声雷达在污染扩散问题中的应用

单点测温声雷达和多普勒测风声雷达能够提供边界层大气中温度层结和风速、风向等气象要素随时间的连续变化和空间分布的资料。与其它遥测技术相比,声雷达的造价比较低廉,维护方便,适合于野外观测使用。近十几年来,声雷达探测在国际上得到了广泛的应用。在我国,中国科学院大气物理研     

模糊贴近度在热带气旋路径预评评价中的应用

本文用1985年──1992年的资料，对主要的热带气旋路径预报方法进行了客观评价。同时将模糊贴近度公式引入评价中，分析表明，与使用平均误差相比，它较为合理。     

SWT声雷达探测系统对大气边界层声回波信号的变换与检测

在SWT声雷达探测系统中,采用作者提出的检测声回波信号的跟踪滤波锁相方法(PLTF),提取Doppler频偏f_d的V-F-BCD变换和模块化设计,减小了锁相环(PLL)的失锁现象,改善了声雷达的测风精度,闭路同源标定结果表明SWT声雷达探测系统的测频精度优于0.1Hz,相当于测风精度可达λ/4/s(λ——发射声波长),由于环境噪声的干扰,将会使测风精度略有降低。     

OIQC技术在雷达反演VAD廓线资料退模糊中的应用研究

多普勒天气雷达在强风速天气条件下经常出现的速度模糊误差,严重限制了风场信息的广泛应用,如反演VAD廓线等。本文将最优插值客观分析质量控制技术(OIQC),应用于雷达反演VAD廓线资料中速度模糊的质量控制。对用于反演VAD风廓线的那些格点圈层上的资料,以简化的多变量统计插值技术(Cressman插值),为被检查的资料提供一个对比分析的参考值,从而确定折叠次数,修正模糊速度。根据多普勒雷达径向速度资料的特点,水平方向采用非各向同性的单变量背景场误差协方差函数,垂直方向协方差函数取为高斯型。修正模糊速度后运用VAD技术得到水平风的垂直廓线。对强龙卷天气过程的数值试验结果表明,OIQC技术应用于雷达资料质量控制,无需引入外界风场,有能力修正模糊速度。结合VAD方法,可以从存在严重折叠的雷达资料中反演出较为准确的风廓线。     

应用声雷达遥测低层大气温度层结

一、引言声雷达(acoustic radar)是遥测低层大气结构特点的一种现代化先进工具,得到了世界性的广泛应用。声雷达可用于大气温度遥测和风向风速遥测。用双点声雷达系统可以得到风的湍流结构资料;从单点声雷达的后向散射回波图片上,可以直观地看出大气混合层结构的时——空实时演变规律。     

雷达和卫星资料在中尺度模式中的初步应用

本文利用非静力中尺度模式MM5对1998年7月20日－21日发生在湖北东部地区的特大暴雨过程作数值模拟，同时将不同时间的雷达和卫星资料适时加入模式改变当时模式中的水汽场，并与控制试验进行比较分析，结果表明：加入雷达和卫星资料后的数值模拟，由于修正了暴雨区及其邻近区域对流层中低层水汽场，雨区位置和雨量中心值比仅用探空资料的控制试验更接近实况。雷达与卫星资料引入模式对于24小时降雨产生的效果不同，雷达资料的影响是局部的，范围较小，卫星资料影响范围较大，而且适时加入雷达、卫星资料能够及时通过水汽场修正，使24小时预报的雨区范围和中心强度与实况更加接近，而二者结合起来的效果与降水系统的特征有关。     

微波传输线原理在701系列雷达天馈系统检测中的应用

传输线理论实质上是分布参数电路理论 ,它是微波电路的理论基础。 70 1系列雷达的天馈系统是用来发射和接收 40 0 M微波信号的装置 ,该系统性能的优劣直接影响雷达的整体性能 ,本文应用传输线原理及它的重要指标—行波系数解决了 70 1系列雷达天馈系统检测及制作过程中的一些关     

雷达在水文预报应用中的研究进展

雷达可随时跟踪雨区范围、暴雨走向和降雨量的变化,而降雨是水文预报最重要的输入信息,对于水文预报、水库蓄放及江河流域水量的短时洪水预报都是很重要的.本文在介绍雷达测雨及国内外雷达测雨业务系统的基础上,重点总结了国内雷达测雨在水文预报中的研究进展,并提出了雷达在水文预报中的应用思路,探讨了雷达测雨在我国水文应用中的前景及其发展方向.数字化雷达测雨、地理信息系统以及数字高程图等系列新信息,将进一步推动新一代分布式降雨-径流模型的开发,并将极大地拓宽水文预报研究的思路和方法,从而提高预报精度.     

