X波段一维扫描有源相控阵天气雷达测试定标方法          下载免费PDF全文

刘黎平  吴翀  汪旭东  葛润生 《应用气象学报》2015,26(2):129-140

该文根据有源相控阵天气雷达的体制特点,参考多普勒天气雷达测试定标方法,提出了一维扫描有源相控阵天气雷达的测试和定标方法,将测试重点放在天馈系统、T/R组件、脉冲压缩、动态范围的测试和定标上,以解决不同观测模式、不同波位的天线增益等参数变化引起的回波强度测量误差问题。测试结果表明:天馈系统在不同观测模式下的天线参数随仰角的变化情况、波束指向的准确度、T/R组件的动态范围等均符合设计要求,回波强度和径向速度定标精度较高。雷达经过测试和定标后,于2014年5—8月分别在安徽定远和四川甘孜进行外场试验,并与附近多普勒天气雷达 (SA) 和C波段双线偏振雷达观测数据进行对比,结果表明:回波强度误差在合理范围内,精细测量、警戒搜索、快速观测3种模式观测的强回波的水平和垂直位置、结构和系统误差均比较一致,数据可靠。  相似文献   

基于正态分布拟合与检验的闪电定位资料控制     

程辉  王颖波  刘隽  刘冰 《气象科学》2015,35(2):195-198

选取福州地区2007—2012年闪电定位资料,使用Matlab对数正态分布拟合方法以及STATA的正态分布检验方法对数据进行质量控制,研究闪电定位数据误差修正方法。结果表明:利用Matlab对数正态分布拟合方法与STATA正态分布检验方法,可以定量找到闪电定位资料小幅值电流干扰区间,对于有效利用闪电定位资料有较好的参考价值。福州地区小幅值雷电流干扰区间为0~1 kA,剔除此区间资料后正闪拟合效果最佳。在使用福州地区闪电定位资料时可先将此区间小幅值闪电误差数据删除,该结论可为福州地区闪电定位数据修正提供参考。  相似文献   

Assessing the Measurement Consistency Between the Jason-2/AMR and SARAL/AltiKa/DFMR Microwave Radiometers Using Simultaneous Nadir Observations     

Bin Zhang  Changyong Cao  John Lillibridge  Laury Miller 《Marine Geodesy》2015,38(3):143-155

SARAL/AltiKa has a Dual Frequency Microwave Radiometer (DFMR), and Jason-2 has an Advanced Microwave Radiometer (AMR). Both microwave radiometer sensors include a 23.8 GHz primary water sensing channel. The measurement consistencies between DFMR and AMR are important for establishing a consistent altimetry data set between SARAL/AltiKa and Jason-2 in order to accurately assess sea level rise in a long-term time series. This study investigates the measurement consistency in the 23.8 GHz channel between DFMR and AMR at the Simultaneous Nadir Overpasses (SNO's) between the two satellites and also at coldest ocean brightness temperature locations. Preliminary results show that while both instruments show no significant trends over the one year since the launch of SARAL, a consistent relative bias of 2.88 K (DFMR higher than AMR) with a standard deviation of 0.98 K is observed. The relative bias at the lowest brightness temperature from the SNO method (-3.82 K) is consistent with that calculated from coldest ocean method (-3.74 K). The relative bias exhibits strong latitude (and scene temperature) dependency, changing from -3.82 K at high latitudes to -0.92 K near the equator. There also exists an asymmetry between the northern and southern hemisphere. The relative bias increases toward the lower end of brightness temperature.  相似文献   

The 2013 Ibiza Calibration Campaign of Jason-2 and SARAL Altimeters     

F. Frappart  N. Roussel  R. Biancale  J.J. Martinez Benjamin  F. Mercier  F. Perosanz 《Marine Geodesy》2015,38(3):219-232

This study presents the results of the 2013 Ibiza (Western Mediterranean) calibration campaign of Jason-2 and SARAL altimeters. It took place from 14 to 16 September 2013 and comprised two phases: the calibration of the GNSS (Global Navigation Satellite System) buoys to estimate the antenna height of each of them and the absolute calibration to estimate the altimeter bias (i.e., the difference of sea level measured by radar altimetry and GNSS). The first one was achieved in the Ibiza harbor at a close vicinity of the Ibiza tide gauge and the second one was performed at ～ 40 km at the northwest of Ibiza Island at a crossover point of Jason-2 and SARAL nominal groundtracks. Five buoys were used to delineate the crossover region and their measurements interpolated at the exact location of each overflight. The overflights occurred two consecutive days: 15 and 16 September 2013 for Jason-2 and SARAL, respectively. The GNSS data were processed using precise point positioning technique. The biases found are of (?0.1 ± 0.9) and (?3.1 ± 1.5) cm for Jason-2 and SARAL, respectively.  相似文献   

Improving the assessment of ICESat water altimetry accuracy accounting for autocorrelation     

Hani Abdallah  Jean-Stéphane Bailly  Nicolas Baghdadi  Nicolas Lemarquand 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(6):833-844

