共查询到19条相似文献，搜索用时 109 毫秒
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提升城市暴雨内涝防治精细化水平是解决城市洪涝问题的关键。采用16种不同时空分辨率的降雨产品,利用暴雨时空异质性评估指标和随机暴雨移置法,在上海地区定量评估降雨数据精度对暴雨事件时空变异性诊断和频率分析的影响。研究发现利用低精度降雨数据得到的年最大暴雨序列发生时间延迟、降水量低估,暴雨过程不均匀性提升、空间不均匀性降低;在不同重现期下,降雨数据精度对频率分析结果影响有显著差异,重现期越大,低精度数据带来的低估程度越大;时间精度的影响占主导地位,可达空间精度的5倍。在城市暴雨洪涝研究中有必要采用更高精度的降雨数据,建议与研究区域类似的小型城市地区在防洪设计中使用精度达(12 h、0.05°)或以上的降雨数据。 相似文献
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被动微波遥感反演中国西部地区雪深、雪水当量算法初步研究 总被引：2，自引：0，他引：2
雪深、雪水当量是积雪研究中重要参数，其在流域水量平衡和融雪径流预报以及雪灾监测与评价中起着重要作用。Chang等(1987)以辐射传输理论和米氏散射为理论基础，假定积雪密度和颗粒大小为常数，利用实测雪深数据和SMMR的亮温数据，通过统计回归方法，建立了雪深与18 GHz和37 GHz水平极化的亮温梯度之间的关系，发展了SMMR半经验的反演雪深的算法。后在此基础上又发展了针对SSM/I的半经验反演雪深算法。2002年发射的装载于Aqua卫星上的AMSR E是新一代的被动微波辐射计，性能较以往星载被动微波辐射计有较大提高，采用了改进后的SSM/I的半经验算法作为其估算全球雪水当量的反演算法。
将AMSR E的雪水当量产品与气象台站观测的雪水当量进行比较，发现在新疆地区和青藏高原地区雪水当量的RMSE分别达到31.8 mm和21 mm。本研究旨在建立基于AMSR E亮温数据，适用于中国西部地区的雪深和雪水当量反演算法。首先收集整理了2003年新疆地区的雪深、雪水当量数据和AMSR E亮温数据，去除错误样本，利用统计回归的方法，建立了新疆的反演雪深、雪水当量的半经验算法，算法中加入积雪覆盖度参数，较以往的算法有所改进，与气象台站观测数据比较，结果也表明新疆地区建立的经验算法较AMSR E的雪水当量算法有较大改进，RMSE为15.7 mm。但青藏高原地区因海拔高，地形复杂，大部分地区积雪较浅,空间分布不均和冻土存在等诸多因素运用同样的方法建立反演算法，结果不甚理想，以后的研究将重点消除这些干扰因素。 相似文献
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古河道对于重现古气候、古生态环境变化有着重要的意义。极化合成孔径雷达（SAR）数据以散射矩阵的形式记录了地物的后向散射信息，能有效地识别隐伏的古河道信息。本文以古河道发育的松嫩平原西部作为研究区域，选取Sentinel-1双极化数据（VV-VH）作为数据源，通过VV-VH双极化模式下的H/α分解处理，构建了由散射熵H与散射角α构成的二维H/α平面。依据雷达波在古河道充填沉积物中发生体散射以及在古河床底界面发生二次散射，并且体散射功率大于二次散射功率，确定了古河道散射类型属于H/α平面上的高熵多次散射。结合此特征与Sentinel-2影像，最终对研究区内的古河道信息进行了提取。研究表明，通过VV-VH双极化模式下的H/α分解方式可以提取到在Sentinel-2影像上无明显特征的古河道信息。 相似文献
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从理论、方法与应用实现三方面,对国家“973 ”项目“复杂自然环境时空定量信息的获取与融合处理的理论与应用”在地球信息科学领域中的研究进展作一个概述。在遥感机制与信息理论上,以合成孔径雷达（ SAR ）研究为背景,发展全极化散射与SAR 成像信息理论;以微波辐射遥感为背景,发展非均匀自然介质矢量辐射传输（ VRT ）理论。在这基础上,开展在轨业务与试验遥感卫
星在多类陆地地表和大气遥感数据验证的方法与算法的研究。结合遥感、辐射传输、地理信息系统、中国陆面水文过程、数据同化技术,建立一个中国陆地水环境数据同化系统（ CLDAS ）;针对我国未来气象卫星的发展,由在轨SSM / I 、AMSU 、MTI 等遥感卫星数据、结合地面台站实测与探空等工作,形成了星载微波大气三水（降水、水汽、云水）反演与气象卫星数据业务算法与数据库;针对我国SAR 技术的发展,由ERS 、RADARSAT 等SAR 数据图像的应用研究,形成SAR - INSAR 多类应用技术研究与软件遥感应用平台。同时,结合多源信息融合理论方法与环境中目标跟踪实验与仿真,发展了目标与环境复合建模与特性数值仿真、开展了沿海区域异常大气结构中波传播实验等
研究。 相似文献
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利用成都地基GPS观测网2007年8月21日～2008年11月30日观测数据,结合地面自动气象站网资料反演GPS大气可降水量(PWV)。选取夏季暴雨,秋季绵雨和冬季雨雪天气过程分析GPSPWV在不同类型降雨天气过程中的演变特征及日变化规律。结果表明,发生在不同季节的暴雨对应PWV的演变有所不同,盛夏暴雨发生在PWV由峰值向波谷变化过程中,夏末的暴雨则出现在由波谷向波峰转变阶段,降雨前GPSPWV的增减速率可很好地预示其后的暴雨强度。在秋季绵雨中PWV的连续大幅递增或递减可作为降雨开始或结束的预报依据。GPSPWV在降雨天气分析及预报中具有重要的指示意义。 相似文献
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基于高站点密度的场次降雨数据对2016年7月20日发生在北京地区的特大暴雨过程进行分析,明晰其时空演变过程。主要结论如下:(1)暴雨中心降雨总量在350mm以上,大致呈带状分布,主要位于海拔高度在200~400m范围内的山麓平原,说明地形抬升作用对暴雨的形成有明显的促进作用;(2)暴雨中心处发生的是长历时、高强度的降雨过程,而位于怀柔区和密云区交界处的暴雨副中心处发生的是短历时、高强度的降雨过程;(3)暴雨过程为一小一大的双峰雨型,第二阶段是整个降雨过程的主过程,降雨总量达到184.7mm,与北京"7·21"暴雨的降雨总量基本持平,超过20年一遇标准;(4)随着降雨总量的增加,各站点最大1h雨强呈线性增加的趋势,且最大雨强出现时刻有所提前,随着统计时段的增加,最大降雨总量增加的速率逐渐变缓,可由对数函数进行拟合。 相似文献
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延河“77.7”特大暴雨洪水 总被引：2，自引：0，他引：2
延河1977年7月5日至6日发生了特大暴雨洪水。6日凌晨,延安东关大桥处最大流量达到8780m~3/s,造成了延安的水灾。与过去1933年8月的最大流量4580m~3/s相比,为近一二百年来所罕见的特大洪水。为加深对延河洪水规律的认识,提供该地区水利工程规划设计作参考,现综合有关资料,对该次暴雨及洪水简介如下。 相似文献
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2016年6月18日7月21日,长江流域安徽段发生暴雨洪水,最大3d、7d雨量位居历史第一,重现期大于50年一遇,最大15d雨量位居历史第二,重现期接近50年一遇,至7月5日长江安徽段全线超警戒水位,给长江流域安徽段造成较为严重的洪涝灾害。收集、整理了本次暴雨洪水的资料,对暴雨的过程和成因进行了分析,并结合历史特征年资料进行了比较。结果表明:强降雨、降雨的空间分布以及前期长江底水高是2016年洪水总体水平位居历史第二的主要因素。 相似文献
