基于小波变换与神经网络的石羊河流域夏季地温预测模型研究   总被引：1，自引：1，他引：0  

贾东于  李开明  聂晓英  袁春霞  李清峰  高福元 《冰川冻土》2020,42(2):412-422

地温变化在气候反馈效应中起着重要作用， 理解地温及其与影响因素之间的时空关系对预测全球温度变化至关重要。利用1998 - 2017年石羊河流域的逐日常规气象观测资料， 采用小波分析结合BP（Back Propagation）神经网络构建了石羊河流域夏季地温预报模型， 结果表明： 日平均地温预测效果在不同站点均为最佳， 其中预测值和观测值的相关系数均大于0.87， 3 ℃以内的预测概率均大于84%。其中， 民勤地区地温预测效果最好， 预测值和观测值的相关系数达到0.91， 3 ℃以内的预测概率达到86%。日最高地温的预测值与观测值的相关系数高于0.8， 但误差平方和、 标准差较大。永昌地区日最高地温的模拟效果最好， 3 ℃以内的预测概率达到83%。日最低地温的预测与观测值的平均相关系数高于0.66， 3 ℃以内的预报概率高于83%， 但预测值略低。其中， 武威地区日最低地温的预测效果最好， 预测值与观测值的相关系数为0.72， 3 ℃以内的预测概率达到94%。研究成果可为有效弥补干旱、 半干旱区地温观测资料缺失和探讨其与局地气候的关系提供一些参考。  相似文献   

Effect of spatially variable saturated hydraulic conductivity with non-stationary characteristics on the stability of reservoir landslides     

Xue  Yang  Wu  Yiping  Miao  Fasheng  Li  Linwei  Liao  Kang  Ou  Guangzhao 《Stochastic Environmental Research and Risk Assessment (SERRA)》2020,34(2):311-329

Stochastic Environmental Research and Risk Assessment - Conventional landslide analyses, based on deterministic methods or simple random variable methods, cannot consider the spatial variability...  相似文献   

Stability analysis of shotcrete supported crown of NATM tunnels with discontinuity layout optimization          下载免费PDF全文

Yiming Zhang  Xiaoying Zhuang  Roman Lackner 《国际地质力学数值与分析法杂志》2018,42(11):1199-1216

For tunnel constructed by New Austrian Tunnelling Method, the crown is the upper part of tunnel section, constructed during excavation process and supported by shotcrete. The stability of the crown has great influence on the safety of tunnel itself and the buildings above, which correlates, among others, with geometrical setup of tunnel and material properties of shotcrete and soil/rock. In this paper, aiming at analyzing the stability of shotcrete supported crown, a recently presented numerical method discontinuity layout optimization is adopted, which introduces a great amount of potential discontinuities cross over one another and provides a wide search space for efficient upper limit analysis. In the analysis, a well‐established hydration model of cementitious material is implemented for accounting the hydration of shotcrete. Then assumptions based on convergence‐confinement method are used for accounting the 3‐dimensional effect in 2‐dimensional analysis, finally providing time‐space–dependent assessments of stability of shotcrete supported crown.  相似文献   

青藏高原热融湖塘的水热过程及其对下伏多年冻土的热影响     

胡晓莹  盛煜  吴吉春  李静  曹伟 《湖泊科学》2018,30(3):825-835

以青藏高原查拉坪地区一处热融湖塘(40 m×50 m,最大深度为1 m)为研究对象,由实测数据对比分析了热融湖塘与天然地表相同深度的温度变化特征.结果表明:与天然地表相比,热融湖塘融化时间长,冻结时间短,且存在接近4℃的水温变化;受太阳辐射及热对流的影响,垂向水温梯度仅在水表从4℃降温及冻结阶段较大,其余时段接近0;湖底年均温度比相同深度的天然地表高约6.4℃,湖底下部存在约14 m深随时间发展的融区,土体吸热增大,放热减小;热融湖塘2.5~3.0 m土体的年内热交换为19592.0 k J/m2,约是天然地表的230倍,其中吸热量及放热量分别为后者的1.4倍及8.7%.湖塘下部的融化夹层是深层冻土的主要热源,湖塘对下部土体放热的抑制作用是湖塘对土体产生热影响的主要原因.  相似文献   

