The formation of runoff-generated debris flow in Southwestern of China: take Gangou as an example   总被引：2，自引：1，他引：1  

Yong Bo Tie  Ru Ge Xu  Ren Ji Ba 《Environmental Earth Sciences》2014,72(5):1479-1490

In the mountain area of Southwestern China, there are large quantities of runoff-generated debris flows that are threatening the local people and facilities seriously. Gangou is a typical runoff-generated debris flow; its source is old deposit from floods and the debris flows downstream of the channel. On June 30, 2005, Gangou occurred debris flow, the debris flow destroying the road, the communications facilities and the farmland at the gully mouth. Unlike the formation mechanisms of other debris flows, the formation of 2005 debris flow in Gangou has its distinctive characteristics as follows. (1) The supply of the loose sources is intensive and distribute near the mouth of the gully; it is rare to see any debris flow initiate at such a lower location. (2) The debris flow finishes its initiation, flow and deposition around the 700-m-long channel, accompanied with the blocking process in the gully when the debris flow ran out; however, 10 min later, it releases and amplifies the peak flow about three times. (3) The topographic condition of the basin does not contribute much to the formation of the 2005 debris flow; instead, its formation is the result of the co-effort of continuous rainfall and a short-time heavy rainfall. In other words, the previous cumulative precipitation enables the moisture content of the soil on the right bank of the gully to reach saturation; then the soil slides into the channel under the action of the heavy rainfall at a later time. Meanwhile, the heavy rainfall accelerates the formation of gully run-off and initiates the loose mass in the channel from slide, thus forming the debris flow.  相似文献   

Influence of Tropical Cyclones of the South China Sea on the Variability of the Vietnamese Coastal Current Structure     

Vlasova  G. A.  Nguyen  Xuan Ba  Le  Mau Dinh  Marchenko  S. S. 《Oceanology》2022,62(1):13-21

The state of the natural environment of the marginal seas of the Northwest Pacific is largely controlled by the interaction of the atmospheric and hydrophysical processes. Tropical cyclones (typhoons), originating in the tropical zone of the Northwest Pacific and over the South China Sea basin, occupy a special place among atmospheric processes. The main destructive impact of typhoons falls on Southeast Asia. However, a significant number of are moving to the Russian Far East. The region of the South China Sea plays a significant role in the formation of tropical cyclones. This determines the importance of studying hydrometeorological processes not only in the Far East, but also in the South China Sea, and the need for cooperation between Vietnamese and Russian scientists. The main hydrodynamic structure of the western South China Sea is the Vietnamese Coastal Current (Western Boundary current), which depends not only on the seasonal monsoons but also on typhoons. The paper presents the results of joint Russian–Vietnamese studies of the dependence of the vertical structure of the Vietnamese Coastal Current on the Pacific tropical cyclones that form in the South China Sea. The study is done with numerical modeling. The period from April to June 1999 was used for modeling, provided with the necessary field data. The simulation results showed that, in general, the structure of water masses depends on the trajectories of tropical cyclones. In all cases considered, the Vietnamese Coastal Current is not a single flow, but represents a zone of eddy structures of different directions. An exception is the only situation in the condition of a tropical cyclone in the central region of the South China Sea when this current acquired the form of a single continuous flow directed from north to south only in the 200-m layer. The general patterns of changes in the dynamic structure of the Vietnamese Coastal Current for all the considered tropical cyclone trajectories include the following: areas with water transport in the northern direction prevail on the surface, while the rest of the water mass continues to flow generally in the southern direction. This transport of surface waters may be due to the influence of the emerging summer monsoon, and the rest of the water mass, which is less exposed to the still weak atmospheric processes of the monsoon type, continues to flow in the winter regime.

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红外相机记录的河西走廊荒漠生态系统中兽类和鸟类的群落动态     