若干声雷达回波图象的分析

本文分析了近些年由声雷达观测到的海（陆）风、大风、下坡风和雾的回波图象和相应气象参数变化的特征。     

Underestimation of Monostatic Sodar Measurements in Complex Terrain

Recent investigations in complex terrain have found that remote sensing instrumentation commonly finds mean wind-speed differences when compared to cup anemometery. In many cases the difference is found to be an underestimation and varies from 2 to 9% depending on topology. We describe these differences in a theoretical sense for a five-beam sodar. An investigation is conducted on a New Zealand ridge with a five-beam sodar and three computational models, consisting of a potential flow model and two computational fluid dynamical simulations, OpenFOAM and the industry standard software WindSim. All models predict the difference to within 0.1–2.5%. A comparative assessment is made and it is found that, given the computing overheads, the potential flow model provides a good compromise in the prediction of mean wind-speed difference.     

Wavy Vertical Motions in the ABL Observed by Sodar

Some characteristics of wavelike motions in the atmospheric boundary layer observed by sodar are considered. In an experiment carried out in February 1993 in Milan, Italy, Doppler sodar measurements were accompanied by in situ measurements of temperature and wind velocity vertical profiles using a tethered balloon up to 600 m. The oscillations of elevated wavy layers containing intense thermal turbulence, usually associated with temperature-inversion zones, were studied by using correlation and spectral analysis methods. The statistics of the occurrence of wavelike and temperature-inversion events are presented. The height distributions of Brunt–Vaisala frequency and wind shear and their correlation within elevated inversion layers were determined, with a strong correlation observed between the drift rate of the wavy layers and the vertical velocity measured by Doppler sodar inside these layers. Spectral analysis showed similarities regarding their frequency characteristics. The phase speed and propagation direction of waves were estimated from the time delay of the signals at three antennae to provide estimates of wavelength. Moreover, wavelengths were estimated from the intrinsic frequency obtained from sodar measurements of the Doppler vertical velocity and oscillations of wavy turbulent layers. The two wavelength estimates are in good agreement.     

Corrections for Wind-Speed Errors from Sodar and Lidar in Complex Terrain

The quality of lidar and sodar wind estimates is generally judged through comparisons with mast-mounted instruments, and the resulting regressions. Evaluation of the relative merits of lidars versus sodars is complicated by the fact that lidars are generally placed close to a mast whereas sodars are generally placed some distance from a mast so that acoustic reflections off the mast are reduced. This leads to the two technologies, lidar and sodar, not being compared in similar situations. Differences arising from the two geometries can be expected to be larger in complex terrain, where the wind regime can vary significantly spatially. The current work explores these differences in moderately complex terrain. Lidar–mast comparisons are performed with the lidar close to an 80 m mast, and sodar–mast comparisons performed with the sodar 300 m from the mast. Systematic variations in estimated wind speed are found to occur with height, consistent with predictions from a simple flow model. When the lidar was moved to the sodar location, further from the mast, there were significant changes in the estimated wind speeds and a reduction in correlation with the mast-based wind speeds, as expected. However, the correlation between collocated lidar and sodar winds was high. This finding emphasizes that any comparison of two remote sensing instruments needs to be through similar experiments, and that differences in accuracy often reported for the lidar and sodar technologies are likely to be contaminated due to poor comparison configurations. A method was devised to simulate the sodar being collocated with the mast, by using the lidar–sodar measurements and the lidar–mast measurements. It was found that there was then no statistically detectable difference between lidar–mast regressions and sodar–mast regressions for the particular lidar and sodar tested. Both remote sensing instruments were also found to be good estimators of Weibull parameters, as compared with those derived from mast data. The conclusion is that the sodar measured the winds above the sodar with a similar accuracy to the lidar measuring winds above the lidar.     

分层垂直累积液态含水量的算法及其在人工影响天气中的应用

应用VIL产品的生成原理,变换VIL产品的理论表达式为实测体扫回波强度不同仰角之间高度层的计算公式,利用与雷达资料时间对应的当天的探空资料,取得当天0℃层的高度,并以0℃层高度为界,将垂直累积液态含水量分为上下两部分,分别计算每一个底面积的垂直柱体中的垂直累积液态含水量以及分层的垂直累积液态含水量,从而得到整个探测区域的VIL分布.通过雷达组网,得到全省的上层VIL的分布,结合雷达资料分析出的回波的移向和移速,科学的选择飞机增雨的作业区域以及作业的时间,从而得到更好的飞机人工增雨效果.利用分层垂直累计液态含水量及其0℃上下层比值,更好的指挥地面高炮火箭人工增雨和消雹作业.     

