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1.
全球的持续变暖导致极地海冰不断融化,北极航道即将全面开通。针对北极东北航道关键海区通航的不确定性、数据的时序性等问题,提出基于动态贝叶斯网络的北极东北航道关键海区通航可行性评估与预测技术。通过对航道通航关键海区的确定、指标的选取、贝叶斯网络的构建与参数学习、基于证据的推理计算、动态贝叶斯技术的检验等流程,建立了基于动态贝叶斯网络的风险评估与预测模型。结果表明,动态贝叶斯网络技术不仅能够很好地处理动态时序信息,且其在推理过程中结合了历史信息,具备信息的累积能力,降低了误差数据对最终结果的影响度,使结果更接近真实值,且动态贝叶斯网络技术的预测结果在短期内准确性较高,对判断北极东北航道的可通航性具有重要的参考意义。 相似文献
2.
全球的持续变暖导致极地海冰不断融化,北极航道即将全面开通。针对北极东北航道关键海区通航的不确定性、数据的时序性等问题,提出基于动态贝叶斯网络的北极东北航道关键海区通航可行性评估与预测技术。通过对航道通航关键海区的确定、指标的选取、贝叶斯网络的构建与参数学习、基于证据的推理计算、动态贝叶斯技术的检验等流程,建立了基于动态贝叶斯网络的风险评估与预测模型。结果表明,动态贝叶斯网络技术不仅能够很好地处理动态时序信息,且其在推理过程中结合了历史信息,具备信息的累积能力,降低了误差数据对最终结果的影响度,使结果更接近真实值,且动态贝叶斯网络技术的预测结果在短期内准确性较高,对判断北极东北航道的可通航性具有重要的参考意义。 相似文献
3.
海冰密度是海冰和气候模型的重要物理变量,也是利用卫星测高数据估算海冰厚度的关键参数。目前各国北极科学考察虽开展了海冰物理观测,但对近期北极海冰密度现场观测资料的综合分析和挖掘应用不足。在此背景下,收集了近15年来北极海冰密度现场观测资料,分析北极海冰密度的变化特征;对海冰密度实测数据进行克里金插值,将插值结果输入静力平衡方程模型计算海冰厚度,探讨海冰密度对海冰厚度卫星测高反演的影响。结果表明,2000—2015年北极海冰密度变化范围为750—950 kg·m^–3,1—9月海冰密度总体上随月份变化呈减小的趋势;6—9月北极海冰密度随着纬度的增加而减少(75°N—90°N);通过对比分析表明,相较于使用海冰密度固定值参与估算海冰厚度,采用经现场观测数据空间插值后的海冰密度估算海冰厚度的结果更为准确。北极海冰密度现场观测资料的整理分析可为海冰与气候变化等进一步研究提供参考。 相似文献
4.
加拿大和俄罗斯分别是北极西北航道与北方海航道的实际管理者。本论文采用对比研究的方式分析两国北极航道管理举措的异同点,以此为切入点,深入解析两国航道主权诉求的异同点,了解两国在诉求北极航道主权及实现航道经济潜能之间的权衡,探究两国对待未来北极航道商业通航的态度。并且,两国不同的北极航道管理举措还可以揭示各自对航道在国家政治军事安全重要性的认知差异、对海域环境保护的不同重视程度。北极航道管理举措折射出两国北极航道的政策现状及走向,围绕其展开的对比研究有助于国际社会更好应对未来北极航道的全面商业通航。 相似文献
5.
基于空间异质分区的残差IDW插值方法 总被引：1，自引：0，他引：1
《地理与地理信息科学》2015,(5)
空间插值可以利用已有观测数据修补缺失的观测数据,也可以利用离散数据构建连续的表面数据,但现有的空间插值方法没有充分考虑空间数据的异质性。该文提出一种基于空间异质分区的残差反距离加权插值方法(RRIDW)。首先根据采样点属性值对研究区域进行空间异质分区;为了进一步去除不同子区域内的空间趋势,对每个子区域计算趋势面,进而计算得到采样点属性值的异质分区残差,利用属性值残差进行反距离加权插值;最后结合趋势计算得到待求点处的空间插值结果。实验采用两组实际PM2.5浓度数据和降雨量数据,运用交叉验证方法对RRIDW方法与其他常用空间插值方法进行对比分析,验证了该方法的优越性和可行性。 相似文献
6.
7.
