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1.
天气雷达的发展大致经历了4个阶段，其主要用于监测强对流天气、定量估计降水，是气象部门的重要探测和监测手段之一。新一代天气雷达观测的实时回波强度（Z）、径向风速（V）、速度谱宽（W）的回波图像中，提供了丰富的有关强对流天气的信息，综合使用Z、V、W的图像分析，有利于较准确和及时地监测灾害性天气。云南滑坡泥石流灾害高发区与云南暴雨中心有很好的对应关系，云南滑坡泥石流灾害空间分布与暴雨空间分布的空间相关系数为0．19，通过了0．05的显著性水平检验，也进一步说明云南暴雨在滑坡泥石流灾害发生中起着重要作用。以2004年7月5日德宏州特大山洪泥石流灾害为例子，探讨了新一代天气雷达在泥石流灾害的临阵预警中的应用。 相似文献
2.
利用石河子C波段Doppler雷达资料,对2008年8月26日下午至傍晚发生在天山北坡带中部石河子垦区全区性的一次强对流天气过程进行分析,结果表明:引起这次全区性的强对流天气风暴具有超级单体风暴的特征.这个超级单体南边出现明显的出流边界,并位于弧形回波带的南部.组合反射率因子垂直剖面图上呈现出有界弱回波区、回波悬垂和有界弱回波区左侧的回波墙,最大回波强度出现在沿着回波墙的一个竖直的狭长区域,其值达到65 dBZ、位于回波墙中上部.在中低层径向速度图上,弧形回波带的北部出现辐合区,其东南部呈现出一个中尺度气旋,旋转速度达到20 m/s,风暴顶为强烈辐散,正负速度差值达52m/s,其中3 000～6 000 m之间表现最为典型;与中气旋对应的回波强度和回波顶高以及垂直液态含水量都在暴雨中心附近达到最大.50dBz的回波顶高达9.8 km、宽度约10 km,60 dBz的回波顶高达到8.7 km、宽度约7 km,65 dBz的回波顶高达到8.0 km、宽度约2 km,垂直液态含水量从16:16的8 kg/m跃增到17:34的70 kg/m,该超级单体的移动方向在盛行风向的右侧约30°,属于右移风暴. 相似文献
3.
Haibo Hu 《International journal of geographical information science》2014,28(9):1765-1780
An algorithm was developed for converting radar data from matrix format into polygons that can be easily visualized, processed, and analyzed using Geographic Information Systems. Spatial operators can be used to overlap radar polygons with land surface features represented by points, lines, and polygons to meet the demands of severe weather identification and tracking and risk recognition. Application and testing of the algorithm demonstrate that the converted radar polygons are suitable for use in weather modification, risk assessments of flash floods in urban areas, and the identification of lightning activity for lightning risk recognition, all of which are essential in real-time severe weather monitoring and warning. 相似文献
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5.
边界层风廓线雷达资料在沙尘天气分析中的应用 总被引：2，自引：2，他引：0
为利用风廓线雷达（WPR）开展沙尘天气研究,分析了2010年4月19—20日塔克拉玛干沙漠腹地WPR探测沙尘天气个例。研究表明,WPR可以在沙尘天气工作,其探测资料能及时反映中小尺度三维流场特征,通过WPR提供的水平风场、信噪比（SNR）、垂直速度、大气温度等资料,可从多角度了解沙尘天气过程。在此次过程中,信噪比出现了比较清晰的大值层,SNR大值层所处高度初步认为是沙尘被输送的高度,SNR大值出现和结束的时间既对应着沙尘天气的开始和结束时间。低空风场出现切变的时刻,正好对应扬沙天气的开始,低空风向转为东风和东南风的时刻正是强沙尘暴开始的时间,低空东风的维持是此次沙尘天气发生的动力条件。此外,RASS系统能监测到沙尘天气过程前后低空大气温度的变化状况。 相似文献
6.