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为研究芦苇盐沼植物在一个生长周期不同生长季节的雷达后向散射系数变化特征,对芦苇分布信息进行提取,探究Sentinel-1A卫星数据在长江口湿地植被监测中的应用前景。以对长江河口崇明东滩南部为研究区域,利用2016年11个时相的Sentinel-1A雷达卫星影像VV（vertical transmit/vertical receive）+VH（vertical transmit/horizontal receive）双极化数据,分析潮滩地带芦苇、白茅、海三棱藨草、水体和光滩在植被生长周期内的雷达后向散射强度变化特征,对芦苇盐沼植被进行识别提取。结果表明：相较于VH极化方式,VV极化方式下不同地物的后向散射强度差异更为明显,芦苇的后向散射强度在枯叶期下显著高于其他地物;进行芦苇植被提取时,需要对植被枯萎期不同潮位状况下的雷达影像进行组合运算,芦苇提取精度可达到88.7%;对芦苇植被雷达后向散射强度和临近时相的光学遥感归一化植被指数（normalized difference vegetation index,INDV）进行相关性分析,发现两者呈良好的正相关关系,相关系数为0.78。 相似文献
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Microwave radiometer SSM/I data and scatterometer QuikSCAT data have been widely used for the icesheet near-surface snowmelt detection based on their sensitivity to liquid water present in snow. In order to improve the Antarctic ice-sheet near-surface snowmelt detection accuracy, a new Antarctic icesheet near-surface snowmelt synergistic detection method was proposed based on the principle of complementary advantages of SSM/I data(high reliability) and QuikSCAT data(high sensitivity) by the use of edge detection model to automatically extract the edge information to get the distribution of Antarctic snowmelt onset date, snowmelt duration and snowmelt end date. The verification result shows that the proposed snowmelt synergistic detection method improves the detection accuracy from about 75% to 86% based on AWS(Automatic Weather Stations) Butler Island and Larsen Ice Shelf. The algorithm can also be applied to other regions, which provides methodological support and supplement for the global snowmelt detection. 相似文献
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A. K. Varma R. M. Gairola A. K. Mathur B. S. Gohil Vijay K. Agarwal 《Journal of Earth System Science》2002,111(3):247-256
In this paper, MSMR geophysical products like Integrated Water Vapour (IWV), Ocean Surface Wind Speed (OWS) and Cloud Liquid
Water (CLW) in different grids of 50, 75 and 150 kms are compared with similar products available from other satellites like
DMSP-SSM/I and TRMMTMI. MSMR derived IWV, OWS and CLW compare well with SSM/I and TMI finished products. Comparison of MSMR
derived CLW with that derived from TMI and SSM/I is relatively in less agreement. This is possibly due to the use of 37 GHz
in SSM/I and TMI that is highly sensitive to CLW, while 37 GHz channels are not available on MSMR. Monthly comparison of MSMR
geophysical products with those from TMI is all carried out for climatological purpose. The monthly comparisons were much
better compared to instantaneous comparisons. In this paper, details of the data analysis and comparison results are presented.
The usefulness of the MSMR vis-à-vis other sensors is also discussed. 相似文献
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Weili Duan Bin He Kaoru Takara Pingping Luo Daniel Nover Yosuke Yamashiki Wenrui Huang 《Natural Hazards》2014,73(3):1255-1267
During July 11–14, 2012, deadly floods and landslides triggered by a series of unprecedented heavy rains hit Kyushu, Japan, causing at least 32 deaths and around 400,000 evacuations. We focus on synoptic anomalies identified after inspecting rainfall patterns and documenting the conditions associated with this tragic event using data combined from the Global Rainfall Map in Near Real Time data, the NCEP/NCAR Reanalysis dataset, and the global forecast system. Rainfall maps indicated that there were many heavy rains in Kyushu in these days and this disaster was associated with the pattern of forecasts and standardized anomalies. A weather trough with positive height anomalies appeared, the center of which moved to the north of Japan over this period, which might cause wind anomalies and whereby lots of water vapor were transported to Kyushu area with up to 90 m s?1, and high values of precipitable water formed with up to 60 mm. These results suggest that a larger-scale pattern is conducive for heavy rainfall and the anomalies put the pattern in context as to the potential for an extreme rainfall event, which can provide insights and methods for predicting extreme events’ or something similar. 相似文献
