共查询到20条相似文献，搜索用时 468 毫秒
1.
一种顾及属性的游程编码“交”运算方法与实验 总被引：1，自引：0，他引：1
考虑到基于直接编码的栅格数据在计算效率和存储能力上的不足,提出一种便于代数操作的游程编码数据结构,以优化基于直接编码栅格数据的代数运算.介绍了基于该数据结构的游程"交"运算的实现方法,并在算法实现过程中完成游程属性的各种代数运算.算法实现思路为:将栅格场中任一行游程集合以链表的形式存储,将欲执行代数运算的新游程单元与对应栅格行游程集合执行游程"交"运算,并在插入删除游程结点的过程中完成属性值的代数运算.该算法通用性较强,在数据精度及计算效率方面比直接栅格编码方法具有优势. 相似文献
2.
基于尺度转折点的空间分析方法研究 总被引：3，自引：0，他引：3
对景观生态学中有关空间分析和尺度转换的方法及基于直方变差图的尺度转换方法进行对比,分析其优缺点;在直方变差图的基础上,结合分形理论引入了尺度转折点这一概念。确定尺度转折点是研究重点,通过各个尺度转折点可以确定遥感图像上的各个尺度域,从而为不同尺度的地表时空多变要素提供一种尺度转换的依据。采用互联网上的IKONOS天安门地区图像数据进行验证。 相似文献
3.
土地空间分形结构的尺度转换特征 总被引：11，自引：1，他引：10
应用分形理论以及多元相关分析、灰色关联分析方法,分析浙江省慈溪市土地空间分形结构的尺度转换特征。结论为:①慈溪市、贵州省不同尺度分割区域的土地空间分形结构均客观存在,不因尺度不同而变化;②尺度转折点因尺度不同而出现,贵州省(省域尺度)土地利用存在尺度转折点,慈溪市(县域尺度)土地利用不存在尺度转折点;③不同尺度的慈溪市、贵州省土地空间结构的分维不仅主要受到土地类型本身几何属性的影响,而且其所受到的影响跨尺度存在;④尺度的差异造成不同影响因子的影响程度随尺度出现变化;平均图斑形状指数对慈溪市土地空间结构的分维影响最大,图斑数则对贵州省土地空间结构分维的影响最大。 相似文献
4.
基于中国1985～2007年30个省级行政区环境污染与经济增长面板数据,运用面板协整工具和动态最小二乘法(DOLS)对环境库兹涅茨曲线进行了实证检验。结果显示我国工业废气污染、工业废水污染和工业固体废弃物污染变量与经济增长变量之间存在长期协整关系,且变量间均呈现出显著的倒U形环境库兹涅茨曲线关系,而EKC转折点并没有出现在过低的水平上;其后基于检验结果探讨了我国环境-经济空间格局,部分东部发达省区已经越过或接近3种污染物EKC的转折点,然而我国大部分的中西部省区并未越过EKC转折点甚至距离较远。目前我国仍面临巨大的环境压力,在减排方面需要花费巨大的经济成本。我国环境经济政策的制定应根据各种不同情况因地因时制宜。 相似文献
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汕头市土地利用景观指数粒度效应初探 总被引：7，自引：0，他引：7
采用决策树、归一化光谱混合分析(NSMA)方法,参照全国土地分类标准,分类解译汕头市2006年ETM 数据,并获取不同粒度系列景观类型图。在此基础上,借助Fragstats 3.3软件,从类型水平和景观水平两方面分别选取8个景观指数指标,探讨不同粒度景观类型图条件下,景观指数随粒度变化的特征。结果表明,类型水平上景观指数粒度效应变化明显,但规律性不易把握;景观水平上,随着粒度的增加,多数指数呈现尺度效应且存在尺度转折点。参照指数特征及转折点确定汕头市ETM 数据土地利用景观指数计算的适宜粒度范围(150～210 m)。 相似文献
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基于风洞试验对青藏铁路沿线不同类型防沙措施防沙效果进行模拟研究,探讨了不同类型挡沙墙的防沙效果。结果表明：挂板式、轨枕式和箱式挡沙墙输沙率随高度基本呈递增缓变型趋势,最大输沙率低于20%;铃铛式和高立式聚乙烯（PE）网挡沙墙随高度呈递减陡降型趋势,距地表6~8 cm处为转折点,转折点以上输沙率随高度增大急剧减小,转折点以下输沙率随高度变化较为平缓,最大输沙率低于50%。随着风速的增大,各挡沙墙的阻沙率呈递减趋势：挂板式和轨枕式挡沙墙对风速的敏感性最弱,整体阻沙效果较优,可大范围推广;箱式挡沙墙对风速的敏感性较弱,建议在风速18 m·s-1以下的地区使用;PE网挡沙墙防沙效果对风速的敏感性最强,建议在风速10 m·s-1以下的地区使用。 相似文献
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北京市经济增长与环境污染水平计量模型研究 总被引：171，自引：10，他引：171