David R. Legates 《The Professional geographer》2000,52(2):235-246
One of the main concerns with precipitation measurements is that gage networks are almost always too sparse to provide an adequate spatial coverage of storm‐scale precipitation. Gage measurements are representative only at the measurement site and are biased underestimates of the actual precipitation, mainly as a result of the effect of wind on the gage. Consequently, storm‐scale, real‐time assessments using only gage‐measured precipitation are frequently inadequate. With the advent of the WSR‐88D (formerly NEXRAD) weather radars, precipitation estimates at higher spatial resolutions (4 km by 4 km) are now available in real time. These radars use the reflectivity of S‐band (10 cm) microwaves to provide an estimate of precipitation. Unfortunately, reflectivity is a function of the surface area of the raindrops and not their volume. As a result of this and other sources of error, radar precipitation estimates using fixed reflectivity‐to‐rainfall relationships are subject to substantial biases. To provide better high‐resolution precipitation estimates, a gage‐radar precipitation compositing procedure has been developed to enhance real‐time precipitation assessments. Radar estimates provide the spatial ‘footprint’ of the storm while gage data are used to enhance accuracy. This procedure calibrates each radar separately (since biases usually vary by radar), provides a composite mosaic of multiple radars for regions that lie under more than one radar umbrella, and determines an estimate of the uncertainty of the calibration. 相似文献
7.
应用新一代天气雷达数据资料,结合飞机定位播撒,在目标云体上截取一个作业区,同时在作业区两侧设立2个对比区,计算3个区域的雷达强度数值。随着雷达观测的继续,可以得到3条雷达强度随时间变化的曲线。对比分析3条曲线的变化趋势,初步得出：飞行播撒催化剂后,作业区、扩散区较上风方的自然区,雷达回波强度值有明显增强趋势。本文应用2007年12月26日的新一代天气雷达回波数据、雷达站上游气象探空以及人工增雪飞机播撒催化剂的航迹等资料,针对新疆冬季层状云的早期催化效果评估,作者设计了新的检验模式,进行了定量化计算。具体方法为：（1）在雷达的平显气象回波（PPI）上,截取一段飞机播撒催化剂航迹;（2）设定宽10 km的带状航迹为“播撒区”,代表播撒状态下云的演变;上风方宽10 km的区域为“对比区A”,代表自然状态下云的演变;下风方宽10 km的区域为“对比区B”,代表扩散状态下云的演变;（3）分别计算3个区域的雷达回波强度（dbz）总值。随着雷达观测的继续,可以得到雷达回波强度（dbz）随时间变化的3条曲线;（4）对比分析3条曲线的变化趋势,初步得出结论：人工增雪飞机进行播撒催化剂后,作业区及“对比区B”的回波强度总值,比“对比区A”的回波强度总值,有明显地增强趋势。 相似文献
8.
EnviSat ASAR数据在水情监测中的应用 总被引：6，自引：0，他引：6
在微波遥感领域,星载雷达是目前获取地球信息最主要的技术手段之一,而欧空局EnviSat卫星上搭载的先进合成孔径雷达ASAR是目前功能最为强大的星载雷达系统。以ASAR作为数据源,通过分析入射角、极化方式等因素对水体后向散射特性的影响,提出遥感水情监测中对ASAR数据产品的选取原则。根据水体在雷达图像数据中具有较低值的特点,使用阈值法识别水体。结果表明,使用H/H极化或V/H极化方式的数据都可以比较准确地提取水体信息。 相似文献
9.
利用加密自动站、卫星云图及雷达图像等资料,对2010年6月7日白天到夜间宁夏中北部地区出现的短时暴雨天气成因及中尺度系统演变进行分析。结果表明,此次短时暴雨是在“东高西低”稳定的环流形势和锋面过境背景下,500 hPa西风槽,700 hPa切变线、低涡、低空急流,850 hPa切变线,地面冷锋等主要影响系统相互配合、共同作用下发生的;大降水落区位于低空急流左侧与切变线尾部的辐合区,这可作为宁夏中尺度暴雨天气系统的一种典型特征;逆风区的出现和S型风场、锋面过境雷达图像特征是此次强降水典型的雷达回波特征,逆风区分布与中尺度系统走向基本一致。 相似文献
10.
