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1.
本文利用中国地磁子午链台站的资料，对1997～1999年期间发生的25次磁暴，用自然正交分量法（NOC）、相关分析和傅里叶分析三种方法，分3个步骤依次分离出依赖于世界时（UT）的暴时变化（Dst）、依赖于地方时（LT）的太阳静日变化（Sq）和太阳扰日变化（SD）.对各种变化时空特征的分析表明：①Dst变化清楚地反映出赤道对称环电流磁扰的空间分布和时间演化特征；②满洲里、北京十三陵和琼中台Sq幅度在多数磁暴主相期间出现极大和极小值，反映了Sq焦点在纬度方向上的移动所产生的地磁效应；③SD变化在主相期间最强，在恢复相期间逐渐减弱；④相关分析和傅里叶分析提供了一种能有效提取Sq和SD变化的方法. 相似文献
2.
当利用无线电电磁波进行远程通信、卫星导航时，传递信号要受到电离层的影响，因此，对电离层中电子含量的研究显得特别重要.虽然国际上有几种电离层的电子含量预报模型，但其预报只能精确到电子含量的50%～60%.本文提出了一种新的电离层电子含量预报方法:即用球谐函数对IGS(国际GPS服务)所给出的离地面450 km高的球面上的每一网点的电离层电子含量进行拟合，对不同的时间所得到的拟合系数所形成的时间序列用时间序列分析理论中的ARMA(p,q)模型进行预报，从而实现全球的电离层电子含量预报.利用本方法对2004年和2005年IGS所给电离层电子含量资料在地理框架中做了分析预报，5天内电子含量预报相对精度在90%左右. 相似文献
3.
介绍了基于伪随机相关辨识理论的电法发送机设计思想.通过分析逆重复m序列伪随机信号的性质，产生原理，以及伪随机信号系统辨识的原理，研究了其在电法勘探应用中的可行性.用工程软件MATLAB仿真产生了逆重复m信号的波形，并分析了频谱和自相关函数，对产生伪随机信号的序列长度和时钟频率等参数的选择作出讨论，以说明其作为电法勘探场源的优良特点.作出了电法发送机系统初步设计，包括主控单元、逆变器、GPS同步，电流测量等模块，发送机信号控制单元采用硬件描述语言VHDL设计，并用CPLD可编程逻辑器件LC4256V实现了硬件产生m序列和逆重复m序列，及各种控制信号.宽频带、密频比，抗干扰能力强是其主要特点，在电法勘探中有良好的应用前景. 相似文献
4.
从理论上探讨如何提高天气预报和气候预测的技巧.气候包括以小时为基本单位的昼夜循环、以日为基本单位的年(季节)循环、年代际循环和世纪循环等时间尺度的变化.这些气候变化存在确定的外强迫,是可以被认识和预报的.相对气候昼夜循环和年(季节)循环的偏差是天气尺度扰动.天气尺度的瞬变大气扰动可引发极端天气事件.有技巧的天气预报正是要通过天气尺度大气扰动信号,提前几天甚至十几天,预报出极端天气事件的发生.相对气候年代际和世纪循环的偏差是气候异常,有技巧的气候预测正是要预报出这种异常.距平天气图会大大提高短期和中期—延伸期天气预报的技巧,距平数值预报模式的研制也会加快提高中期—延伸期天气预报和气候预测的技巧. 相似文献
5.
针对地震勘探资料湮没在随机噪声中的微弱同相轴问题提出基于混沌理论的混沌振子检测算法. 利用修正的Duffing_Holmes方程建立检测微弱同相轴的混沌振子系统,之后经过对同相轴的扫描处理,构成新子波等时间间隔序列W(t),与此同时对随机噪声也进行相同的截断. 截断的随机噪声在混沌振子系统中可以具有与周期信号相同的表现;经过大量仿真实验确定出满足通常地震勘探子波延续时间的使混沌振子检测子波不呈现周期相态的随机噪声截断时间范围. 选用与松辽盆地T1、T2反射层类似的子波函数并构成待检微弱周期信号,经过MATLAB仿真试验成功地检测出该弱信号,信噪比达到约-103dB. 相似文献
6.
