三维社区建模与分析的共形几何代数方法     

罗文  袁林旺  胡勇  易琳  闾国年 《地理与地理信息科学》2012,28(3):20-23,53

利用共形几何代数的多维统一表达与分析优势,研究了集成多源数据的三维社区统一建模与分析方法。构建了基于多重向量存储结构的社区场景整体建模流程,实现了CityGML、DXF等多源数据的导入与集成,并设计了基于共形几何代数的对象运动表达与插值方法。以德国Waldbruecke村为例的验证结果显示,基于共形几何代数的三维社区建模可以较好地表达复杂社区对象,并可以有效支撑几何度量、动态对象跟踪、运动轨迹重建等功能实现。  相似文献   

Snow water equivalent over Eurasia in the next 50 years projected by aggregated CMIP3 models     

LiJuan M  Yong Luo  DaHe Qin 《寒旱区科学》2012,4(2):0093-0106

Based on remote sensing snow water equivalent (SWE) data, the simulated SWE in 20C3M experiments from 14 models attending the third phase of the Coupled Models for Inter-comparison Project (CMIP3) was first evaluated by computing the different percentage, spatial correlation coefficient, and standard deviation of biases during 1979–2000. Then, the diagnosed ten models that performed better simulation in Eurasian SWE were aggregated by arithmetic mean to project the changes of Eurasian SWE in 2002–2060. Results show that SWE will decrease significantly for Eurasia as a whole in the next 50 years. Spatially, significant decreasing trends dominate Eurasia except for significant increase in the northeastern part. Seasonally, decreasing proportion will be greatest in summer indicating that snow cover in warmer seasons is more sensitive to climate warming. However, absolute decreasing trends are not the greatest in winter, but in spring. This is caused by the greater magnitude of negative trends, but smaller positive trends in spring than in winter. The changing characteristics of increasing in eastern Eurasia and decreasing in western Eurasia and over the Qinghai-Tibetan Plateau favor the viewpoint that there will be more rainfall in North China and less in the middle and lower reaches of the Yangtze River in summer. Additionally, the decreasing rate and extent with significant decreasing trends under SRES A2 are greater than those under SRES B1, indicating that the emission of greenhouse gases (GHG) will speed up the decreasing rate of snow cover both temporally and spatially. It is crucial to control the discharge of GHG emissions for mitigating the disappearance of snow cover over Eurasia.  相似文献   

Effect of Length Scale Tuning of Background Error in WRF-3DVAR System on Assimilation of High-Resolution Surface Data for Heavy Rainfall Simulation     

Ji-Hyun HA  Dong-Kyou LEE 《大气科学进展》2012,29(6):1142-1158

We investigated the impact of tuning the length scale of the background error covariance in the Weather Research and Forecasting(WRF) three-dimensional variational assimilation(3DVAR) system.In particular,we studied the effect of this parameter on the assimilation of high-resolution surface data for heavy rainfall forecasts associated with mesoscale convective systems over the Korean Peninsula.In the assimilation of high-resolution surface data,the National Meteorological Center method tended to exaggerate the length scale that determined the shape and extent to which observed information spreads out.In this study,we used the difference between observation and background data to tune the length scale in the assimilation of high-resolution surface data.The resulting assimilation clearly showed that the analysis with the tuned length scale was able to reproduce the small-scale features of the ideal field effectively.We also investigated the effect of a double-iteration method with two different length scales,representing large and small-length scales in the WRF-3DVAR.This method reflected the large and small-scale features of observed information in the model fields.The quantitative accuracy of the precipitation forecast using this double iteration with two different length scales for heavy rainfall was high;results were in good agreement with observations in terms of the maximum rainfall amount and equitable threat scores.The improved forecast in the experiment resulted from the development of well-identified mesoscale convective systems by intensified low-level winds and their consequent convergence near the rainfall area.  相似文献   

雷达径向风速同化对台风麦莎模拟的影响   总被引：7，自引：1，他引：6  

陈锋  冀春晓  董美莹  滕卫平  林惠娟 《气象》2012,38(10):1170-1181

本文应用WRF-3DVAR系统同化多普勒雷达径向风速资料,并利用WRF模式对台风麦莎（2005年8月6日00时至7日00时）进行数值模拟,以此检验多普勒雷达径向风速资料在改进模式初始场及提高台风路径和降水预报准确度等方面的应用效果及意义,探讨不同同化时间间隔对同化效果的影响。通过对比同化试验和控制试验发现：雷达径向风速资料能通过调整初始风场结构,改进对台风结构的模拟,从而提高模式对台风麦莎的路径、强度和降水的模拟能力;雷达资料信号在进入模式后有一定的时效性,在一定程度上缩小同化时间间隔有助于提高同化效果。  相似文献   

Model-Experimental Analysis of Variational Assimilation of Dust Concentration with GRAPES Sand-Dust Numerical Forecasting System in a Sand-Dust Storm     

《高原气象》2012,31(3)

为了提高沙尘模式的预报准确率,通过在区域天气数值模式GRAPEs（G10bal／RegionalAs-similationandPrEdictionSystem）的三维变分同化系统中增加沙尘浓度这一控制变量的方法建立了GRAPES-3DVAR-DusT沙尘同化系统。利用中国北方8个观测站提供的沙尘PM10数据和沙尘模式（GRAPEs-CUAcE／Dust系统）提供的背景场,对2008年2月29日-3月1日发生在中国北方的一次沙尘暴天气进行了控制试验和一次同化与间断同化的敏感性试验,结果表明：（1）引入该同化系统后,一次同化和间断同化试验模拟的地面沙尘浓度分布较未同化的控制试验结果更接近卫星监测,而间断同化的结果又好于一次同化;（2）一次同化试验与控制试验对单站PM10浓度的演变预报较差;（3）间断同化试验较准确地再现了单站PM10浓度的连续演变;（4）间断同化试验效果整体上优于一次同化试验。总体而言,引入沙尘同化系统在一定程度上可以提高沙尘模式对沙尘天气的预报准确率。  相似文献   