δ函数在云的反射率计算中的应用

本文证明了二流模式和s-w模式,两种计算散射大气反射率的简化方法,都具有δ-相函数的特点.结合δ函数并通过由二流模式得到的计算结果作为一次近似再代入辐射传输方程中而导出一种更精确计算云层反照率的简单方法.     

The application of delta function to the albedo of clouds

It is verified that there is δ-phase function characteristic in both of TS and SW simplified models, and on the basis of TS model, a more accurate model calculating the albedo and transmissivity of cloud layers is derived.     

Some Statistics of the Temperature Structure Parameter in the Convective Boundary Layer Observed by Sodar

The characteristics of the temporal and height variations of the temperature structure parameter $C_\mathrm{T}^{2}$ in strongly convective situations derived from the sodar echo-signal intensity measurements were analyzed for the first 100 m. It was corroborated that the probability density function (pdf) of the logarithm of $C_\mathrm{T}^{2}$ in the lower convective boundary layer is markedly non-Gaussian, whereas turbulence theory predicts it to be normal. It was also corroborated that the sum of two weighted Gaussians, which characterize the statistics of $C_\mathrm{T}^{2}$ within convective plumes and in their environment and the probability of plume occurrence, well approximates the observed pdfs. It was shown that the height behaviour of the arithmetic mean of $ C_\mathrm{T}^{2}$ (both total and within plumes) follows well a power law $C_\mathrm{T}^{2} (z) \sim z^{-q}$ with the exponent $q$ close to the theoretically predicted value of 4/3. But for the geometrical means of $C_\mathrm{T}^{2}$ (both total and within the plumes), $q$ is close to 1. The difference between arithmetically and geometrically averaged $C_\mathrm{T}^{2}$ profiles was analyzed. The vertical profiles of the standard deviation, skewness and kurtosis of $\hbox {ln}C_\mathrm{T}^{2}$ pdfs were analyzed to show their steady behaviour with height. The standard deviations of the logarithm of $C_\mathrm{T}^{2}$ within the plumes and between them are similar and are 1.5 times less than the total standard deviation. The estimate of the variability index $F_\mathrm{T}$ and its height behaviour were obtained, which can be useful to validate some theoretical and modelling predictions. The vertical profiles of the skewness and kurtosis show the negative asymmetry of pdfs and their flatness, respectively. The spectra of variations in $\hbox {ln}C_\mathrm{T}^{2}$ are shown to be satisfactorily fitted by the power law $f^{-\gamma } $ in the frequency range 0.02 and 0.2 Hz, with the average exponent $\approx $ 1.27  $\pm $  0.22.     

Evaluation of Sodar methods for the determination of the atmospheric boundary layer mixing height

Summary It is the purpose of this paper to evaluate the different Sodar approaches and methods for the determination of the atmospheric mixing height against direct measurements. To achieve this objective a specific experiment was designed and performed incorporating, a research home made Sodar, a tethered balloon and a radiosonde facility as well as a conventional ground based meteorological station. The obtained data were statistically treated and analyzed to high-light the advantages and disadvantages of the various methods during different meteorological conditions. The results indicate that all three manual methods produce reasonable estimates during convective conditions, while for the stable cases the acceptable techniques are reduced to two. For the automated approach however, the two methods produced quite acceptable estimates during convective conditions, while for the stable cases none was found suitable for use.     

The work intensity function in the detection of greenhouse induced global temperature trends

Summary A work intensity function is defined as the product of the frequencies exhibited by a column in a histogram and the magnitude of the midpoint of the class interval of the column. An intensity distribution is defined as the cumulative sum of the function along the abscissa. These functions are examined first for a normal distribution, and then for the expected deviations shown by a sample assumed to be drawn from a normal distribution. The theoretical maximum of the intensity is found at one standard deviation for the normal distribution and at 2 s.d. (standard deviation) for a sample drawn from a normal distribution. The cumulative sum of the intensity is more biased towards outlying values of larger magnitude for the sample than for the normal distribution. 10% of the cumulative sum of the intensities is generated at s.d. greater than 3 for the sample compared to only 1% for the normal distribution itself. These statistics are compared with similar ones computed for the Jones-Parker (1991) series of mean global surface temperature anomaly interannual differences. The agreement between theory and the data series is good. The data series appears to possess those properties which would be expected of it if the series was a sample drawn from a normal distribution. It is concluded that the work intensity and its cumulative sum are useful tools in diagnosing the behaviour of a population of anomaly values. These statistics do not clarify the problem of identifying a greenhouse gas induced global warming but they do suggest that its identification continues to be as difficult as ever, due to the effect of occasional outlying values.With 2 Figures