SAR图像纠正的数学模型   总被引：3，自引：0，他引：3  

肖国超 《测绘学院学报》1994,(3)

本文对Ｇ．Ｋｏｎｅｃｎｙ等提出的平距投影的合成孔径雷达（ＳＡＲ）图像纠正的数学模型给子证明，并指出其近似性。随后推导了斜距投影的雷达图像纠正的数学模型，且以雷达图像的模拟数据，验证了该数学模型与Ｇ．Ｋｏｎｅｃｎｙ的数学模型具有相同的数学精度。  相似文献   

多卜勒雷达经向速度资料的预处理方法     

周建芬  周文贤 《南京气象学院学报》1994,17(2):213-218

利用变分法原理提出了对雷达速度资料进行预处理的一种方法，数值试验表明该法能有效地消除雷达速度资料中的小尺度运动径向速度分量及“噪声”。  相似文献   

ERROR COMPARISON OF WIND FIELD RETRIEVAL FROM SINGLE AND DUAL-DOPPLER RADAR OBSERVATIONS          下载免费PDF全文

Tao Zuyu 《Acta Meteorologica Sinica》1994,8(3):337-345

The error distributions of the wind fields retrieved from single and dual-Doppler radar observations are given inthis paper.The results indicate that the error of dual-Doppler retrieval depends on the position in the scan region of thedual-Doppler radar.The error of single-Doppler retrieval by using velocity azimuth processing(VAP)technique de-pends on the angle between the directions of wind and the radar beam.Generally,the winds retrieved from single Doppl-er radar are close to those retrieved from dual-Doppler radar.But,the error distribution of the single-Doppler retrievalis different from the dual-Doppler retrieval.We simulate the retrievals of single Doppler observation by the use of theoutput wind data from a 3-D numerical model of severe convection.The comparison of the simulated single-anddual-Doppler retrievals shows that the VAP may be a suitable technique for the operational analysis of mesoscale windfields.It can also be used as a supplement to wind field retrieval in the field experiment.  相似文献   

RETRIEVAL OF HORIZONTAL WIND PERTURBATION FIELDS FROM SIMULATED SINGLE DOPPLER RADAR OBSERVATIONS^*          下载免费PDF全文

Gu Songshan  I. Zawadzki  S. Laroche 《Acta Meteorologica Sinica》1994,8(1):89-108

The application of the single Doppler radar dataset analysis is usually confined to the assumption that the actual wind is linearly distributed or uniform locally.Following some dynamic features of convective weather,a conceptual model of moderate complexity is constructed,wherewith a horizontal wind perturbation field is retrieved directly from the single Doppler radar measurements.The numerical experiments are based on a 3-D cloud model-generated convective cell,whose radial velocity component is taken as the radar observations that are put into the closed equations based on the conceptual model to retrieve the horizontal wind perturbation field.After the initial field is properly treated,the retrieval equation is solved in terms of the 2-D FFT technique and the sensitivity to noise is examined.Finally,contrast analysis is done of the retrieved and the cloud model output wind fields,indicating the usefulness of the approach proposed in this paper.  相似文献   

多物理参量检验防雹效果的研究   总被引：1，自引：0，他引：1  

王雨曾  郁青 《气象》1995,21(10):3-8

除使用地面冰雹资料（即冰雹动能、质量、降雹强度等）外，还选用了反映雹云变化的雷达回波参量等１０个物理参量，作为作业效果的检验量，检验防雹效果。结果表明：高炮作业后雷达回波顶高、强度及３０ｄｂｚ强回波顶高显著地比作业前小；作业区比未作业区冰雹动能、冰雹质量、冰雹动能通量、质量通量、最大冰雹直径、数密度以及降雹持续时间也有明显减小。  相似文献   

Modern Numerical Ephemerides of Planets and the Importance of Ranging Observations for Their Creation     

E.V. Pitjeva 《Celestial Mechanics and Dynamical Astronomy》2001,80(3-4):249-271

The JPL planetary and lunar ephemerides – DE200/LE200, DE403/LE403, DE405/LE405 and the planetary and lunar ephemerides, EPM87, EPM98, and EPM2000, constructed in the Institute of Applied Astronomy of RAS are described. Common properties and differences of the various ephemerides are given. Graphical comparisons of the DE ephemerides with each other and with the EPM ephemerides are presented. A fairly good agreement of planetary orbits is between DE403, DE405 and EPM98, EPM2000, respectively, over the interval of 120 years (1886–2006) covered by EPM98 and EPM2000. Some differences are explained by a slight disagreement in representing the orbits of Ceres, Pallas, and Vesta as they affect the planets. The accurate radar observations of planets and spacecraft make it possible not only to improve the orbital elements of planets but to determine a broad set of astronomical constants as well: km/AU, parameters of Mars rotation including its precessional rate, the masses of Jupiter, Ceres, Pallas, and Vesta, relativistic parameters of the PPN formalism, the variability of the gravitational constant G. These have been obtained in the fitting process of the DE405 and EPM2000 ephemerides to observational data, including nearly 80000 American and Russian radar observations of planets (1961–1997), ranging and doppler to the Viking and Pathfinder landers, and other miscellaneous measurements from various sources and spacecraft.  相似文献   