本文探讨了OH Meinel夜气辉辐射的光化学模式，给出OH(ν≤9)分子数密度分布的计算通式，重点研究了化学反应HO\-2+O→OH(ν≤6)+O2对ν≤6各振动能级上OH分子数密度分布以及(ν′—ν″)(ν′≤6)振动带气辉辐射的影响.结果表明，该反应对数密度的贡献随振动能级的减小而增大，对(ν′—ν″)振动带辐射的贡献随着较高振动能级ν′的减小而增大，以春分时为例，它可使第1振动能级上的OH分子最大数密度和（1—0）带的最大辐射率增加约33%，第6振动能级上的最大数密度和（6—ν″）带的最大辐射率增加约7%，（1—0）带的辐射强度增加约30%，（6—ν″）带的强度增加约11%.该反应使各振动能级上分子数密度的高度分布剖面以及各振动带体辐射率的高度分布剖面变宽，最大数密度、最大发射率所处的高度下降1 km左右.此外，该反应的影响程度随着原子氧密度的降低而增大，随着温度的升高而增大，并且在夏至时最大，在冬至时最小. 相似文献
7.
利用一个电离层理论模式，模拟了太阳活动低年、地磁宁静情况下，中低纬和赤道地区电离层F2区峰值电子浓度(NmF2)的半年变化规律，重点讨论了电离层电场对NmF2半年变化的影响.模拟结果表明，当输入的电场没有周年和半年变化时，磁赤道地区电离层NmF2本身就具有一定的半年变化特征，而在稍高的纬度上，NmF2半年变化的强度较弱.当输入的电场具有一定的半年变化时，电离层NmF2的半年变化强度有明显的改变，且这种改变随地方时和地磁纬度不同有明显的差别.在地磁赤道附近的电离层赤道槽地区，从上午到午夜的时间内，具有半年变化的电场对电离层NmF2半年变化的强度是减弱的作用，在其他的时间内，电场对电离层NmF2半年变化强度是加强的作用.而在稍高纬度的电离层驼峰地区，情况明显不同.从上午一直到翌日日出前，具有半年变化的电场对电离层NmF2半年变化的幅度都是加强的作用.在其他的时间内，电场对电离层NmF2半年变化的幅度是减弱的作用.同时，研究表明电离层电场对NmF2半年变化的作用和“赤道喷泉”现象强烈相关. 相似文献
8.
最小二乘支持向量机（LS-SVM）用于拟合回归处理时的参数设置一直是一个难题，它会受到信号类型和强度、核函数类型、噪声强度、计算精度要求等因素的影响.本文针对Ricker子波核LS-SVM去除地震勘探信号中随机噪声问题，讨论和分析了向量机参数、核参数对去噪性能的影响.实验表明，核参数f可取为地震记录的主频，不能较准确估计时宁大勿小；向量机参数γ只要不取得过小，一般情况下都是能接受的.采用此方法对含不同强度噪声的地震勘探信号进行了去噪处理. 相似文献
9.
面波压制是地震数据处理中的一个重要问题. 常规的处理方法虽然能在一定程度上压制面波，但是在处理过程中只是单一的利用面波的一种特性,例如频率域滤波中利用面波与有效信号频率之间的差别，因此难以有效地压制面波. 利用Ridgelet变换可将原始地震记录拓展到（a,τ,p）三维空间，从而可以同时利用地震记录的视速度、时间和尺度域特性差别，实现有效信号与面波的分离. 文中通过理论合成记录及实际地震记录的算例，证实了基于Ridgelet变换的面波压制方法是有效且可行的. 相似文献
10.