利用MICAPS系统提供的大量天气实况和有关物理量格点资料,多普勒雷达回波,分析了2004年5月15日富宁特大洪灾的物理成因,揭示了其产生的环流场特征。 相似文献
11.
Michael Demuth & Alain Pietroniro 《Geografiska Annaler: Series A, Physical Geography》1999,81(4):521-540
The capability of RADARSAT synthetic aperture radar (SAR) for the purpose of snow-line/accumulation area mapping for a temperate alpine glacier is examined. In agreement with other orbital C-band SAR studies, RADARSAT can discriminate between firn and bare ice facies. Limited observations are reported with respect to the electromagnetic variability of the ice facies in the ablation area, but they are inconclusive. Operational considerations are discussed with respect to reconciling the uncertainties of late-summer weather and their possible impact on the dielectric and scattering properties of the glacier surface. Vagaries associated with other glacier settings, mass balance states and their associated facies configurations are discussed including the difficulty of using the transient snow-line to define the equilibrium line and the lower extent of the accumulation area for glaciers where superimposed ice may form.
The radar remote-sensing reconnaissance of equilibrium line altitude (ELA) and accumulation area ratio (AAR) for estimating glacier mass balance requires serious consideration in those instances where traditional ground measurements used in the direct glaciological method are absent. However, with respect to the ELA, such estimates can vary depending on the accuracy of the reference digital elevation information. Moreover, for many glacier configurations, where mass balance variations due to altitude are influenced or in some cases completely masked by local balance variations, defining the ELA may be an irreconcilable problem. Using the AAR may be more robust in this regard. It is further determined that the total error inherent in the reconnaissance method would have serious implications for the confident estimation of mass balance normals and climate-related trends if the method were to be utilized over the longer term. 相似文献
The radar remote-sensing reconnaissance of equilibrium line altitude (ELA) and accumulation area ratio (AAR) for estimating glacier mass balance requires serious consideration in those instances where traditional ground measurements used in the direct glaciological method are absent. However, with respect to the ELA, such estimates can vary depending on the accuracy of the reference digital elevation information. Moreover, for many glacier configurations, where mass balance variations due to altitude are influenced or in some cases completely masked by local balance variations, defining the ELA may be an irreconcilable problem. Using the AAR may be more robust in this regard. It is further determined that the total error inherent in the reconnaissance method would have serious implications for the confident estimation of mass balance normals and climate-related trends if the method were to be utilized over the longer term. 相似文献
12.
利用2019年冬季吐鲁番和2020年冬季若羌共14次完整机载探测气溶胶资料,结合宏观天气资料及大气污染数据,研究飞机爬升或降落阶段两地上空气溶胶粒子数浓度、粒子平均粒径的垂直变化规律,分析不同高度的粒子谱分布特征。结果表明：（1） 两地冬季气溶胶粒子数浓度及粒子直径存在明显差异。在无明显天气过程下,若羌气溶胶粒子数浓度均值（5354·cm-3）明显高于吐鲁番（3948·cm-3）;粒子平均粒径来看,均值差异不大,但吐鲁番出现大直径粒子（0.16 ）数量高于若羌（0.13 ）。2019年12月15日大风后最为明显,粒子直径最大值达到0.21 ,这与沙尘气溶胶多有关联。从垂直变化情况来看,两地气溶胶粒子数浓度均随高度增加而升高,若羌各层普遍高于吐鲁番,但吐鲁番近地面粒子直径随高度增加有明显下降,若羌整层变化很小。（2） 吐鲁番、若羌气溶胶粒子数浓度和粒子平均粒径受大风、降水等天气过程以及逆温层的影响十分明显。两地高层均主要为输入型气溶胶,低层差异主要是由于吐鲁番地区人为源气溶胶粒子的排放导致的大气环境污染。（3） 吐鲁番、若羌两地粒子谱分布在0.10~3.00 范围内变化趋势大体一致,主要以小粒径为主,谱分布受天气过程影响变化较为明显。（4） 从三模态粒径相似度对比可以得出,无论是吐鲁番还是若羌,在第一模态中数谱分布差异不大,若羌平均相似度为50.330%,略高于吐鲁番46.770%。有明显天气过程时,吐鲁番气溶胶数谱在二、三模态相似度（小于0.020%）急剧下降,而若羌第二模态相似度仍满足置信度95%,但第三模态中变化凸显,相似度不足0.020%。 相似文献
13.
