黄土丘陵沟壑区典型流域土地利用变化对水沙关系的影响   总被引：5，自引：1，他引：4  

刘淑燕  余新晓  信忠保  李庆云  李海光  雷凤燕 《地理科学进展》2010,29(5)

以黄土丘陵沟壑区内相邻的2条支沟(桥子东沟和桥子西沟)为研究对象,基于遥感影像获得土地利用数据,利用水文站1986-2004年观测的次降雨-径流-泥沙过程资料,研究了小流域土地利用变化(主要以增加水土保持措施为主)对径流输沙的影响。结果表明:在黄土丘陵沟壑区,增加土地利用/土地覆被能够有效地减少小流域的径流量、产沙量;在次降雨量、降雨强度较小,土地利用变化不明显的情况下,两流域次降雨水沙关系差异不显著,在次降雨量、降雨强度较大和土地利用变化明显时,两流域次降雨水沙关系差异显著,坡耕地改梯田的农田水利建设可能是导致水沙变化的主要原因。  相似文献   

Wave prediction in a port using a fully nonlinear Boussinesq wave model   总被引：1，自引：0，他引：1  

Choi Young-Kwang  Seo Seung-Nam  Choi Jin-Yong  Shi Fengyan  Park Kwang-Soon 《海洋学报(英文版)》2019,38(7):36-47

A wave forecasting system using FUNWAVE-TVD which is based on the fully nonlinear Boussinesq equations by Chen(2006) was developed to provide an accurate wave prediction in the Port of Busan, South Korea. This system is linked to the Korea Operational Oceanographic System(KOOS) developed by Park et al.(2015). The computational domain covers a region of 9.6 km×7.0 km with a grid size of 2 m in both directions, which is sufficient to resolve short waves and dominant sea states. The total number of grid points exceeds 16 millions,making the model computational expensive. To provide real-time forecasting, an interpolation method, which is based on pre-calculated results of FUNWAVE-TVD and SWAN forecasting results at the FUNWAVE-TVD offshore boundary, was used. A total of 45 cases were pre-calculated, which took 71 days on 924 computational cores of a Linux cluster system. Wind wave generation and propagation from the deep water were computed using the SWAN in KOOS. SWAN results provided a boundary condition for the FUNWAVE-TVD forecasting system. To verify the model, wave observations were conducted at three locations inside the port in a time period of more than 7 months. A model/model comparison between FUNWAVE-TVD and SWAN was also carried out. It is found that, FUNWAVE-TVD improves the forecasting results significantly compared to SWAN which underestimates wave heights in sheltered areas due to incorrect physical mechanism of wave diffraction, as well as large wave heights caused by wave reflections inside the port.  相似文献   

An Analytical Solution for Nearshore Circulation Driven by Focused/Defocused Waves     

Ding  Yu-mei  Shi  Fengyan 《中国海洋工程》2019,33(5):544-553

An offshore shoal or bar refracts ocean surface waves and causes wave focusing/defocusing on the adjacent beach.Wave focal patterns characterized by alongshore variations in wave height, wave angle, and breaking location induce alongshore non-uniformities of wave setup and nearshore circulation, e.g., rip currents and alongshore currents, in the surfzone. A simplified analytic model for nearshore circulation generated by focused/defocused waves on a planar beach is developed and theoretical solutions are obtained using transport stream function and perturbations in alongshore distributions of wave height and wave angle at the breaker line. The analytic model suggests that alongshore currents are strongly affected by a pair of counter-rotating vortices generated shoreward of the wave focal zone. The vortices are persistent, and their strengths depend on the amplitudes of alongshore variations in wave height and wave angle. The alongshore gradient in wave height tends to intensify the vortices while the convergence of wave angle tends to weaken the vortices. Divergent flows associated with the vortices in the surfzone are intense,strengthening alongshore currents in the downstream of the wave focal zone and weakening alongshore currents or causing flows reversal in the upstream. Alongshore currents are modulated by rip currents associated with the wave focusing/defocusing patterns.  相似文献   

一种面向对象的最优分割尺度计算模型     

白韬  杨国东  王凤艳  刘佳为 《吉林大学学报(地球科学版)》2020,50(1):304-312

作为信息提取和分类的前提,面向对象的影像分割尺度参数的设置直接影响到提取和分类的精度。本文以GF-2影像数据为例,在已有分割理论和方法的基础上提出一种基于最优分割尺度的计算模型（OS模型）。该模型以主成分分析所得的主成分以及新建的归一化植被指数（normalized vegetation index,NDVI）特征层作为分割参考层,综合考虑均质因子的影响,构建加权尺度评价指数,插值拟合最优分割尺度。构建误差系数（E_c）对模型进行评价,结果表明：OS模型误差系数（E_c=1.15%）小于传统模型（E_c=3.28%）,且分割对象更均匀、与实际地物更接近。  相似文献   

