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161.
Sheng?YueEmail author Chun Yuan?Wang 《Stochastic Environmental Research and Risk Assessment (SERRA)》2004,18(5):291-305
Scaling properties of Canadian low flows, namely annual minimum mean 1-, 5- and 7-day flows, are evaluated across Canada and in its sub-climatic regions. Across the entire country, the log relationship between the kth product moments (PMs, E[Qik]) of low flows and drainage area (Ai) can be represented by: ln(E[Qik])=ak+bkln(Ai)and bk=k, with = 0.86, 0.94 and 0.93 for annual minimum mean 1-, 5- and 7-day flows, respectively. The log linear relationships between the kth probability weighted moments (PWMs, ) and Ai are ln()=ck+Hln(Ai), in which H is constant and is independent of k. The values of H are 0.87, 0.97, and 0.96 for annual minimum mean 1-, 5- and 7-day flows, respectively, which are almost the same as the values. The coefficients of variation (Cv) are almost independent of drainage area. These results demonstrate that Canadian low flows generally exhibit simple scaling and drainage area alone describes most of the variability in the moments of the low flows. Low flows in each of the sub-climatic regions also obey a simple scaling law. The values of , H and Cv are different in each region, which may stem from physiographical and climatological differences among these regions. The finding lays a basis for applying the index flood method to conduct regional low flow frequency analysis as simple scaling is equivalent to the index flood method.Acknowledgements The authors thank Prof. Thian Yew Gan of University of Alberta, Canada for providing additional pristine data sites for regions 4 and 10. A constructive comments provided by an anonymous reviewer improved the quality of the paper. 相似文献
162.
N. Sifakis D. Paronis I. Keramitsoglou 《International Journal of Applied Earth Observation and Geoinformation》2004,5(4):305
This paper describes an operational application of AVHRR satellite imagery in combination with the satellite-based land cover database CORINE Land Cover (CLC) for the comprehensive observation and follow-up of 10000 fire outbreaks and of their consequences in Greece during summer 2000. In the first stage, we acquired and processed satellite images on a daily basis with the aim of smoke-plume tracking and fire-core detection at the national level. Imagery was acquired eight times per day and derived from all AVHRR spectral channels. In the second stage, we assessed the consequences of fire on vegetation by producing a burnt-area map on the basis of multi-annual normalised vegetation indices using AVHRR data in combination with CLC. In the third stage we used again CLC to assess the land cover of burnt areas in the entire country. The results compared successfully to available inventories for that year. Burnt area was estimated with an accuracy ranging from 88% to 95%, depending on the predominant land cover type. These results, along with the low cost and high temporal resolution of AVHRR satellite imagery, suggest that the combination of low-resolution satellite data with harmonised CLC data can be applied operationally for forest fire and post-fire assessments at the national and at a pan-European level. 相似文献
163.
164.
利用S波纯波形拟合法以及T函数法反演了苏鲁地区壳幔剪切波速度结构,并利用长周期P波T函数反演得到了连云港和莱阳台下方800km深度的速度结构。结果显示:(1)苏鲁地区大部分台站地壳表层及上地壳浅部速度偏高,分别对应高压、超高压物质和古老基底出露地区;(2)沿郯庐断裂带分布的台站均显示明显低速层,并具有北浅南深的特点;(3)连云港和莱阳台超深度反演结果显示两台均在150km深度下出现高速层,反映扬子板块的俯冲深度为100km以下,俯冲板片厚度在100km以上;板片拆离下沉深度甚至达到300km或者更深;(4)地震深度分布与低速层关系密切,沿郯庐断裂和烟台—五莲断裂的中小地震震源深度都比较深,有的甚至达到地壳的底部,反映这两条断裂目前切割深度都比较大,而且地幔物质相对比较活跃。 相似文献
165.
据中新社兰州10月21日电,中国科学院寒区旱区环境与工程研究所蓝永超研究员根据代表黄河上游流域径流动态变化的唐乃亥水文站1920年至2004年的径流系列统计资料,以及此间数十个气象站四十余年的降水观测数据,分析得出的初步结论显示,从上世纪20年代初到90年代,黄河大体上经历了5个枯水期和4个丰水期。每个丰、枯水期段持续的时间长短不一,枯水期持续时间为4~15年,平均为9年;丰水段持续时间为7~14年,平均为9.25年。总体上黄河上游每个丰、枯水周期平均持续时间基本相同,一个完整的丰枯循环周期大约在18年左右[1]。18.6年是典型的潮汐周期。月… 相似文献
166.
