基于压缩感知原理的L1范数AVO反演算法     

周红伟  林松 《大地测量与地球动力学》2020,40(4):366-370

基于压缩感知稀疏信号采样与重构理论,利用AVO反演方法将传统的L2范数改变为L1范数,反演地下地层在L1范数下的稀疏脉冲反射系数。反演得到的稀疏尖峰将局部地下结构通过有限数量的层状结构的叠加来表示,能够提高纵向精度,与传统的AVO反演算法相比提高了薄层的反演效果且具有一定的抗噪性。数值模型及实际数据的结果表明,基于压缩感知原理的L1范数AVO反演方法更加准确、分辨率更高。  相似文献   

Intel MKL在Bernese GNSS数据处理中的应用     

孔垚  孙保琪  张小贞  王源昕 《大地测量与地球动力学》2020,40(7):736-740

为提高Bernese GNSS software数据处理效率，将英特尔数学核心函数库(math kernel library，MKL)应用于Bernese 精密定轨数据处理，对比分析多个MKL矩阵求逆函数与Bernese 原有程序的计算效率。使用2019-03全球200个测站北斗/GNSS数据进行实验分析，结果表明，采用参数预消除策略时，参数预消除步骤消耗时间明显大于矩阵求逆，使用MKL处理数据效率提升不明显；而未采用参数预消除策略时，使用MKL矩阵求逆函数可显著提高矩阵求逆效率，其中dpotri函数矩阵求逆计算效率最高，消耗时间平均值为133 s，相比Bernese 原有程序计算速度可提高13倍。  相似文献   

地理图斑智能计算及模式挖掘方法研究     

骆剑承  吴田军  吴志峰  周亚男  郜丽静  孙营伟  吴炜  杨颖频  胡晓东  张新  沈占锋 《地球信息科学学报》2020,22(1):57-75

在大数据时代,高分辨率对地观测技术实现了对地球表层地理现象和地理过程最为真实、量化、全面覆盖又快速更新的数据化记录,可为地理空间认知研究的新发展奠定时空信息聚合与挖掘计算的基准。地理图斑是影像空间映射到地理空间中对于地理实体的抽象化表达,是构建地理场景和承载地理空间各类信息进而开展模式挖掘的最小单元。本文以地理图斑为基本对象,通过分析其中视觉模拟、符号推测等几类机器学习的协同计算机制,从空间、时间与属性等维度构建了集“分区分层感知”、“时空协同反演”、“多粒度决策”三者于一体的地理图斑智能计算模型,并以在贵州息烽县、广西江州区开展的农业种植结构制图与规划决策为应用案例,探索了地理图斑分布、生长以及功能3种模式的挖掘方法,并进一步设计了动态视角下开展图斑动力模式挖掘的研究思路。  相似文献   

1980—2020年中国九大流域蒸散发及其组分时空评估     

杨泽龙  李艳忠  白鹏  杜深文  郝奕  钱畅  李超凡 《地球信息科学学报》2022,24(5):889-901

蒸散发是地表陆气水分交换的纽带,准确量化蒸散发的时空演变格局对于水资源规划与管理至关重要。本文基于GLEAM模型的蒸散发及其组分数据集,借助7个通量观测站数据、120个流域的流域水量平衡及PML_V2蒸散发产品,在中国九大流域系统评估了GLEAM-ET产品,分析了植被恢复背景下,蒸散发（ET）及其组分（植被蒸腾Ec,截留蒸发Ei,土壤蒸发Es）在1980—2020年的时空演变格局。本文主要得到以下结论：① GLEAM-ET产品在中国九大流域具有较好的适用性,其性能与气候类型有关,干旱区效果优于湿润区。此外,GLEAM与PML_V2模型在九大流域相关性较好（R>0.7）,分布格局与变化趋势整体保持一致。② 全国尺度上,ET均值为416.88 mm,增长速率为1.21 mm/a。Ec与ET均呈自东南向西北递减的分布格局,而Es与其相反。Ec、ET在九大流域均呈显著增加趋势（p<0.001）。Ei、Es在季风区流域分别呈显著增加和显著减小趋势;在内陆区流域呈不显著减小（p>0.05）和显著增加趋势。③在植被恢复背景下,ET组分比例发生了变化。Ec占比变化存在南北差异,南方流域Ec占比均减小,北方流域均增加。Ei占比在各流域均增加,Es占比均减小。黄河流域ET组分对植被恢复的响应最为明显,Ec占比增加了5.21%,Es占比减小了5.56%。  相似文献   