采用多层紧支撑径向基函数对离散数据内插生成DEM。首先对采样数据进行预处理,在原始数据上删除最小距离点对上的点,每次删除后将剩下的数据点存储并作为下一次删除操作的数据源,重复删除操作至点数为给定的初值;然后在已存储的数据集中选取均匀度较大的m个子集作为插值的数据源,分别进行紧支撑径向基函数插值,将上一层的误差作为下一层的插值属性值,求解插值矩阵系数。将规则格网点作为插值点通过插值矩阵内插生成DEM,并且与各种径向基函数插值方法进行比较。实验分析表明,基于多层紧支撑径向基函数的DEM具有较高的插值精度,可作为一种DEM插值方法。 相似文献
8.
全球气候变暖和北极海冰快速减少背景下,北极航道正在开通,提高海冰和气象预报能力是北极地区船只航行的重要保障。通过获取不同国家的北极高纬共享信息(包括观测数据、预报产品和历史分析资料),分析国际北极地区海冰和气象预报信息特点及存在的问题,能够为我国北极观测预报的常态化、业务化发展提供参考。通过对7个环北极国家、3个非北极国家以及3个信息发布平台共23家机构海冰和气象预报信息的对比,发现近年来各国北极预报水平提升,合作交流扩大,但是仍存在一些问题,如观测数据没有充分应用于预报、北极中央区的预报能力偏弱、预报信息共享度不够、信息应用时需要加以选择、仍需提升信息发布技术。通过上述分析,建议我国持续增加北极科考、国际合作、冰区安全航行预报保障技术研究等的投入,以系统提升我国的极地预报能力,为我国北极科考和极地航运事业提供更加及时有效的预报保障。 相似文献
9.
北极海冰的融化使得北极西北航道通航成为可能,有必要探讨北极西北航道的安全通航风险控制问题。针对北极西北航道冰情和复杂通航环境下的船舶通航窗口期,本研究采用时间维度上的过程风险评估方法,构建了基于系统动力学的北极西北航道通航风险评估模型,结合北极西北航道6条航线的场景条件,通过2015—2021年7年间风、雾、浪、海冰的月平均变化的数据分析,进行北极西北航道船舶通航过程风险仿真,提出了北极西北航道船舶通航窗口期。仿真结果表明:北极西北航道全年可通航的时间窗口为8月下旬至9月上旬,而选择阿蒙森湾—威尔士亲王海峡—巴罗海峡—巴芬湾和阿蒙森湾—维多利亚海峡—皮尔海峡—巴芬湾两条航线的船舶通航风险相对较低,从发展上看,随着海冰快速融化北极西北航道具有较高的通航潜力。 相似文献
10.
近年来随着北极冰区航道的开辟与成功通航,船舶航行安全广受重视,因冰区通航条件对船舶交通安全影响因素特殊且变化大,有必要分析极地冰区船舶航行时航路过程中的风险。探讨低温、浮冰、高纬度等特殊属性对船舶极地冰区航行安全的影响,结合船舶交通风险的特点,提出北极冰区东北航道船舶航行风险状态概率转移的过程风险,构建北极冰区东北航道船舶航行过程风险模型。基于马尔科夫过程假设,建立基于马尔科夫链-蒙特卡洛方法的云仿真模型,利用该模型对北极冰区东北航道船舶航行进行时间连续的过程风险动态仿真。研究表明:夏季时期船舶在北极冰区东北航道航行过程风险整体上处于可通航状态,离散风险程度随时间而连续变化,总体呈现"M"型趋势,风险波动明显。 相似文献
11.
Mark B. Dyurgerov & Mark F. Meier 《Geografiska Annaler: Series A, Physical Geography》1999,81(4):541-554
Seasonal mass balance components bw (winter balance) and bs (summer balance) as well as ct (total accumulation) and at (total ablation), can be used directly to infer climate variables. In contrast, ac (net balance of the accumulation area) and aa (net balance of the ablation area), and ba or bn (annual or net balance) can not. The traditional Alpine system of observations of ac and aa , however, can be converted to true seasonal values bw and bs if both pairs of components are simultaneously observed for some years, because a correlation between the two pairs of components exists. We analyzed bw and bs data and their mean, standard deviations and ratios of these to the corresponding net or annual balances for 50 glaciers with relatively long records representing different regions in the northern hemisphere. We also investigated correlations between seasonal components. A negative correlation between bw and bs exists at many glaciers. About two-thirds of the glaciers show insignificant correlations (?0.3 < r < 0.3), implying independence of summer and winter balances. In a few unusual cases the correlations are positive. These different correlations, or lack thereof, may offer insight into feedback conditions that must exist in this climate-related system. The correspondence of the bw and ct , and bs and at , appears to depend largely on the relative amounts of summer snowfall, a function of their climatic environment expressed as [α = (bw+bs)/2]. The contribution of variability of bs to the net balance increases markedly with decreasing values of α. The variability of bw and bs , and therefore the net balance, has been increasing with time; whether this is due to an increase in climate variability or to other causes is not clear. It appears that bw has been increasing with time at the highest altitudes, but bs has been increasing more rapidly especially at low altitudes; the many-glacier average net balance is becoming more negative. 相似文献
12.