M. Fendekova Z. Zenisova P. Nemethy M. Fendek Z. Makisova S. Kupcova R. Flakova 《Environmental Geology》2005,48(8):1029-1039
The main goal of the research was a detailed study of the consequences, caused by groundwater abstraction in the Neresnica
brook catchment (Slovak Republic) since the water supply source Podzamcok was put in operation in 1973. This goal was supplemented
by research of groundwater origin, groundwater chemical composition and its changes. Field measurements, analyses of water
samples and statistical evaluation of hydrometeorological data were used to gain and process the data. It was showed that
overexploitation of groundwater in the catchment resulted in distinct diminishing of stream flow discharges in low flow periods,
groundwater level dropping and disturbance of hydraulic connection between surface and groundwater. Groundwater quality was
quite stable during the whole period of observation. Groundwater modeling was proposed to be used for the re-estimation of
utilizable groundwater amounts in the catchment. 相似文献
167.
Yasushi Watanabe 《Mineralium Deposita》2005,40(3):307-323
Kyushu Island, Japan, is located at the junction of the Southwest Japan arc and the Ryukyu arc. There are two major late Cenozoic
epithermal gold-silver provinces in Kyushu, which are termed the Northern and Southern provinces. The provinces are characterized
by: 1) Pliocene volcanism dominated by calc-alkaline andesite, followed by Quaternary volcanism including extrusion of both
calc-alkaline and tholeiitic magmas; 2) formation of extensional grabens; 3) Pliocene to Pleistocene mineralization, which
was dominated by abundant low sulfidation (LS) epithermal deposits with a few high sulfidation (HS) examples. The two epithermal
gold-silver provinces have evolved differently since about 5 Ma; the Northern province has exhibited diminished hydrothermal
activity from the Pliocene to Pleistocene, whereas the Southern province has witnessed increased hydrothermal activity mainly
in easterly and northerly directions. Changes of tectonic setting from the Pliocene to Pleistocene account for the variable
trends in epithermal gold deposit formation. Westward oblique subduction of the Philippine Sea plate beneath the Southwest
Japan arc caused development of the Hohi graben and arc-related volcanism at about 6 Ma. This was associated with widespread
LS mineralization in and surrounding the Hohi graben, as is represented by the Bajo and Taio deposits. The subduction of the
relatively buoyant Kyushu-Palau ridge during the early Pliocene strengthened the coupling between the slab and overriding
Ryukyu arc, leading to polygenetic andesite volcanism with associated HS (Kasuga, Iwato, and Akeshi) and LS (Kushikino) mineral
deposits forming in the Southern province. A change of the subduction direction of the Philippine Sea plate, from west to
north-northwest in the early Pliocene, increased the orthogonal convergence rate between the Southwest Japan arc and the Philippine
Sea plate, resulting in a decrease of volcanic and hydrothermal activity in the Hohi graben of the Northern province. The
more northerly subduction of the Philippine Sea plate shifted the locus of the Kyushu-Palau ridge subduction northward, resulting
in underplating of the older (85–60 Ma), negatively buoyant Amami basin oceanic slab in the Southern province, rather than
continued subduction of the young (27–15 Ma), buoyant Shikoku basin slab. This replacement caused steepening of the slab angle
and slab-rollback in the Southern province, which was associated with regional extension, an eastward shift of the Ryukyu
volcanic front, and development of the Kagoshima and Shimabara grabens, as well as the Okinawa trough. Rhyolite and basalt
volcanism, in addition to andesite volcanism, have occurred since 2 Ma in the area of the Ryukyu back arc; coincident LS mineralization
at Hishikari and Ohkuchi was affiliated with the rhyolite volcanism. Another change of the subduction direction of the Philippine
Sea plate to the northwest occurred at 2–1 Ma. The forearc sliver of the Southwest Japan arc shifted westward, in association
with right-lateral strike-slip faulting along the Median tectonic line, due to the increase of the westward convergence rate.
This shift resulted in shortening and cessation of graben development in the Hohi area, restricting the subsequent volcanism
and related hydrothermal activity to the central part of the graben. 相似文献
168.
低纬高原地区降水量资源年际变化的特征时间尺度及其时空演变 总被引:1,自引:0,他引:1
应用三维数据的时间小波变换方法,分析研究了低纬高原地区降水量资源在年际变化上的特征时间尺度及其时空演变。结论为:低纬度高原地区降水量资源在年际变化上的特征时间尺度分别约为2a、7a和15a。2a、78和158特征时间尺度的较大振幅能量活动区,分别主要位于滇西北到滇东南、滇东北到滇西南和滇中一带。与2a特征时间尺度相对应的较大振幅能量活动中心纬度的降水量,表现出了明显的东西向波动的时间演变特征,而与78和158特征时间尺度相对应的较大振幅能量活动中心纬度的降水量,则表现出了在东西向较为稳定少变的时间演变特征。与2a特征时间尺度相对应的较大振幅能量活动中心经度的降水量,也表现出了明显的南北向波动的时间演变特征,而与7a和15a特征时间尺度相对应的较大振幅能量活动中心经度的降水量,则表现出了一种明显向南移动的时间演变趋势。 相似文献
169.
170.