A STUDY OF NEAR SURFACE WIND PROFILES IN THE HEBEI COASTAL AREA BASED ON OBSERVATIONAL EXPERIMENTS     

龚玺  朱蓉  李泽椿 《热带气象学报(英文版)》2018,24(4):508-514

In order to provide wind profiles for the microscale numerical simulation of wind farm with complex terrain,using the 100 m tower atmospheric turbulence observation experiment data in 2010 in Hebei Province offered by National Climate Center, the variation characteristics of wind profile under the different atmospheric stability conditions are analyzed, and the wind profile expression based on the local similarity theory is established. The results show that:(1) In spring, the occurrence probability of unstable stratification in the Hebei coastal area is as high as 28%, and the probability of stable stratification is more than 43% while, in summer, the probability of occurrence of unstable stratification is as high as 80% with a lower probability for stable stratification; and(2) for stable stratification, the characteristics of atmosphere change is dramatic in terms of the vertical direction, which need to be treated layer by layer.According to the atmospheric turbulence observation experiment data above, under stable stratification, the relationship between the dimensionless velocity gradient and the stability ζ can be expressed as 1 +βmζ, with βm changing with the height: βm takes 4.1-4.3 under 30 m, βm takes 4.6-4.7 between 30-50 m, and βm takes 6.3-6.7 over 50 m.  相似文献   

Fictive motion extraction and classification     

Ekaterina Egorova  Ludovic Moncla  Mauro Gaio  Christophe Claramunt  Ross S. Purves 《International journal of geographical information science》2018,32(11):2247-2271

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基于微雨雷达的降水参数反演和粒子相态识别     

王洪  杨洁帆  龚佃利  王俊  张佃国  孙莎莎  陈澍 《大气科学》2023,(3):739-755

本文基于微雨雷达原始的后向散射信号,采用一种新的功率谱处理算法（RaProM算法）,在功率谱计算、噪声去除、退模糊等处理的基础上计算了雷达基本参量,并反演了液态降水参数,例如雷达反射率因子、雨强等,并对粒子相态进行识别。RaProM算法综合考虑粒子下落速度、等效雷达反射率因子、不同相态粒子的尺度特征以及是零度层亮带位置等信息,可识别的粒子相态包括雪、毛毛雨、雨、冰雹以及混合相态。选取了三个山东地区较为典型的个例对RaProM反演算法进行验证,即2021年7月2日典型层状云降水个例、2019年12月25日雨雪转换个例以及2018年3月4日零度层高度逐渐降低的降水个例。结果显示：粒子识别方法应用于典型层状云降水,垂直方向上不同相态粒子的分层较为明显,过冷层里的固态降水雪花、零度层附近冰水转换区的混合相态降水以及零度层以下的液态降水符合现有认识,验证了反演算法以及粒子识别算法的有效性。将结果进一步在雨雪转换降水相态识别中和零度层高度的检测,该反演算法均能得到较好应用,与同址同步观测的微波辐射计、云雷达、二维视频雨滴谱仪等观测结论一致。另外,与微雨雷达标准反演算法对比,RaProM算法的优势是...  相似文献   

一种适用于PPP动力学模型异常的自适应Kalman滤波     

胡豪杰  赵兴旺  刘超  田先才 《大地测量与地球动力学》2020,40(8):822-826

为了削弱PPP参数估计中动力学模型异常对Kalman滤波解的影响,针对PPP状态向量中各类参数不符值对动力学模型异常描述特性的不同,以位置相关为条件对参数进行分类,构建分类因子自适应Kalman滤波用于PPP参数估计。选取6个IGS站点3 d的数据,使用标准Kalman滤波与构建的自适应Kalman滤波进行PPP解算分析。结果表明,相较于标准Kalman滤波,自适应Kalman滤波能通过自适应因子调节状态预测协方差,加速PPP收敛。静态模式下,平均收敛时间从28.2 min缩减到19.4 min,N、E、U方向的平均精度为1.50 cm、3.34 cm、5.55 cm,分别提高7%、14%、19%;动态模式下,构建的自适应Kalman滤波解N、E、U方向偏差的RMS值为2.7 cm、3.6 cm、6.3 cm,较标准Kalman滤波分别提高13%、28%、43%。  相似文献   

面向复杂地形的坡位K-means聚类划分研究     

高海峰  葛莹  张杰  肖胜昌  陈科 《地球信息科学学报》2020,22(3):474-481

土壤植被研究建立在精准坡位划分的基础上。但现有的坡位大多采用手工划分的方式,存在着自动化程度低、划分精度不高且耗时较长等问题。本文提出一种顾及复杂地形的坡位自动划分算法,尝试采用机器学习K-means方法解决高海拔山区坡位划分的问题,并在山峰区域提取、聚类数确定、以及初始聚类中心选取等关键技术进行了算法的优化。为了验证算法的有效性,以云南省姚安县为研究区,运用提出的算法对研究区坡位进行自动划分,再采用Calinski-Harabasz聚类评价指标、调整兰德系数ARI和误差平方和SSE等一系列方法对坡位K-means聚类划分实验进行分析和评价。研究结果表明,利用该算法所生成的复杂地形坡位与研究区实测等高线相匹配。其次,再从姚安县规划风电场任选4个场址,比较13×13、25×25、37×37三种适宜窗口下坡位自动划分结果,结果表明选取25×25适宜窗口进行坡位划分可靠性最强。再者,计算的规划风电场内山脊、坡肩及背坡比例高达57.13%,也从一个侧面证实了利用该算法划分的坡位结果良好。  相似文献   