Partition-coordinated control of soil and water loss for chestnut forests in the Yanshan Mountain Region,China   总被引：1，自引：0，他引：1  

Xinhui Ding  Guangquan Liu  Xiaoying Liu  Yongsheng Xie  Zhichun Yue 《国际泥沙研究》2019,34(1):58-64

Soil erosion from chestnut forests is one of the most important factors causing land degradation in the Yanshan Mountain Region. A 2-year field study was done to compare the effects on erosion of a control plot (CP), a repaired and maintained horizontal ditch built with an engineering baffle every 6?m (MP 1), and a repaired and maintained horizontal ditch built with an engineering baffle every 8?m (MP 2). The results showed that the slope runoff of chestnut forests was influenced by rainfall characteristic factors. No single rainfall characteristic factor showed dominance for hill slope runoff. The runoff reduction effect of the partition-coordinated erosion control measures (MP 1 and MP 2) was substantial for chestnut forests under high rainfall intensity conditions. However, the runoff reduction efficiency was higher under the conditions of heavy rainfall and low average rainfall intensity than for storms with higher intensity and lower total rainfall. The reduction effect of the partition-coordinated erosion control measures on the runoff and sediment yield of chestnut forest slopes was MP 2 > MP 1 > CP. The runoff reduction rate and erosion reduction rate of MP 2 reached 61.70% and 97.41%, respectively, and that for MP 1 was 54.15% and 85.31%, respectively. Therefore, after a comprehensive comparison, MP 2 was determined to be more effective for soil erosion control for a sloping chestnut forest.  相似文献   

物探方法在预防路面塌陷中的应用     

徐晓英  徐万祥  张俊伟  欧阳伟 《华北地震科学》2020,38(2):68-71,77

城市地下空间的开发利用不可避免地在基础设施建设中造成土体流失或土层沉降,形成的地下“病害体”易导致城市道路塌陷的发生。文章以滁州琅琊大道为例,采用地质雷达法和浅层地震勘探法对城市老城区排水管网周边进行探测。结果表明:①在探测深度不超过7.0 m范围内,地质雷达法可以满足探测要求;②在场地条件复杂、干扰较多的情况下,需辅以浅层地震勘探法。利用上述方法,可以更准确地查明地下“病害体”的位置,防止了路面塌陷的发生。  相似文献   

Evolution of permafrost in China during the last 20 ka     

Jin  Huijun  Jin  Xiaoying  He  Ruixia  Luo  Dongliang  Chang  Xiaoli  Wang  Shaoling  Marchenko  Sergey S  Yang  Sizhong  Yi  Chaolu  Li  Shijie  Harris  Stuart A 《中国科学:地球科学(英文版)》2019,62(8):1207-1223

The formation and evolution of permafrost in China during the last 20 ka were reconstructed on the basis of large amount of paleo-permafrost remains and paleo-periglacial evidence, as well as paleo-glacial landforms, paleo-flora and paleofauna records. The results indicate that, during the local Last Glacial Maximum(LLGM) or local Last Permafrost Maximum(LLPMax), the extent of permafrost of China reached 5.3×106-5.4×106 km2, or thrice that of today, but permafrost shrank to only0.80×106-0.85×106 km2, or 50% that of present, during the local Holocene Megathermal Period(LHMP), or the local Last Permafrost Minimum(LLPMin). On the basis of the dating of periglacial remains and their distributive features, the extent of permafrost in China was delineated for the two periods of LLGM(LLPMax) and LHMP(LLPMin), and the evolution of permafrost in China was divided into seven periods as follows:(1) LLGM in Late Pleistocene(ca. 20000 to 13000-10800 a BP)with extensive evidence for the presence of intensive ice-wedge expansion for outlining its LLPMax extent;(2) A period of dramatically changing climate during the early Holocene(10800 to 8500-7000 a BP) when permafrost remained relatively stable but with a general trend of shrinking areal extent;(3) The LHMP in the Mid-Holocene(8500-7000 to 4000-3000 a BP)when permafrost degraded intensively and extensively, and shrank to the LLPMin;(4) Neoglaciation during the late Holocene(4000-3000 to 1000 a BP, when permafrost again expanded;(5) Medieval Warming Period(MWP) in the late Holocene(1000-500 a BP) when permafrost was in a relative decline;(6) Little Ice Age(LIA) in the late Holocene(500-100 a BP), when permafrost relatively expanded, and;(7) Recent warming(during the 20 th century), when permafrost continuously degraded and still is degrading. The paleo-climate, geography and paleopermafrost extents and other features were reconstructed for each of these seven periods.  相似文献   

