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排序方式: 共有922条查询结果,搜索用时 281 毫秒
821.
研究了 190 0年以来我国东北北部地区浅源中强震活动的特征。结果表明 ,地震活动具有突发性、成组性和序列地震数量少的特点。应根据本区地震活动特点 ,开展震后早期趋势预测 ,以最大限度地减轻地震灾害。  相似文献   
822.
A technique is presented for developing an isohyet map for the Hualapai Valley, a closed hydrologic basin of about 315 square miles in the northwestern Great Basin in Nevada. In this basin there is practically no climatic data, and in the northwest Great Basin there are too few stations for determination of rainfall on a detailed basis. Using a vegetational typing to represent a range in elevation and precipitation, an initial mean annual rainfall is determined for selected points on a grid pattern. This rainfall is then modified by using topographic parameters of slope, orientation, exposure, and rainfall shadow effect. The resulting point determinations of mean annual rainfall are then smoothed using a trend surface analysis, and an isohyetal map is drawn from the smoothed points. The technique provides an estimated accuracy of one inch of mean annual precipitation and one mile of resolution on isohyets.  相似文献   
823.
Ethics and Environmental Attitudes With Implications for Economic Valuation   总被引:1,自引:0,他引:1  
This paper tests the hypothesis that different ethical belief systems are unrelated to the attitude an individual takes towards the environment. More specifically, the neoclassical economic approach is seen to require a belief in utilitarianism while many individuals may operate on the basis of a deontological or rights-based approach to decision-making. The concern with this relationship arises from the use of the cost–benefit analysis approach to environmental policy and the specific application of the contingent valuation method. Evidence is found to support the view that environmentalists choose to operate on a rights-based approach which rejects the relative welfare arguments of economics and positively attributes compensation to future generations for environmental damages. This implies that the contingent valuation of environmental attributes will lead to values which are biased towards technocentric optimists and against the environmental movement. In terms of policy, environmental management on the basis of totalling economic values is liable to be undemocratic because of the systematic exclusion of a section of the general public.  相似文献   
824.
825.
曾用灰色系统方法预测1996年全年的地震趋势,本次南黄海Ms6.1级地震的发生表明震级和时间的预测效果较好,因而认为作为一种手段,灰色系统方法可以加入地震综合预报的行列  相似文献   
826.
Coal combustion in the power sector gives rise to the emission of primary and secondary particulate pollutants. Since the emission of pollutants depends on coal quality and combustion technology, and given that transport, transformation and deposition of contaminants depend on regional climatic conditions, specific studies for the power stations is needed to evaluate their environmental impacts. Monitoring of ambient respirable suspended particulate matter (RSPM) and suspended particulate matter (SPM) levels around a large coal-fired power station in India was carried out. The specific objectives were the determination of spatial and seasonal variability in RSPM and SPM levels, and their relationship with meteorological parameters such as wind velocity and relative humidity. The results have shown a marked seasonal trend and spatial variability in RSPM and SPM levels in the study area. Higher concentrations of ambient RSPM and SPM were found in downwind monitoring stations compared to upwind direction. Ratios of RSPM to SPM and correlation coefficient values between RSPM and SPM along with meteorological parameters were also worked out. Relative humidity and wind velocity have shown an inverse relation with particulate deposition pattern.  相似文献   
827.
Water quality variables – Turbidity, pH, Electrical Conductivity(EC), Chlorides and Total Hardness (TH) were monitored at adownstream location in the Tamiraparani River during 1978–1992. The observations were made at weekly intervals in a watertreatment and supply plant using standard methods. Graphical andstatistical analyses were used for data exploration, trenddetection and assessment. Box-Whisker plots of annual andseasonal changes in variables indicated apparent trends beingpresent in the data and their response to the seasonal influenceof the monsoon rainfall. Further, the examination of the medianvalues of the variables indicated that changes in the directionof trend occurred during 1985–1986, especially in pH, EC and TH. The statistical analyses were done using non-parametric methods,the ANCOVA on rank transformed data and the Seasonal Man-Kendalltest. The presence of monotonic trend in all the water qualityvariables was confirmed, however, with independent direction ofchange. The trend line was fitted by the method of leastsquares. The estimated values indicated significant increases inEC (28 S cm-1) while significant decreases were observed inturbidity (90 NTU), pH (0.78), and total hardness (23 ppm) in a span of 15 years. The changes induced in river flow by the addition of a stabilizing reservoir, the influence of seasonal and spatialpattern of monsoon rainfall across the river basin and the increased agriculture appear causative factors for the water quality trends seen in the Tamiraparani River system.  相似文献   
828.
