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宁夏耕地压力与社会经济发展耦合时空特征分析 总被引：2，自引：0，他引：2
根据耕地压力指数和重心坐标模型,计算了宁夏回族自治区1980-2012年耕地压力指数及GDP重心坐标,在此基础上分析了耕地压力指数在时间上的动态变化及空间上的差异;并通过地理关联率的计算,进一步探讨了耕地压力指数与GDP在空间上的耦合关系。结果表明:30多年耕地面积减少了37.8×104 hm2,最小人均耕地面积和实际人均耕地面积不断减小,耕地压力指数总体随时间呈减小趋势,到2012年减小到0.72;但各县(区)耕地压力差异较大,北部能源开发区一直是宁夏耕地压力最大的地区;中部干旱区和南部黄土丘陵沟壑区在2000年以前耕地压力较大,而后明显减轻。经济发展、农业科技、水利工程及生态移民政策共同影响了耕地压力变化。到2012年耕地压力和GDP地理关联率为0.85,表明两者之间的地理联系率较高。 相似文献
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近年来我国商品住宅价格持续高涨,对城市居民购买住房造成巨大压力。鉴于城市居民购房压力评价中客观存在的不确定性和模糊性,将熵值理论与模糊物元分析法相结合,应用于购房压力的综合测评,建立了基于熵权的城市居民购房压力模糊物元分析模型,借助该模型对国家级5大区域及中心城市居民购房压力进行了测评,提出了缓解城市居民购房压力的对策。 相似文献
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北方土石山区的土地压力及其缓解途径 总被引：5，自引：0，他引：5
以北方土石山区27个小流域样本数据为基础,针对流域粮食生产、经济发展和生态保护对土地的需求,构建了土地压力定量评估方法,评估了各流域的土地压力,并将其与实际土地生产力进行了比较,进而从各小流域的经验事实中提取出使两者平衡的有效途径。结果表明,土地压力在空间上具有非均衡性,但相对于土地生产力的相对土地压力则存在空间均衡化的趋势。2000年前后,只有76%的样本小流域能够支撑人均300 kg/a的粮食生产压力,只有约20%的样本小流域能够支撑其经济发展压力,但这些小流域的土地压力最终都得到了有效缓解。劳动力转移、发展经济林果和特色产业等是缓解上述压力的主要途径。 相似文献
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西安市城市资源压力与城市化水平的灰色关联分析 总被引：5，自引：3，他引：2
统计结果显示西安城市化水平的提高也伴随着城市资源压力的加大,为了找出它们之间定量的数字特征关系,运用综合评价法对西安市近15年的城市化水平进行了测度.同时,使用资源压力指数法对西安市城市资源压力进行了定量评价,最后,用灰色关联分析方法对城市资源压力指数与城市化水平的各相关因子之间的关系进行研究.结果表明,城市资源压力与最能体现城市化发展水平的"城市现代化水平"因子之间存在着极强的关联,针对这一现状,提出了缓解城市资源压力和协调加快城市化发展进程之间矛盾的几点建议. 相似文献
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土地是承载粮食生产、经济发展和生态环境建设的基石,面对生产技术进步和人类对土地的大强度开发,有限的土地正承受着前所未有的压力.科学地测度土地的压力状态,是合理制定区域土地可持续利用管理的重要依据.从粮食生产、经济发展和生态环境安全三方面,探讨了黑龙江省土地的压力状态测度方法及其压力状态的空间分布格局与成因机理.结果表明:黑龙江省土地压力的各项指标具有明显的空间梯度分异规律,土地综合压力指数自西向东逐渐由高到低分布,耕地压力指数由北向南从低到高,建设用地沿西北-东南轴线方向逐渐减小,并在这一轴线的两翼向西南和东北方向逐渐降低,生态用地压力呈面状和团粒状分布格局. 相似文献
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以342个地级行政区为基本单元,利用耕地压力指数、GDI指数、空间自相关、平均增长指数等方法分析2001-2013年中国耕地压力的时空分异格局与过程;在粮食生产因素基础上重点分析社会经济因素对耕地压力变动的影响。结果表明:(1)2001年以来中国耕地压力状况逐渐减轻,但空间分异程度扩大、空间集聚趋势增强;(2)中国耕地压力格局总体稳定、局部变化,南北分化趋势显著;(3)耕地质量是决定中国耕地压力的基础性因素,农民收入、产业结构和经济水平等社会经济因素对耕地压力变动有更为显著的影响,作用超过了粮食生产投入因素。 相似文献
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基于空间自相关的湖北省耕地压力时空演变特征 总被引：4，自引：0，他引：4
借助耕地压力指数模型和空间自相关分析法定量测算了1999—2011年湖北省17个行政单元的耕地压力指数并分析了空间差异特征。结果表明:1999—2011年湖北省耕地压力呈弱倒"U"型,根据耕地压力指数的时序变化可将17个单元分为持续拉升区、和缓保持区、平稳下降区;1999—2011年的Moran’s I值表明湖北省耕地压力具有较明显的空间聚集特征,2001年Moran’s I值最高,2005年Moran’s I值最低;2011年17个单元的局部自相关指数表明湖北省各行政单元的耕地压力在空间上也具有一定的集聚或分异特征,尤其是以武汉市为中心形成了一个湖北省耕地压力的热点(高峰)地区。研究结果对制定湖北省区域空间发展战略、因地制宜地兼顾粮食安全和经济发展对土地的需求具有重要的参考意义。 相似文献
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中国水-能源-粮食压力时空变动及驱动力分析 总被引：2，自引：1，他引：1
采用主成分分析法,把构建的水资源、能源和粮食的压力指数分解为3个正交向量,以矢量合成法计算水-能源-粮食（W-E-F）总压力指数。在考察1997~2015年30个省区（香港、澳门和台湾无数据,西藏缺能源数据）的水资源压力指数、能源压力指数、粮食压力指数和W-E-F总压力指数的时序变化后,选取8个反映总压力指数变化的指标,截取1997、2004、2015年3个断面,采用地理加权回归（GWR）模型对影响中国W-E-F压力指数变化的因素进行分析。结论如下：① 时间上看,W-E-F总压力先升后降;空间上看,从东南沿海向西北内陆W-E-F总压力逐渐递减,东北和沿海城市化水平高的地区压力较大。② 能源压力对中国W-E-F总压力的贡献最大,中东部地区的能源压力指数更高,淮河以北地区的水资源压力指数更高,东部的长江口以南沿海区域和广大西部地区的粮食压力指数更高。③ 1997~2015年,全国水资源压力指数多数地区上升,能源压力指数和粮食压力指数大部分地区下降。④ 不同时段,W-E-F压力变化的驱动力不同。总体上看,大部分指标与W-E-F压力变化同向,人均受教育水平和人均GDP与W-E-F压力变化反向,人口密度增大、食物构成变化、粮食生产条件和经济发展是W-E-F压力升高的主因。在分析时段内,随着时间推移,社会因素和经济因素的影响在增大,提高人均受教育水平和经济转型发展是降低W-E-F压力的有效途径。 相似文献