气候序列的均一化——定量评估气候变化的基础 总被引：1，自引：0，他引：1
长期气象观测序列是反映气候变化的最基本依据.然而,几乎所有气象站都要经历迁址或观测仪器、规则和方法等方面的变更,导致观测序列相应时段的系统性偏差.均一化就是要校订这类系统性偏差,以确切评估时间序列中的变化趋势.近年来随着气候变化研究的深入,均一化也从早期主要着眼于平均态校订发展到更注重极端天气气候信息的校订.本文结合理想的和实际的气候序列分析,演示均一化的基本思路;简介近年来就中国区域气候序列的均一化研究取得的一些新认识,并就该领域存在的（特别是涉及气候极值或极端天气以及多要素物理联系等方面）问题,展望进一步研究. 相似文献
11.
Long-term meteorological observation series are fundamental for reflecting climate changes.However,almost all meteorological stations inevitably undergo relocation or changes in observation instruments,rules,and methods,which can result in systematic biases in the observation series for corresponding periods.Homogenization is a technique for adjusting these biases in order to assess the true trends in the time series.In recent years,homogenization has shifted its focus from the adjustments to climate mean status to the adjustments to information about climate extremes or extreme weather.Using case analyses of ideal and actual climate series,here we demonstrate the basic idea of homogenization,introduce new understanding obtained from recent studies of homogenization of climate series in China,and raise issues for further studies in this field,especially with regards to climate extremes,uncertainty of the statistical adjustments,and biased physical relationships among different climate variables due to adjustments in single variable series. 相似文献
12.
Byung Sik Kim Hung Soo Kim Byung Ha Seoh Nam Won Kim 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(4):457-373
The main purpose of this study is to investigate and evaluate the impact of climate change on the runoff and water resources
of Yongdam basin, Korea. First, we construct global climate change scenarios using the YONU GCM control run and transient
experiments, then transform the YONU GCM grid-box predictions with coarse resolution of climate change into the site-specific
values by statistical downscaling techniques. The downscaled values are used to modify the parameters of a stochastic weather
generator model for the simulation of the site-specific daily weather time series. The weather series is fed into a semi-distributed
hydrological model called SLURP to simulate the streamflows associated with other water resources for the condition of 2CO2. This approach is applied to the Yongdam dam basin in the southern part of Korea. The results show that under the condition
of 2CO2, about 7.6% of annual mean streamflow is reduced when it is compared with the current condition. Seasonal streamflows in
the winter and autumn are increased, while streamflow in the summer is decreased. However, the seasonality of the simulated
series is similar to the observed pattern
An erratum to this article can be found at 相似文献
13.
Spectral analysis of climate data 总被引：2，自引：0，他引：2
The complexity of climate variability on all time scales requires the use of several refined tools to unravel its primary dynamics from observations. Indeed, ideas from the theory of dynamical systems have provided new ways of interpreting the information contained in climatic time series.We review the properties of several modern time series analysis methods. Those methods belong to four main classes: Fourier techniques (Blackman-Tukey and Multi-Taper), Maximum Entropy technique, Singular-spectrum techniques and wavelet analysis. Their respective advantages and limitations are illustrated by numerical experiments on synthetic time series. As climate data can be irregularly spaced in time, we also compare three interpolating methods on those time series. Those tests are aimed at showing the pitfalls of the blind use of mathematical or statistical techniques on climate data.We apply those methods to real climatic data from temperature variations over the last century, and the Vostok ice core deuterium record over the last glacial cycle. Then we show how interpretations on the dynamics of climate can be derived on those time scales. 相似文献
14.
