共查询到20条相似文献，搜索用时 78 毫秒
1.
2.
根据197l～2001年吐鲁番站的大风资料，分析了吐鲁番市短时大风的气候特征和天气学特征。就变压风和无锋面气旋对解决大风预报难点的作用进行了探讨。 相似文献
3.
在结构风工程中, 风湍流统计参数计算的正确与否直接影响到风荷载的计算精度。在实际风参数计算与分析中, 多选用风速较大的样本资料, 但过分强调大风可能产生不合理的计算结果。利用超声风速仪瞬时风速观测资料, 分别划分成相对强风和持续强风样本, 计算并比较其湍流统计特性参数, 发现湍流统计参数特性值 (湍流度、阵风因子、摩擦速度等) 与风速大小并不能很好匹配, 有时风速不大但其湍流特性值却很大, 反之也然。研究表明:选取的湍流风资料样本或统计方法不同, 都会影响风特性参数的计算结果, 进而影响到风荷载计算的精度。这一结果对于提高结构风工程中风参数计算与设计的科学性和合理性具有现实意义。 相似文献
4.
黄、渤海沿海大风变化特征及影响系统 总被引：1，自引：1，他引：0
利用1981—2010年黄、渤海沿海44个气象站大风资料,根据中央气象台对近海海区的划分,分析了近30 a黄、渤海近海5海区大风的气候特征,以及通过天气分型对2008—2012年黄、渤海沿海大风的影响系统进行了统计,结果表明:近30 a黄、渤海沿海5海区日最大风速≥6级和≥8级日数呈递减趋势,1980s大风日数较多,各海区≥6级大风在1981年和1987年前后均有两个峰值。≥6级大风日数随季节变化的峰值,渤海海区出现在春季,黄海南部海区是春季、夏季8月和秋季11月,渤海海峡、黄海北部和中部海区则主要是春季和冬季。渤海海区以偏北风和南南西风为主导风向,与其他海区以北或西北风为主的特征明显不同。冷锋是黄、渤海沿海大风最主要的影响系统,其次是气旋型和高低压型大风。另外以850 h Pa温度平流的强度、冷/暖中心的强度、等温线密集带梯度、地面高/低压强度、地面大风前3 h/24 h最强变压中心强度和地面气压梯度等要素为着眼点,对不同类型的大风指标进行了分析。 相似文献
5.
北京地区雷暴大风的天气—气候学特征研究 总被引：13，自引：2，他引：11
依据北京近郊地区沙河、南苑和西郊3个测站15年(1990~2004年)的观测资料和常规探空资料,对北京地区局地雷暴大风发生的天气、气候特征和日变化特征进行了统计分析。研究从环流形势、探空结构和环境参数特征入手,分析了有利于北京地区产生雷暴大风的不稳定度指数和能量特征,得出在此期间最有利于雷暴大风产生的探空结构为:低层暖湿,中高层有干冷空气,不稳定度较大,风垂直切变较大。还探讨了一些对流参数,如最佳对流有效位能BCAPE、下沉对流有效位能DCAPE、风暴相对螺旋度SREH、大风指数WINDEX、风暴强度指数SSI、深厚对流指数DCI等对北京地区强对流天气发展潜势的指示意义。 相似文献
6.
基于1971-2008年黄渤海北部沿海18个基本气象站风向、风速历史资料和NCEP再分析资料,利用统计学、小波分析和天气学分型方法分析了黄渤海北部辽宁沿海风场时空变化特征。结果表明：黄渤海北部沿海大风呈明显减少趋势,大风主要出现在春季,4月最多,11月份次之。风向主要以偏北风和偏南风为主,夏半年主要以南风为主,冬半年盛行偏北风。海上大风的天气学分型主要划分为冷锋后部型、高压后部型、台风型和气旋型,其中气旋型又包括江淮气旋型、华北气旋型、蒙古气旋型和东北低压型;冷锋后部型大风出现次数最多,气旋型次之,台风型最少。 相似文献
7.
8.