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W. F. Waite L. A. Stern S. H. Kirby W. J. Winters D. H. Mason 《Geophysical Journal International》2007,169(2):767-774
Thermal conductivity, thermal diffusivity and specific heat of sI methane hydrate were measured as functions of temperature and pressure using a needle probe technique. The temperature dependence was measured between −20°C and 17°C at 31.5 MPa. The pressure dependence was measured between 31.5 and 102 MPa at 14.4°C. Only weak temperature and pressure dependencies were observed. Methane hydrate thermal conductivity differs from that of water by less than 10 per cent, too little to provide a sensitive measure of hydrate content in water-saturated systems. Thermal diffusivity of methane hydrate is more than twice that of water, however, and its specific heat is about half that of water. Thus, when drilling into or through hydrate-rich sediment, heat from the borehole can raise the formation temperature more than 20 per cent faster than if the formation's pore space contains only water. Thermal properties of methane hydrate should be considered in safety and economic assessments of hydrate-bearing sediment. 相似文献
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An underlying wetland surface comprises soil, water and vegetation and is sensitive to local climate change. Analysis of the degree of coupling between wetlands and the atmosphere and a quantitative assessment of how environmental factors influence latent heat flux have considerable scientific significance. Using data from observational tests of the Maduo Observatory of Climate and Environment of the Northwest Institute of Eco-Environment and Resource, CAS, from June 1 to August 31, 2014, this study analysed the time-varying characteristics and causes of the degree of coupling(Ω factor)between alpine wetlands underlying surface and the atmosphere and quantitatively calculated the influences of different environmental factors(solar radiation and vapour pressure deficit) on latent heat flux. The results were as follows:(1) Due to diurnal variations of solar radiation and wind speed, a trend developed where diurnal variations of the Ω factor were small in the morning and large in the evening. Due to the vegetation growing cycle, seasonal variations of the Ω factor present a reverse "U" trend. These trends are similar to the diurnal and seasonal variations of the absolute control exercised by solar radiation over latent heat flux. This conforms to the Omega Theory.(2) The values for average absolute atmospheric factor(surface factor or total) control exercised by solar radiation and water vapour pressure are 0.20(0.02 or 0.22) and 0.005(-0.07 or-0.06) W/(m2·Pa), respectively. Generally speaking, solar radiation and water vapour pressure deficit exert opposite forces on latent heat flux.(3) At the underlying alpine wetland surface, solar radiation primarily influences latent heat flux through its direct effects(atmospheric factor controls). Water vapour pressure deficit primarily influences latent heat flux through its indirect effects(surface factor controls) on changing the surface resistance.(4) The average Ω factor in the underlying alpine wetland surface is high during the vegetation growing season, with a value of 0.38, and the degree of coupling between alpine wetland surface and atmosphere system is low. The actual measurements agree with the Omega Theory. The latent heat flux is mainly influenced by solar radiation. 相似文献