水稻时域散射特征分析及其应用研究     

邵芸  郭华东  范湘涛  刘浩 《遥感学报》2001,5(4):340-345

通过对肇庆试验区1996年和1997年获取的多时相、多模式雷达卫星（RADARSAT）数据分析,从图像上直接提取地物的后向散射系数,结合实地测量水稻的生长结构参数,建立了水稻生长模型,分析了不同生长周期（从80天到120－125天）4种类型水稻的时域散射特性。利用1997年4月至7月获取的7景标准模式雷达卫星数据,对试验区内三个县和两个行政区共5000km^2面积范围内的作物进行分类和水稻产量预估算,水稻类型分类及面积量算精度达91％。结果表明：利用雷达遥感数据进行水稻种植面积量算和估产需要水稻生长期间三个时相的数据,即插秧期、抽穗期、收割前期。若能够获得多参数雷达图像,可以用插秧期和收割前期的两个时相图像来代替上述的三个时相图像同样可以达到种植面积量算和估产的效果。这一结果充分说明多时相雷达卫星数据对我国南方水稻长势监测及估产具有明显优势和潜力。  相似文献   

On the relationship of thunderstorm ice hydrometeor characteristics and total lightning measurements   总被引：1，自引：0，他引：1  

Wiebke Deierling  John Latham  Walter A. Petersen  Scott M. Ellis  Hugh J. Christian  Jr.   《Atmospheric Research》2005,76(1-4):114

Satellite-borne and ground-based devices for the detection of lightning offer the opportunity to explore relationships–on all significant scales up to global–between lightning frequency, f, and other thundercloud parameters. Calculations predict that f is proportional to the product of the downflux p of solid precipitation and the upward mass flux, I, of ice crystals. This prediction has received support from limited computational studies. The physical reasons for such a relationship are explained in terms of the paramount role of ice in the electrification of thunderstorms. Herein, this prediction is subjected to further, preliminary examination through analysis of lightning and dual-polarimetric radar data collected during the STERAO experiment conducted in Northern Colorado during the summer of 1996. The analysis has yielded some highly provisional support for this flux hypothesis. Computed trends of radar derived hydrometeor fractions of solid precipitation and small ice show correlation to the total lightning frequency and raise the possibility of determining values of p and/or I from lightning measurements.It is shown that the extent to which the observed correlations between f and both solid precipitation and small ice trends are or are not strong can provide an indication as to whether the lightning activity is limited by the available concentrations of precipitating or non-precipitating ice in the upper regions of the charging zone of the thundercloud, where most of the charge transfer occurs. It is demonstrated that the most accurate determinations of precipitation rate p from measurements of lighting frequency f are likely to be for conditions where the field-growth is limited by the availability of graupel pellets. It is shown that the simultaneous time variations of f and solid precipitation trends of the type obtained in the STERAO experiment could enable us to determine the nature of the dominant glaciation process operative in the thunderclouds studied.  相似文献   

Comparison of lightning activity and radar-retrieved microphysical properties in EULINOX storms     

Thorsten Fehr  Nikolai Dotzek  Hartmut Hller 《Atmospheric Research》2005,76(1-4):167

A combined analysis of microphysical thunderstorm properties derived by C-band polarimetric Doppler radar measurements and lightning observations from two ground-based systems are presented. Three types of storms, a multicell, a supercell, and a squall line, that were observed during the European Lightning Nitrogen Oxides project (EULINOX) are investigated. Correlations are sought between the mass of rain, graupel, hail, and snow derived form radar observations at different height levels and the electrical activity, represented either by cloud-to-ground or intracloud flashes. These relationships are explained by connecting the radar-derived properties with the non-inductive charging process. For the multicell and the supercell storm, the lightning activity can be linearly correlated to both the hydrometeor total mass and class specific mass in the upper part of the storm. It is shown that the fractions of graupel and hail above the −20 °C-level in these storms positively correlate with the intracloud flash activity in the supercell, and negatively for the cloud-to-ground lightning frequency in the multicell. No such relation can be established for the squall line, indicating that the convective organization plays a crucial role in the lightning development. The analysis of the masses in the different storms shows that lightning activity cannot be parameterized by total mass alone, other parameters have to be identified. The results provide important information for all lightning studies that rely on bulk properties of thunderstorms, e.g., the parameterization of lightning in mesoscale models or the nowcasting of lightning by radar.  相似文献   

Application of the hydrologic visibility concept to estimate rainfall measurement quality of two planned weather radars     

D. Faure  G. Delrieu  P. Tabary  J. Parent Du Chatelet  M. Guimera 《Atmospheric Research》2005,77(1-4):232

This paper presents a practical application of the “hydrologic visibility” concept to select the future site of two planned weather radars of the French national network ARAMIS. This selection was realised by simulating the errors in radar rainfall measurement due to interactions of the radar beam with relief, and to the vertical variation of the radar reflectivity with altitude. Results show the interest of these simulations to optimise the radar location according to the objectives of radar coverage. Beyond these results, this paper highlights aspects interesting for hydrology: this type of simulation can be used to assess the radar measurement quality before initiating a quantitative exploitation of radar data, and before making a comparison or a combination with rain gauge data.  相似文献