利用地面激光雨滴谱仪捕捉2017年7月14日夜间发生在六盘山区的一次强对流天气降雹过程，其降雨和降雹微物理特征表明：降雹时，粒子各项微物理特征量明显增大，其中数浓度和平均动能通量增幅最为明显，分别增长了6.3倍和13倍。降雹初期，粒径较大的冰雹粒子增长较快，随着能量的释放，对流减弱，粒径较小的冰雹粒子增加较快。Gamma型分布更适合拟合降雹前后的粒子谱。用粒子下落末速度公式V=aDb拟合此次降雹过程中的粒子速度效果很好，相关系数超过0.98，a的变化范围在4.55～5.02之间，b[WTBZ]的变化范围在0.53～0.59之间。 相似文献
14.
利用文山新一代天气雷达回波资料及PUP提供的雷达产品对2008年4月12日下午发生在文山州东北部的强对流降雹过程进行分析。结果表明：此次强对流风暴表现为一带状单体强降雹回波分裂为2条EN-W S向带状强对流回波带。在两条带状回波沿雷达径向的伸展方向又有多个强对流回波单体的生成发展。在强对流发展旺盛阶段一直有风向辐合和逆风区伴随。最大回波强度达61.2 dB z,≥50 dB z的强回波高度,最高≥10 km,回波垂直伸展高度大于13 km,最高≥16 km。在强对流风暴发展旺盛阶段,相应的垂直液态水含量和密度分别超过50kg/m2和10 kg/m2,最大达55 kg/m2。强降雹过程具有非常典型的冰雹云回波特征：＂V＂型缺口、回波悬垂结构、回波墙及有界弱回波区非常明显。 相似文献
15.
Stefan Maus Chris M. Green & J. Derek Fairhead 《Geophysical Journal International》1998,134(1):243-253
The ocean geoid can be inferred from the topography of the mean sea surface. Satellite altimeters transmit radar pulses and determine the return traveltime to measure sea-surface height. The ERS-1 altimeter stacks 51 consecutive radar reflections on board the satellite to a single waveform. Tracking the time shift of the waveform gives an estimate of the distance to the sea surface. We retrack the ERS-1 radar traveltimes using a model that is focused on the leading edge of the waveforms. While earlier methods regarded adjacent waveforms as independent statistical events, we invert a whole sequence of waveforms simultaneously for a spline geoid solution. Smoothness is controlled by spectral constraints on the spline coefficients. Our geoid solutions have an average spectral density equal to the expected power spectrum of the true geoid. The coherence of repeat track solutions indicates a spatial resolution of 31 km, as compared to 41 km resolution for the ERS-1 Ocean Product. While the resolution of the latter deteriorates to 47 km for wave heights above 2 m, our geoid solution maintains its resolution of 31 km for rough sea. Retracking altimeter waveform data and constraining the solution by a spectral model leads to a realistic geoid solution with significantly improved along-track resolution. 相似文献
16.