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Heat capacities of solid sediments and pore fluids within a basin can influence geothermal gradients when sedimentation or erosion is rapid. This paper provides data on specific heat capacities of pore fluids and porous rocks. It includes data on specific heat capacities of water, ice, and gas hydrates at reference temperatures, as well as equations for calculating the specific heat capacity of those substances as a function of temperature. It also provides values for specific heat capacities of oil and natural gases at low temperatures, as well as equations describing the temperature and pressure dependence of the specific heat capacities of those substances. Finally, it shows how to calculate the specific heat capacity of mixtures of solid materials, or of mixtures of solids and pore fluids. The data and equations provided herein can be incorporated directly into existing modeling software by users and software developers. 相似文献
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A Review and Evaluation of Specific Heat Capacities of Rocks,Minerals, and Subsurface Fluids. Part 1: Minerals and Nonporous Rocks 总被引：1，自引：0，他引：1
Heat capacities of the rocks within a sedimentary basin can significantly influence geothermal gradients if sedimentation or erosion is rapid. This paper provides data on specific heat capacities of minerals and nonporous rocks at 20°C, derives equations for calculating specific heat capacities of minerals and nonporous rocks at temperatures between 0°C and 1200°C, and shows that pressure effects on heat capacities of solids can be neglected. It derives an equation for estimating specific heat capacity of any mineral or nonporous rock as a function of density. Finally, it shows how to calculate the specific heat capacity of any mixture of solid materials. A companion paper discusses specific heat capacities of the fluids in pore spaces of rocks and of fluid-filled porous rocks. The data for minerals and rocks provided herein can be incorporated directly into existing modeling software by users. However, the temperature-dependent equations would have to be incorporated by software developers. 相似文献
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基于2008、2010、2012和2014年我国北极科学考察期间在白令海获取的水文观测数据,结合历史共享资料,通过对白令海水团、上层海洋热含量、净热通量变化、风场及海平面气压分布情况等的分析,探讨了白令海水文结构的年际变化特征及其原因。研究发现,白令海夏季的水团包括白令海上层水团(BUW)、中层水团(BIW)、深层水团(BDW)和白令海陆架水团(BSW)。白令海温盐分布差异最大、年际变化最剧烈的情况主要集中在上层水团。对比4年水团分布情况,最明显的变化是2012年7月调查区上层海水温度偏低,2014年7月上层海水温度偏高。这种异常变化在热含量方面表现为:2012年7月调查区各个测站上的热含量异常低,而2014年7月测站上的热含量都高于平均水平。着重研究了2014年7月海温偏高的原因,认为是由于陆架和海盆区分别有两种不同的形成机制造成:陆架区累积净热通量偏高,海水吸收热量升温;海盆区在异常强大而持久的海面气压(SLP)高压系统下,海面负的风应力旋度得到加强,从而引起持续的暖平流输送及强烈的Ekman抽吸作用,最终导致了上层海水偏暖。 相似文献
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Winter climate change and sea ice-atmosphere interaction at high northern latitudes in ERA40 dataset 
