阵风锋自动识别算法的试验研究          下载免费PDF全文

何红红  慕熙昱  赵宏玲  王志刚  张洪峰 《气象科学》2013,33(5):519-525

利用江苏省6部S波段全相参多普勒天气雷达测得的2007-2011年28个阵风锋观测实例,检验多普勒天气雷达的阵风锋自动识别算法的效果。该算法主要包括熵函数模板的反射率强度边界识别、风切变算法,并综合依据径向速度及谱宽进行阵风锋识别。在阵风锋的识别中,多普勒速度的径向切变有利于判别雷达波束垂直于阵风锋边界的辐合,旋转切变可更好地显示平行于波束的阵风锋边界。在参与检测的28个个例中,成功检测出的有13个;因雷达资料质量影响,7个个例检测出部分阵风锋;8个个例未检测到阵风锋。经过检验,该算法的识别效果较好,但仍存在一些不足,需要进一步完善雷达资料的质量控制,和对低层弱切变特征的提取研究。  相似文献   

胶州湾风暴潮增水重现值的长期预测   总被引：1，自引：0，他引：1  

董胜  许鹏婧  刘伟 《中国海洋大学学报(自然科学版)》2009,39(5)

以胶州湾30 a风暴潮过程的极值增水值为统计序列,按照年、季、月等不同时段,分别抽样极值增水样本,提出泊松最大熵分布,采用年极值法和过阈法对增水重现值进行长期预测,统计分析结果对于胶州湾防潮减灾有参考作用,其随机分析方法对于遭受风暴潮影响的海岸区域有借鉴意义。  相似文献   

基于PSE模型的矿业城市经济发展脆弱性研究   总被引：8，自引：0，他引：8  

孙平军  修春亮 《地理研究》2011,30(2):301-310

脆弱性是可持续发展的一个时间函数和空间函数.区域经济发展过程是一个不断抑制脆弱性实现螺旋式上升的过程.矿业城市经济发展的脆弱性具有典型的"压力(P)-敏感(S)-弹性(E)"的特征.据此,构建了一个矿业城市经济发展脆弱性评价模型,结合主成分分析法和熵值法,选取东北地区矿业城市作为案例进行评价,从脆弱性的视角来研究矿业城...  相似文献   

Indian summer monsoon rainfall (ISMR) forecasting using time series data: A fuzzy-entropy-neuro based expert system     

Pritpal Singh 《地学前缘(英文版)》2018,9(4):1243-1257

This study presents a model to forecast the Indian summer monsoon rainfall(ISMR)(June-September)based on monthly and seasonal time scales. The ISMR time series data sets are classified into two parts for modeling purposes, viz.,(1) training data set(1871-1960), and(2) testing data set(1961-2014).Statistical analyzes reflect the dynamic nature of the ISMR, which couldn't be predicted efficiently by statistical and mathematical based models. Therefore, this study suggests the usage of three techniques,viz., fuzzy set, entropy and artificial neural network(ANN). Based on these techniques, a novel ISMR time series forecasting model is designed to deal with the dynamic nature of the ISMR. This model is verified and validated with training and testing data sets. Various statistical analyzes and comparison studies demonstrate the effectiveness of the proposed model.  相似文献   

Estimation of ecological high flow     

Jen‐Yang Lin  Yen‐Chang Chen  Eric Hsienshao Tsao 《水文研究》2006,20(2):319-328

Floods can destroy fish habitat. During a flood a fish has to seek shelters (refuges) to survive. It is necessary to know the maximum discharge that the fish can sustain against the strong current. Ecological and hydraulic engineers can simulate the flow condition of high flow for designing the refuge when restoring and enhancing the rivers are needed. Based on the average ratio of the mean and maximum velocities invariant with time, discharge and water level, this paper tries to introduce the concept of ecological high flow. The mean‐maximum velocity ratio can be used to estimate the mean velocity of the river. If the maximum velocity of the cross section is replaced by the maximum sustained swimming speeds of fish, the mean velocity of ecological high flow can be calculated with the constant ratio. The cross‐sectional area can be estimated by the gage height. Then the ecological high flow can be estimated as the product of mean velocity of ecological high flow multiplied by the cross‐sectional area. The available data of the upstream of the Dacha River where is the habitat of the Formosan landlocked salmon were used to illustrate the estimation of the ecological high flow. Any restoration project at Sonmou that try to improve the stream habitat can use the ecological high flow to design the hydraulic structure at suitable location to offer refuges for the Formosan landlocked salmon that is an endangered species in Taiwan Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Thermal expansion of Mg(OH)<Subscript>2</Subscript> brucite under high pressure and pressure dependence of entropy   总被引：1，自引：1，他引：0  

H.?FukuiEmail author  O.?Ohtaka  T.?Suzuki  K.?Funakoshi 《Physics and Chemistry of Minerals》2003,30(9):511-516