Meng Zhiyong Zhang Fuqing Luo Dehai Tan Zhemin Fang Juan Sun Jianhua Shen Xueshun Zhang Yunji Wang Shuguang Han Wei Zhao Kun Zhu Lei Hu Yongyun Xue Huiwen Ma Yaping Zhang Lijuan Nie Ji Zhou Ruilin Li Sa Liu Hongjun Zhu Yuning 《中国科学:地球科学(英文版)》2019,62(12):1946-1991
Synoptic meteorology is a branch of meteorology that uses synoptic weather observations and charts for the diagnosis,study,and forecasting of weather.Weather refers to the specific state of the atmosphere near the Earth's surface during a short period of time.The spatial distribution of meteorological elements in the atmosphere can be represented by a variety of transient weather phenomena,which are caused by weather systems of different spatial and temporal scales.Weather is closely related to people's life,and its development and evolution have always been the focus of atmospheric scientific research and operation.The development of synoptic meteorology is closely related to the development of observation systems,dynamical theories and numerical models.In China,observation networks have been built since the early 1950 s.Up to now,a comprehensive meteorological observation systembased on ground,air and space has been established.In particular,the development of a new generation of dense radar networks,the development of the Fengyun satellite series and the implementation of a series of large field experiments have brought our understanding of weather from large-scale environment to thermal dynamics,cloud microphysical structure and evolution characteristics of meso and micro-scale weather systems.The development of observation has also promoted the development of theory,numerical model and simulation.In the early days,China mainly used foreign numerical models.Lately,China has developed numerical model systems with independent intellectual property rights.Based on the results of high-resolution numerical simulations,in-depth understanding of the initiation and evolution mechanism and predictability of weather at different scales has been obtained.Synoptic meteorology has gradually changed from an initially independent development to a multidisciplinary approach,and the interaction between weather and the change of climate and environment has become a hot and frontier topic in atmospheric science.This paper reviews the important scientific and technological achievements made in China over the past 70 years in the fields of synoptic meteorology based on the literatures in China and abroad,from six aspects respectively including atmospheric dynamics,synoptic-scale weather,typhoon and tropical weather,severe convective weather,numerical weather prediction and data assimilation,weather and climate,atmospheric physics and atmospheric environment. 相似文献
15.
This paper presents a brief review of selected publications concerning dynamical chaos and persistence in various solar–terrestrial phenomena ranging from solar activity to climate dynamics. It draws attention to the advanced approaches known in many research areas (meteorology, hydrology, biology, economics, etc.), but not yet sufficiently used in solar–terrestrial physics. First, we introduce the concepts of dynamical (deterministic) chaos and fractional Brownian motion. Next, we discuss appropriate methods—fluctuation analysis and nonlinear time series analysis—for treatment of erratic time series based on these concepts. We outline some pitfalls and problems in the application of the discussed methods to empirical data. Finally, we present selected empirical evidence for persistence and dynamical chaos in solar activity, solar wind, magnetosphere and ionosphere, weather and climate systems. 相似文献
16.
《水文科学杂志》2012,57(2):227-241
ABSTRACTThe study addresses homogeneity testing of annual discharge time series for eight hydrological stations and five annual climate time series for one weather station in the Kupa River Basin, between Slovenia and Croatia, and global annual average surface temperature time series for the period 1961–2010. The standard normal homogeneity test (SNHT) was used to detect both abrupt and gradual linear trend homogeneity breaks. The results reveal natural change points at the beginning of the 1980s. Absolute homogeneity testing of average annual weather station-level air pressure, annual precipitation, differences between precipitation totals and potential evapotranspiration and surface runoff from the independent observation time series confirmed an abrupt shift, also at the beginning of the 1980s. The trend of local air temperature for 1985–2000, which partly coincides with global surface temperature trend for 1974–2005, strengthened the river discharge regime shift since the beginning of the 1980s. These results could improve climate variation monitoring and estimation of the impact of climate variation on the environment in the area. Generally, an indication of climate regime change points and an assessment of their duration could provide significant benefits for the society. 相似文献
17.
Ivana Nemešová Jaroslava Kalová Martin Dubrovský 《Studia Geophysica et Geodaetica》1999,43(2):201-222
Three-dimensional general circulation models (GCMs) are 'state-of-the-art' tools for projecting possible changes in climate. Scenarios constructed for the Czech Republic are based on daily outputs of the ECHAM-GCM in the central European region. Essential findings, derived from validating, procedures are summarized and changes in variables between the control and perturbed experiments are examined. The resulting findings have been used in selecting the most proper methods of generating climate change projections for assessing possible hydrological and agricultural impacts of climate change in selected exposure units. The following weather variables have been studied: Daily extreme temperatures, daily mean temperature, daily sum of global solar radiation, and daily precipitation amounts. Due to some discrepancies revealed, the temperature series for changed climate conditions (2×CO
2
) have been created with the help of temperature differences between the control and perturbed runs, and the precipitation series have been derived from an incremental scenario based on an intercomparison of the GCMs' precipitation performance in the region. Solar radiation simulated by the ECHAM was not available and, therefore, it was generated using regression techniques relating monthly means of daily extreme temperatures and global radiation sums. The scenarios published in the paper consist of monthly means of all temperatures, their standard deviations, and monthly means of solar radiation and precipitation amounts. Daily weather series, the necessary input to impact models, are created (i) by the additive or multiplicative modification of observed weather daily series or (ii) by generating synthetic time series with the help of a weather generator whose parameters have been modified in accord with the suggested climate change scenarios. 相似文献
18.