This article examines instrumental climate records from a varietyof stations associated with the following Biosphere Reserves across Canada: (i) Waterton Lakes, (ii) Riding Mountain, (iii) Niagara Escarpment, (iv) Long Point, and (v) Kejimkujik (Candidate Biosphere Reserve). Annual series are generated fromdaily temperature and precipitation values. In addition, homogeneous data are used from other stations and regional records to supplement the records from the local biosphere stations. Long term trends are identified over the period of the instrumental record. In general, data from the interval 1900 to 1998 show cooler temperatures in the 1920's, warmingfrom the early 1940's into the early 1950's, cooling into the1970's, and subsequent warming. At many stations, 1998 is the warmest in the instrumental record. Comparisons with the regional data sets show good agreements between the temperatureseries. The 20th century warming is approximately 1.0 °C in the Riding Mountain area and 0.6 °Cin the Long Point, Niagara Escarpment, and Waterton Lakes areas.There has been slight cooling in the Kejimkujik area over the past half century. Precipitation data show increasing trends inthe Kejimkujik, Long Point, Niagara Escarpment, and Waterton Lakes areas with no long term trend in the Riding Mountain area. This work is part of the Canadian Biosphere Reserves Association (CBRA) Climate Change Initiative (CCI), designed to present climate change information to Biosphere Reserve communities to allow local organizations to understand climate change and adapt to potential impacts.  相似文献   
829.
新时代下中国自然资源安全的战略思考   总被引:6,自引:4,他引:2  
中国特色社会主义进入新时代,经济处于转型升级的攻关期,自然资源安全保障被赋予了新的使命和要求。刚成立的自然资源部为新时代中国自然资源安全保障和综合管理的发展带来了新机遇。新时代是30 a以上的大尺度,其中长期战略安排需基于对自然资源历史变化的系统总结和对未来中长期的资源供需形势的战略研判。综合来看,未来中长期中国水资源需求仍将上升,耕地的粮食供应压力增大,直接影响民生福祉;矿产资源需求整体仍处于高位,不同矿种需求由“普涨”转向“结构性分异”;森林资源木材供给压力加重,关联着现代化经济体系的建设目标。以生态文明战略为统领,践行“绿水青山就是金山银山(两山)”的理念,坚持节约资源和保护环境,是保障中国自然资源安全的关键。为缓解中国整体资源安全压力,提高自然资源综合保障能力,以更有力地支撑中国“两个百年”战略目标的实现,建议:抓紧开展面向新时代的中国自然资源战略研究及顶层规划设计;实行严格的自然资源管理和环境保护制度;优化资源供给结构,加快资源开发利用的科技创新;立足国内,提高资源利用效率,促进循环利用,加强资源领域的国际合作。  相似文献   
830.
京津冀城市扩张对植被和地表城市热岛的影响   总被引:3,自引:0,他引:3  
基于MODIS-LST、EVI以及土地利用/覆盖数据,分析了2000~2015年京津冀13个城市生长季及不同季节城市扩张对植被(ΔEVI)和地表城市热岛影响的时间变化趋势以及二者之间的关系,结果表明,京津冀13个城市主城区生长季及不同季节的城市扩张对植被均存在消极影响(ΔEVI<0),对夏季植被的影响最大(ΔEVI=-0.131);白天和夜间的地表城市热岛强度(SUHII)最大值均出现在夏季,分别为2.594℃和1.859℃;不同季节的ΔEVI均值呈现显著下降趋势,其速率分别为-0.0038,-0.0033,-0.0045和-0.0018/a(P<0.01);生长季、春季和夏季白天SUHII均呈显著增加趋势,速率分别为0.076,0.093和0.106℃/a(P<0.01),不同季节夜间SUHII均呈显著增加的趋势,其增加速率分别为0.05,0.055,0.049,0.054和0.046℃/a;京津冀13个城市主城区的ΔEVI均值和SUHII均值呈显著负相关(P<0.01),其相关系数介于-0.959~-0.592之间;白天SUHII与ΔEVI的相关性最高为生长季(r=-0.959),夜间SUHII与ΔEVI的相关性最高为春季(r=-0.936).  相似文献   
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