共查询到20条相似文献，搜索用时 35 毫秒
1.
M. Ćurić 《Theoretical and Applied Climatology》1989,40(4):227-235
Summary A brief review of numerical models of thunderstorms is presented. The attempts of modeling these clouds have to deal with an extremely broad range of microphysical and dynamic processes. Basic concepts of thunderstorm modeling, 1-D, 2-D and 3-D models are considered. Particular attention is given to the basic equations and to the capability of these models to predict characteristics of the tunderstorms. A brief treatment is also given of hail growth in thunderstorm models.
With 8 Figures 相似文献
Zusammenfassung Im folgenden wird eine knappe Übersicht numerischer Gewittermodelle präsentiert. Bei der Modellierung von Gewitterwolken muß ein ausgesprochen weiter Bereich von mikrophysikalischen und dynamischen Prozessen beachtet werden. Grundkonzepte der Gewittermodellierung, 1-D-, 2-D- und 3-D-Modelle werden hierzu herangezogen. Besondere Aufmerksamkeit gilt dabei den Ausgangsgleichungen sowie den potentiellen Möglichkeiten dieser Modelle, Charakteristika der Gewitter vorherzusagen. Weiters wird auch das Hagelwachstum in Gewittermodellen kurz behandelt.
With 8 Figures 相似文献
2.
Micrometeorologists have traditionally set aside consideration of horizontal variability and have studied boundary-layer structure with horizontal homogeneity. The numerical forecasting of boundary-layer structures, over normally varying terrain and including normal disturbances such as fronts, requires selection of an appropriate horizontal scale.A simple analysis of steady-state balance between horizontal advection and vertical diffusion provides estimates of the vertical scale (or depth) of surface-induced features. The scale height is a function of the horizontal scale of the variations. Models neglecting important terrain scales of length below ~ 1000 km can predict down to levels of ~ 0.5 to 1 km while those that neglect important terrain scales below ~ 100 km can predict down to ~ 0.2 to 0.6 km. Below these levels, any predicted features will be dominated by the vertical diffusion so that they are solutions of a one-dimensional boundary-value problem.The boundary-induced advection effects dominate free atmosphere advection effects in the lowest few hundred meters as well. This means that if mesoscale advections are resolved and terrain influences are strong, the predictions in the layer ~ 0.2 to 0.8 km can provide mesoscale detail without mesoscale initial conditions above the surface, because the surface forcing will dominate the solution. 相似文献
3.
4.
Marek Brabec Viorel Badescu Marius Paulescu 《Meteorology and Atmospheric Physics》2013,120(1-2):61-71
In this paper, we present a formalized approach to statistical modeling of the sunshine number, binary indicator of whether the Sun is covered by clouds introduced previously by Badescu (Theor Appl Climatol 72:127–136, 2002). Our statistical approach is based on Markov chain and logistic regression and yields fully specified probability models that are relatively easily identified (and their unknown parameters estimated) from a set of empirical data (observed sunshine number and sunshine stability number series). We discuss general structure of the model and its advantages, demonstrate its performance on real data and compare its results to classical ARIMA approach as to a competitor. Since the model parameters have clear interpretation, we also illustrate how, e.g., their inter-seasonal stability can be tested. We conclude with an outlook to future developments oriented to construction of models allowing for practically desirable smooth transition between data observed with different frequencies and with a short discussion of technical problems that such a goal brings. 相似文献
5.
Regional modeling: A theoretical discussion 总被引：4，自引：0，他引：4
A. Staniforth 《Meteorology and Atmospheric Physics》1997,63(1-2):15-29
Summary The goal of regional modeling is to make a detailed forecast for a given limited area of interst by focusing resolution over it and the immediate vicinity. As a consequence, the period of validity is necessarily more restricted than would otherwise be the case, and this is the price that must be paid for locally-enhanced resolution. The principal attributes of the non-interactive and interactive strategies for regional modeling are described. For the non0interactive strategy, particular emphasis is placed on the importance, difficulty, and impact, of well-posedness for open-domain problems. A methodology is given for estimating the size of numerical buffer zones required to obtain a forecast uncontaminated by the inward propagation of inaccurately-specified lateral boundary conditions. The interactive strategy addresses the well-posedness issue of (non-interactive) limited-area models. A computational overhead is incurred but this can be reduced through the use of variable resolution. It is argued that regardless of the preferred regional modeling strategy, experiments should be undertaken to today's regional models under carefully-controlled conditions, to reflect the significant reduction over the past two decades of other sources of error.With 7 Figures 相似文献
6.
