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1.
城市表面粗糙度长度的确定 总被引：10，自引：0，他引：10
讨论了动量粗糙度长度与热量和水汽等标量粗糙度长度在形式上和物理本质上的不同，以及造成这些不同的原因和条件，分析了决定动量粗糙度的几种因素，并给出了确定动量粗糙度长度的简化关系式，并且根据城市冠层与其上惯性次层能量和动量守衡的原因，建立了热量和水汽粗糙度与动量粗糙度之间的联系，得到了确定热量和水汽粗糙度长度的简化关系式，最后，通过数值试验，表明了动量粗糙度和标量粗糙度变化特征以及对一些主要参数的敏感程度，以及动量粗糙度与标量粗糙度的动态关系。 相似文献
2.
贵州夏秋麦气候生产潜力评价及种植前景 总被引：1，自引：0，他引：1
采用ＦＡＯ计算作物生产力的生态区域法，以贵阳花溪为代表，估算和评价了贵州夏秋麦的光温生产潜力和气候生产潜力，并进行了土壤订正，完成了一套地区生产力评价的程序，阐述了夏秋麦在贵州生产种植的意义和前景。为贵州充分利用气候和土地资料，提高复咎指数增加粮食产量提供了依据。 相似文献
3.
人工神经网络与遗传算法结合的时间序列预测模式 总被引：6，自引：1，他引：6
介绍了遗传算法的基本概念和流程，阐述了人工神经网络作为时间序列预测模式的可行性和不足之处，并提出了人工网络与遗传算法相结合的时间序列预测模式，最后给出了该算法的计算结果，并对结果和模式作了讨论。 相似文献
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5.
根据史料和器测资料重建的气温和旱涝年代序列，对长江中游近５２０年的气候变率，变化趋势，准周期变动和突变特性进行了诊断研究，并对近百年气候变化的基本特征进行较细致的讨论，分析了旱涝变化与太阳活动的联系，得到了一些有意义的结果；在上述基础上对未来１５年气候的可以变化趋势进行了推测，在防灾减灾方面提出了看法和建议。 相似文献
6.
青岛地区边界层结构的数值模拟 总被引：8，自引：1，他引：8
本文建立了一个非静力的三维细网格边界层模式，对青岛地区复杂下垫面条件下的边界层结构和湍流特征作了数值模拟，模式采用能量闭合方案，舍弃了静力近似，以提高空间分辨率和模式精度。模拟以实测资料为初始输入，对该地区风场和湍流场作了较细致的模拟分析，与观测资料相比，结果合理地一致。结果表明了陡峭地形和不规则海岸线对局地风场和湍流场影响很大。 相似文献
7.
贵州开展气象有偿服务以来，已经过了近10年的历程。在这段时间中，该项工作从无到有，由小到大，由窄至宽，发展趋势令人高兴，不仅在经济收入方面有了长足进步，绘事业费用的不足和改善职工福利，生活待遇带来了好处，而且在为社会服务，支持气象事业主渠道的发展，进一步深入结构调整，培养人材等方面都起到了积极作用。但与发达省（市）相比仍有较大差距。从现在起，这就要求各级领导和气象人员，要正确估价和分析有偿服务的过去、现在和未来，制定出结合实际的，切实可行的发展规划，找出我省开展有偿服务的难点和对策。本文就是从这一… 相似文献
8.
本对呼盟牧区白灾出现的气候规律作了分析和研究，指出了白灾对畜牧业生产的危害和防御措施，确定了白灾的综合气象指数和计算系统，分析了白灾的时空分布，并对白灾的预报在数理统计方面作了探讨，给出了准确率较高的预报方程。 相似文献
9.
