广东一次补充型冷空气过程分析     

翁向宇  毛绍荣 《广东气象》2001,(4):1-3

本文通过对2001年1月的一次强冷空气过程分析，总结出在500hPa南槽北脊高低纬反位相配置形势下，不利于冷空气南下越时南岭，低层冷空气只能在南岭北侧堆积，但当冷空气堆积到南岭两侧温差超过10℃以上，南岭以北的冷空气积聚已达临界值，一次不太强的冷空气补充也会使冷空气冲破南岭屏障，这时影响广东的冷空气已经是前几次叠加，强度明显加强。  相似文献   

The mechanism of barrier river reaches in the middle and lower Yangtze River     

Xingying You  Jinwu Tang  Xiaofeng Zhang  Weiguo Hou  Yunping Yang  Zhaohua Sun  Zhaohui Weng 《地理学报(英文版)》2017,27(10):1249-1267

Alluvial channel has always adjusted itself to the equilibrium state of sediment transport after it was artificially or naturally disturbed. How to maintain the equilibrium state of sediment transport and keep the river regime stable has always been the concerns of fluvial geomorphologists. The channel in the middle and lower reaches of the Yangtze River is characterized by the staggered distribution of the bifurcated river and the single-thread river. The change of river regime is more violently in the bifurcated river than in the single-thread river. Whether the adjustment of the river regime in the bifurcated river can pass through the single-thread river and propagate to the downstream reaches affects the stabilities of the overall river regime. Studies show that the barrier river reach can block the upstream channel adjustment from propagating to the downstream reaches; therefore, it plays a key role in stabilizing the river regime. This study investigates 34 single-thread river reaches in the middle and lower reaches of the Yangtze River. On the basis of the systematic summarization of the fluvial process of the middle and lower reaches of the Yangtze River, the control factors of barrier river reach are summarized and extracted: the planar morphology of single-thread and meandering; with no flow deflecting node distributed in the upper or middle part of the river reach; the hydraulic geometric coefficient is less than 4; the longitudinal gradient is greater than 12‰, the clay content of the concave bank is greater than 9.5%, and the median diameter of the bed sediment is greater than 0.158 mm. From the Navier-Stokes equation, the calculation formula of the bending radius of flow dynamic axis is deduced, and then the roles of these control factors on restricting the migration of the flow dynamic axis and the formation of the barrier river reach are analyzed. The barrier river reach is considered as such when the ratio of the migration force of the flow dynamic axis to the constraint force of the channel boundary is less than 1 under different flow levels. The mechanism of the barrier river reach is such that even when the upstream river regime adjusts, the channel boundary of this reach can always constrain the migration amplitude of the flow dynamic axis and centralize the planar position of the main stream line under different upstream river regime conditions, providing a relatively stable incoming flow conditions for the downstream reaches, thereby blocking the upstream river regime adjustment from propagating to the downstream reaches.  相似文献   

单台多震和达法研究山西地区的波速比变化特征     

翁钊强  梁向军  吴昊昱  刘林飞  李丽 《中国地震研究》2015,29(4):514-526

基于山西数字地震台网2001年1月～2014年10月ML≥2.0地震震相到时数据,利用单台多震和达法计算山西地区波速比,并结合2010年3次MS≥4.5地震探讨地震前后波速比的变化特征。结果表明,在3次地震前远台波速比异常出现时间较早,为震前6个月至1年;而近台波速比异常出现时间相对较晚,为震前10天至2个月不等,因此可通过远台、近台所围限的范围来缩小地震预测地点。东山台计算结果表明,发震时刻残差大小会影响波速比变化细节,因此在实际应用中,应首先确定每个台站发震时刻的残差阈值,以确保波速比计算结果的科学性和稳定性。  相似文献   

河北省滨海旅游发展动力系统的因子分析   总被引：1，自引：0，他引：1  

翁钢民  贾苗苗  徐晓娜 《地域研究与开发》2010,29(1)