Use of Nash's IUH and DEMs to identify the parameters of an unequal‐reservoir cascade IUH model     

Chaoqun Li  Shenglian Guo  Wenhua Zhang  Jun Zhang 《水文研究》2008,22(20):4073-4082

Under the assumption that hydrograph generation was affected by n linear reservoirs with the same value of storage coefficient k, Nash proposed the formulation of the Instantaneous Unit Hydrograph (IUH), which has been widely used in rainfall–runoff simulation and flood forecasting. However, the assumption of the parameter k having the same value in all reservoirs is obviously unphysical as it results in the estimated value of n not being integral. In this study, for parameter n integral, the different k value for each reservoir was derived using the Laplace transform and developing a general rule for the equation of the IUH of any order. The relationship between parameter k and the slope of the river channel estimated using digital elevation model (DEM) data is established, the parameter estimation procedures are given. As in most unit hydrograph studies, only isolated storm events are considered here. Seventeen flood events in three catchments were selected for the case studies. Application results show that the proposed method is slightly better than Nash's IUH with higher model efficiency and smaller absolute relative errors. This work provides a new methodology for the formulation of the IUH. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Changes in streamflow regime following vegetation changes from paired catchments     

Fangfang Zhao  Zongxue Xu  Lu Zhang 《水文研究》2012,26(10):1561-1573

Vegetation changes can significantly affect catchment water balance. It is important to evaluate the effects of vegetation cover change on streamflow as changes in streamflow relate to water security. This study focuses on the use of statistical methods to determine responses in streamflow at seven paired catchments in Australia, New Zealand, and South Africa to vegetation change. The non‐parametric Mann–Kendall test and Pettitt's test were used to identify trends and change points in the annual streamflow records. Statistically significant trends in annual streamflow were detected for most of the treated catchments. It took between 3 and 10 years for a change in vegetation cover to result in significant change in annual streamflow. Presence of the change points in streamflow was associated with changes in the mean, variance, and distribution of annual streamflow. The streamflow in the deforestation catchments increased after the change points, whereas reduction in streamflow was observed in the afforestation catchments. The streamflow response is mainly affected by the climate and underlying vegetation change. Daily flow duration curves (FDCs) for the whole period and pre‐change and post‐change point periods also were analysed to investigate the changes in flow regime. Three types of vegetation change effects on the flow regime have been identified. The relative reductions in most percentile flows are constant in the afforestation catchments. The comparison of trend, change point, and FDC in the annual streamflow from the paired experiments reflects the important role of the vegetation change. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Using a H∞ filter assimilation procedure to estimate root zone soil water content     

Haishen Lü  Xiaoli Li  Zhongbo Yu  Robert Horton  Yonghua Zhu  Zhenchun Hao  Long Xiang 《水文研究》2010,24(25):3648-3660

Root zone soil water content impacts plant water availability, land energy and water balances. Because of unknown hydrological model error, observation errors and the statistical characteristics of the errors, the widely used Kalman filter (KF) and its extensions are challenged to retrieve the root zone soil water content using the surface soil water content. If the soil hydraulic parameters are poorly estimated, the KF and its extensions fail to accurately estimate the root zone soil water. The H‐infinity filter (HF) represents a robust version of the KF. The HF is widely used in data assimilation and is superior to the KF, especially when the performance of the model is not well understood. The objective of this study is to study the impact of uncertain soil hydraulic parameters, initial soil moisture content and observation period on the ability of HF assimilation to predict in situ soil water content. In this article, we study seven cases. The results show that the soil hydraulic parameters hold a critical role in the course of assimilation. When the soil hydraulic parameters are poorly estimated, an accurate estimation of root soil water content cannot be retrieved by the HF assimilation approach. When the estimated soil hydraulic parameters are similar to actual values, the soil water content at various depths can be accurately retrieved by the HF assimilation. The HF assimilation is not very sensitive to the initial soil water content, and the impact of the initial soil water content on the assimilation scheme can be eliminated after about 5–7 days. The observation interval is important for soil water profile distribution retrieval with the HF, and the shorter the observation interval, the shorter the time required to achieve actual soil water content. However, the retrieval results are not very accurate at a depth of 100 cm. Also it is complex to determine the weighting coefficient and the error attenuation parameter in the HF assimilation. In this article, the trial‐and‐error method was used to determine the weighting coefficient and the error attenuation parameter. After the first establishment of limited range of the parameters, ‘the best parameter set’ was selected from the range of values. For the soil conditions investigated, the HF assimilation results are better than the open‐loop results. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Towards a comprehensive approach to parameter estimation in land surface parameterization schemes     