利用NCEP FNL资料、FY 4卫星红外云图资料、雷达资料和自动站资料，对2021年4月15日渤海西岸由大尺度冷空气和中尺度对流系统共同作用形成的极端大风进行特征和成因分析。结果表明：①FY 4卫星红外云图云顶亮温表现出指状特征，雷达反射率因子表现为两个弱回波带在渤海西岸合并加强为一条带状回波，随着系统东移由带状回波演变为弓状回波。②上冷下暖的不稳定层结为锋面触发对流提供有利环境条件，在径向速度图上出现较大范围速度模糊和中层径向辐合。③此次大风过程具有雷暴大风和冷空气大风混合的大风特征，大风成因是由大尺度冷空气产生的动量下传、大尺度变压风、梯度风以及中尺度雷暴冷池出流共同导致的。 相似文献
9.
我国沿海气旋大风天气气候分析 总被引：2，自引：1，他引：2
气旋大风是我国沿海大风预报中较难掌握的天气过程,要提高对气旋大风的预报能力,必须了解其气候特征。本文对1949—1978年30年1835个气旋过程和1959—1978年1246个气旋中出现的633次大风过程资料进行统计分析,揭示了我国沿海地区的气旋及其大风朐气候概况和大风天气形势特点。 一、气旋气候特征 我国沿海气旋主要来自黄河气旋、江淮 相似文献
10.
城市化对近地层风速概率分布及参数的影响 总被引：1，自引：0，他引：1
通过地面风速Weibull概率分布参数的阶段变化来描述城市化对地面风速的影响,并通过理论分析得出城市化进程导致其尺度参数c缩小,位置参数r增大的趋势效应的结论。将北京等8个城市1982—2005年地面天气资料定时数据按时间划分为前、后两个时段,分别拟合分布曲线的参数,对比前、后两个时段的拟合结果,验证了理论分析所得结论,即随城市的发展,各城市风参数c不同程度地缩小,r不同程度地增大,同时概率密度曲线的峰值均增大;不同城市的风速概率密度函数曲线变化特征有所不同,根据前、后时段概率密度曲线变化的特征,8个城市风速概率分布变化大致可分为A、B两种类型,两者的主要差异是A型变化特征为在曲线两端(大风和静风)的概率都减少,曲线分布更加集中;B型则是大风概率减少而静风的概率则增大,曲线向左移动;A型变化城市的r参数平均增大46.3%,明显大于B型城市的15.7%。初步资料分析还表明,风参数c和r变化幅度与城市化扩张速度有关。 相似文献
11.
Rapid and significant advances in issues relevant to weather modification have been made in the
last decade in China due to high water resource stresses and severe weather hazards induced by climate
change. This paper reported some progress in aspects of theoretical modeling, field experiment and
cloud-seeding tools, as well as research projects regarding weather modification during the ten years
from 1997 to 2007.
More advanced theoretical models such as cloud models with bin-microphysics and
glaciogenic and hygroscopic seeding processes, and mesoscale cloud-resolving models with AgI-seeding
processes have been developed to study seeding-induced changes of cloud structure and precipitation
as well as to understand critical issues in association with weather modification. More advanced
cloud-seeding tools such as mobile ground-based launching system of AgI-rockets and aircraft-based
AgI-flares have been developed and used in operation. Several important projects aimed at exploring
weather modification techniques and their applications have been conducted during this period. 相似文献
12.
Probability distribution of basic instabilities appearing in stratified flows and point density fluctuations have been studied. Various parameters of the mixing process have been changed in the experiments, to investigate mixing. Detailed flow visualization as well as density measurements have been used in zero-mean-flow laboratory experiments involving grid-stirred turbulent mixing across a density interface and bubble-induced mixing. The overall mixing efficiency of the processes depends on the local Richardson number as well as on the local vorticity. Parameter distributions of low and high mixedness corresponding to different instabilities are presented, showing that dipolar vortices penetrating the interface are the most efficient mixing instabilities. 相似文献
13.
In most of the studies on scale properties in the rainfall process, multifractal behavior has been investigated without taking into account the different rain generation mechanisms involved. However, it is known that rain processes are related to certain scales, determined by climatological characteristics as well as regional and local meteorological features. One of the implications derived from these correspondences is the possibility that the multifractal parameters of the rainfall could depend on the dominant precipitation generation mechanism. Fractal analysis techniques have been applied in this work to rainfall data recorded in the metropolitan area of Barcelona in the period 1994–2001, as well as to a selection of synoptic rainfall events registered in the same city in the period 1927–1992. The multifractal parameters obtained have been significantly different in each case probably showing the influence of the rain generation mechanisms involved. This influence has been revealed also in the analysis of the effects of seasonality on the multifractal behavior of rainfall in Barcelona. 相似文献
14.