河北省滨海旅游在全省旅游业中占有重要地位。了解有哪些因素在推动河北省滨海旅游的发展,这些因素以何种组织关联构成一个动力系统,是确定河北省滨海旅游未来发展战略的必然要求。通过对河北省滨海旅游发展现状的分析,探讨其滨海旅游发展的动力系统,运用因子分析法对该省滨海旅游发展动力因子进行量化计算,根据计算结果对提取的主因子进行解释并提出相关建议,以期推动河北省滨海旅游的科学发展。  相似文献   

福建石牛山水蚀花岗岩石蛋地貌特征及成因研究   总被引：2，自引：0，他引：2  

梁诗经  文斐成  陈斯盾  揭育金  魏勇  胡祚林 《福建地质》2006,25(2):65-74

石牛山主峰出露晚白垩世石牛山组晚期侵入相钾长花岗斑岩,山体浑厚壮观,石蛋千姿百态。石蛋、石堡及崖壁上分布着深浅不一的石脊、石槽及大小不同的石臼、石盆、石穴等微地貌,构成独具特色的“水蚀花岗岩石蛋地貌”。经研究,钾长花岗斑岩是形成水蚀花岗岩石蛋的物质基础,风化剥蚀、大气降水击蚀及其流水侵蚀是形成石脊、石槽、石臼、石盆、石穴的主要外动力地质作用。  相似文献   

基于数字高程模型的水系自动生成     

张渭军  王文科  孔金玲  翁晓鹏 《大地测量与地球动力学》2006,26(4):41-44

为从数字高程模型(DEM)中自动提取区域水流特征,分析了DEM中地形的形态特征,并进行洼地填充和平地抬升的预处理,应用坡面流模拟方法进行了水流方向的确定及水流方向数字阵列的生成,最后根据水流方向阵列和河流栅格网络图生成需要的水系,其结果与手工数字化的水系基本一致,证明该方法是有效的。  相似文献   

Deep origin of Cenozoic volcanoes in Northeast China revealed by 3-D electrical structure     

Shiwen LI  Aihua WENG  Jianping LI  Xuanlong SHAN  Jiangtao HAN  Yu TANG  Yanhui ZHANG  Xueqiu WANG 《中国科学:地球科学(英文版)》2020,63(4):533-547

The three-dimensional(3-D)electrical structure of the upper-mantle was used to examine the deep origins of and relationship among the Cenozoic volcanoes located in Northeast China(NEC).High-quality,long-period magnetotelluric(LMT)full-impedance tensor data were collected in NEC and subjected to 3-D Gauss-Newton inversion in order to construct a resistivity model.The resulting model reveals the presence of multiple localized low-resistivity anomalies(LRAs)within the high resistivity lithosphere beneath NEC.These LRAs partially coincide with Cenozoic volcanoes on the surface.Three LRAs that form a larger,annular LRA were observed in the deep upper mantle beneath the Songliao Basin,whereas vein-like LRAs were found in the asthenosphere that connect the lithosphere and deep upper mantle.Petrophysical analyses suggest that the LRAs may have been caused by fluid-induced melting.Based on our electrical model,we propose that,following dehydration of the subducted Western Pacific slab into the mantle transition zone(MTZ)beneath NEC,the released water migrated upward and caused partial melting at the top of the MTZ beneath the Songliao Basin.Under the effect of buoyancy,the melted mantle formed a thermal upwelling that caused melting of asthenosphere before diapiring at the base of the dry lithosphere.The magma then penetrated structural boundaries(such as thinner,weaker,or activated suture zones)and finally reached the Earth's surface.This melting and upwelling of hot mantle materials may have resulted in large-scale volcanism in the region throughout the Cenozoic,including the eruption of Changbai Mountain and Halaha Volcanoes.Our results suggest that the Cenozoic NEC volcanoes may all share a similar mode of genesis,and probably originated from the annular LRA in the deep upper mantle.  相似文献   

