共查询到20条相似文献，搜索用时 343 毫秒
1.
This paper presents a new algorithm to classify convective clouds and determine their intensity, based on cloud physical properties retrieved from the Spinning Enhanced Visible and Infrared Imager (SEVIRI). The convective rainfall events at 15 min, 4 × 5 km spatial resolution from 2006 to 2012 are analysed over northern Algeria. The convective rain classification methodology makes use of the relationship between cloud spectral characteristics and cloud physical properties such as cloud water path (CWP), cloud phase (CP) and cloud top height (CTH). For this classification, a statistical method based on ‘naive Bayes classifier’ is applied. This is a simple probabilistic classifier based on applying ‘Bayes’ theorem with strong (naive) independent assumptions. For a 9-month period, the ability of SEVIRI to classify the rainfall intensity in the convective clouds is evaluated using weather radar over the northern Algeria. The results indicate an encouraging performance of the new algorithm for intensity differentiation of convective clouds using SEVIRI data. 相似文献
2.
基于多层DEM与QTPV的混合数据模型及其在地质建模中的应用 总被引：8，自引：1，他引：7
提出一种基于多层DEM与似三棱柱体元（QTPV）的混合三维数据模型。模型包含顶点、线段（棱边、三角形边）、三角形、侧面四边形、似三棱柱体元和DEM 6个基本元素,同时包含点对象、线对象、面对象、体对象、复杂对象、空间对象等6个对象。设计了6个基本元素和2种地质对象的数据结构和它们之间的拓扑关系。研究了基于原始采样点和基于内插点的两种建模方法。以模拟数据和地质钻探数据对开发的原型系统进行验证。研究表明,基于多层DEM与似三棱柱体元的混合三维数据模型具有同时表达空间对象的表面和内部结构的能力,适合地质勘探领域的三维建模。 相似文献
3.
Estela Collini María Soledad Osores Arnau Folch José G. Viramonte Gustavo Villarosa Graciela Salmuni 《Natural Hazards》2013,66(2):389-412
We modelled the transport and deposition of ash from the June 2011 eruption from Cordón Caulle volcanic complex, Chile. The modelling strategy, currently under development at the Argentinean Naval Hydrographic Service and National Meteorological Service, couples the weather research and forecasting (WRF/ARW) meteorological model with the FALL3D ash dispersal model. The strategy uses volcanological inputs inferred from satellite imagery, eruption reports and preliminary grain-size data obtained during the first days of the eruption from an Argentinean ash sample collection network. In this sense, the results shown here can be regarded as a quasi-syn-eruptive forecast for the first 16 days of the eruption. Although this article describes the modelling process in the aftermath of the crisis, the strategy was implemented from the beginning of the eruption, and results were made available to the Buenos Aires Volcanic Ash Advisory Centers and other end users. The model predicts ash cloud trajectories, concentration of ash at relevant flight levels, expected deposit thickness and ash accumulation rates at relevant localities. Here, we validate the modelling strategy by comparing results with satellite retrievals and syn-eruptive ground deposit measurements. Results highlight the goodness of the combined WRF/ARW-FALL3D forecasting system and point out the usefulness of coupling both models for short-term forecast of volcanic ash clouds. 相似文献
4.
M. K. Rama Varma Raja G. C. Asnani P. S. Salvekar A. R. Jain D. Narayana Rao S. Venkoba Rao P. Kishore M. Hareesh 《Journal of Earth System Science》1999,108(4):287-295
Contrary to the prevalent belief that tropical region is characterized by convective clouds rather than by layer clouds, we
have suggested that deep convective clouds occur on meso-scale, but layer clouds occur on larger synoptic-scale with a relatively
small region of deep convective clouds. Sustenance of deep convective clouds is inhibited by the presence of inertio-gravity
waves, which have alternating layers of upward and downward motion in the vertical. We have also shown that inertio-gravity
waves generate regions of relatively strong horizontal velocity, vertically separated by layers of relatively weak horizontal
velocity. Layers of strong horizontal velocity are created by inertio-gravity wave system through convergence of vertical
flux of horizontal momentum. We have also suggested that horizontal convergence/divergence of moisture flux is generated by
inertio-gravity waves, giving rise to vertically alternating layers of high/low humidity, and visible or sub-visible clouds.
Layers of high humidity become layers of strong radar reflectivity at frequency of 53 MHz at which MST Radar at Gadanki, near
Tirupati, India, operates. These observations, more than 2,50,000 in number, for vertical grid points, spread over all the
months of the year, have helped us, among other observations, to arrive at these conclusions. Further, the analysis suggests
that the main source of strong MST radar reflectivity is not mechanical turbulence as is commonly believed. 相似文献
5.