选取北京市 1985～ 1999年经济与环境数据 ,通过分析经济因子与环境因子相互关系 ,探究北京市经济增长与环境质量演替轨迹 ,以建立北京市经济增长与环境污染水平计量模型 ,为评价北京市环境政策提供依据。实证研究表明 :北京市自 1985年以来随着经济增长其环境恶化程度在下降 ,且已进入经济与环境协调发展后期阶段。北京市各环境指标与人均GDP演替轨迹呈现显著的环境库兹涅茨曲线特征 ,但比发达国家较早实现了其环境库兹涅茨曲线转折点 ,且到达转折点的时间跨度小于发达国家。这主要归功于中国及北京市政府近 10年来 ,尤其 1995年以来有效环境政策和巨额环境投资以及科技后发优势。 相似文献
8.
1960 年以来新疆地区蒸发皿蒸发与实际蒸发之间的关系 总被引：3，自引：0，他引：3
利用中国新疆地区1960-2005 年109 个设有蒸发皿蒸发观测的常规气象站资料, 并结 合不同驱动场和不同陆面模式的模拟结果, 对蒸发皿蒸发及模拟的实际蒸发的年、各个季节 的变化及其它们的相互联系进行了详细的分析和讨论。结果发现, 在过去的46 年里, 年蒸发 皿蒸发总体上都表现为明显的下降趋势, 而实际蒸发在总体上显著上升, 与蒸发皿蒸发的变 化趋势相反。在80 年代中后期, 蒸发皿蒸发、实际蒸发和降水的转折点(1986 年) 一致, 进 一步说就是无论在转折点的前后, 降水增加的转折性变化与模拟的实际蒸发的转折性增加变 化一致, 而与蒸发皿蒸发减小的转折性变化相反, 这表明, 在新疆地区, 蒸发皿蒸发和实际 蒸散之间具有相反的变化关系, 这支持Brutsaert and Parlange 提出的蒸发皿蒸发和实际蒸散 之间具有互补相关关系(变化趋势相反) 的理论。分析气温、降水、湿度、云量和日照时数等 环境变量的变化趋势发现： 降水、云量等表征大气中水分特征的变量表现为明显的上升趋势, 这也间接的证明了蒸发皿蒸发和实际蒸散之间存在相反的关系, 而与各个环境变量之间相关 系数的分析则表明, 气温日较差、风速、低云量和降水是与蒸发皿蒸发和实际蒸发关系最紧 密的环境因子, 它们的变化可能是导致蒸发皿蒸发和蒸散量变化的原因。 相似文献
9.
我国于1912年在北京设立了中央观象台(包括天文与气象),但只限于气候观测,谈不到气候学的研究。我国气候学研究迄今可以说有两个转折点。一个转折点就是1928年在南京成立了中央研究院气象研究所,开始了气候学的研究。第二个转折点就是新中国成立后在南京大学气象系于1952年设立了气候专业。国际上的气候学发展在70年代确已从描述性进入定量性的阶段,发展了动力气候学与统计气候学数值模拟,并且向气候预报方向逐渐发展,尤其是统计预报发展更快。 相似文献
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More than 240 items of historical records containing climatic information were retrieved from official historical books, local
chronicles, annals and regional meteorological disaster yearbooks. By using moisture index and flood/drought (F/D) index obtained
from the above information, the historical climate change, namely wet-dry conditions in borderland of Shaanxi Province, Gansu
Province and Ningxia Hui Autonomous Region (BSGN, mainly included Ningxialu, Hezhoulu, Gongchanglu, Fengyuanlu and Yan’anlu
in the Yuan Dynasty) was studied. The results showed that the climate of the region was generally dry and the ratio between
drought and flood disasters was 85/38 during the period of 1208–1369. According to the frequencies of drought-flood disasters,
the whole period could be divided into three phases. (1) 1208–1240: drought dominated the phase with occasional flood disasters.