Rafael Rosolem  Hoshin V. Gupta  W. James Shuttleworth  Luis Gustavo Gonçalves de Gonçalves  Xubin Zeng 《水文研究》2013,27(14):2075-2097

In climate models, the land–atmosphere interactions are described numerically by land surface parameterization (LSP) schemes. The continuing improvement in realism in these schemes comes at the expense of the need to specify a large number of parameters that are either directly measured or estimated. Also, an emerging problem is whether the relationships used in LSPs are universal and globally applicable. One plausible approach to evaluate this is to first minimize uncertainty in model parameters by calibration. In this paper, we conduct a comprehensive analysis of some model diagnostics using a slightly modified version of the Simple Biosphere 3 model for a variety of biomes located mainly in the Amazon. First, the degree of influence of each individual parameter in simulating surface fluxes is identified. Next, we estimate parameters using a multi‐operator genetic algorithm applied in a multi‐objective context and evaluate simulations of energy and carbon fluxes against observations. Compared with the default parameter sets, these parameter estimates improve the partitioning of energy fluxes in forest and cropland sites and provide better simulations of daytime increases in assimilation of net carbon during the dry season at forest sites. Finally, a detailed assessment of the parameter estimation problem was performed by accounting for the decomposition of the mean squared error to the total model uncertainty. Analysis of the total prediction uncertainty reveals that the parameter adjustments significantly improve reproduction of the mean and variability of the flux time series at all sites and generally remove seasonality of the errors but do not improve dynamical properties. Our results demonstrate that error decomposition provides a meaningful and intuitive way to understand differences in model performance. To make further advancements in the knowledge of these models, we encourage the LSP community to adopt similar approaches in the future. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Numerical modeling and neural networks to identify model parameters from piezocone tests: I. FEM analysis of penetration in two‐phase continuum     

Rafał F. Obrzud  Andrzej Truty  Laurent Vulliet 《国际地质力学数值与分析法杂志》2011,35(16):1703-1730

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Subsurface lateral flow generation in aspen and conifer‐dominated hillslopes of a first order catchment in northern Utah     

Amy R. Burke  Tamao Kasahara 《水文研究》2011,25(9):1407-1417

Mountain headwater catchments in the semi‐arid Intermountain West are important sources of surface water because these high elevations receive more precipitation than neighboring lowlands. This study examined subsurface runoff in two hillslopes, one aspen dominated, the other conifer dominated, adjacent to a first order stream in snow‐driven northern Utah. Snow accumulation, soil moisture, trenchflow and streamflow were examined in hillslopes and their adjacent stream. Snow water equivalents (SWEs) were greater under aspen stands compared to conifer, the difference increasing with higher annual precipitation. Semi‐variograms of shallow spatial soil moisture patterns and transects of continuous soil moisture showed no increase in soil moisture downslope, suggesting the absence of subsurface flow in shallow (～12 cm) soil layers of either vegetation type. However, a clear threshold relationship between soil moisture and streamflow indicated hillslope–stream connectivity, deeper within the soil profile. Subsurface flow was detected at ～50 cm depth, which was sustained for longer in the conifer hillslope. Soil profiles under the two vegetation types varied, with deep aspen soils having greater water storage capacity than shallow rocky conifer soils. Though SWEs were less under the conifers, the soil profile had less water storage capacity and produced more subsurface lateral flow during the spring snowmelt. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献