多普勒天气雷达风场反演技术研究进展 总被引：15，自引：0，他引：15
多普勒天气雷达是研究中小尺度天气系统的重要工具，但却只能提供风场的径向速度，因而必须通过风场反演技术来求解二维或三维风场。详细分析了各种单部、多部和多基地多普勒天气雷达风场反演技术及其优缺点，同时指出了应重点研究的方向。从反演结果来看，基于变分法的反演技术明显优于其它方法，这是今后的一个主要研究方向；利用四维同化理论，在数值模式初始场中使用反演数据，是反演技术应用的重点。 相似文献
6.
一种面向对象的三维地下空间矢量数据模型 总被引：1，自引：0，他引：1
针对地下空间的真三维连续特性以及建模过程的动态交互编辑与分析要求,提出了一种新的三维地下空间矢量数据模型。该模型采用面向对象思想对地下各种空间对象进行抽象描述;利用模型中的线段要素增强几何元素之间拓扑连接关系的维持,为地质体的切割和地下工程体的开挖等分析提供了算法上的便利;引入拓扑面更好地表达了地下空间对象之间的拓扑邻接关系。该模型在三维地下空间数据的存储管理、查询分析以及实时逼真绘制等方面都表现出较好的性能,适用于地下勘探工程的建模与分析。 相似文献
7.
Rakesh K. Kushwaha M. K. Pandit Rohit Goyal 《Journal of the Geological Society of India》2009,74(4):449-458
A direct approach to designing MODFLOW finite difference model is tedious and less intuitive, specifically for complex boundary
and initial conditions. Therefore, a MODFLOW model can be developed either using a grid or conceptual model approach. The
conceptual model is created using Geographic Information System (GIS) objects including points, arcs and polygons so that
it can more accurately represent real world condition. It is a simplified representation of the site to be modelled including
the model domain, boundary conditions, sources, sinks and material zones. Advantage of conceptual model is that most of the
input can be in terms of physical objects, such as wells, lakes, recharge zones etc which can then be converted to a grid
based mathematical model with the help of preprocessor software.
This paper presents the results of a mathematical groundwater model developed for the northern part of Mendha sub-basin in
the semi arid region of northeastern Rajasthan, employing conceptual groundwater modelling approach. For this purpose, Groundwater
Modelling Software (GMS) was used which supports the MODFLOW-2000 code. For the purpose of modelling the Source/ Sink Coverage,
Recharge Coverage, Extraction Coverage, Return Flow Coverage and Soil Coverage were considered. The model was calibrated against
the historical and observed water level data for periods 1998 to 2003 and 2003 to 2005 respectively. 相似文献
8.
机载多普勒天气雷达及应用研究进展 总被引：1，自引：1，他引：0
机载多普勒天气雷达由于其灵活机动性,在台风、暴雨等灾害性天气系统中尺度三维精细结构研究中发挥着重要作用.对机载多普勒天气雷达技术及其资料应用进行了概要性综述,主要从机载多普勒天气雷达发展历程、4种主要机载多普勒雷达技术特点、雷达天线扫描策略、单多普勒雷达风场反演技术、双多普勒雷达风场反演技术、雷达资料同化以及目标观测等方面进行阐述和分析;着重讨论了应用中需要解决的问题.最后,指出发展具有快速扫描和双偏振功能的机载相控阵多普勒雷达是机载天气雷达的发展方向,它可以获取高时空分辨率的探测数据,能够对云和降水系统的三维精细动力结构、热力结构以及微物理结构等进行综合研究. 相似文献
9.
一种基于似三棱柱体元的地质三维建模方法研究 总被引：4，自引：0，他引：4
三堆空间建模方法是三堆地劫工程GIS研究的核心问题之一。提出一种基于似三棱柱体元的三堆数据模型，模型包含顶点、线段(棱边、三角形边)、三角形、侧面四边形、三棱柱体元5个基本元素。和点对象、线对象、面对象、体对象、复杂对象、空间对象等6个对象。设计了5个基本元素和3种地质对象的数据结构和它们之间的拓扑关系。以岩体和巷道为例。给出了似三棱柱体建模思路和算法。利用内蒙古某矿区实际钻孔资料和模拟巷道数据对所开发的系统原型进行验证。研究表明。基于似三棱柱体元的数据模型的优势在于可以表示空间对象的表面和内部结构。便于建模和节省存储空间，同时便于不规劓的自然地质体和规则勘探工程建模。 相似文献
10.