浅谈储层渗透率变异系数计算方法          下载免费PDF全文

马光华  魏文懂  钱凤燕 《地质找矿论丛》2013,28(2):256-262

储层的渗透率变异系数、极差、突进系数等是渗透率非均质程度的定量表征。文章探讨了渗透率变异系数的计算方法,认为:变异系数等计算方法与数据分布类型有关,变异系数等参数的计算需根据数据分布特征来选取适合的方法。劳伦兹系数与数据分布类型无关;劳伦兹系数是有界的,分布于0～1之间。尤其是在对数正态分布条件下,劳伦兹曲线、基尼系数完全由标准差σ决定,劳伦兹曲线、基尼系数以及σ这三者间存在着一一对应关系。劳伦兹系数可以用于储层非均质性定量评价。  相似文献   

Far-Field Tsunami Impact in the North Atlantic Basin from Large Scale Flank Collapses of the Cumbre Vieja Volcano,La Palma     

Babak Tehranirad  Jeffrey C. Harris  Annette R. Grilli  Stephan T. Grilli  Stéphane Abadie  James T. Kirby  Fengyan Shi 《Pure and Applied Geophysics》2015,172(12):3589-3616

  相似文献   

大兴安岭中段索伦地区满克头鄂博组火山岩年龄、地球化学特征及其构造环境   总被引：2，自引：2，他引：0  

高龙飞  和钟铧  隋振民  陆凯杰  刘峰岩 《地质通报》2018,37(5):881-894

对大兴安岭中段索伦地区满克头鄂博组火山岩进行了岩石地球化学、锆石U-Pb及Hf同位素研究,讨论该地区火山岩的形成时代和构造背景。用LA-ICP-MS测得索伦地区满克头鄂博组2个流纹岩样品的锆石206Pb/238U年龄分别为138.0±1.5Ma和139.9±2.5Ma,表明火山岩的形成时代是早白垩世早期,而非晚侏罗世;地球化学数据显示其具有高硅、富碱、弱过铝质-过铝质(A/CNK=0.99~1.34)、分异程度高的特点,属于高钾钙碱性系列,相对富集轻稀土元素和部分大离子亲石元素(Rb、Th、U、K),亏损高场强元素(Nb、Ta、Ti、P)。锆石Hf同位素组成表明,该区满克头鄂博组火山岩具有较高的εHf(t)值(+4.06~+8.24),二阶段模式年龄为936~664Ma,暗示其可能起源于从亏损地幔增生的年轻地壳物质的部分熔融。结合区域地质资料分析,满克头鄂博组火山岩形成于造山后伸展环境,可能与蒙古-鄂霍茨克洋闭合后造山带的垮塌密切相关。  相似文献   

中蒙俄经济走廊沿海与内陆NDVI分布特征     

王凤艳  王梓铭  王明常  姜琦刚  杨天亮  张馨月  赵明宇 《吉林大学学报(地球科学版)》2021,51(3):864-876

为了研究中蒙俄经济走廊沿海与内陆地区归一化植被指数（NDVI）的分布特征,利用MOD13Q1 NDVI数据集、MERRA2气象再分析数据和AVHRR土地覆盖数据,以中蒙俄经济走廊研究区内2种代表性植被（林地和树木茂盛的草地）为例,采用回归分析法和相关性分析法研究了近年来研究区NDVI在不同纬度、距海岸线不同距离及不同时间的变化特征,并分析了气温与降水对NDVI的影响。结果表明：2015—2019年内5月下旬—9月,沿海地区植被生长状态基本优于内陆地区,从距离海岸线500 km左右开始,NDVI明显下降;沿海地区（0~500 km）与内陆地区NDVI在时间变化上也略有不同,沿海地区2种代表性植被的NDVI时序变化模型拟合效果较好。受沿海与内陆地区降水、气温差异影响,在植被生长顶峰期（0719—0723）,随着纬度上升,沿海与内陆地区NDVI差异逐渐减小：沿海地区NDVI在上升期比内陆地区约提前1个月进入饱和,下降期滞后约1个月;低纬度地区2种植被对降水量更为敏感,相关系数最高为0.393（显著性水平P<0.01）,而高纬度地区两种植被对气温更为敏感,相关系数最高为0.534（P<0.01）。  相似文献   

Numerical study on residual current and its impact on mass transport in the Hangzhou Bay and the Changjiang Estuary Ⅱ. Residual current and its impact on mass transport in winter     

Zhu Shouxian  Dang Pingxing  Shi Fengyan  Zhu Jianrong 《海洋学报(英文版)》2001,20(2):153-169

I~IOWIn winter, on the impacts Of the Chriolis force and the current along the shore of the EastChina ho, the residual current from the Changjiang River flows south along the shore and enters the ~ Bay in the north, then it moves out of the bay in the south and flows southin the East China Sea (Su and Wang, 1989; Zhu and Shen, 1997). In recent years, scholars have made further analyse on obSerVed date, and have obtained more profound viewson the residual current and mass transport (Pn …  相似文献   

风暴潮漫滩数值预报模式分析与探讨   总被引：2，自引：0，他引：2  

孙文心  杨宗严  史峰岩 《中国海洋大学学报(自然科学版)》1994,(3)

用Ｆｌａｔｈｅｒ可变边界模式数值模拟黄河三角洲的风暴潮漫滩，比较计算的三种漫滩模式，讨论可变边界条件。  相似文献