MM5三维变分系统在北京地区冷暖季背景场误差的对比分析   总被引：4，自引：2，他引：2  

范水勇  张朝林  仲跻芹 《高原气象》2006,25(5):855-861

NMC方法是目前较广泛采用的一种对模式背景场误差协方差进行统计分析的一种方法。本文根据积累的2002年8月份和2003年2月份各一个月模式预报结果,采用NMC方法,计算了中尺度模式MM5V3在北京地区的冷暖季背景场误差,详细给出其气候统计特征。通过对比分析发现,背景场误差特征对于不同的模式变量、水平分辨率、垂直层各不相同,冷暖季背景场误差也有不同的特征,其差别主要表现在风场。这些特征与模式模拟区域的平均天气状况相对应,同化应该在各模式区域分别进行。MM5三维变分系统在北京地区的实际应用中,应发展根据实际季节变换背景场误差协方差矩阵的方法。  相似文献   

BACKGROUND VALUES AND TREND DISTRIBUTION OF Cu, Zn AND Ni IN SOILS IN CHINA     

王景华 《中国地理科学(英文版)》1992,2(4):357-366

The background values of Cu, Zn and Ni are discussed based on the analytical data of 21 main soil types collected from various regions in China. According to statistics of many samples, the background value of Cu is 23.4±10.2 mg/ kg (482 samples), Zn 77.9±2.39 mg/ kg (474 samples), Ni 30.0±12.8 mg/kg (482 samples).  相似文献   

Redshift quantization - a review     

W. G. Tifft 《Astrophysics and Space Science》1995,227(1-2):25-39

Redshift quantization has three main facets: 1) the internal organization of galaxies, 2) differential effects between galaxies in physical systems, 3) global effects linking all galaxies and cosmology. The subject originated as an outgrowth of redshift correlation studies including studies of internal kinematics of galaxies. While possibly central to understanding redshift quantization, this aspect is complex and largely undeveloped. The bulk of the evidence for redshift quantization comes from differential and global periodicity testing. More recently redshift variability has been associated with the phenomenon. Early work in theory led to a determination ofq0 close to 0.5. A new association between quantization and the Cosmic Background Radiation further links redshift quantization with basic cosmology.  相似文献   

Comparison of UAV and WorldView-2 imagery for mapping leaf area index of mangrove forest     

《International Journal of Applied Earth Observation and Geoinformation》2017

Unmanned Aerial Vehicle (UAV) remote sensing has opened the door to new sources of data to effectively characterize vegetation metrics at very high spatial resolution and at flexible revisit frequencies. Successful estimation of the leaf area index (LAI) in precision agriculture with a UAV image has been reported in several studies. However, in most forests, the challenges associated with the interference from a complex background and a variety of vegetation species have hindered research using UAV images. To the best of our knowledge, very few studies have mapped the forest LAI with a UAV image. In addition, the drawbacks and advantages of estimating the forest LAI with UAV and satellite images at high spatial resolution remain a knowledge gap in existing literature. Therefore, this paper aims to map LAI in a mangrove forest with a complex background and a variety of vegetation species using a UAV image and compare it with a WorldView-2 image (WV2).In this study, three representative NDVIs, average NDVI (AvNDVI), vegetated specific NDVI (VsNDVI), and scaled NDVI (ScNDVI), were acquired with UAV and WV2 to predict the plot level (10 × 10 m) LAI. The results showed that AvNDVI achieved the highest accuracy for WV2 (R² = 0.778, RMSE = 0.424), whereas ScNDVI obtained the optimal accuracy for UAV (R² = 0.817, RMSE = 0.423). In addition, an overall comparison results of the WV2 and UAV derived LAIs indicated that UAV obtained a better accuracy than WV2 in the plots that were covered with homogeneous mangrove species or in the low LAI plots, which was because UAV can effectively eliminate the influence from the background and the vegetation species owing to its high spatial resolution. However, WV2 obtained a slightly higher accuracy than UAV in the plots covered with a variety of mangrove species, which was because the UAV sensor provides a negative spectral response function(SRF) than WV2 in terms of the mangrove LAI estimation.  相似文献   

Separation of a geochemical anomaly from background by fractal and U-statistic methods,a case study: Khooni district,Central Iran     