R. M. Dargám 《International Journal of Salt Lake Research》1994,3(2):137-158
This paper reports on hydrochemical features of diluted waters in the source areas and the brine end-members dominant in the playa of the Salinas Grandes Basin, Córdoba, Argentina. Special emphasis was placed on the study of the relationship between geomorphology and the resulting hydrochemical fractionation. Inflow is from springs and mountain streams which disappear before reaching the saline complex. The playa and intermittent saline lakes are mainly fed by groundwater flow and a few moderately saline and perennial springs. Conversely, ephemeral lakes are fed by atmospheric precipitation and groundwater, whereas small ponds are only fed by atmospheric precipitation. The absence of a clear linkage between geomorphological units and water types was evident in the source areas. Up to four types of water were recognized in a given geomorphological unit. From the sandflat downward towards the playa, the correspondence between geomorphological units and water types was clear, coinciding with a decreased hydrochemical heterogeneity. In this subenvironment, I have recognized two dominant types of water (SO
4
2–
–Cl––HCO
3
–
–Na+ and Cl––SO
4
2–
–HCO
3
–
–Na+), which can be considered the original members of the neutral brine in the playa (Cl––SO
4
2–
–Na+ where Ca2++Mg2+ do not surpass 5 meq per cent), and an intermediate type in the mudflat (Cl––SO
4
2–
–Na+ where the contribution of Ca2++Mg2+ reaches up to 15 meq per cent). It seems evident that in the zone between the source areas and the sandflat, hydrochemistry is governed by chemical weathering. In stream floodplains and in the distal alluvial plain, close to the saline complex, the increase in water types as well as the increase of HCO
3
–
with respect to SO
4
2–
, were explained by the mixture of aquifers controlled by the Salinas Grandes-Salinas de Ambargasta fracture. In the saline complex, the more concentrated end-members are the result of evaporation of the two more frequent water-types in the sandflat subenvironment, and salt dissolution of ancient evaporite deposit. 相似文献
13.
Caspian Sea amphipods: biodiversity,systematic position and ecological peculiarities of some species
Galina M. Pjatakova Anatolyi G. Tarasov 《International Journal of Salt Lake Research》1996,5(1):63-79
In the Caspian Sea, one group of crustaceans, the Amphipoda, is represented by 72(70?) species, 60(58?) of which are gammarids, arranged in 20 genera. Almost all are endemic to the Ponto-Caspian zoogeographical region. To simplify the taxonomy of the genusGammarus Fabricius s.l., the Caspian gammarids ought to be grouped in 4 genera:Dikerogammarus Stebbing,Pontogammarus Sowinsky,Stenogammarus Martynov, andChaetogammarus Martynov. Taking into account the influence of different ecological factors on the external morphology of gammarids, we consider that all described forms ofDikerogammarus haemobaphes (Eichwald),D. villosus (Sowinsky),D. palmatus Martynov,D. fluviatilus Martynov, and perhapsD. aralensis (Uljanin) are one species —D. haemobaphes. Study of the ecological area and distribution ofIphigenella andrusovi Sars,Pandorites podoceroides (Grimm) andChaetogammarus placidus Sars indicates that these species are endemic to the Caspian Sea. 相似文献
14.