气候多层次的趋势预报 总被引：11，自引：0，他引：11
论述了子波气候诊断中的边界效应和非周期性对趋势预报的影响，在消除子波变换边界效应基础上，将气候层次理论和子波诊断技术相结合，提出了气候多层趋势预报法则和评判标准，最后利用若干气候资料进行了多层次趋势预报，试验表明，相似延伸法能有效地消除边界效应，提出了气候多层次趋势预报法是可行的。 相似文献
10.
我们经过３年多的开发，建立了一套“农业气象情报，预报和资料综合处理服务系统”软件。它集农气资料管理，情报资料采集，译码，图形分析，统计分析于一体，自动化程度高，减轻了劳动强度，增强了农气服务的能力，提高了服务质量和时效，收到显著的业务服务效益。 相似文献
11.
作者介绍了分形和分维的概念、性质和意义，重点讨论了从一维时间序列中提取维数信息的方法，并给出了一些在天气和气候中的应用。 相似文献
12.
The data analyses indicated that the occurrence of EL Nino event is closely related to intraseasonal oscillation (ISO) in the tropical atmosphere: The intraseasonal oscillation is very strong in tile tropics (particularly over the equatorial western Pacific) prior to the occurrence of El Nino; But the ISO is evidently reduced and the quasistationary system is enhanced after the outbreak of El Nino. A simple air-sea coupled model study shows that the periodical self-excited oscillation can be produced in the air-sea-coupled system, but the pattern is different from the observed ENSO mode. When there is external (atmospheric) forcing with interannual time scale, a coupled mode, which looks like the ENSO mode, will be excited in the air-sea system. Synthesizing the results in data analyses and the theoretical investigation. the mechanism of ISO in the tropical atmosphere exciting the El Nino event can be suggested : The interannual anomalies (variations) of the tropical ISO play an important role in the exciting El Nino event through the air-sea interaction. 相似文献
13.
《Atmospheric Research》2009,94(4):673-679
Since climate trends are getting considerable attention in recent years, we aimed in this study to compare trends and rhythms of complexity (fractal dimension, FD) of rainfall data series between two continents: Latin America and Europe. Two parallel nonlinear methods for calculating FD of a temporal data series, Higuchi's and consecutive differences, were combined with Fast Fourier Transform (FFT) to obtain FD oscillations of monthly accumulated rainfall. The data were collected for the last thirty years in Pastaza province, Ecuador and Veneto province, Italy. In order to calculate their FD time dependence, FD(t), moving windows of different lengths (short, 10–20 and long 21–350 samples), were applied. Both methods, each combined with FFT, detected identical (or very similar) rhythms of detrended FD(t) in the two data series, but frequencies with dominant amplitudes differed (4.4 years in Ecuador, 10.3 years in Italy). Long-term FD(t) trends were also studied using optimized long window lengths (~ 200 samples). A linear positive trend was obtained for the Ecuadorian rainfall data over the whole recorded period. Italian fractal trend profile was, however, characterized by two periods: a constant high value for years 1974–1993, followed by a linear decrease for 1993–2005. Trend results, obtained with two different methods, were also similar. Accordance of the results, reported in the present paper by applying these two methods, validates their use as a tool in future fractal meteorological measurements. As well, these results indicate that positive FD trend obtained for Pastaza (Ecuador) and negative trend computed for Veneto (Italy) account for a local or regional phenomenon, most probably caused by extensive deforestation and land use change (Ecuador) and continental or global atmospheric pattern variability (Italy). 相似文献
14.