Real-time nowcast of a cloudburst and a thunderstorm event with assimilation of Doppler weather radar data 总被引：1，自引：1，他引：0
Extreme weather events such as cloudburst and thunderstorms are great threat to life and property. It is a great challenge for the forecasters to nowcast such hazardous extreme weather events. Mesoscale model (ARPS) with real-time assimilation of DWR data has been operationally implemented in India Meteorological Department (IMD) for real-time nowcast of weather over Indian region. Three-dimensional variational (ARPS3DVAR) technique and cloud analysis procedure are utilized for real-time data assimilation in the model. The assimilation is performed as a sequence of intermittent cycles and complete process (starting from reception, processing and assimilation of DWR data, running of ARPS model and Web site updation) takes less than 20 minutes. Thus, real-time nowcast for next 3 h from ARPS model is available within 20 minutes of corresponding hour. Cloudburst event of September 15, 2011, and thunderstorm event of October 22, 2010, are considered to demonstrate the capability of ARPS model to nowcast the extreme weather events in real time over Indian region. Results show that in both the cases, ARPS3DVAR and cloud analysis technique are able to extract hydrometeors from radar data which are transported to upper levels by the strong upward motion resulting in the distribution of hydrometeors at various isobaric levels. Dynamic and thermodynamic structures of cloudburst and thunderstorm are also well simulated. Thus, significant improvement in the initial condition is noticed. In the case of cloudburst event, the model is able to capture the sudden collisions of two or more clouds during 09–10 UTC. Rainfall predicted by the model during cloudburst event is over 100 mm which is very close to the observed rainfall (117 mm). The model is able to predict the cloudburst with slight errors in time and space. Real-time nowcast of thunderstorm shows that movement, horizontal extension, and north–south orientation of thunderstorm are well captured during first hour and deteriorate thereafter. The amount of rainfall predicted by the model during thunderstorm closely matches with observation with slight errors in the location of rainfall area. The temporal and spatial information predicted by ARPS model about the sudden collision/merger and broken up of convective cells, intensification, weakening, and maintaining intensity of convective cells has added value to a human forecast. 相似文献
11.
Meso-scale characteristics of disturbances that bring about atmospheric disasters in pre- and mature monsoon seasons in Bangladesh
are analyzed. Several types of meteorological instruments capable of observations with high temporal and spatial resolutions
were introduced for the first time in this area to capture the meso-scale structure of rainfall systems. We installed an automatic
weather station (AWS) and several automatic raingauges (ARGs) and utilized the weather radar of Bangladesh Meteorological
Department (BMD). From the radar image in the summer of 2001 (16–18 July), a striking feature of the systematic diurnal variation
in this area was elucidated. In these 3 days, the diurnal evolutions of convective activity were remarkably similar to each
other, implying that this pattern can be understood as a typical response of local cloud systems to the diurnal variation
of insolation under some summer monsoon situations. The ARG data show the difference in characteristics of rainfall between
pre- and mature monsoon seasons. The short intense downpour tends to occur more frequently in the pre-monsoon season than
in the mature monsoon season. The pre-monsoon rainfall also has clear diurnal variation with a peak that is more strongly
concentrated in time. In the northern part the rainfall peak is found in between midnight and early morning, while it is observed
in the daytime in central to western parts of the country. Two disaster cases caused by meso-scale disturbances are analyzed.
Although they occurred in the same season, the structures of the cloud systems were largely different from each other. The
disturbance brought about tornadoes on 14 April 2004, consisting of many spherical cloud systems of approximately 20 km size.
On the other hand, another one that caused the tragic river water transport accident on 23 May 2004 had meso-scale rain band
structure. The latter case was captured by the AWS located at Dhaka. Sudden changes in temperature, wind and pressure were
observed clearly, showing the typical structure of convective rain bands. 相似文献
12.
基于钻孔数据的地层三维建模与可视化研究 总被引：24，自引：0，他引：24
地质体三维建模是地学信息系统核心课题之一,对现有建模方法进行分析,结合地层特点,提出首先引入虚拟钻孔,利用Kriging插值方法建立地层三维模型;其次把虚拟钻孔参数的调试结果及专家知识等资料在建模流程中予以充分体现,从而建立相对精确的三维地层模型;最后基于本文建模方法开发了一个三维地层模型,并用实际资料进行了验证,能有效满足工程需求。 相似文献
13.
I. Vilibić K. Horvath N. Strelec Mahović S. Monserrat M. Marcos Á. Amores I. Fine 《Natural Hazards》2014,74(1):25-53
We investigated the atmospheric processes and physics that were active during a tsunami-like event hitting Boothbay Harbor area (Maine, USA) on 28 October 2008. The data collected by tide gauges, ground and sounding stations and meteo–ocean buoys in the area were analyzed, together with satellite and radar images. The atmospheric processes were reproduced by the weather research and forecasting model, verified by in situ and remote sensing data. A cold front moved over the area at the time of the event, with embedded convective clouds detected by satellite and radar data and the internal gravity waves (IGWs) detected by radar and reproduced by the model at the rear of the frontal precipitation band. According to the model, the IGWs that passed over Boothbay Harbor generated strong ground air-pressure oscillations reaching 2.5 hPa/3 min. The IGWs were ducted towards the coast without significant dissipation, propagating in a stable near-surface layer capped by an instability at approximately 3.5 km height and satisfying all conditions for their maintenance over larger areas. The intensity, speed and direction of the IGWs were favourable for generation of a meteotsunami wave along the Gulf of Maine shelf. Operational observation systems were not capable of sufficiently capturing the ground disturbance due to a too coarse sampling rate, while the numerical model was found to be a useful tool in eventual future detection and warning systems. 相似文献
14.
