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131.
Spatiotemporal variation and driving forces of reference evapotranspiration in Jing River Basin,northwest China 总被引:1,自引:0,他引:1 下载免费PDF全文
Lihong Xu Zhongjie Shi Shulan Zhang Xinzheng Chu Pengtao Yu Wei Xiong Haijun Zuo Yunni Wang 《水文研究》2015,29(23):4846-4862
Evapotranspiration is an important component of the hydrological cycle, which integrates atmospheric demands and surface conditions. Research on spatial and temporal variations of reference evapotranspiration (ETo) enables understanding of climate change and its effects on hydrological processes and water resources. In this study, ETo was estimated by the FAO‐56 Penman–Monteith method in the Jing River Basin in China, based on daily data from 37 meteorological stations from 1960 to 2005. ETo trends were detected by the Mann–Kendall test in annual, seasonal, and monthly timescales. Sensitivity coefficients were used to examine the contribution of important meteorological variables to ETo. The influence of agricultural activities, especially irrigation on ETo was also analyzed. We found that ETo showed a decreasing trend in most of the basin in all seasons, except for autumn, which showed an increasing trend. Mean maximum temperature was generally the most sensitive parameter for ETo, followed by relative humidity, solar radiation, mean minimum temperature, and wind speed. Wind speed was the most dominant factor for the declining trend in ETo. The more significant decrease in ETo for agricultural and irrigation stations was mainly because of the more significant decrease in wind speed and sunshine hours, a mitigation in climate warming, and more significant increase in relative humidity compared with natural stations and non‐irrigation stations. Changes in ETo and the sensitivity coefficient of meteorological variables in relation to ETo were also affected by topography. Better understanding of ETo response to climate change will enable efficient use of agricultural production and water resources, which could improve the ecological environment in Jing River Basin. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
132.
Using statistically downscaled atmospheric forcing, we performed a numerical investigation to evaluate future climate's impact on storm surges along the Gulf of Mexico and U.S. east coast. The focus is on the impact of climatic changes in wind pattern and surface pressure while neglecting sea level rise and other factors. We adapted the regional ocean model system(ROMS) to the study region with a mesh grid size of 7–10 km in horizontal and 18 vertical layers. The model was validated by a hindcast of the coastal sea levels in the winter of 2008. Model's robustness was confirmed by the good agreement between model-simulated and observed sea levels at 37 tidal gages. Two 10-year forecasts, one for the IPCC Pre-Industry(PI) and the other for the A1 FI scenario, were conducted. The differences in model-simulated surge heights under the two climate scenarios were analyzed. We identified three types of responses in extreme surge heights to future climate: a clear decrease in Middle Atlantic Bight, an increase in the western Gulf of Mexico, and non-significant response for the remaining area. Such spatial pattern is also consistent with previous projections of sea surface winds and ocean wave heights. 相似文献
133.
在滑坡的动态监测中通常存在先验几何信息和物理信息,现有的滤波算法并不能够充分利用这些信息,为控制几何观测异常对形变参数估计的影响,提出一种利用滑坡力学状态信息的约束滤波模型.同时,利用约束方程获得有益信息,精确地确定测量的等价权,给出相应的自适应约束抗差滤波算法,并通过实例说明了带有约束的滤波算法更能提高状态参数估计的... 相似文献
134.
根据厦门东孚井水氡多年的观测资料,分析了水氡异常与地震活动的关系。分析结果认为,该井点映震效果较好,特别是对发生在长乐-诏安断裂带上的地震,映震能力尤为明显。 相似文献
135.
Multiscale anisotropic diffusion for ringing artifact suppression in geophysical deconvolution data 下载免费PDF全文
Ringing artifact degradations always appear in the deconvolution of geophysical data. To address this problem, we propose a postprocessing approach to suppress ringing artifacts that uses a novel anisotropic diffusion based on a stationary wavelet transform (SWT) algorithm. In this paper, we discuss the ringing artifact suppression problem and analyze the characteristics of the deconvolution ringing artifact. The deconvolution data containing ringing artifacts are decomposed into different SWT subbands for analysis, and a new multiscale adaptive anisotropic filter is developed to suppress these degradations. Finally, we demonstrate the performance of the proposed method and describe the experiments in detail. 相似文献
136.