Ruwim Berkowicz 《Boundary-Layer Meteorology》1984,30(1-4):201-219
The rate of diffusion of a cloud depends on cloud dimensions. As the cloud enlarges, larger eddies come into play and the rate of diffusion increases. The turbulent diffusion process is scale-dependent. The gradient-transfer theory (K-theory) is only appropriate when the dimensions of the dispersed material are much larger than the size of the turbulent eddies. Introduction of a spectral turbulent diffusivity function (STD) makes it possible to treat the diffusive transport in a Eulerian system, with diffusivity effectively dependent on the actual size of the concentration distribution. The basic innovation is that diffusion is treated in the Fourier space and the diffusion coefficient is dependent on the wave number of the Fourier components of the concentration distribution. It is shown that the concept of the wave-number-dependent diffusivity leads to a non-local flux-gradient relation. 相似文献
7.
Networks of rain gauges can provide a better insight into the spatial and temporal variability of rainfall, but they tend to be too widely spaced for accurate estimates. A way to estimate the spatial variability of rainfall between gauge points is to interpolate between them. This paper evaluates the spatial autocorrelation of rainfall data in some locations in Peninsular Malaysia using geostatistical technique. The results give an insight on the spatial variability of rainfall in the area, as such, two rain gauges were selected for an in-depth study of the temporal dependence of the rainfall data-generating process. It could be shown that rainfall data are affected by nonlinear characteristics of the variance often referred to as variance clustering or volatility, where large changes tend to follow large changes and small changes tend to follow small changes. The autocorrelation structure of the residuals and the squared residuals derived from autoregressive integrated moving average (ARIMA) models were inspected, the residuals are uncorrelated but the squared residuals show autocorrelation, and the Ljung–Box test confirmed the results. A test based on the Lagrange multiplier principle was applied to the squared residuals from the ARIMA models. The results of this auxiliary test show a clear evidence to reject the null hypothesis of no autoregressive conditional heteroskedasticity (ARCH) effect. Hence, it indicates that generalized ARCH (GARCH) modeling is necessary. An ARIMA error model is proposed to capture the mean behavior and a GARCH model for modeling heteroskedasticity (variance behavior) of the residuals from the ARIMA model. Therefore, the composite ARIMA–GARCH model captures the dynamics of daily rainfall in the study area. On the other hand, seasonal ARIMA model became a suitable model for the monthly average rainfall series of the same locations treated. 相似文献
8.
随着防雷元件制造技术和工艺的不断发展,半导体放电管(Thyristor Surge Suppresser,TSS)以其精确导通、无限重复、快速响应等显著优点在防雷产品仿真、设计中占有越来越重要的地位.基于半导体放电管的电气特性和PNPN四层结构特点,利用Spice算法建立TSS的子电路仿真模型,考虑了TSS响应时间和波尾转折特性,利用1.2/50μs-8/20μs和10/700μs-5/320μs两种组合波冲击设备进行实测,验证了仿真模型的正确性,并给出了仿真波形误差.该模型的建立对基于防雷元件的仿真设计有一定的使用价值. 相似文献
9.
Stefano Pierini Adam M. Fincham Dominique Renouard Maria Rosaria D&#x;Ambrosio Henry Didelle 《Dynamics of Atmospheres and Oceans》2002,35(3)
The physical modeling of topographic Rossby normal modes carried out at the “Coriolis” Rotating Platform (Grenoble), is presented. The basic feature of the bottom topography is a linear slope of 4.3 m×2 m delimited by two lateral walls. Since the studied motions are essentially barotropic, homogeneous water was used. Unsheared currents were generated by a simple movement of a wavemaker located in front of the topographic barrier. The conservation of potential vorticity for the currents flowing onto the channel slope produced Rossby waves: reflections at the lateral boundaries then led to the formation of propagating barotropic Rossby normal modes, whose frequencies and spatial structures were selected by the physical system. The currents were measured through the correlation imaging velocimetry (CIV) method, which allowed an extremely detailed synoptic map of the horizontal velocities in an area (13 m2) including the slope to be obtained every 30 s.A variety of experiments were performed in order to provide a complete process study in which the effect of different channel lengths and rotation periods could be tested. Two different lengths of the linear slope, 4.3 and 3.3 m, and rotation periods ranging from 30 to 50 s were considered. The qualitative analysis of the 2D current patterns, and the good agreement found between the measured eigenperiods and the periods obtained by means of a simple analytical model, show that in all cases the first Rossby normal mode was generated. Moreover, numerical simulations based on the shallow-water equations, for a geometry and paddle movements that match closely the experimental setup, allow to calibrate the analytical model and provide useful information on a discrepancy found between experimental and analytical eigenperiods due to an oscillation of the normal mode trajectory. 相似文献
10.
