Statistical Characteristics of Convective Initiation in the Beijing-Tianjin Region Revealed by Six-Year Radar Data          下载免费PDF全文

WANG Yu  HAN Lei  WANG Hongqing 《Acta Meteorologica Sinica》2014,28(6):1127-1136

Characteristics of convective initiation (CI) in the Beijing-Tianjin region during the warm season of2008-2013 are examined. A total of 38877 CI cases are identified by a thunderstorm identification, tracking, analysis, and nowcasting algorithm. CI cases are evaluated in the context of associated terrain, weather systems, and land cover properties. The spatial distribution of all CI cases shows that there are dense CI activities around the 200-m elevation, which means that convective storms are more easily triggered over foothills. From 1500-1800 to 0300-0600 BT (Beijing Time), the high-occurrence CI region tends to propagate southeastward (i.e., from mountains to plains, then to ocean). Among the four local weather systems, the Mongolian cold vortex has the highest CI frequency while the after-trough system has the lowest CI frequency. For the land cover relationships with CI, the urban land cover has the highest CI density and the forest-type land cover has the second highest CI density; these two types of land cover are more conducive to CI formation.  相似文献   

2004年台风“艾利”与“米雷”路径异常变化分析   总被引：9，自引：1，他引：8  

段晶晶  吴立广  倪钟萍 《气象学报》2014,72(1):1-11

2004年西北太平洋上生成的台风"艾利"和"米雷"开始都是向西北方向移动,当快要进入东海时两个台风的路径均发生变化,"艾利"转向西南方向,形成倒抛物线形的路径,而"米雷"突然向东北方向转折。通过对这两个台风的不同时间尺度环境场及其与台风相互作用的分析表明,对于西南转向的"艾利",副热带高压(副高)西伸明显,台风位于副高的南侧,天气尺度风场对副高低频分量的涡度平流,使得台风西北侧出现负涡度,同时由于罗斯贝波能量频散,台风东南侧出现负涡度,与负涡度相联系的天气尺度异常环流导致台风西北侧和东南侧的天气尺度引导气流的作用相互抵消,台风主要在低频环流引导下向西南方向移动;对于突然向东北转向的"米雷",副高位置偏东,转向时刻只有东南侧增强的天气尺度西南风,天气尺度引导气流导致台风向东北转折。  相似文献   

Surface rainfall and cloud budgets associated with mei-yu torrential rainfall over eastern China during June 2011     

ZHAI Guoqing  LI Xiaofan  ZHU Peijun  SHEN Hangfeng  ZHANG Yuanzhi 《大气科学进展》2014,31(6):1435-1444

Surface rainfall and cloud budgets associated with three heavy rainfall events that occurred over eastern China during the mei-yu season in June 2011 were analyzed using 2D cumulus ensemble model simulation data.Model domain mean rainfall showed three peaks in response to three prescribed ascending motion maxima,primarily through the mean moisture convergence during the torrential rainfall period.Prescribed ascending motion throughout the troposphere produced strong convective rainfall during the first （9 June） and third （17-18 June） rainfall events,whereas strong prescribed ascending motion in the mid and upper troposphere and weak subsidence near the surface generated equally important stratiform and convective rainfall during the second rainfall event （14 June）.The analysis of surface rainfall budgets reveals that convective rainfall was associated with atmospheric drying during the first event and moisture convergence during the third event.Both stratiform and convective rainfall responded primarily to moisture convergence during the second event.An analysis of grid data shows that the first and third mean rainfall maxima had smaller horizontal scales of the precipitation system than the second.  相似文献   

Weather extremes and street life in India—Implications of Fuzzy Cognitive Mapping as a new tool for semi-quantitative impact assessment and ranking of adaptation measures     

《Global Environmental Change》2014

The potential impacts of progressing climate change are alarming. Some adverse consequences are now unavoidable and adaptation measures are increasingly needful. This poses enormous challenges for emerging megacities in the Global South, which barely manage in current weather conditions. This paper introduces Fuzzy Cognitive Mapping as a new tool for structured, semi-quantitative assessments of climate change impacts and adaptation measures.Fuzzy Cognitive Mapping is used to evaluate differences in sensitivities to heatwaves and rainstorms across socio-economic groups and for the ranking of useful adaptation options, based on 188 individual interviews to the impacts of extreme weather events in Hyderabad, India. The results of this multi-stakeholder assessment indicate that rainstorms affect low-income residents more than heatwaves, while the opposite is true for medium-income respondents. The latter are also less seriously affected by extreme weather in general. Profession, though, not income determines the kind of impact that people feel most affected by. Individual characteristics like age and gender do not significantly explain differences in the data, but religion does. This is because, in Hyderabad, Muslims live in the older, less serviced and more affected parts of the city. However, semi-quantitative scenario analyses suggest that, under future climate change, many parts of the city will become increasingly exposed to the effects of extreme weather. Planned investments in urban infrastructure will be seriously challenged by climate change and preventive adaptation measures are urgently needed to at least maintain the current level of quality of life. Investments in the health infrastructure appear to be most effective in reducing the impact of heatwaves and investments in the traffic infrastructure most effective in reducing the impact of rainstorms. However, looking at heat and rain events together—which is realistic as they are both projected to increase and often occur in the same year—reveals that investments in water infrastructure and management have greatest potential to reduce impacts across all localities and on all social groups, particularly the lower-income classes. This is because first-order impacts caused by inadequate water infrastructure often give rise to second- or third-order impacts. Addressing the root cause is the most effective way to break cause-and-effect chains and prevent proliferation of negative consequences. Similar studies are suggested in other cities in order to support adaptation mainstreaming in complex urban environments. Fuzzy Cognitive Mapping proved a useful, semi-quantitative tool for climate change impact and adaptation assessments.  相似文献   