利用FY-3星载微波资料对热带气旋云系和暖核特征的分析   总被引：1，自引：0，他引：1  

刘喆  白洁  邱红  张文军 《气象科学》2012,32(5):534-541

介绍了中国FY-3系列卫星搭载的微波遥感仪器性能特点,以“1109”超强台风“梅花”为研究个例.通过微波湿度计单通道微波图像和微波成像仪双极化通道散点图,分析了台风云系中云雨粒子对遥感通道辐射的吸收和散射效应,揭示了台风在微波图像上表现形式的内在物理原因.利用微波向量辐射传输模式的模拟表明:微波温度计各氧气吸收通道对热带气旋系统水汽和水凝物含量变化的敏感性不大.因此,可利用权重函数峰值位于对流层中上层的通道3,探测出台风暖核辐射信息.根据两者相匹配的5个较理想时次数据,选取距“梅花”中心400 km范围为研究区域,并提出用于修正扫描点分辨率不均匀所带来取样偏差的方法,分别计算出订正临边效应后的暖核强度,发现它同表征台风强度的中心海平面气压变化趋势相一致.  相似文献   

采用SilviScan-3TM研究木材性质的方法及其在气候变化研究中的应用          下载免费PDF全文

徐金梅  吕建雄  鲍甫成  肖军  Robert Evans  黄荣凤  徐明 《气候变化研究进展》2012,8(2):124-130

系统介绍了利用SilviScan-3TM测量细胞结构、木材密度、微纤丝角和划分年轮界线的方法,并以祁连山青海云杉为例,分析青海云杉6个木材性质参数(年轮细胞直径、年轮细胞壁厚、年轮宽度、年轮密度、年轮微纤丝角、年轮弹性模量)与气候因子的关系,以期为利用多个树轮参数研究气候提供参考。结果表明:6个木材性质参数与月平均气温和月降水量都有显著相关的月份,但显著相关的时间段不同,并且微纤丝角和细胞结构参数中包含的气候信息强于常用的年轮宽度和年轮密度。SilviScan-3TM测量木材性质参数的优越性体现在:测量精度高、速度快,能在同一个试样上测量多个参数并能精确定年。  相似文献   

3G通信技术在移动气象视频会商咿的研究与应用     

苏轶  刘树峰  孟令旺  马骏 《气象与环境科学》2012,35(1)

目前山东省气象部门已有多部移动气象台投入业务使用,在防御气象灾害和突发气象事件应急服务中发挥了重要作用。由于移动气象台通信（通过通信卫星连接互联网和气象局内音旷网）费用高,且需提前向运营商申请增加宽带以满足视频会商需求,因此提出了利用3G通信技术,建立VPDN网络访问气象局内部网络,来实现移动气象台和济南市气象台视频会商的方案。该方案的应用,大大降低了移动一气象台的通信费用,提高了传输效率。  相似文献   

Monsoon Change in East Asia in the 21st Century: Results of RegCM3          下载免费PDF全文

SUI Yue  LANG Xian-Mei 《大气和海洋科学快报》2012,5(6):504-508

The authors investigate monsoon change in East Asia in the 21st century under the Special Report on Emissions Scenarios (SRES) A1B scenario using the results of a regional climate model, RegCM3, with a high horizontal resolution. First, the authors evaluate the model’s performance compared with NCEP-NCAR reanalysis data, showing that the model can reliably reproduce the basic climatology of both winter and summer monsoons over East Asia. Next, it is found that the winter monsoon in East Asia would slightly weaken in the 21st century with spatial differences. Over northern East China, anomalous southerly winds would dominate in the mid-and late-21st century because the zonal land-sea thermal contrast is expected to become smaller, due to a stronger warming trend over land than over ocean. However, the intensity of the summer monsoon in East Asia shows a statistically significant upward trend over this century because the zonal land-sea thermal contrast between East Asia and the western North Pacific would become larger, which, in turn, would lead to larger sea level pressure gradients throughout East Asia and extending to the adjacent ocean.  相似文献   

Distinguished Effects of Interannual Salinity Variability on the Development of the Central-Pacific El Nino Events          下载免费PDF全文

ZHENG Fei  WAN Li-Ying  WANG Hui 《大气和海洋科学快报》2012,5(2):123-127

El Nio events in the central equatorial Pacific (CP) are gaining increased attention,due to their increasing intensity within the global warming context.Various physical processes have been identified in the climate system that can be responsible for the modulation of El Nio,especially the effects of interannual salinity variability.In this work,a comprehensive data analysis is performed to illustrate the effects of interannual salinity variability using surface and subsurface salinity fields from the Met Office ENSEMBLES (EN3) quality controlled ocean dataset.It is demonstrated that during the developing phase of an El Nio event,a negative sea surface salinity (SSS) anomaly in the western-central basin acts to freshen the mixed layer (ML),decrease oceanic density in the upper ocean,and stabilize the upper layers.These related oceanic processes tend to reduce the vertical mixing and entrainment of subsurface water at the base of the ML,which further enhances the warm sea surface temperature (SST) anomalies associated with the El Nio event.However,the effects of interannually variable salinity are much more significant during the CP-El Nio than during the eastern Pacific (EP) El Nio,indicating that the salinity effect might be an important contributor to the development of CP-El Nio events.  相似文献