Power Spectrum Density of Stochastic Oscillating Accretion Disk     

G.?B.?Long  J.?W.?Ou  Y.?G.?ZhengEmail author 《Journal of Astrophysics and Astronomy》2016,37(2):10

In this paper, we employ a stochastic oscillating accretion disk model for the power spectral index and variability of BL Lac object S5 0716+714. In the model, we assume that there is a relativistic oscillation of thin accretion disks and it interacts with an external thermal bath through a friction force and a random force. We simulate the light curve and the power spectrum density (PSD) at (i) over-damped, (ii) critically damped and (iii) under-damped cases, respectively. Our results show that the simulated PSD curves depend on the intrinsic property of the accretion disk, and it could be produced in a wide interval ranging from 0.94 to 2.05 by changing the friction coefficient in a stochastic oscillating accretion disk model. We argue that accretion disk stochastic oscillating could be a possible interpretation for observed PSD variability.  相似文献   

The evolution of the terrestrial-terminating Irish Sea glacier during the last glaciation     

Richard Christopher Chiverrell  Geoff Stephen Powell Thomas  Matthew Burke  Alicia Medialdea  Rachel Smedley  Mark Bateman  Chris Clark  Geoffrey A. T. Duller  Derek Fabel  Geraint Jenkins  Xianjiao Ou  Helen Marie Roberts  James Scourse 《第四纪科学杂志》2021,36(5):752-779

Here we reconstruct the last advance to maximum limits and retreat of the Irish Sea Glacier (ISG), the only land-terminating ice lobe of the western British Irish Ice Sheet. A series of reverse bedrock slopes rendered proglacial lakes endemic, forming time-transgressive moraine- and bedrock-dammed basins that evolved with ice marginal retreat. Combining, for the first time on glacial sediments, optically stimulated luminescence (OSL) bleaching profiles for cobbles with single grain and small aliquot OSL measurements on sands, has produced a coherent chronology from these heterogeneously bleached samples. This chronology constrains what is globally an early build-up of ice during late Marine Isotope Stage 3 and Greenland Stadial (GS) 5, with ice margins reaching south Lancashire by 30 ± 1.2 ka, followed by a 120-km advance at 28.3 ± 1.4 ka reaching its 26.5 ± 1.1 ka maximum extent during GS-3. Early retreat during GS-3 reflects piracy of ice sources shared with the Irish-Sea Ice Stream (ISIS), starving the ISG. With ISG retreat, an opportunistic readvance of Welsh ice during GS-2 rode over the ISG moraines occupying the space vacated, with ice margins oscillating within a substantial glacial over-deepening. Our geomorphological chronosequence shows a glacial system forced by climate but mediated by piracy of ice sources shared with the ISIS, changing flow regimes and fronting environments.  相似文献   

广西糖料蔗寒冻害风险评估与风险区划研究     

谭宗琨  刘世业  欧钊荣 《气象研究与应用》2015,36(1)

基于广西1961~2013年冬季寒冻害过程最低气温资料、地理信息数据及地表反射率资料,采用统计学中的多元回归法,构建了基于地理信息与地表反射率相耦合的最低气温降尺度模型及区域250m×250m网格点逐年冬季寒冻害过程最低气温数据库。在此基础上,结合糖料蔗寒冻害等级指标,对广西区域糖料蔗寒冻害时空分布特征进行了分析,并编制了广西区域糖料蔗不同寒冻害等级频率图及糖料蔗寒冻害产量损失率图,同时对广西糖料蔗寒冻害风险等级进行划分及评述。这一结果对糖料蔗种植优化布局及政策性农业保险费率的确定有积极意义。  相似文献