《Chemie der Erde / Geochemistry》2016,76(4):491-499

Separation of geochemical anomalies from background are one of the important steps in mineral exploration. The Khooni mineral district (Central Iran) has complex geochemical surface expression due to a complex geological background. This region was chosen as a study area for recognition of the spatial distribution of geochemical elements and separating anomalies from background using stream sediment geochemical data. In the past decades, geochemical anomalies have been identified by means of various methods. Some of these separation methods include: statistical analysis methods, spatial statistical methods and fractal and multi-fractal methods. In this article, two efficient methods, i.e. U-statistics and the fractal concentration-area for separation and detection of anomalous areas of the background were used. The U spatial statistic method is a weighted mean, which considers sampling point positions and their spatial relation in the estimation of anomaly location. Also, fractal and multi-fractal models have also been applied to separate anomalies from background values. In this paper, the concentration–area model (C–A) was suggested to separate the anomaly of background. For this purpose, about 256 stream sediment samples were collected and analyzed. Then anomaly maps of elements were generated based on U spatial statistics and the C-A fractal methods for Au, As and Sb elements. According to obtained results, the U-statistics method performed better than C-A method. Because the comparisons of the known deposits and occurrences against the anomalous area created using thresholds from U-statistics and C-A method show that the spatial U-statistics method hits all of 3 known deposits and occurrences, the C-A fractal method hits 1 and fails 2. In addition, the results showed that these methods with regard to spatial distribution and variability within neighboring samples, in addition to concentration value frequency distributions and correlation coefficients, have more accurate results than the traditional approaches.  相似文献   

基于HOT影像优化的遥感影像去雾算法     

薛现光  周杨  许继伟  张龙 《测绘科学技术学报》2017,34(2)

针对BSHTI和IBSHTI两种算法对卫星影像云雾校正后,地表的色调和纹理等细节缺失严重的问题,提出OIBSHTI算法对IBSHTI算法得出的雾厚度图像进行地表信息削减。通过填洼算法去除暗色区域,并引入纹理和边缘信息等进行优化处理,在彻底去除云雾的同时保留地表的色调和纹理,特别是蓝色或红色建筑物房顶的校正效果较为明显。  相似文献   

城市规划机助设计系统(CPCAD)的研究     

王延亮  王晏民  黄明  张琼 《测绘工程》1995,(2)

城市总体规划是城市建设和改造的重要基础之一,用计算机进行辅助规划是当前规划技术的发展方向。本文着重讨论底图数字化、对话窗、多边形拓扑等关键问题。  相似文献   

西藏土壤环境背景值的研究   总被引：11，自引：1，他引：11  

张晓平 《地理科学》1994,14(1):49-55

  相似文献   

武汉地区“98.7”暴雨过程大气稳定性分析   总被引：1，自引：0，他引：1       下载免费PDF全文

安洁  张立凤 《应用气象学报》2005,16(3):313-321

文章从环境场的稳定性角度进行研究，取boussinesq近似的二维数学模型，从数值模式每小时输出的预报场中提取暴雨过程中的环境场，通过计算函数极小值的方法，求取层结参数及加热率，讨论实际暴雨过程中不稳定的作用。其结果表明，凝结加热对暴雨不稳定的发生发展作用明显。暴雨初期和强盛期的环境场都可以出现动力不稳定，且不稳定扰动传播方向与基本气流有一个斜交角，属于二维平面波的不稳定。“98.7”暴雨的发生发展是热力和动力共同作用的结果。  相似文献   

临安和上甸子大气本底站大气中NMHCs组成与浓度的变化特征   总被引：4，自引：0，他引：4  

王木林  程红兵  丁国安  汤洁  俞向明  刘国平  周怀刚 《气象学报》2006,64(5):658-665

为研究中国大气中非甲烷烃(NMHCs)区域性本底浓度与变化特征,采用吸附富集—热脱附—气相色谱法,测定了临安(30°25′N,119°44′E,海拔132.0 m)和上甸子(40°19′N,117°07′E,海拔286.5 m)大气本底站大气中NMHCs的组成与浓度。从2003年10月至2004年7月,先后按季度分4次观测与取样,共获145个有效样品。检测出C2-C10的NMHCs组分52个,其中包括26个烷烃、17个烯烃和9个芳香烃化合物。在临安和上甸子大气中非甲烷烃总烃(TNMHCs)的平均质量浓度分别为(238.5±126.0)×10-9C,(278.7±185.5)×10-9C。两站烷、烯、芳香烃在TNMHCs中所占的比例相近,分别约为21%—33%,7%—19%,54%—70%。受源、汇和气象条件的共同影响,NMHCs浓度存在明显地日变化和季节性变化,但变化趋势两地略有不同。TNMHCs平均浓度的峰值都出现在10月,谷值分别出现在1,7月。气象要素以风向和风速的影响最为明显。TNMHCs高浓度大多与上风向存在较强污染源有关。另外发现,临安TNMHCs浓度比10 a前有明显增加。  相似文献