An equation of state for Mg(OH)₂ brucite under high-pressure and high-temperature conditions has been obtained by measuring temperature dependence of volume up to 600 K at ambient pressure and pressure dependence of volume up to 16 GPa at 300, 473, 673, and 873 K with in situ X-ray diffraction. Pressure dependence of entropy of brucite has been calculated with thermal expansion coefficient and volume which are derived from the present EoS. This dependence indicates that generation of secondary OH dipoles affects entropy. The OH dipoles probably appear around 2 GPa and the number seems not to change over 8 GPa at 300 K.  相似文献   

Capturing the essential spatial variability in distributed hydrological modelling: Hydraulic roughness     

Baxter E. Vieux  Nadim S. Farajalla 《水文研究》1994,8(3):221-236

The spatial variability of each parameter affecting storm runoff must be accounted for in distributed modelling. The objective of the work reported here is to assess the effects of using distributed versus lumped hydraulic roughness coefficients in the modelling of direct surface runoff. A spatially variable data set composed of Manning roughness coefficients is used to model direct surface runoff. To assess the information content (as measured by entropy) of spatially variable data and its significance in distributed modelling, various degrees of smoothing are applied. The error resulting from smoothing the hydraulic roughness coefficients is determined by modelling overland flow using a finite element solution. The Manning roughness coefficients were taken from field measurements of the Manning roughness coefficient at 0.6 m on a 14 m hillslope. These values were then used in a numerical simulation of outflow hydrographs to investigate the dependence of error on spatial variability. Our study focuses on the characteristics of spatial data used in distributed hydrological modelling. The field sites have fractal dimensions of ≈? 1.4, which is close to a Brownian variation. The sampling interval that captures the essential spatial variability of the Manning roughness coefficient does not seem to matter due to its Brownian variation in the field sites. Hence due to the nearly uniform random distribution, measurements at 0.6 m intervals are not necessary and larger intervals would yield results that are just as acceptable provided the mean value together with a uniformly random distribution is maintained for any size of finite element or sampling resolution. Because detailed measurements of hydraulic roughness are not practically available for deterministic catchment modelling, it is important to know that larger sampling resolutions may be used than 0.6 m.  相似文献   

Heat-capacity measurements and absolute entropy of ɛ-Mg2PO4OH     

Catherine Leyx  J. Cornelis Van Miltenburg  Christian Chopin  Lado Cemič 《Physics and Chemistry of Minerals》2005,32(1):13-18

The low-temperature heat capacity of -Mg₂PO₄OH was measured between 10 and 400 K by adiabatic calorimetry. No phase transition was observed over this temperature range. A relative enthalpy increment of 22,119 J mol^–1 and an absolute entropy value of 127.13±0.25 J mol^–1 K^–1 at 298.15 K are derived from the results. The low-temperature heat-capacity data are compared with the DSC data obtained from 143 K to 775 K and show marginal differences in the common temperature range. The latter data are fitted by the polynomial which allows extrapolation to high temperatures.Software information: WINDOWS operating system, WORD word processing, SigmaPlot diagrams exported in tiff format.  相似文献   

The Entropy Score and its Uses in Earthquake Forecasting   总被引：1，自引：0，他引：1  

David Harte  David Vere-Jones 《Pure and Applied Geophysics》2005,162(6-7):1229-1253

Suppose a forecasting scheme associates a probability p^* with some observed outcome. The entropy score given to this forecast is then –logp^*. This article provides a review of the background to this scoring method, its main properties, and its relationships to concepts such as likelihood, probability gain, and Molchans - diagram. It is shown that, in terms of this score, an intrinsic characterization can be given for the predictability of a given statistical forecasting model. Uses of the score are illustrated by applications to the stress release and ETAS models, electrical signals, and M8.  相似文献   

Assessing the spatial distribution of crop areas using a cross-entropy method   总被引：1，自引：0，他引：1  

Liangzhi You  Stanley Wood 《International Journal of Applied Earth Observation and Geoinformation》2005,7(4):310-323

While crop production statistics are reported on a geopolitical – often national – basis, we often need to know, for example, the status of production or productivity within specific sub-regions, watersheds, or agro-ecological zones. Such re-aggregations are typically made using expert judgments or simple area-weighting rules. We describe a new, entropy-based approach to the plausible estimates of the spatial distribution of crop areas. Using this approach tabular crop production statistics are blended judiciously with an array of other secondary data to assess the areas of specific crops within individual ‘pixels’—typically 25–100 km² in size. The information utilized includes crop production statistics, farming system characterization, satellite-based interpretation of land cover, biophysical crop suitability assessments, and population density. An application is presented in which Brazilian state level production statistics are used to generate pixel level crop area data for eight crops. To validate the spatial allocation we aggregated the pixel estimates to obtain synthetic estimates of municipality level areas in Brazil, and compared those estimates with actual municipality statistics. The approach produced extremely promising results. We then examined the robustness of these results compared to simplified approaches to spatializing crop production statistics and showed that, while computationally intensive, the cross-entropy method does provide more reliable spatial allocations.  相似文献