Given that water resources are scarce and are strained by competing demands, it has become crucial to develop and improve techniques to observe the temporal and spatial variations in the inland water volume. Due to the lack of data and the heterogeneity of water level stations, remote sensing, and especially altimetry from space, appear as complementary techniques for water level monitoring. In addition to spatial resolution and sampling rates in space or time, one of the most relevant criteria for satellite altimetry on inland water is the accuracy of the elevation data. Here, the accuracy of ICESat LIDAR altimetry product is assessed over the Great Lakes in North America. The accuracy assessment method used in this paper emphasizes on autocorrelation in high temporal frequency ICESat measurements. It also considers uncertainties resulting from both in situ lake level reference data. A probabilistic upscaling process was developed. This process is based on several successive ICESat shots averaged in a spatial transect accounting for autocorrelation between successive shots. The method also applies pre-processing of the ICESat data with saturation correction of ICESat waveforms, spatial filtering to avoid measurement disturbance from the land–water transition effects on waveform saturation and data selection to avoid trends in water elevations across space. Initially this paper analyzes 237 collected ICESat transects, consistent with the available hydrometric ground stations for four of the Great Lakes. By adapting a geostatistical framework, a high frequency autocorrelation between successive shot elevation values was observed and then modeled for 45% of the 237 transects. The modeled autocorrelation was therefore used to estimate water elevations at the transect scale and the resulting uncertainty for the 117 transects without trend. This uncertainty was 8 times greater than the usual computed uncertainty, when no temporal correlation is taken into account. This temporal correlation, corresponding to approximately 11 consecutive ICESat shots, could be linked to low transmitted ICESat GLAS energy and to poor weather conditions. Assuming Gaussian uncertainties for both reference data and ICESat data upscaled at the transect scale, we derived GLAS deviations statistics by averaging the results at station and lake scales. An overall bias of −4.6 cm (underestimation) and an overall standard deviation of 11.6 cm were computed for all lakes. Results demonstrated the relevance of taking autocorrelation into account in satellite data uncertainty assesment.  相似文献   

DLT方法在遥感相机几何定标中的应用     

郑逢杰  余涛  陈兴峰  谢东海  袁国体  兰进京 《测绘与空间地理信息》2011,34(2):26-29

为建立适用于遥感相机定标的实验室,需要有几何标定的算法和软件对摄影图像进行计算.使用近景摄影测量中基于3维控制场的定标方法,对单CCD四波段遥感相机进行了几何定标,研究并自主编程实现了直接线性变换DLT(Direct Linear Transformation)算法,与基于空间后方交会算法的定标结果进行了精度对比.结论...  相似文献   

Adaptive split-operator methods for modeling transport phenomena in porous medium systems     

Sarah E. Gasda 《Advances in water resources》2011,34(10):1268-1282

Split-operator methods are commonly used to approximate environmental models. These methods facilitate the tailoring of different approximation approaches to different portions of the differential operator and provide a means to split large coupled problems into pieces that are more amenable to parallel computation than the original fully-coupled problem. However, split-operator methods introduce an additional source of approximation error into the solution, which is typically either ignored or controlled heuristically. In this work, we develop two methods to estimate and control the error in split-operator methods, which lead to a dynamic adjustment of the temporal splitting step based upon the error estimators. The proposed methods are shown to yield robust solutions that provide the desired control of error. In addition, for a typical nonlinear reaction problem, the new methods are shown to reduce the solution error by more than two orders of magnitude compared to standard methods for an identical level of computational effort. The algorithms introduced and evaluated have widespread applicability in environmental modeling.  相似文献   

EGNOS数据处理模型与实例     

陈刘成  陈金平 《测绘科学》2004,29(5):53-55

主要分析研究了EGNOS系统测试采用的误差修正模型和定位保护精度算法,并通过比较一次实测静态数据单点解算和差分解算的不同效果来说明误差模型的修正效果和保护精度算法的有效性。事实证明EGNOS系统数据处理采用的误差修正模型效果是明显的,采用的定位保护精度算法是有效的。  相似文献   

Preliminary Calibration of GPS Signals and Its Effects on Soil Moisture Estimation   总被引：1，自引：0，他引：1       下载免费PDF全文

WAN Wei  LI Huang  CHEN Xiuwan  LUO Peng  WAN Jiahuan 《Acta Meteorologica Sinica》2013,27(2):221-232

In recent years, Global Navigation Satellite Systems Reflectometry (GNSS-R) is developed to estimate soil moisture content (SMC) as a new remote sensing tool. Signal error of Global Positioning System (GPS) bistatic radar is an important factor that affects the accuracy of SMC estimation. In this paper, two methods of GPS signal calibration involving both the direct and reflected signals are introduced, and a detailed explanation of the theoretical basis for such methods is given. An improved SMC estimation model utilizing calibrated GPS L-band signals is proposed, and the estimation accuracy is validated using the airborne GPS data from the Soil Moisture Experiment in 2002 (SMEX02). We choose 21 sites with soybean and corn in the Walnut Creek region of the US for validation. The sites are divided into three categories according to their vegetation cover: bare soil, mid-vegetation cover (Mid-Veg), and high-vegetation cover (High-Veg). The accuracy of SMC estimation is 11.17% for bare soil and 8.12% for Mid-Veg sites, much better than that of the traditional model. For High-Veg sites, the effect of signal attenuation due to vegetation cover is preliminarily taken into consideration and a linear model related to Normalized Difference Vegetation Indices (NDVI) is adopted to obtain a factor for rectifying the "over-calibration", and the error for High-Veg sites is finally reduced to 3.81%.  相似文献   

Probabilistic Approach of Coastal Defense Against Typhoon Attacks for Nuclear Power Plant     

刘德辅  韩凤亭  庞亮  李华军  谢波涛  王风清 《中国海洋工程》2010,24(2):265-275

With the global wanning and sea level rising, it is widely recognized that there is an increasing tendency of typhoon occurrence frequency and intensity. The defenses code against typhoon attacks for nuclear power plant should be calibrated because of the increasing threat of typhoon disaster and severe consequences. This paper discusses the probabilistic approach of definitions about "probable maximum typhoon" and "probable maximum storm surge" in nuclear safety regulations of China and has made some design code calibrations by use of a newly proposed Double Layer Nested Multi-objective Probability Model (DLNMPM).  相似文献