Nonlinear dynamics of meteorological variables: multifractality and chaotic invariants in daily records from Pastaza, Ecuador 总被引：1，自引：0，他引：1
Humberto Millán Aleksandar Kalauzi Milena Cukic Riccardo Biondi 《Theoretical and Applied Climatology》2010,102(1-2):75-85
Weather represents the daily state of the atmosphere. It is usually considered as a chaotic nonlinear dynamical system. The objectives of the present study were (1) to investigate multifractal meteorological trends and rhythms at the Amazonian area of Ecuador and (2) to estimate some nonlinear invariants for describing the meteorological dynamics. Six meteorological variables were considered in the study. Datasets were collected on a daily basis from January 1st 2001 to January 1st 2005 (1,460 observations). Based on a new multifractal method, we found interesting fractal rhythms and trends of antipersistence patterns (Fractal Dimension >1.5). Nonlinear time series analyses rendered Lyapunov exponent spectra containing more than one positive Lyapunov exponent in some cases. This sort of hyperchaotic structures could explain, to some extent, larger fractal dimension values as the Kaplan–Yorke dimension was also in most cases larger than two. The maximum prediction time ranged from ξ?=?1.69 days (approximately 41 h) for E/P ratio to ξ?=?14.71 days for evaporation. Nonlinear dynamics analyses could be combined with multifractal studies for describing the time evolution of meteorological variables. 相似文献
15.
A. Mazzarella 《Theoretical and Applied Climatology》1998,59(3-4):147-150
Summary The catalogue of sea-floodings in Venice, accurately reconstructed for a period of 12 centuries (interval: 872–1996) has
been analysed according to the Cantor Dust method. This provides a means of testing whether clustering in time is a scale-invariant
process: if the fraction R of the intervals of length t containing flooding events is related to the time interval by: R∼t
(1−D)
, then the fractal clustering is occurring with fractal dimension D (0<D<1). The main result is the evidence for a gradual increase of the fractal clustering starting from 1914, when the soil subsidence
of the lagoon basin determines an increase in its hydrodynamic response to the marine forcing with a gradual increase of flooding
occurrences.
Received October 1, 1996 Revised September 10, 1997 相似文献
16.
The El Nin o-Southern Oscillation (ENSO) is modulated by many factors; most previous studies have emphasized the roles of wind stress and heat flux in the tropical Pacific. Freshwater flux (FWF) is another environmental forcing to the ocean; its effect and the related ocean salinity variability in the ENSO region have been of increased interest recently. Currently, accurate quantifications of the FWF roles in the climate remain challenging; the related observations and coupled ocean-atmosphere modeling involve large elements of uncertainty. In this study, we utilized satellite-based data to represent FWF-induced feedback in the tropical Pacific climate system; we then incorporated these data into a hybrid coupled ocean-atmosphere model (HCM) to quantify its effects on ENSO. A new mechanism was revealed by which interannual FWF forcing modulates ENSO in a significant way. As a direct forcing, FWF exerts a significant influence on the ocean through sea surface salinity (SSS) and buoyancy flux (Q B ) in the western-central tropical Pacific. The SSS perturbations directly induced by ENSO-related interannual FWF variability affect the stability and mixing in the upper ocean. At the same time, the ENSO-induced FWF has a compensating effect on heat flux, acting to reduce interannual Q B variability during ENSO cycles. These FWF-induced processes in the ocean tend to modulate the vertical mixing and entrainment in the upper ocean, enhancing cooling during La Nin a and enhancing warming during El Nin o, respectively. The interannual FWF forcing-induced positive feedback acts to enhance ENSO amplitude and lengthen its time scales in the tropical Pacific coupled climate system. 相似文献
17.
Classification of daily solar irradiation by fractional analysis of 10-min-means of solar irradiance
Summary This paper deals with fractal analysis of daily solar irradiances measured with a time step of 10 minutes at Golden and Boulder located in Colorado. The aim is to estimate the fractal dimensions in order to perform classification of daily solar irradiances. The estimated fractal dimension
and the clearness index KT are used as classification criteria. The results show that these criteria lead to three classes: clear sky, partially covered sky and overcast sky. The results also show that the evaluation of the fractal dimension of the irradiance signal based on a data set with 10 minutes time step is possible. 相似文献
18.