林永一  王永珍  赵文智  李锋瑞  巴义彬  刘继亮 《中国沙漠》2022,42(3):159-169

河西走廊地势狭长,位于两山之间,主要由荒漠构成,生境一旦遭到破坏,当地物种将很难找到替代的栖息地。本文以河西走廊中部典型砾质戈壁为研究区,经由2019—2020年红外相机和人工观测等方式监测到的兽类和鸟类数据为基准,探讨其群落动态及活动节律。结果表明：砾质戈壁兽类中的国家Ⅱ级重点保护及“三有”（有重要生态、科学、社会价值）动物有6种,而砾质戈壁鸟类中的国家Ⅱ级重点保护及“三有”动物有8种。兽类群落的季节变化小,春季鹅喉羚（Gazella subgutturosa）等的相对多度指数略高于其他季节,三趾跳鼠（Dipus sagitta）在4月大量出现;鸟类群落季节变化明显,春、夏季和秋季鸟类的相对多度指数高于冬季,物种数在夏季和秋季达到峰值。兽类和鸟类的相对多度变化趋势相似,均在夏末和春季达到顶峰。兽类的月相对多度指数与土壤含水量呈极显著的负相关,鹅喉羚和沙狐（Vulpes corsac）等日活动节律受人类活动影响出现在夜间、黄昏或黎明。鸟类的月相对多度指数与人类活动、空气温度、土壤温度和节肢动物均呈显著正相关,但人类活动在生长季会降低一些鸟类的活动频率。总之,河西走廊中部戈壁是鹅喉羚、沙狐、红隼（Falco tinnunculus）、锲尾伯劳（Lanius sphenocercus）、黑尾地鸦（Podoces hendersoni）、沙鵖（Oenanthe isabellina）、漠鵖（Oenanthe deserti）和短趾百灵（Calandrella cheleensis）等兽类和鸟类的主要栖息地,建立沙化土地封禁保护区对保护荒漠动物多样性具有重要的生态意义。  相似文献   

酸雨观测中pH测量负偏差的统计分析   总被引：3，自引：0，他引：3       下载免费PDF全文

汤洁  巴金 《应用气象学报》2013,24(1):55-64

该文对1992—2011年的酸雨观测资料中存在的pH测量负偏差进行统计分析。结果显示:除西北地区、青藏高原外的大部分酸雨观测站不同程度地出现pH值测量负偏差,总体上南方地区台站的pH测量负偏差问题较北方地区突出;随着测量仪器的更新换型、观测业务规范化管理水平的提升以及一些针对性技术措施的实施,存在pH测量负偏差问题的观测台站比例从20世纪90年代的40%以上下降为25%,观测资料中受pH测量负偏差影响的数据比例由10%下降到2%。pH负偏差的量值与降水pH值之间存在一定依存关系:降水pH值越低,负偏差问题越严重,pH负偏差的主要量值分布区间为-0.6~0,约占负偏差数据的80%。  相似文献   

A new set of integrals of motion to propagate the perturbed two-body problem     

Giulio Baù  Claudio Bombardelli  Jesús Peláez 《Celestial Mechanics and Dynamical Astronomy》2013,116(1):53-78

A formulation of the perturbed two-body problem that relies on a new set of orbital elements is presented. The proposed method represents a generalization of the special perturbation method published by Peláez et al. (Celest Mech Dyn Astron 97(2):131–150, 2007) for the case of a perturbing force that is partially or totally derivable from a potential. We accomplish this result by employing a generalized Sundman time transformation in the framework of the projective decomposition, which is a known approach for transforming the two-body problem into a set of linear and regular differential equations of motion. Numerical tests, carried out with examples extensively used in the literature, show the remarkable improvement of the performance of the new method for different kinds of perturbations and eccentricities. In particular, one notable result is that the quadratic dependence of the position error on the time-like argument exhibited by Peláez’s method for near-circular motion under the $J_{2}$ perturbation is transformed into linear. Moreover, the method reveals to be competitive with two very popular element methods derived from the Kustaanheimo-Stiefel and Sperling-Burdet regularizations.  相似文献   

Accurate analytical approximation of asteroid deflection with constant tangential thrust     

Claudio Bombardelli  Giulio Baù 《Celestial Mechanics and Dynamical Astronomy》2012,114(3):279-295

We present analytical formulas to estimate the variation of achieved deflection for an Earth-impacting asteroid following a continuous tangential low-thrust deflection strategy. Relatively simple analytical expressions are obtained with the aid of asymptotic theory and the use of Peláez orbital elements set, an approach that is particularly suitable to the asteroid deflection problem and is not limited to small eccentricities. The accuracy of the proposed formulas is evaluated numerically showing negligible error for both early and late deflection campaigns. The results will be of aid in planning future low-thrust asteroid deflection missions.  相似文献   

3D scattering of obliquely incident plane SV waves by an alluvial valley embedded in a fluid-saturated,poroelastic layered half-space     

Zhenning Ba  Jianwen Liang  Xiongyi Mei 《地震学报(英文版)》2013,(2):107-116

The indirect boundary element method is used to study the 3D dynamic response of an infinitely long alluvial valley embedded in a saturated layered half-space for obli- quely incident SV waves. A wave-number transform is first applied along the valley＇s axis to reduce a 3D problem to a 2D plane strain problem. The problem is then solved in the section perpendicular to the axis of the valley. Finally, the 3D dynamic responses of the valley are obtained by an inverse wave-number transform. The validity of the method is con- firmed by comparison with relevant results. The differences between the responses around the valley embedded in dry and in saturated poroelastic medium are studied, and the effects of drainage conditions, porosity, soil layer stiffness, and soil layer thickness on the dynamic response are dis- cussed in detail resulting in some conclusions.  相似文献   