基于伪语义相似度模型的中文地址匹配方法     

郁汀  王铎  陈钦 《测绘通报》2022,(3):101-106

地址匹配中,由于传统相似度模型受字符重叠数影响大,在处理简写、缩写地址要素单元时,错误匹配问题突出;深度学习方法需要大量样本支撑,但庞大的数据量和多样的形式,导致生成样本的成本过高。为解决上述问题,本文首先应用基于条件随机场和双向长短时记忆神经网络的模型,对地址进行分词;然后通过建立一种伪语义相似度,对地址要素进行分级匹配。通过对公安业务中地址数据进行测试,在对缩写、简写等不规范地址描述方面,本文模型能较理想地完成任务,各参考指标均高于0.9。  相似文献   

基于BP神经网络的昆明天顶湿延迟模型     

丁仁军  王友昆  张君华  刘晨 《测绘通报》2022,(3):107-110

为了满足昆明市卫星定位综合服务系统(KMCORS)对高精度天顶湿延迟(ZWD)的需要,本文开发了适用于昆明地区的ZWD模型KM。KM模型是根据昆明探空站2015-2018年的探空资料,基于误差反向传播(BP)神经网络建立的,同时采用2019年的探空数据,验证了KM模型的预测性能。测试结果表明,与广泛使用的SA模型相比,KM模型的RMSE由4.0 cm降至2.2 cm,精度提升了45%;KM和SA模型的Bias分别为0和-3.1 cm。该结果表明KM模型对ZWD估计具有无偏性,而SA模型在高原区存在过度估计的问题,KM模型具有比SA经验模型更优的预测性能,其应用将有助于提升KMCORS的服务质量。  相似文献   

机场净空区建筑物的识别与监测     

童矿  宋洋  孔祥芬 《测绘通报》2022,(3):127-131

目前,在建筑物识别与监测方面,基于单幅高分辨率遥感影像的阴影测高法和基于多视角影像的立体像对法将建筑物轮廓或名称识别与高度监测相独立,因此导致其自动化水平较低、数据冗余度与成本较高。基于数字表面模型(DSM)和兴趣点(POI)数据,本文提出了一种机场净空区建筑物识别与监测集成的方法,并以某国际机场为试验区对该方法的可行性进行了验证。试验结果表明:①该方法在建筑物识别与监测方面的准确率只取决于DSM的精度,而对DSM的数据来源没有限制;②以潜在危险建筑物高程变化速率为依据进行不定期的动态监测,在确保监测间隔期间机场净空区安全的同时可以降低数据成本和重复识别与监测所有建筑物造成的数据冗余度。  相似文献   

基于北京二号影像辅助nDSM的建筑物自动提取     

毛斌  韩文泉  谢宏全  吕海扬 《测绘通报》2022,(3):132-137

针对建筑物提取方法缺乏泛化性的问题,本文提出了将nDSM、北京二号影像、NDVI、BAI的七通道图像相结合作为数据源的提取方法。采用随机森林、梯度提升机、支持向量机、BP神经网络分类器对建筑物进行提取获取最佳分类器模型,并运用二值化与开闭运算,以建筑物面积与最小外接矩形面积的比值为阈值,对建筑物分别进行最小外接矩形、DP算法拟合,优化建筑物提取结果。试验结果表明,梯度提升机(GBDT)较其他分类模型在不同场景下综合效果较好,F-score精度更高。  相似文献   

利用稀少卫星影像控制点生产1:10 000 DOM——以阿拉善盟测区为例     

逯中香  樊彦国  李国胜 《测绘通报》2022,(3):138-142+156

青藏铁路沿线地表受多年冻土的影响会产生抬升和沉降,形变监测对于其安全运行至关重要。本文采用41景C波段Sentinel-1A升轨数据,结合均匀网格划分子区域的方法,探测分布相对均匀的永久散射体,以作为SBAS InSAR技术的地面控制点,对青藏线羊八井站至乌玛塘站段铁路及其沿线地表进行形变监测。试验结果表明,该段铁路年形变速率范围为-8~2 mm/a,该区域形变受周围冻土的影响随季节呈周期性变化;SBAS InSAR技术和本文的PS-SBAS InSAR技术在同名点形变趋势与形变程度方面的对比结果保持一致性,进一步说明了本文方法的可靠性。  相似文献   

基于GIS的东川区生态环境敏感性分析     

杨艺苑  杨存建 《测绘通报》2022,(3):7-12

利用地理信息系统技术与层次分析法对东川区生态环境进行敏感性分析,本文共选取5个评价指标,首先对其进行单因子评价;然后基于GIS空间分析功能,将东川区综合生态敏感性分为5个等级;最后构建东川区综合生态环境敏感性分布图。研究结果显示:①5个生态评价因子中,坡度因子对东川区生态环境敏感性影响最大,权重值为0.36。根据对生态敏感性影响程度从大到小排序为:坡度、高程、土地利用、NDVI和水域缓冲区。②东川区生态环境敏感性总体偏高,极高敏感区与高敏感区共占区域总面积的44.17%;中敏感区占比最高,为26.1%;低敏感区和极低敏感区两者占比之和为29.73%。③东川区生态环境极高敏感区和高敏感区主要分布在西北部;极低敏感区和低敏感区主要分布在东北部及中部河谷地区。  相似文献