The comparison of PCA and discrete rough set for feature extraction of remote sensing image classification – A case study on rice classification, Taiwan     

T. C. Lei  S. Wan  T. Y. Chou 《Computational Geosciences》2008,12(1):1-14

Texture information offers an extensive solution for image classification by providing better accuracy of image information. However, huge amounts of improper additional texture information may result in a chaotic state, and this leads to uncertainty in the classification process. Considerable portion of earlier works have been carried out through the generally acknowledged procedure of Principal Components Analysis (PCA). However, the PCA method has flaws in the area of influenced and non- influenced attributes. On the whole, whether PCA provides an effective solution to determine the value of knowledge rule in image information still remains a question. This study proposes an innovative method, called Discrete Rough Set method, as a tool for image classification. This study focuses on two crucial issues: (1) The core attributes of the target categories in image classification are systematically analyzed while eliminating surplus attributes rationally; (2) The unique point of each attribute, which influenced the target categories, is successfully found. This is a crucial aspect that is very helpful for the construction of decision rule. Finally, in this study we utilized the expert knowledge classifier and the overall accuracy of Discrete Rough Set (96.67%) exceeds that of the conventional PCA (86.00%) of paddy rice area evaluation from Quickbird image. This result shows that the appropriate classification knowledge can be presented by Discrete Rough Set, and this information can effectively improve the accuracy of image classification. An erratum to this article can be found at  相似文献   

海拉尔盆地查干诺尔凹陷下白垩统层序地层格架及沉积体系研究   总被引：1，自引：0，他引：1  

袁红旗  柳成志  赵利华  张文华  吕延防 《地层学杂志》2008,32(4)

依据岩芯、测井、录井和地震资料,以层序地层学理论为指导对海拉尔盆地查干诺尔凹陷下白垩统的扎赉诺尔群进行层序地层划分。扎赉诺尔群可划分为1个超层序,形成于凹陷断陷发育期,自下而上可划分为5个三级层序(Sq1、Sq2、Sq3、Sq4、Sq5)。进而在层序框架内对沉积体系类型和时空展布特征进行了分析。凹陷主要发育冲积扇、扇三角洲、湖底扇、滨浅湖和半深—深湖沉积体系,并且层序地层格架对各沉积体系分布具有控制作用。  相似文献   

南华系“渫水河组”的对比及其冰川沉积特征的探讨     

张启锐  储雪蕾  冯连君 《地层学杂志》2008,32(3)

在著名的湖南省石门县杨家坪剖面,围绕"渫水河组"的地层对比问题长期存在争论,有对比于宜昌峡区莲沱组的,有对比于本省板溪群的,也有对比于广西北部富禄组的。最近获得的年龄数据似乎确认了它对比于莲沱组的方案,但是当莲沱组年龄在原始数据基础上采用先进方法重新进行计算所得的年龄,却和广西三门街组刚发表的年龄值十分相似,于是"渫水河组"的地层位置又出现了新的问题。在目前已经看不到的一些重要冰川沉积构造的基础上,论证它应该是江口冰期的地层,并确认它与富禄组的对比。它实际上应对比于黔东北的"两界河组"。"两界河组"和"铁丝坳组"或"古城组"合起来相当于富禄组。根据地层命名规则,应该取消"渫水河组",而代之以两界河段,成为富禄组下部的一个次一级地层单位。  相似文献   

考虑暴雨成因的大伙房水库洪水分类研究   总被引：2，自引：1，他引：1  

王本德  张静 《水文》2008,28(1):15-20

暴雨洪水形成机制十分复杂,它既具有随机性,又具有确定性.可是现行的流域防洪调度设计中强调的是随机性,忽略了客观上存在的确定性,因此使得设计结果与实际脱节,不能充分发挥防洪与兴利效益.本文针对这一问题,考虑到特定流域内产生暴雨的天气系统所具有的相对稳定性规律,及其形成的暴雨洪水过程存在的确定性关系,以大伙房水库流域为例,归纳出依据暴雨成因对流域内洪水过程分类的方法.通过各类洪水过程线图及各类洪水过程相似性系数计算,证明了洪水过程分类的合理性.这种分类,对了解流域洪水规律,提高水库防洪能力、提高洪水资源利用率,及深入研究水库防洪分类预报调度方式设计具有重要的现实意义.  相似文献   

Assessing land use and land cover change in the Wassa West District of Ghana using remote sensing   总被引：1，自引：0，他引：1  

John Manyimadin Kusimi 《GeoJournal》2008,71(4):249-259

Vast tracts of forests are lost globally every year especially in the developing countries of the tropics due to various human activities such as lumbering, farming, bush fires, surface mining and urbanization. The rainforest in Ghana has experienced rapid depletion since the 1980s. The impact of deforestation is widespread, affecting the livelihoods of local people and disrupting the tropical ecosystem. There is a serious concern in the study area about climatic change, soil erosion, siltation of rivers and loss in biodiversity which have an adverse impact on traditional medicinal plants of the local people. The study examined the extent of land cover change through image differencing of Landsat TM 1986 and 2002. The image classification indicated that, vegetative cover from 1986 to 2002 has been reducing whiles land use activities have been increasing. Closed canopy, open canopy and plantation have significantly diminished and land use activities especially built ups, farms, mining and openfields are more than doubled. The driving forces for the change in land cover are population growth, lumbering, socio-economic and cultural practices of the people. Lumbering and mining have been some of the major causes of the changing landscape in primary forest. Also the reliance on wood for domestic energy and the need to increase food productivity to feed growing population have also contributed greatly to the rapid depletion of the vegetative cover.  相似文献