Stochastic weather generators are widely used in hydrological, environmental, and agricultural applications to simulate weather time series. However, such stochastic models produce random outputs hence the question on how representative the generated data are if obtained from only one simulation run (realization) as is common practice. In this study, the impact of different numbers of realizations (1, 25, 50, and 100) on the suitability of generated weather data was investigated. Specifically, 50 years of daily precipitation, and maximum and minimum temperatures were generated for three weather stations in the Western Lake Erie Basin (WLEB), using three widely used weather generators, CLIGEN, LARSWG and WeaGETS. Generated results were compared with 50 years of observed data. For all three generators, the analyses showed that one realization of data for 50 years of daily precipitation, and maximum and minimum temperatures may not be representative enough to capture essential statistical characteristics of the climate. Results from the three generators captured the essential statistical characteristics of the climate when the number of realizations was increased from 1 to 25, 50 or 100. Performance did not improve substantially when realizations were increased above 25. Results suggest the need for more than a single realization when generating weather data and subsequently utilizing in other models, to obtain suitable representations of climate. 相似文献
19.
Decadal prediction using climate models faces long-standing challenges. While global climate models may reproduce long-term shifts in climate due to external forcing, in the near term, they often fail to accurately simulate interannual climate variability, as well as seasonal variability, wet and dry spells, and persistence, which are essential for water resources management. We developed a new climate-informed K-nearest neighbour (K-NN)-based stochastic modelling approach to capture the long-term trend and variability while replicating intra-annual statistics. The climate-informed K-NN stochastic model utilizes historical data along with climate state information to provide improved simulations of weather for near-term regional projections. Daily precipitation and temperature simulations are based on analogue weather days that belong to years similar to the current year's climate state. The climate-informed K-NN stochastic model is tested using 53 weather stations in the Northeast United States with an evident monotonic trend in annual precipitation. The model is also compared to the original K-NN weather generator and ISIMIP-2b GFDL general circulation model bias-corrected output in a cross-validation mode. Results indicate that the climate-informed K-NN model provides improved simulations for dry and wet regimes, and better uncertainty bounds for annual average precipitation. The model also replicates the within-year rainfall statistics. For the 1961–1970 dry regime, the model captures annual average precipitation and the intra-annual coefficient of variation. For the 2005–2014 wet regime, the model replicates the monotonic trend and daily persistence in precipitation. These improved modelled precipitation time series can be used for accurately simulating near-term streamflow, which in turn can be used for short-term water resources planning and management. 相似文献
20.
Based on cross-dating tree rings from the Tianmu Mountain, Zhejiang Province, the tree rings α-cellulose δ 13C time series was measured. By spectrum analysis, the variation of tree-ring δ13C sequence shows a quasi periodicity of 4.4 years, which is coincident with the standard cycle of El Nino. After removing the long-term decrease trend of the δ13C variation related to atmospheric CO2 concentration, the response of the δ13C to climate elements was analyzed using meteorology data from a nearby weather station. The results suggest that there is a distinct relativity between high-frequency variation of tree ring δ 13C series and seasonal climate parameters, e.g. Temperature and precipitation, with a significant time-lag effect. In addition, the high frequency also reflects the strength change of the East Asian Monsoon. The multiple regression method was employed to reconstruct the historical climate, and to analyze the climate change and trend in the last 160 years in the northern Zhejiang Province. 相似文献