This study integrates past research methodologies, data from the National Lightning Detection Network (NLDN), and geographic information system techniques to assess the lightning and severe weather hazard relationship for the 27–28 April 2011 United States tornado outbreak. NLDN and Doppler radar data are used to examine the cloud-to-ground (CG) lightning characteristics associated with seven supercell thunderstorms that produced long-track, significant and/or violent tornadoes. Analyses indicate that CG lightning flashes alone do not provide enough information for the detection of a lightning jump prior to tornadogenesis. All seven supercells were dominated by negative-polarity CG lightning flashes; which is expected due to the geographic location and elevated low-level moisture found in the outbreak environment. The correlation between low-level mesocyclone strength and total CG lightning flash rate was varied and inconsistent among all storms despite their formation and sustenance in similar environmental and geographic space. Additional case studies, as well as climatological approaches, are required to discover if the varying lightning–tornado relationships found in this study are consistent with other tornadic environments. 相似文献
17.
Richard J. Pike 《The Professional geographer》1987,39(2):131-145
Extraterrestrial geography has become a reality, as we move from Earth's moon to the planets. A broad-scale regional physiography is being established on twenty planets and satellites through remote sensing techniques. Spacecraft images yield most of the information on Solar System landscapes. Topographic measurements are extracted by monoscopic image-processing, stereophotogrammetry, and radar analysis. Invisible parts of the spectrum furnish non-topographic data. 相似文献
18.
Motorists are vulnerable to extreme weather events, which are likely to be exacerbated by climate change throughout the world. Traffic accidents are conceptualized in this article as the result of a systemic failure that includes human, vehicular, and environmental factors. The snowstorm and concurrent accidents that occurred in the Northeastern United States on 26 January 2011 are used as a case study. Traffic accident data for Fairfax County, Virginia, are supplemented with Doppler radar and additional weather data to characterize the spatiotemporal patterns of the accidents resulting from this major snowstorm event. A kernel density smoothing method is implemented to identify and predict patterns of accident locations within this urban area over time. The predictive capability of this model increases over time with increasing accidents. Models such as these can be used by emergency responders to identify, plan for, and mitigate areas that are more susceptible to increased risk resulting from extreme weather events. 相似文献
19.
M. Amin 《Geophysical Journal International》1982,68(1):57-78
Summary. Long-period tidal records from eight ports on the west coast of Great Britain are analysed, using both the harmonic method and the response function. Time series up to 9.5 yr were used so that fine structure of certain regions of high energy in the tidal residual spectrum may be examined. This also assisted in accurate separation of tides from surges. According to the currently accepted formulation of M1 , its composition is not compatible with its actual composition in the real tide and, as such, has no useful purpose to serve in computation of predictions. Constituents Sa, Ssa, MA, and MB, are adversly affected by weather and long records are essential for their accurate separation. It has been observed that annual perturbations of S2 , similar to those confirmed in recent years for M2 , also exist but these are not readily recognisable because their speeds are the same as those of constituents T2 and R2 . These perturbations, being highly sensitive to meteorological forces, are mainly responsible for cusps or humps in the vicinity of major tidal constituents in tidal residual spectra. The relationship of radiational and gravitational tides is found to be in very good agreement with theoretical results. In summer months non-predictable variance reduces to about half of the annual variance, reflecting the regional weather conditions of summer and winter. 相似文献
20.
利用NCEP再分析资料和新一代天气雷达资料对干旱区一次持续阴雪天气的分析研究 总被引：2，自引：1，他引：1
利用NCEP再分析资料和银川新一代天气雷达资料,对2008年元月中下旬宁夏持续阴雪极端天气进行了环流背景及雷达回波特征分析。分析表明:欧洲阻高的建立与崩溃、里海到巴湖切断低压的维持加深与减弱、东亚大槽的稳定维持、副高的偏北偏强及高原东侧西南气流的存在,为宁夏持续阴雪天气提供了有利的环流背景及较好的水汽条件,低层辐合、高层辐散为降雪天气提供了持续的上升运动,而低层高原低值系统的作用,是造成局地大降雪的主要原因。降雪雷达回波强度一般维持在10～25 dBz,超过30 dBz的回波面积小,回波顶比较平整,顶高普遍在4.0～6.0 km,最高达到7.0 km左右,零速度线有时可表现为明显的 “S”型结构;利用Z-I关系进行雷达定量降水估测对降雪有一定的反演能力。 相似文献