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下载免费PDF全文 Based on the reanalysis dataset ERA40 of European Center of Medium Range Weather Forcast (ECMWF), winter climate change and characteristics of sea ice-atmosphere interaction at high northern latitudes for recent several tens of years are analyzed. Superposed upon the background of global warming, the amplitude of temperature increase in winter at high northern latitudes is bigger and it exhibits different features in different regions. From the end of 1970 s, the Greenland Sea, the Barents Sea and most part of Euro-Asian continent and North American continent are getting warmer, whereas the Labrador Sea, the Greenland and the area around the Bering Strait are getting colder. Meanwhile, the sea level pressure in the central part of the northern polar region and the place where the climatic Icelandic low exist decreases, but in places farther southward it increases. Since the 1970 s, the sensible heat flux and latent heat flux sent to the atmosphere from the Greenland Sea and the Barents Sea has increased, this is mainly due to the reduction of sea ice concentration and the weakening of insulator and shield effect of the solid ice accordingly caused by the increase of air temperature. In sea ice free area of the Norwegian Sea, the sensible heat flux and latent heat flux sent to the atmosphere has reduced due to decrease of temperature and humidity differences between the air and the sea surface caused by increase of air temperature and humidity. In the Labrador Sea, due to decrease of air temperature and humidity and increase of temperature and humidity differences between the air and the sea surface accordingly, the sea gives more sensible heat flux and latent heat flux to the air. This will lead to the growth of sea ice extent there. The features of linear regression of sea level pressure, sea ice concentration and sum of sensible heat flux and latent heat flux toward time series of the leading mode of EOF expansion of surface air temperature are close to those of their own EOF expansion for the leading mode, respectively. This shows that these variables share similar features of variation with time linearly. 相似文献
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Energy exchange is one of the most importantprocesses in wetland ecosystems,because it has agreat influence on temperature,water transport,plantgrowth,productivityetc.(Dennison and Berry,1989).On small scales,understanding of surface en-ergy exchange is n… 相似文献
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高原环境因素与自由基反应 总被引：5，自引：0，他引：5
高原环境是一个特殊的生态环境系统,其复杂多变的自然地理条件使移居和新进高原环境的人群或生物出现高原反应或发生“高原(山)病”。大气压低、氧分压低、太阳辐射强所导致的氧化应激反应是高原反应或高原病的主要原因之一。本文从高原气候因素与自由基反应,不同海拔高度对不同民族人群自由基反应的影响,相同海拔高度不同人群的自由基反应,海拔高度与机体抗氧化营养物质变化的关系,不同海拔高度紫外线强度与自由基反应及高原环境地球化学异常与自由基反应等6个方面,论述了高原环境因素与不同人群自由基反应的关系,不仅对探讨环境应激反应所产生的自由基反应与世居高原地区人群起源和进化有重要意义,而且对研究移居人群高原反应和高原病的预防、治疗及经济、国防建设具有现实应用价值。 相似文献
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天山季节性积雪的能量平衡研究和融雪速率模拟 总被引：5，自引：0，他引：5
本文采用能量平衡法模拟计算中国西部天山山地季节性积雪的融雪速率。结果表明:在融雪期,净辐射和感热通量分别占融雪能量输入的75.3%和22.6%;用于融雪和雪面蒸发所消耗的能量分别占吸收能量的95.1%和4.9%。用能量平衡法所计算的融雪速率和实测的雪面数据吻合的较好,表明用能量平衡法估算天山山地季节性积雪的融雪速率是可行的。 相似文献