.3–6.3%) and irrigation water needs (2.8–16.7%) for all scenarios. Regarding rainfall projections, both positive (4.8–12.5%) and negative (??2.3 to ??15.2%) signals were observed. Most models and scenarios project that annual river flow will decrease. Lower future water availability was detected by the less positive water-deficit index. Improved irrigation efficiency is a key measure for the adaptation to higher future levels of water demand, as climate change impacts could be compensated by gains in irrigation efficiency (water demand changes varying from ??1.7 to ??35.2%).  相似文献   

16.
Winter wheat yields over a large area of the United States Great Plains are described as functions of the monthly surface atmospheric pressure pattern over North America. Seventy-eight years of pressure data were spatially decomposed with principal components analysis, and linear combinations of the resulting eigenvectors were used to fit a time series of five sensible climatic variables that are generally considered to be important to wheat yields. This surrogate data set was then used to fit the yield time series. The yield data were initially detrended with a simple linear estimator and adjusted with base constants specific for each crop reporting district.Interannual variation in the pressure field explains approximately 40% of the remaining variance in the yield data over the states of Colorado, Kansas, Oklahoma, Nebraska and Texas. When a reduced model was tested on five years of data simultaneously withheld, a similar amount of the variance was explained. Twentyone eigenvectors are consistently associated with the twelve sensible climatic parameters to which yields are most sensitive. Of these, five were found to be significantly changing (at between the 95 and 99% levels), in either linear or quadratic fashion, over the length of the pressure record. It is concluded that long-term change can and does take place in features of the general circulation that are important determinants of large area crop yields.  相似文献   

17.
Water resources in northern Cameroon have continuously been reducing over the past years. Many studies have suggested two principal causes: (1) human activities such as poor farming practices, unsustainable use of water resources, increased demand of water, deforestation, land-use change, etc., (2) human-induced climate change. Northern Cameroon in this study includes: the Adamawa, North and Far North regions located closer to the Sahel regions of Africa. These regions are already water stressed because of their location and any further change in climate with rising temperature would impact water resource either positively or negatively. Time series analysis and a 12-month standardized precipitation index (SPI12) with digital data between 1957 and 2006 were used to investigate the variation of water resources in northern Cameroon. Results obtained varies between the different regions with an increased annual trend in temperature and precipitation for Ngaoundere (Adamawa region) and Garoua (north region), whereas Maroua (far north region) had a decreased annual trend in both precipitation and temperature. Further variability results obtained from a SPI12 show that wetter period out number drought period in all three regions. The study concluded that water resources vary with the changing climatic condition and the severity of the impact varies from region to region. Furthermore, water deficiency in northern Cameroon might not be due to climate change. The reasons might be a combination of poor water management and other factors such population growth, the environmental condition, etc.  相似文献   

18.
Arid and semi-arid environments have been identified with locations prone to impacts of climate variability and change. Investigating long-term trends is one way of tracing climate change impacts. This study investigates variability through annual and seasonal meteorological time series. Possible inhomogeneities and years of intervention are analysed using four absolute homogeneity tests. Trends in the climatic variables were determined using Mann–Kendall and Sen’s Slope estimator statistics. Association of El Niño Southern Oscillation (ENSO) with local climate is also investigated through multivariate analysis. Results from the study show that rainfall time series are fully homogeneous with 78.6 and 50% of the stations for maximum and minimum temperature, respectively, showing homogeneity. Trends also indicate a general decrease of 5.8, 7.4 and 18.1% in annual, summer and winter rainfall, respectively. Warming trends are observed in annual and winter temperature at 0.3 and 1.5% for maximum temperature and 1.7 and 6.5% for minimum temperature, respectively. Rainfall reported a positive correlation with Southern Oscillation Index (SOI) and at the same time negative association with Sea Surface Temperatures (SSTs). Strong relationships between SSTs and maximum temperature are observed during the El Niño and La Niña years. These study findings could facilitate planning and management of agricultural and water resources in Botswana.  相似文献   

19.
王丽琴  邵生俊  赵聪  鹿忠刚 《岩土力学》2018,39(9):3223-3228
黄土是一种典型的具有结构强度的欠压密土,其特殊的结构性会使黄土的压缩曲线出现类似超固结土的明显转折点（对应的压力称为结构压缩屈服应力）。为分析黄土的初始结构性对其压缩屈服的影响,对6个场地的黄土进行了侧限压缩试验及单轴抗压强度试验,分别得到了各个场地不同含水率黄土的压缩屈服应力和构度指标。研究表明：黄土的构度指标与压缩屈服应力均随含水率的增大而减小,同时随含水率的增大,构度变化幅度小的黄土,其压缩屈服应力变化幅度也小;沉积时代相同的黄土,构度越大,其压缩屈服应力越大,两者呈线性关系;黄土的沉积时代不同,其构度与压缩屈服应力的线性关系就不同。分别给出了Q3、Q2黄土的构度与压缩屈服应力的线性关系式,并通过实例初步验证了此线性关系的适用性,为以构度为桥梁,利用简便易得的物理指标计算压缩屈服应力提供了一种途径。  相似文献   

20.
There is empirical evidence of a nonlinear relation between annual precipitation, or accumulation, and summer mean temperature at the equilibrium line altitude (ELA) on glaciers around the world. The degree-day model gives a similar relation between accumulation and summer temperature, although instead of a single universal curve there is a family of curves depending upon the annual temperature range. Furthermore, the degree-day model also gives nonlinear relations between accumulation and annual mean temperature. Thus, estimations of accumulation can be made from both summer and annual temperatures at the ELA of former reconstructed glaciers, such as those in Greece. This is particularly useful since these climatic variables have major implications for biological proxies, such as vegetation history indicated in the pollen record, and for periglacial proxies, such as permafrost distributions indicated in the geomorphological record. The close relationship between glaciers and climate provides one of the most precise methods for reconstructing former climates and offers considerable potential for resolving our understanding of Pleistocene cold-stage climates.  相似文献   

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