A new fluid factor and its application using a deep learning approach     

Changcheng Liu  Deva Prasad Ghosh  Ahmed Mohamed Ahmed Salim  Weng Sum Chow 《Geophysical Prospecting》2019,67(1):140-149

Amplitude interpretation for hydrocarbon prediction is an important task in the oil and gas industry. Seismic amplitude is dominated by porosity, the volume of clay, pore-filled fluid type and lithology. A few seismic attributes are proposed to predict the existence of hydrocarbon. This paper proposes a new fluid factor by adding a correct item based on the J attribute. The algorithm is verified through stochastic Monte Carlo modelling that contains various rock physical properties of sand and shale. Both gas and oil responses are separated by the new fluid factor. Furthermore, an approach based on the neural network model is trained using the deep learning method to predict the new fluid factor. The confusion matrix shows that this model performs well. This model allows the application of the new fluid factor in the seismic data. In this study, the Marmousi II data set is used to examine the performance of the new fluid factor, and the result is good. Most hydrocarbon reservoirs are identified in the shale–sandstone sequences. The combination of deep learning and the new fluid factor provides a more accurate way for hydrocarbon prediction.  相似文献   

Numerical simulation of dam-break flow and bed change considering the vegetation effects     

Zhiguo He  Ting Wu  Haoxuan Weng  Peng Hu  Gangfeng Wu 《国际泥沙研究》2017,32(1)

Existing numerical investigations of dam-break flows rarely consider the effects of vegetation.This paper presents a depth-averaged two-dimensional model for dam-break flows over mobile and vegetated beds.In the model,both the consequences of reducing space for storing mass and momentum by the existence of vegetation and dragging the flow are considered:the former is considered by introducing a factor (1-c) to the flow depth,where c is the vegetation density;the later is considered by including an additional sink term in the momentum equations.The new governing equations are discretized by the finite volume method;and an existing second-order central-upwind scheme embedded with the hydrostatic reconstruction method for water depth,is used to estimate the fluxes;the source terms are estimated by either explicit or semi-explicit methods fulfilling the stability requirement.Laboratory experiments of dam-break flows or quasi-steady flows with/without vegetation effects/sediment transport are simulated.The good agreements between the measurements and the numerical simulations demonstrate a satisfactory performance of the model in reproducing the flow depth,velocity and bed deformation depth.Numerical case studies of six scenarios of dam-break flows over a mobile and vegetated bed are conducted.It is shown that when the area of the vegetation zone,the vegetation density,and the pattern of the vegetation distribution are varied,the resulted bed morphological change differs greatly,suggesting a great influence of vegetation on the dam-break flow evolution.Specifically,the vegetation may divert the direction of the main flow,hindering the flow and thus result in increased deposition upstream of the vegetation.  相似文献   

Future hydro-meteorological drought of the Johor River Basin,Malaysia, based on CORDEX-SEA projections     

Mou Leong Tan  Liew Juneng  Fredolin T. Tangang  Ngai Weng Chan  Sheau Tieh Ngai 《水文科学杂志》2019,64(8):921-933

Water scarcity issues in the Johor River Basin (JRB) could affect the populations of Malaysia and Singapore. This study provides an overview of future hydro-meteorological droughts using climate projections from an ensemble of four Coordinated Regional Climate Downscaling Experiments – Southeast Asia (CORDEX-SEA) domain outputs under the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios for the 2021–2050 and 2071–2100 periods. The climate projections were bias corrected using the quantile mapping approach before being incorporated into the Soil and Water Assessment Tool (SWAT) hydrological model. The Standardized Precipitation Index (SPI) and Standardized Streamflow Index (SSI) were used to examine the meteorological and hydrological droughts, respectively. Overall, future annual precipitation, streamflow, and maximum and minimum temperatures are projected to change by about ?44.2 to 24.3%, ?88.7 to 42.2%, 0.8 to 3.7ºC and 0.7 to 4.7ºC, respectively. The results show that the JRB is likely to receive more frequent meteorological droughts in the future.  相似文献