在贵州重冰区3个气象站和海拔2500m的梅花山野外观测点开展了3a冬季的导线覆冰自动观测实验,利用观测实验获取的大量连续覆冰过程数据,对导线覆冰重量及其气象条件逐小时演变特征进行了深入分析.结果表明:一次完整的连续导线覆冰过程包括覆冰开始、增长、维持、减弱、消融到结束五个不同的阶段,持续时间较长的覆冰过程中间可能出现间断,而覆冰增长、维持、减弱几个阶段可能重复交替出现.覆冰过程开始一般以气温下降到0℃以下且相对湿度90%以上为标志,当出现浓雾或降水时覆冰出现增长,当既无降水也无雾时覆冰进入维持阶段;整个覆冰过程中温度均低于0℃且维持很高的湿度,中途若温度上升且无雾和降水则覆冰有明显减弱,当气温稳定上升到0℃以上同时湿度下降时覆冰过程结束.覆冰过程的开始和增长一般持续时间较长,而覆冰的消融和结束则十分迅速.在气象站观测到的覆冰以雨雾混合冻结为主,降水对覆冰过程的开始和增长有重要作用,而在梅花山野外观测到的多为雾凇覆冰,降水对覆冰的作用不如地势较低地区显著. 相似文献
137.
Fractal modeling is demonstrated to be an effective and rapid tool to distinguish between mineral phases in rock samples.
It supplements work that previously could be performed only by observing the interpenetrational or metasomatic phenomena between
different minerals with the aid of mineralographic microscope. The Gejiu tin district in southwestern China was chosen as
a study area for the recognition and characterization of the spatial distribution of two phases (Types I and II) of cassiterite.
Vector patterns used for this study were extracted from digital photomicrographs and analyzed with the aid of MapGIS. Perimeter–area
fractal dimension, cumulative number–area exponent, and shape index were determined in order to quantify geometrical irregularities
and spatial cassiterite phase distribution characteristics. The results show that fractal dimensions based on area and perimeter
are larger for crystals of Type I than for those of Type II. The mean shape index (SI) increases from 0.54 (Type I) to 0.64 (Type II), indicating an increase in regularity. The number–area exponent also increases
from 0.88 to 1.15, indicating the smaller crystals of Type II. The cumulative number–shape index log–log plot shows two separate
straight-line segments. One of these probably represents a background shape realized during the original process of natural
crystallization, whereas the other likely represents anomalous shapes because of weathering or other superimposed processes.
Two parallel lines can be constructed on the perimeter–area log–log plots. The upper line, with a larger intercept, represents
crystals with lower SI. The lower line represents crystals with higher SI, indicating that the intercept provides a measure of the irregularity of grains. By combining the perimeter–area model with
cumulative number–area plot and shape index, the two phases of cassiterite can be distinguished and characterized. One phase
has fewer crystals of large size, and the other has smaller crystals. This difference can be explained by assuming that under
higher-temperature conditions, the large cassiterite crystals formed earlier than the smaller crystals. Consequently, the
large cassiterites underwent longer, high-intensive weathering than the small crystals so that their shapes became more irregular.
The younger, more abundant small cassiterites retained their original regular shapes. 相似文献
138.
139.
利用COSMIC掩星2009年电子密度剖面数据,筛选数据进行网格划分,网格内数据统计平均,基于球谐函数计算模型值,分析电离层中低纬度地区最大电子密度的地磁季节变化、昼夜测分布相对变化,及地磁活动对电子密度的分布影响.结果表明,最大电子密度昼测值明显高于夜测值,在中纬度部分区域增大明显.电子密度昼测值在地磁活动期间高度150-550 km中低纬度范围为正相扰动,随纬度变化存在区域差异,随高度增加,扰动加强. 相似文献
140.
Abstract This work makes explicit an algebraic expression giving the matrix of transient influence coefficients associated with a one-dimensional semi-confined aquifer model. The domain studied is divided into a series of connected and completely mixed compartments over which the governing equation is discretized. The discrete equations obtained are solved for the compartmental hydraulic head and used to derive the algebraic expression in question. The basic properties of the so-called algebraic influence coefficients are investigated. In particular, their consistency with the exact Green function is highlighted. Finally, the newly derived influence coefficients are applied to a simplified aquifer system in order to formulate and solve the problem of identifying illegal groundwater pumping. 相似文献