In order to research the interactions between the atmosphere and ocean as well as their important role in the intensive weather systems of coastal areas, and to improve the forecasting ability of the hazardous weather processes of coastal areas, a coupled atmosphere-ocean-wave modeling system has been developed. The agent-based environment framework for linking models allows flexible and dynamic information exchange between models. For the purpose of flexibility, portability and scalability, the framework of the whole system takes a multi-layer architecture that includes a user interface layer, computational layer and service-enabling layer. The numerical experiment presented in this paper demonstrates the performance of the distributed coupled modeling system. 相似文献
11.
L. Bodri 《Theoretical and Applied Climatology》1995,51(1-2):51-58
Summary The structure of the temporal variability of temperature records has been investigated by means of different statistical methods including also fractal analysis. Data both from meteorological stations and averaged over wider networks show very similar behaviour; combine a long-run persistence (characterized by a fractal dimension ofD = 1.2–1.3) and short-run properties indicating high year-by-year variability. Synthetic temperature records were created with the use of Mandelbrot's fast fractional Gaussian noise generating algorithm. These fractal sets show the same stochastic properties as real temperature records do, and have even a very similar appearance. The results suggest that the fractal reconstruction algorithm could be used to extrapolate the present tendencies to the future and to forecast future fluctuations.With 8 Figures 相似文献
12.
Dabang Jiang Ge Yu Ping Zhao Xing Chen Jian Liu Xiaodong Liu Shaowu Wang Zhongshi Zhang Yongqiang Yu Yuefeng Li Liya Jin Ying Xu Lixia Ju Tianjun Zhou Xiaodong Yan 《大气科学进展》2015,32(2):250-275
This paper provides a review of paleoclimate modeling activities in China. Rather than attempt to cover all topics, we have chosen a few climatic intervals and events judged to be particularly informative to the international community. In historical climate simulations, changes in solar radiation and volcanic activity explain most parts of reconstructions over the last millennium prior to the industrial era, while atmospheric greenhouse gas concentrations play the most important role in the20 th century warming over China. There is a considerable model–data mismatch in the annual and boreal winter temperature change over China during the mid-Holocene [6000 years before present(ka BP)], while coupled models with an interactive ocean generally perform better than atmospheric models. For the Last Glacial Maximum(21 ka BP), climate models successfully reproduce the surface cooling trend over China but fail to reproduce its magnitude, with a better performance for coupled models. At that time, reconstructed vegetation and western Pacific sea surface temperatures could have significantly affected the East Asian climate, and environmental conditions on the Qinghai–Tibetan Plateau were most likely very different to the present day. During the late Marine Isotope Stage 3(30–40 ka BP), orbital forcing and Northern Hemisphere glaciation, as well as vegetation change in China, were likely responsible for East Asian climate change. On the tectonic scale,the Qinghai–Tibetan Plateau uplift, the Tethys Sea retreat, and the South China Sea expansion played important roles in the formation of the East Asian monsoon-dominant environment pattern during the late Cenozoic. 相似文献
13.
Mikhail Ya Verbitsky 《Climate Dynamics》1992,7(2):105-110
A set of simple scaling formulas related to ice sheet evolution is derived from the dynamic and thermodynamic equations for ice and is used to consider two common situations: (a) when we wish to estimate potential ice sheet characteristics given the prescribed net snow accumulation over an area; and (b) when we wish to reconstruct net snow accumulation and vertical temperature difference within the ice sheet given empirical data only concerning ice sheet area and volume. The scaling formulas are applied to the present day Antarctic and Greenland ice sheets, as well as to some ancient ice sheets, and are used to estimate the potential global sea level change due to greenhouse warming. 相似文献
14.
After introductory remarks on similarity laws to be satisfied in wind tunnel experiments simulating small-scale meteorological processes, mean and turbulence characteristics of wind tunnel boundary layers are presented and compared with the characteristics of the atmospheric boundary layer. The results are used to evaluate the possibilities and limitations of physical modeling of pollutant dispersion in general. In the second part of the paper, the potential of wind tunnels to solve micro-meteorological problems of real practical interest will be demonstrated. The example involves the investigation of the effects of building downwash on ground-level concentrations for flue gases discharged from natural draft wet cooling towers. 相似文献
15.