(2) 1240–1320: long-time drought disasters and extreme drought events happened frequently. (3) 1320–1369: drought disasters
were less severe when flood and drought disasters happened alternately. Besides, the reconstructed wet-dry change curve revealed
obvious transition and periodicity in the Mongol-Yuan Period. The transitions occurred in 1230 and 1325. The wet-dry change
revealed 10- and 23-year quasi-periods which were consistent with solar cycles, indicating that solar activity had affected
the wet-dry conditions of the study region in the Mongol-Yuan Period. The reconstructed results were consistent with two other
study results reconstructed from natural evidences, and were similar to another study results from historical documents. All
the above results showed that the climate in BSGN was characterized by long-time dry condition with frequent severe drought
disasters during 1258 to 1308. Thus, these aspects of climatic changes might have profound impacts on local vegetation and
socio-economic system. 相似文献
12.
基于汉江流域雨雪分寸等史料记录的特点,以发生地区、影响程度和持续时间为衡量标准,提出了利用史料重建汉江流域季节旱涝等级序列的方法,重建了1735—1911汉江流域7府（州）四季的旱涝等级序列,据此分析了各府（州）1735—1911年季节上的旱涝变化特征。结果表明：① 汉中府、兴安府、商州和南阳府有更多的春季、夏季、冬季偏旱年,而郧阳府、襄阳府和安陆府有更多的春季、夏季偏涝年和秋季偏旱年;② 夏季和秋季旱涝等级的波动明显,而春季和冬季旱涝等级的波动较小;③ 年代际尺度上来看,汉江流域,1820s—1840s偏涝,1850s、1870s偏旱;④ 影响较大的季节连旱事件多发生在19世纪,而影响较大的季节连涝事件多发生在夏季和秋季。这一研究,对汉江流域定量化气候研究具有一定的价值,也为汉江流域未来的降水变化研究提供了数据支持。 相似文献
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1 IntroductionThe natural disasters, especially the flood and drought disasters, have occurred frequently inG uangdong area since ancienttim es.A ccording to historic statisticaldata,since the 17th century,the occurrence of the flood and drought disasters… 相似文献
15.
新疆洪旱灾害与大尺度气候强迫因子的联系 总被引：13，自引：6，他引：7
通过对新疆洪灾灾害历史资料和太阳黑子、ENSO事件年数据以及北大西洋涛动指数的分析,表明在太阳黑子极低值年或不活跃年,新疆易发生重大洪灾,而在太阳黑子低值年或相对不活跃年,新疆也易发生重大旱灾。近200a来,新疆重大洪旱灾害绝大部分都发生在太阳黑子的低谷时期。ENSO事件对新疆夏季降水的影响效应明显。因而该事件对新疆的洪旱灾害也产生了影响。对近50年来灾害统计资料分析显示,与拉尼娜年相比,在厄尔尼诺年新疆更易发生洪旱灾害。20世纪后半段新疆洪旱灾害指数与北大西洋涛动指数进行对比可以发现．夏季NAO指数与新疆洪水灾害之间存在大致上的反相关系。而冬季NAO指数与新疆干旱灾害之间存在比较明显的反相关系。 相似文献
16.