《The Professional geographer》1997,49(3):372-389
Aryeetey-Attoh, SamuelGeography of Sub-Saharan Africa Chew, Sing C. and Denemark, Robert A.(eds) The Underdevelopment of Development: Essays in Honor of Andre Gunder Frank Chinn, Jeff and Kaiser, RobertRussians as the New Minority: Ethnicity and Nationalism in the Soviet Successor States Curtis, Sarah and Taket, AnnHealth and Societies: Changing Perspectives Dudley, Nigel; Jeanrenaud, Jean-Paul and Sullivan, FrancisBad Harvest? The Timber Trade and the Degradation of the World's Forests Ellis, Steven and Mellor, AnthonySoils and Environment Gradus, Yehuda and Lithwick, Harvey (eds)Frontiers in Regional Development Green, Milford B. and McNaughton, Rod B. (eds)The Location of Foreign Direct Investment: Geographic and Business Approaches Greenberg, Michael and Schneider, DonaEnvironmentally Devastated Neighborhoods: Perceptions, Policies, and Realities Griffiths, Ieuan Ll.The African Inheritance Harrison, Lynn C. and Husbands, Winston (eds)Practicing Responsible Tourism: International Case Studies in Tourism Planning, Policy, and Development Jensen, John R.Introductory Digital Image Processing: A Remote Sensing Perspective Pacione, MichaelGlasgow: The Socio-Spatial Development of the City Platt, Rutherford H.Land Use and Society: Geography, Law, and Public Policy Rhodes, Martin (ed.)The Regions and the New Europe: Patterns in Core and Periphery Development Salant, Priscilla and Waller, Anita J.Guide to Rural Data Schnell, Izhak; Sofer, Michael and Drori, Israel Arab Industrialization in Israel: Ethnic Entrepreneurship in the Periphery Shelley, Fred M.; Archer, J. Clark; Davidson, Fiona M. and Brunn, Stanley D.Political Geography of the United States Taffe, Edward J.; Gauthier, Howard L. and O'Kelly, Morton E.Geography of Transportation 相似文献
15.
Field experiments were conducted in Nellis Dunes Recreational Area (Clark County, Nevada, USA) to investigate emission of dust produced by off-road driving. Experiments were carried out with three types of vehicles: 4-wheelers (quads), dirt bikes (motorcycles) and dune buggies, on 17 soil types characteristic for a desert environment. Tests were done at various driving speeds, and emissions were measured for a large number of grain size fractions. This paper reports the results for two size fractions of emissions: PM10 (particles < 10 μm) and PM60 (particles < 60 μm). The latter was considered in this study to be sufficiently representative of the total suspendable fraction (TSP). Off-road driving was found to be a significant source of dust. However, the amounts varied greatly with the type of soil and the characteristics of the top layer. Models predicting emission of dust by off-road driving should thus consider a number of soil parameters and not just one key parameter. Vehicle type and driving speed are additional parameters that affect emission. In general, 4-wheelers produce more dust than dune buggies, and dune buggies, more than dirt bikes. Higher speeds also result in higher emissions. Dust emitted by off-road driving is less coarse than the parent sediment on the road surface. Off-road driving thus results in a progressive coarsening of the top layer. Exceptions to this are silty surfaces with no, or almost no, vegetation. For such surfaces no substantial differences were observed between the grain size distribution of road dust and emitted dust. Typical emission values for off-road driving on dry desert soils are: for sandy areas, 30–40 g km− 1 (PM10) and 150–250 g km− 1 (TSP); for silty areas, 100–200 g km− 1 (PM10) and 600–2000 g km− 1 (TSP); for drainages, 30–40 g km− 1 (PM10) and 100–400 g km− 1 (TSP); and for mixed terrain, 60–100 g km− 1 (PM10) and 300–800 g km− 1 (TSP). These values are for the types of vehicles tested in this study and do not refer to cars or trucks, which produce significantly more dust. 相似文献
16.
Microcoleus vaginatus isolated from a desert algal crust of Shapotou was cultured in BG-11 medium containing 0.2 mol l−1 NaCl or 0.2 mol l−1 NaCl plus 100 mg l−1 sucrose, extracellular polymeric substances (EPS) or hot water-soluble polysaccharides (HWP), respectively. Photosynthetic oxygen evolution rates, photosystem II activity (Fv/Fm) and dark respiration of NaCl-stressed cells were enhanced significantly by the added sucrose or EPS under salt stress conditions (0.2 mol l−1 NaCl). Compared with cells treated with salt alone, sodium contents in cells reduced significantly; the content of cellular total carbohydrate did not change, and intracellular sucrose, water-soluble sugar increased significantly following the addition of exogenous carbohydrates. Sucrose synthase (SS) activity of NaCl-stressed cells increased following the addition of sucrose, and sucrose phosphate synthase (SPS) activity of NaCl-stressed cells increased following the addition of exogenous sucrose, EPS or HWP compared with cells stressed with NaCl only. The results suggested that the extruded EPS might be re-absorbed by cells of M. vaginatus as carbon source, they could increase salt tolerance of M. vaginatus through the changes of carbohydrate metabolism and the selective uptake of sodium ions. 相似文献
17.