P. Hosseinzadeh Talaee 《Theoretical and Applied Climatology》2014,118(3):481-489
Soil temperature is an important meteorological parameter which influences a number of processes in agriculture, hydrology, and environment. However, soil temperature records are not routinely available from meteorological stations. This work aimed to estimate daily soil temperature using the coactive neuro-fuzzy inference system (CANFIS) in arid and semiarid regions. For this purpose, daily soil temperatures were recorded at six depths of 5, 10, 20, 30, 50, and 100 cm below the surface at two synoptic stations in Iran. According to correlation analysis, mean, maximum, and minimum air temperatures, relative humidity, sunshine hours, and solar radiation were selected as the inputs of the CANFIS models. It was concluded that, in most cases, the best soil temperature estimates with a CANFIS model can be provided with the Takagi–Sugeno–Kang (TSK) fuzzy model and the Gaussian membership function. Comparison of the models’ performances at arid and semiarid locations showed that the CANFIS models’ performances in arid site were slightly better than those in semiarid site. Overall, the obtained results indicated the capabilities of the CANFIS model in estimating soil temperature in arid and semiarid regions. 相似文献
16.
Interpolation of climate variables and temperature modeling 总被引：1，自引：0，他引：1
Sailesh Samanta Dilip Kumar Pal Debasish Lohar Babita Pal 《Theoretical and Applied Climatology》2012,107(1-2):35-45
Geographic Information Systems (GIS) and modeling are becoming powerful tools in agricultural research and natural resource management. This study proposes an empirical methodology for modeling and mapping of the monthly and annual air temperature using remote sensing and GIS techniques. The study area is Gangetic West Bengal and its neighborhood in the eastern India, where a number of weather systems occur throughout the year. Gangetic West Bengal is a region of strong heterogeneous surface with several weather disturbances. This paper also examines statistical approaches for interpolating climatic data over large regions, providing different interpolation techniques for climate variables' use in agricultural research. Three interpolation approaches, like inverse distance weighted averaging, thin-plate smoothing splines, and co-kriging are evaluated for 4°?×?4° area, covering the eastern part of India. The land use/land cover, soil texture, and digital elevation model are used as the independent variables for temperature modeling. Multiple regression analysis with standard method is used to add dependent variables into regression equation. Prediction of mean temperature for monsoon season is better than winter season. Finally standard deviation errors are evaluated after comparing the predicted temperature and observed temperature of the area. For better improvement, distance from the coastline and seasonal wind pattern are stressed to be included as independent variables. 相似文献
17.
Results of numerical simulations using the WRF-ARW nonhydrostatic model are presented for eight episodes of intense convection over European Russia in the summer of 2007. The calculations were performed on four nested grids with horizontal grid meshes of 27, 9, 3, and 1 km. Convection was parametrized on the first two grids and explicitly resolved on the other two. It has been found that simulations on finer grids with explicit calculation of convective flows make it possible to reproduce heavy rainfalls and strong-wind zones in the areas of intense convection. A preliminary verification of the short-range predictions of convective systems shows that the maximum 12-h precipitation totals and the maximum winds at 10 m are close, in the order of magnitude, to the observed values. Prediction of convection centers is the weakest point. Difficulties in the model verification associated with the absence of data with high space-time resolution are discussed. 相似文献
18.
A computer complex is described developed for the detailed temperature forecasting in large megalopolises. It consists of
the global and microclimatic models implementing the modeling of the thermal regime within Moscow. To increase the modeling
quality, an improved technique is proposed of computation of temperature characteristics within the urban canyon. A spatial
resolution of output modeling data reaches 500 m. A comparison with the station data demonstrates that the accuracy of air
temperature simulation in Moscow and in its nearest vicinities is quite satisfactory. 相似文献
19.
一维时空光化学模式引进垂直运动及离子反应生成的氮氧(NOx)、氢氧(HOx)化合物。模式中采用1978到1983年期间的太阳紫外辐射通量及南极73度的纬向八月份平均温度。 计算结果表明:春季南极出现臭氧洞,主要是第21太阳黑子周峰值期太阳紫外辐射减少造成的。其次,在太阳黑子周峰值期伴随多次大的太阳质子事件,产生大量氮氧、氢氧化合物。在极区太阳质子事件产生的化合物催化破坏平流层臭氧可持续几天至几年。 南极冬春季节强大的下降垂直运动是南极臭氧洞形成发展极其重要的局部动力条件,特别是在极夜期间。太阳升起后,垂直运动的影响不明显。 南极臭氧洞的形成主要是通过光化变化过程,动力过程是其局部的充要条件,人为活动产生的含氯化合物对低层大气臭氧的直接破坏不可忽视。基于上述论点,可以预期进入第22太阳黑子周期,南极及全球大气臭氧的分布状态将会改变,大自然本身自复。 相似文献