Summary Atmospheric flows exhibit long-range spatiotemporal correlations manifested as the fractal geometry to the global cloud cover pattern concomitant with inverse power law form for power spectra of temporal fluctuations on all space-tie scales ranging from turbulence (centimetersseconds) to climate (kilometers-years). Long-range spatiotemporal correlations are ubiquitous to dynamical systems in nature and are identified as signatures ofself-organized criticality. Standard models in meteorological theory cannot explain satisfactorily the observed self-organized criticality in atmospheric flows. Mathematical models for simulation and prediction of atmospheric flows are nonlinear and do not possess analytical solutions. Finite precision computer realizations of nonlinear models give unrealistic solutions because ofdeterministic chaos, a direct consequence of round-off error growth in iterative numerical computations. Recent studies show that roundoff error doubles on an average for each iteration of iterative computations. Round-off error propagates to the main stream computation and gives unrealistic solutions in numerical weather prediction (NWP) and climate models which incorporate thousands of iterative computations in long-term numerical integration schemes. An alternative non-deterministic cell dynamical system model for atmospheric flows described in this paper predicts the observed self-organized criticality as intrinsic to quantumlike mechanics governing flow dynamics. The model provides universal quantification for self-organized criticality in terms of the statistical normal distribution. Model predictions are in agreement with a majority of observed spectra of time series of several standard climatological data sets representative of disparate climatic regimes. Universal spectrum for natural climate variability rules out linear trends. Man-made greenhouse gas related atmospheric warming will result in intensification of natural climate variability, seen immediately in high frequency fluctuations such as QBO and ENSO and even shorter timescales. Model concepts and results of analyses are discussed with reference to possible prediction of climate change.With 11 Figures 相似文献
19.
Scott B. Power 《Theoretical and Applied Climatology》2011,104(1-2):251-259
The El Ni?o-Southern Oscillation (ENSO) is a major driver of climate variability in many parts of the world. Impressive progress has been made in the last 25?years in consolidating the scientific and mathematical basis to our understanding of ENSO. This includes the development and analysis of a hierarchy of models??including simple analogue models??to simulate and understand ENSO physics. The delayed-action oscillator (DAO) equation has been a particularly important analogue model in the historical development of our understanding of ENSO physics, and numerical solutions of this equation have been explored in detail in previous studies. Given this importance, it is surprising that no exact analytic solutions to the equation have been provided previously in the ENSO literature. This situation is rectified here by deriving and presenting analytic solutions to the linear DAO equation $ \frac{{dT}}{{dt}} = aT - bT\left( {t - \tau } \right) $ for parameter values relevant to ENSO. Here, T is an index for ENSO variability at time t; a, b, and ?? (the delay time >0) are real parameters. A comparison between observations and (linear) theory suggests that ENSO behaves as a damped oscillator with a period of 3.8?years and a damping time-scale of 0.9?years. The parameter $ \gamma = b\tau {e^{ - a\tau }} $ is found to be crucial in understanding the behavior of the solution and the lowest frequency mode. For example, if ???>?1/e the solution is oscillatory. Exact analytic solutions to the DAO equation which are phase-locked to the annual cycle??as is the case for ENSO??are also obtained. The overall (annual average) stability of a phase-locked system and its intrinsic periodicities differ from the corresponding properties of the system with parameters set to their annual averages (i.e., the corresponding solution which is not phase-locked). Phase-locking therefore alters the growth rate and period of the lowest frequency mode. 相似文献
20.
Time series of vertically integrated concentrations (VIC) across neutrally buoyant plumes are used to study the fractal and multifractal characteristics of passive scalar fluctuations in turbulent flow fields. Here, the multifractal analysis is based on a novel definition of the singularity spectrum-F() of the time records. Approximations for quantities such as the fractal dimension and the spectral exponent are derived as functions ofF() and are compared with the experimental results. Among other things, we show that VIC records are characterized by two typical subdomains. One domain, which is related to integrated concentration fluctuations, is a subfractal process; whereas the second one, which is directly related to the concentration fluctuations, is a fractal process. 相似文献