长江口潮滩沉积物－水界面无机氮交换通量 总被引：11，自引：1，他引：10
对长江口滨岸潮滩7个典型断面三态氮的界面交换通量进行了三年多的季节性连续观测,结果表明无机氮的界面交换行为存在复杂的空间分异和季节变化。NO-3-N和NH+4-N的界面交换通量正负变化范围较大,分别介于-32.82~24.13 mmol.m-2.d-1和-18.45~10.65mmol.m-2.d-1之间;而NOsup>-2-N的界面交换通量很小,仅为-1.15~2.82 mmol.m-2.d-1。NO-3-N的界面交换具有明显的上下游季节性时空分异特征,而NH+4-N的界面交换则表现为南北岸季节性时空分异现象。盐度是控制长江口滨岸潮滩NH+4-N界面交换行为的主要因素,而沉积物粒度、水体 NO-3-N浓度、沉积物有机质含量、水温和溶解氧含量则以不同的组合方式,共同制约着 NO-3-N在潮滩界面交换的时空分异格局。 相似文献
18.
《The Professional geographer》2002,54(3):454-478
Books Reviewed Colbert C. Held, Middle East Patterns: Places, People, and Politics Barbara A. Weightman, Dragons and Tigers: A Geography of South, East, and Southeast Asia Henry J. Bruman, Alcohol in Ancient Mexico Brian W. Blouet, Geopolitics and Globalization in the Twentieth Century M. A. B. Siddique (ed.), International Migration into the 21st Century: Essays in Honour of Reginald Appleyard Michael R. Haines and Richard H. Steckel (eds.), A Population History of North America Emilio Moran, Human Adaptability: An Introduction to Ecological Anthropology Jeremy Leggett, The Carbon War: Global Warming and the End of the Oil Era Susan B. Marriott and Jan Alexander (eds.), Floodplains: Interdisciplinary Approaches William S.Logan, Hanoi: Biography of a City Alex Krieger and David Cobb (eds.) with Amy Turner, Mapping Boston Eric Sandweiss, St. Louis: The Evolution of an American Urban Landscape Carl Abbott, Greater Portland: Urban Life and Landscape in the Pacific Northwest Arthur D. Murphy, Colleen Blanchard and Jennifer A. Hill (eds.), Latino Workers in the Contemporary South Yanek Mieczkowski, The Routledge Historical Atlas of Presidential Elections 相似文献
19.
Horizontal and vertical zones of influence for root systems of four Mojave Desert shrubs 总被引：3，自引：0，他引：3
Horizontal and vertical zones of influence for root systems of four Mojave Desert shrubs were characterized using 32P as a nutrient tracer. Larrea tridentata's horizontal zone of influence was sparse near the plant's stem base, with a maximum probability of accessing 32P (Pmax) of 41%. However, its horizontal zone of influence extended beyond 5 m, and the distance from the stem base at which the probability of accessing 32P was half Pmax (L503 m) was significantly greater than the other three shrubs. Ambrosia dumosa's zone of influence was dense near the plant's stem base (Pmax78%), but was rare at distances >2 m (L501 m). Zones of influence for Lycium andersonii and Lycium pallidum were intermediate between those of L. tridentata and A. dumosa. For vertical zones of influence, L. tridentata was more likely to obtain 32P from 5 m soil depths than A. dumosa, but L. pallidum was not significantly different from either A. dumosa or L. tridentata. Horizontal zones of influence did not change with treatments that altered soil water and nitrogen availability, but vertical zones of influence increased with a flood irrigation treatment that increased water availability to 5 m soil depth. These differences among species likely reflect compromises between their shoot growth strategies and their need to acquire spatially and temporally limited soil resources, especially through competitive interactions. 相似文献
20.
AbstractCharacterizing gully cross sections (GCs) is essential for calculating the volume and erosion rate of the gully. However, little research has focused on modeling the morphology of GCs. This study investigated 456 GCs with a laser distance meter located at the mouth, middle, and head of 152 gullies in the Yuanmou Dry-hot Valley of China; mapped them with AutoCAD software; fitted them with 2nd–6th degree polynomial functions, and discussed the correlation between the coefficients and the morphology of GCs. The results showed that: (1) using a 2nd-degree polynomial function (y = ax2 + bx + c) to describe the morphology of GCs produced a better result than other polynomial functions; (2) the coefficient a of 2nd-degree polynomial function was correlated with depth (r = ?0.226, p < 0.01), gradient (r = 0.545, p < 0.01), and activities; and (3) the symmetry axis (?b/2a) of 2nd-degree polynomial function increased with gully change from left-deflection to right-skewed, and the absolute value showed the asymmetrical degree (r = 0.216, p < 0.01). This study will not only help to understand the morphology and evolution of gullies, but will also provide a scientific basis for prevention of gully erosion. 相似文献