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简单介绍了微波辐射的原理与应用现状,利用美国国防气象卫星计划DMSP F系列卫星携带的SSM/I辐射计南极地区极投影网格亮温数据进行了分析与处理。结合微波亮温等温线图和南极等高线图分析了南极地区亮温分布的特点。选取8个特征区域,对1992-2000年的日亮温数据进行了时间序列分析,分析了冰盖和冰架的亮温特性、季节和年度变化、短期波动等特征。研究表明南极大陆外围冰架和南极半岛地区的亮温呈增高趋势,而内陆冰盖地区则保持相对稳定;揭示了近年来随全球气候的变暖,南极冰架和南极半岛的融化正在加剧的趋势。 相似文献
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The potential risk from cyanobacteria blooms is the basis for predicting, preventing, and managing eutrophication. Poyang Lake lies on the southern bank of the middle and lower reaches of the Yangtze River. This lake is a large shallow lake connected to the Yangtze River and is affected by monsoon. The comprehensive evaluation index system, evaluation model, and method of the potential risk from cyanobacteria blooms were constructed based on the nutrient zoning in Poyang Lake, and the potential risk from cyanobacteria blooms was evaluated in 2013. (1) The evaluation index system comprises physical, chemical, and biological indicators. The physical indicators consist of blocking degree, lake region location, transparency (Secchi disk depth, SD), and temperature; the chemical indicators consist of total nitrogen (TN) and total phosphorus (TP); and the biological indicators consist of chlorophyll a (Chla) and phytoplankton biomass. Among the indicators, blocking degree and lake region location along with the prevailing wind direction were selected to represent the indicators affected by water retention time and wind direction. (2) We established a comprehensive evaluation method for assessing the potential risk from cyanobacteria blooms by adopting both analytic hierarchy process weighting and a comprehensive evaluation method. (3) Results show that the high-risk periods for cyanobacteria blooms were August, July, and December, and the high-risk regions were in the Northeastern Lake Region, Western Lake Region and Northern Lake Region. The Northeastern Lake Region is particularly in high risk in August and July. These cyanobacteria blooms presented heavy risk or close to heavy risk. Based on the risk evaluation indicators, outbreaks of cyanobacteria blooms are limited by temperature and location. Chla and phytoplankton biomass were the key indices affecting the level of potential risk from cyanobacteria blooms during the high-water-level period (July and August). In contrast, TN and TP are the key indices affecting the level of harm during the low-water-level period. Within a year, Chla, phytoplankton biomass, and TP are key indicators for the prediction of cyanobacteria blooms in Poyang Lake. 相似文献
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中国西部积雪日数类型划分及与卫星遥感结果的比较 总被引：12，自引：6，他引：6
根据中国105°E以西地区232个地面气象台站1951-2004年积雪日数观测资料和1980-2004年SMMR、SSM/I逐日雪深资料,划分中国西部积雪类型并分析其年代际变化,并对两种资料的结果进行了比较.结果表明:北疆、天山和青藏高原东部地区年平均积雪日数大于60 d,为稳定积雪区;南疆盆地中心、四川盆地和云南省南... 相似文献
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近30年上海地区暴雨的气候变化特征 总被引：7，自引：1，他引：6