More than 240 items of historical records containing climatic information were retrieved from official historical books, local chronicles, annals and regional meteorological disaster yearbooks. By using moisture index and flood/drought (F/D) index obtained from the above information, the historical climate change, namely wet-dry conditions in borderland of Shaanxi Province, Gansu Province and Ningxia Hui Autonomous Region (BSGN, mainly included Ningxialu, Hezhoulu, Gongchanglu, Fengyuanlu and Yan’anlu in the Yuan Dynasty) was studied. The results showed that the climate of the region was generally dry and the ratio between drought and flood disasters was 85/38 during the period of 1208–1369. According to the frequencies of drought-flood disasters, the whole period could be divided into three phases. (1) 1208–1240: drought dominated the phase with occasional flood disasters. (2) 1240–1320: long-time drought disasters and extreme drought events happened frequently. (3) 1320–1369: drought disasters were less severe when flood and drought disasters happened alternately. Besides, the reconstructed wet-dry change curve revealed obvious transition and periodicity in the Mongol–Yuan Period. The transitions occurred in 1230 and 1325. The wet-dry change revealed 10- and 23-year quasi-periods which were consistent with solar cycles, indicating that solar activity had affected the wet-dry conditions of the study region in the Mongol–Yuan Period. The reconstructed results were consistent with two other study results reconstructed from natural evidences, and were similar to another study results from historical documents. All the above results showed that the climate in BSGN was characterized by long-time dry condition with frequent severe drought disasters during 1258 to 1308. Thus, these aspects of climatic changes might have profound impacts on local vegetation and socio-economic system. 相似文献
17.
1788年夏季,长江流域持久性洪水暴雨范围广,特大洪水暴雨时空分布趋势呈现绳套形.这种持久性洪水暴雨前期冬春两季,前冬系流域性范围降雪,嗣后,流域主要为持时长和范围广的多雨水气候异常现象,中下游流域入梅期早. 相似文献
18.
The reliability of paleoclimatic inferences from lake-sediment records rests on the understanding of how various sediment
indicators respond to environmental changes. Despite the recent proliferation of paleoclimatic records, only a limited number
of studies have rigorously evaluated potential indicators by comparing lake-sediment records with instrumental weather data.
We analyzed annually laminated sediments of the past 100 years from a lake in north-central Minnesota for a suite of variables
commonly used for climatic reconstructions. Results were compared with time series of climatic or climate-derived variables,
as well as with indices of climate modes thought to influence the regional climate of the midwestern United States. The oxygen-isotopic
composition of calcite (δ18Oc) shows trends similar to those of effective moisture (as measured by precipitation [P] minus actual evapotranspiration [AET],
P-AET, and the Palmer Drought Severity Index [PDSI]), with high δ18Oc values generally corresponding to low P-AET and low PDSI. δ18Oc also exhibits striking correspondence with the index of Pacific Decadal Oscillation (PDO) but it lags behind PDO by 3 years.
Elevated δ18Oc values during the warm PDO phase probably reflect warm and dry climatic conditions in the midwestern US, especially during
winter months. The carbon-isotopic composition of calcite (δ13Cc) shows some similarity with δ18Oc but also displays stratigraphic patterns resembling those of lake-productivity indicators, including biogenic silica, inverse
of inorganic carbon, ratio of organic carbon to nitrogen, and to a lesser extent, organic carbon. δ13Cc is correlated with mean annual air temperature (MAAT) and the index of Atlantic Multidecadal Oscillation (AMO), probably
because elevated MAAT stimulates the rate of algal carbon uptake, lengthens growing season, and/or enhances CO2 degassing. Varves are typically thicker during periods of lower δ18Oc and higher P-AET (or PDSI) values, because wet climatic conditions probably increase nutrient availability and lake productivity.
Gray-scale intensity does not co-vary with any of the above climatic variables or climate-mode indices. These results demonstrate
the utility of lake-sediment analyses for reconstructing temperature, drought, and large-scale climatic modes at Steel Lake.
However, application to down-core reconstructions may be compromised by a number of factors, including the site specificity
and non-stationarity of such relationships. 相似文献
19.
全球增暖下我国旱涝灾害可能情景的初步研究 总被引：6，自引：0，他引：6
在全球变暖的情况下,我国东南沿海、西南、西北、内蒙古和东北部分地区,洪涝灾害可能增加;而黄河中游以南和华北平原干旱可能增加.这一变化特征与本世纪暖期降水分布变化,以及与CO_2倍增情况下气候模似结果基本一致. 相似文献
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