Early Paleoproterozoic magmatism in the Quanji Massif, northeastern margin of the Qinghai-Tibet Plateau and its tectonic significance: LA-ICPMS U-Pb zircon geochronology and geochemistry   总被引：5，自引：0，他引：5  

Songlin Gong  Nengsong Chen  Qinyan WangT.M. Kusky  Lu Wang  Lu ZhangJin Ba  Fanxi Liao 《Gondwana Research》2012,21(1):152-166

The Quanji Massif is located on the north side of the Qaidam Block and is interpreted as an ancient cratonic remnant that was detached from the Tarim Craton. There are regionally exposed granitic gneisses in the basement of the Quanji Massif whose protoliths were granitic intrusive rocks. Previous studies obtained intrusion ages for some of these granitic gneiss protoliths. The intrusion ages span a wide range from ~ 2.2 Ga to ~ 2.47 Ga. This study has determined the U-Pb zircon age of four granitic gneiss samples from the eastern, central and western parts of the Quanji Massif. CL images and trace elements show that the zircons from these four granitic gneisses have typical magmatic origins, and experienced different degrees of Pb loss due to strong metamorphism and deformation. LA-ICPMS zircon dating yields an upper intercept age of 2381 ± 41 (2σ) Ma from monzo-granitic gneiss in the Hudesheng area and 2392 ± 25 (2σ) Ma from granodioritic gneiss in the Mohe area, eastern Quanji Massif, and 2367 ± 12 (2σ) Ma from monzo-granitic gneiss in the Delingha area, central Quanji Massif, and 2372 ± 22 (2σ) Ma from monzo-granitic gneiss in the Quanjishan area, western Quanji Massif. These results reveal that the intrusive age of the protoliths of the widespread granitic gneisses in the Quanji Massif basement was restricted between 2.37 and 2.39 Ga, indicating regional granitic magmatism in the early Paleoproterozoic, perhaps related to the fragmentation stage of the Kenorland supercontinent. Geochemical results from the granodioritic gneiss from the Mohe area indicate that the protolith of this gneiss is characterized by adakitic rocks derived from partial melting of garnet-amphibolite beneath a thickened lower crust in a rifting regime after continent-continent collision and crustal thickening, genetically similar to the TTG gneisses in the North China Craton. This suggests that the Quanji Massif had a tectonic history similar to the Archean Central Orogenic Belt of North China Craton during the early Paleoproterozoic. We tentatively suggest that the Quanji Massif and the parental Tarim Craton and the North China Craton experienced rifting in the early Paleoproterozoic, after amalgamation at the end of the Archean. The Tarim Craton and North China Craton might have had close interaction from the late Neoarchean to the early Paleoproterozoic.  相似文献   

Modern climate of the Cát Tiên National Park (Southern Vietnam): Climatological data for ecological studies     

O. A. Deshcherevskaya  V. K. Avilov  Ba Duy Dinh  Cong Huan Tran  J. A. Kurbatova 《Izvestiya Atmospheric and Oceanic Physics》2013,49(8):819-838

A method of using the standard network weather station data for local ecosystem research is considered on the example of the modern climate of the Cát Tiên National Park (Southern Vietnam) and local climate change in 1980–2010. Special attention is focused on the environmental parameters, which play a role of the limiting factors. It is shown that the climate of Southern Vietnam responds with statistical significance to global climate change. Suggestions about the possible reactions of tropical monsoon forest ecosystem to climate change are given.  相似文献   

粤北桃村坝花岗岩锆石U-Pb年代学、地球化学及成因研究          下载免费PDF全文

单芝波  李坤  凌洪飞  沈渭洲  黄国龙  朱捌 《高校地质学报》2014,20(3):314

桃村坝花岗岩体位于粤北贵东复式花岗岩体中部。锆石U-Pb年龄为161.5±1.8 Ma (MSWD=1.7),属于燕山早期岩浆 活动产物。该岩体具有稍低的硅、富铝、富碱、钾大于钠、贫钙镁和高FeO*/MgO等特征。富集Rb,Th,U而亏损Ba, Sr,Ti和Nb;LREE富集(LREE/HREE=7.39~16.4, (La/Yb)N=8.79~25.5),Eu亏损较为明显(δEu=0.44~0.59);Ga/Al比值较高(平 均值为2.99),Zr+Nb+Ce+Y含量(平均为518×10-6)大于350×10-6,可归属于A2型花岗岩;εNd(t)值低,为-9.7~-8.95,Nd模式 年龄为1.66~1.76 Ga;锆石的εHf(t)值为-20.0~-14.6,相应的Hf模式年龄为2.12~2.46 Ga。综合以上特征表明桃村坝花岗岩是 在地壳伸展-减薄的构造背景下、由古元古代地壳组分部分熔融的方式形成。  相似文献