利用上海地区11个气象站1979-2008年5～9月降水资料分析了近30年上海地区暴雨的年、月际及暴雨成因的变化特征.结果表明:1995年以来,上海地区暴雨逐渐向强、局部、特短时间方向变化.7、8月暴雨较多,以短时局部性暴雨为主;6、9月暴雨次之,6月长和特长暴雨要多于短和特短暴雨,9月反之;5月暴雨最少.从形成上海地区暴雨天气系统的分析表明,静止锋暴雨最多,稳定时能形成持续时间长的强暴雨,不稳定时形成短的弱暴雨;其次是暖区暴雨,它是上海地区形成夏季短时局部性强暴雨的主要天气型;另外,台风、台风切变、台风倒槽、低压、冷锋、暖锋和东风扰动形成的暴雨也占有一定的比例.1995年以来,暖区暴雨整体增加,而静止锋暴雨进入21世纪逐渐减少,这可能主要归因于气候变暖和城市热岛效应. 相似文献
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Rainfall variability and indices of extreme rainfall-analysis and perception study for two stations over Central Himalaya,India 总被引：1，自引：1，他引：0
The analysis of rainfall pattern and indices of extreme rainfall events is performed for two meteorological stations located in the Central Himalayan Region which is highly vulnerable to rain-induced hazards. The records of these rain-induced disasters suggest that such events are generally observed in later part of monsoon season, when soil is saturated after monsoon rains. An attempt is made here to test trends of 19 different extreme rainfall indices that have been widely used in the literature, using daily rainfall data for two urban centres (Nainital and Almora) over the period 1992–2005. We have used statistical tools such as Sen’s method and Mann–Kendall test for detection of trend in annual rainfall, monsoon rainfall, number of rainy days and 1-day extreme rainfall. Principal component analysis gives the correlation between different extreme rainfall indices. Time series of principal components are representing the trends of extreme indices, their variation and interrelation between different indices. The perception study conducted in the same sites indicates that extreme rainfall events and change in rainfall amount and timing are well perceived by the local people. 相似文献
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To deeply understand the micro-/mesoscale dynamic characteristics of the torrential rain process in Urumqi and improve the levels of torrential rain monitoring, forecasting and early warning, this paper analyzed the wind profile features and related scientific problems of three typical torrential rain events seen in 2013–2015 in this region. The research results suggested that: (1) Radar wind profiler can record in detail the movement condition of the atmosphere during the process of torrential rains. Carrying out detailed analyses on the wind profile data is conductive to the improvement in monitoring, forecasting and warning to torrential rain event at a single observation station. (2) When Urumqi experiences heavy rain weather, noticeable wind shear is usually observed above the observation station. In the upper air, it is southwest wind, while in the lower air it is northwest wind, which is the typical wind profile pattern for heavy rain events in the Urumqi region. (3) Obvious northwest low-level jet stream is found to go together with precipitation, and the jet is positively correlated with precipitation intensity. The velocity of low-level jet stream greatly impacts the amount and intensity of precipitation. (4) The rainstorm weather phenomena are clearly presented by the time–height chart of radar reflectivity factors. The high reflectivity values correspond positively to the height range of cloud–rain particles as well as the duration and intensity of precipitation, so it can be used as a reference index of precipitation monitoring and early warning. In a word, this research deepens on the recognition to the micro-/mesoscale weather systems during the process of heavy rains in Urumqi. Moreover, it would contribute to the application improvement of wind profiler data in analyzing the heavy rainfalls in this region. 相似文献