三维地质模型构建方法的研究及应用 总被引：25，自引：3，他引：22
地质体三维建模是地学信息系统的核心问题之一.对三维GIS及地学领域的空间构模方法的现状进行分析,结合地质体工程特点,提出一种三维地学空间构模方法--似三棱柱(STP)法.该方法以似三棱柱体作为三维地质体建模的基本体元,并采用5类基本元素和6组拓扑关系对似三棱柱体的数据结构进行描述.它能有效地表达各种三维地质现象,也可以更好地与传统的多层TIN模型结合,维护好空间实体的拓扑关系.基于本文的建模方法开发了一个适合地质领域的三维GIS初步原型,并用实际钻孔数据进行了验证. 相似文献
15.
由于雷达数据不受天气影响,且具有一定的穿透能力,近年来已被广泛的运用在地质构造信息提取研究中。ALOS PALSAR与RADARSAT2是近年发展的最先进的雷达传感器,其全极化模式同时又具有较高的空间分辨率,这为植被区地质构造研究提供了良好的数据源。本文选取非洲埃塞俄比亚西部为研究区,通过对研究区域两种全极化雷达数据进... 相似文献
16.
17.
利用2006—2010年夏季6~8月CloudSat资料对念青唐古拉峰地区云水分布和云类型特征进行分析,从而为研究高原天气过程与其水循环过程的相互作用提供理论依据。结果表明,云水含量垂直分布结构与云类型有关,而冰川区和非冰川区云类型差异主要为降水云类型不同,其中有冰川覆盖的高山上空降水云以深厚对流云为主,无冰川覆盖的高山降水云类型以雨层云为主。念青唐古拉峰南坡冰川区云水平均含量为0.14 g/m3,非冰川区云水平均含量为0.18 g/m3,一定程度说明来自孟加拉湾的水汽在经过冰川附近时,多会产生降水,反映了冰川对水汽传输的阻碍作用。 相似文献
18.
一种机载雷达点云数据的快速分类方法 总被引：1，自引：0，他引：1
机载激光雷达扫描技术可以以点云形式快速获取地形表面高精度三维信息。基于激光雷达扫描数据及建筑物本身的拓扑信息就可以对建筑物进行精确的重建,而重建中最关键的技术是对点云数据进行分类,进而进行地物识别。对大规模三维点云数据进行快速分类,提出一种采用区域分割结合基于最小二乘平差的多项式拟合方法,将大量离散的三维点云分割后进行多项式拟合,并将二维数据分类转化为一维数据分类。在分类的基础上,将建筑物几何规则作为约束条件提取了房屋边缘。实验分析表明,该方法既能去除多余噪声,又能有效保留特征点,分类的总误差率低于3%。 相似文献
19.
毫米波测云雷达的特点及其研究现状与展望 总被引：17，自引：2，他引：15
云在大气的能量分配、辐射传输,尤其是水循环系统中有不可忽视的作用。云探测对云物理、人工影响天气、气候变化和航空航天等领域有重要意义,是大气科学研究的热点之一。尽管目前已经发展了很多种遥感设备对云进行观测(如激光雷达、卫星、云幂仪等),但这些设备无法得到高时空分辨率的云水平和垂直结构,而毫米波雷达是云三维精细结构探测的重要工具。由于毫米波雷达具有更接近小粒子尺度的短波长,因此更适合用来探测弱云,同时毫米波雷达也存在衰减严重的缺点。介绍了毫米波雷达的特点以及其探测小粒子的优势;对比分析了其与新一代多普勒天气雷达、晴空风廓线雷达的差异,得出：毫米波雷达具有高时空分辨率,能够更精确地反映云的垂直和水平结构,比普通天气雷达更适合监测云的变化。概括了国内外毫米波测云雷达的发展现状以及在云物理研究方面的情况,并展望了国内毫米波雷达未来研究的方向。 相似文献
20.
基于三维激光扫描的空间地物建模 总被引：4，自引：0，他引：4
利用地面三维激光扫描仪获取的空间数据,进行了三维空间地物建模研究。以建筑物建模为例,首先从原始数据中分离提取建筑物,然后对得到的建筑物数据进行去噪处理,再通过整体匹配纠正并对原始测量数据进行重新采样和拼接配准,建立了由三角网构成的三维表面模型。结果表明,所构建的三维表面模型较好地表达了建筑物的几何特征,户外实验也验证了上述过程可以实现对建筑物快速三维建模。 相似文献