本文利用射线跟踪法对冰晶粒子散射、吸收进行了研究。从理论上对一些常见的近似处理方法进行了讨论，计算了长为300μm，半径为30μm的六棱柱状冰晶粒子在不同波段的光散射相函数以及在波长2.2μm时，五种不同大小冰晶粒子的单次散射反照率。结果表明，即使在有吸收情况下，Snell公式和Lambert公式仍是近似成立的，而吸收效应对散射相函数有明显影响。 相似文献
15.
The parameterization of the non-neutral atmospheric surface layer has been reexamined using the basic principles of small-scale
energetics and thermodynamics. On the basis of this more complete treatment, theK-parameterization has been reformulated. It is found that the linear regression laws between fluxes and driving gradient forces
of the turbulent heat and humidity exchanges in the surface layer can be derived in a much more comprehensive manner than
by using the commonly used K-theory.
With respect to stationary conditions and in the context of similarity concepts, a system of algebraic equations has been
formulated which provides reasonable estimates of the distributions of the dimension less rates of viscous energy dissipation
as well as turbulent kinetic and thermal-diffusive energy transport as functions of the variablez/L. Quantitative calculations have been performed using the scaling height formulations of Takeuchi and Yokoyama, Prandtl, and
von Karman as closure conditions of the equations. 相似文献
16.
G. Gross 《Boundary-Layer Meteorology》1987,40(4):311-327
A three-dimensional non-hydrostatic numerical model has been used to investigate the air flow and turbulence around a single tree.The results for velocity and turbulence distributions have been compared with available data from windtunnel experiments; the agreement is satisfactory.Simulations have been carried out for different meteorological conditions (wind speed, thermal stratification) as well as for different canopy characteristics (stem height, crown diameter, crown height, porosity).Dedicated to Prof. F. Wippermann on the occasion of his 65th birthday. 相似文献
17.
B. Parthasarathy A. A. Munot D. R. Kothawale 《Theoretical and Applied Climatology》1994,49(4):217-224
Summary The Indian rainfall has often been used as a proxy data for the Asian monsoon as a whole for understanding the energy budget of the major circulation features and also used as an input parameter in estimating the other regional parameters. In view of this, a long homogeneous rainfall series of All-India (India taken as one unit) has been prepared based on a fixed and well distributed network of 306 raingauge stations over India by giving proper area-weightage. This paper contains a listing of All-India monthly, seasonal and annual homogeneous data series for the period 1871–1993. Some statistical details and long-term changes of the All-India monsoon rainfall have been discussed.With 4 Figures 相似文献
18.
19.
K. YA. Kondratyev V. G. Bondarenko V. I. Khvorostyanov 《Boundary-Layer Meteorology》1992,61(3):265-285
A 3-D mesoscale numerical model of cloud formation, fog, and aerosol transport in an orographically inhomogeneous atmospheric boundary layer (ABL) has been considered. Streamlining of the flow around isolated obstacles in steady-state stratified flow has been studied. An account of radiation transfer in the ABL has made it possible to analyze the combined effect of orography and radiation on the formation of fog and cloud, to analyze the interaction between radiation and cloudiness, as well as their effect on the change of mesoscale circulation in the atmosphere and on variations in the optical characteristics of the atmosphere. The transport of aerosols from various sources has been modelled. The impact of orography, cloudiness and atmospheric stratification, governed by the radiative regime of the ABL, on the propagation of admixtures and surface deposition has been studied. The atmospheric aerosol turbidity in zones of intensive industrial pollution has been assessed. 相似文献
20.
The parameterization of the non-neutral atmospheric surface layer has been reexamined using the basic principles of small-scale energetics and thermodynamics. On the basis of this more complete treatment, the K- parameterization has been reformulated. It is found that the linear regression laws between fluxes and driving gradient forces of the turbulent heat and humidity exchanges in the surface layer can be derived in a much more comprehensive manner than by using the commonly used K-theory. With respect to stationary conditions and in the context of similarity concepts, a system of algebraic equations has been formulated which provides reasonable estimates of the distributions of the dimension-less rates of viscous energy dissipation as well as turbulent kinetic and thermal-diffusive energy transport as functions of the variable z/L. Quantitative calculations have been performed using the scaling height formulations of Takeuchi and Yokoyama, Prandtl, and von Kármán as closure conditions of the equations. 相似文献