Integrating radar stratigraphy with high resolution visible stratigraphy of the north polar layered deposits,Mars     

S. Christian  J.W. Holt  S. Byrne  K.E. Fishbaugh 《Icarus》2013

Shallow Radar (SHARAD) on board NASA’s Mars Reconnaissance Orbiter has successfully detected tens of reflectors in the subsurface of the north polar layered deposits (NPLD) of Mars. Radar reflections are hypothesized to originate from the same material interfaces that result in visible layering. As a first step towards verifying this assumption, this study uses signal analyses and geometric comparisons to quantitatively examine the relationship between reflectors and visible layers exposed in an NPLD outcrop. To understand subsurface structures and reflector geometry, reflector surfaces have been gridded in three dimensions, taking into account the influence of surface slopes to obtain accurate subsurface geometries. These geometries reveal reflector dips that are consistent with optical layer slopes. Distance–elevation profiling of subsurface reflectors and visible layer boundaries reveals that reflectors and layers demonstrate similar topography, verifying that reflectors represent paleosurfaces of the deposit. Statistical and frequency-domain analyses of the separation distances between successive layers and successive reflectors confirms the agreement of radar reflector spacing with characteristic spacing of certain visible layers. Direct elevation comparisons between individual reflectors and discrete optical layers, while necessary for a one-to-one correlation, are complicated by variations in subsurface structure that exist between the outcrop and the SHARAD observations, as inferred from subsurface mapping. Although these complications have prevented a unique correlation, a genetic link between radar reflectors and visible layers has been confirmed, validating the assumption that radar reflectors can be used as geometric proxies for visible stratigraphy. Furthermore, the techniques for conducting a stratigraphic integration have been generalized and improved so that the integration can be undertaken at additional locations.  相似文献   

A technique for calculating meteor plasma density and meteoroid mass from radar head echo scattering     

S. Close  M. Oppenheim  A. Coster 《Icarus》2004,168(1):43-52

Large-aperture radars detect the high-density plasma that forms in the vicinity of a meteoroid and moves approximately at its velocity; reflections from these plasmas are called head echoes. To determine the head plasma density and configuration, we model the interaction of a radar wave with the plasma without using assumptions about plasma density. This paper presents a scattering method that enables us to convert measurements of radar cross-section (RCS) from a head echo into plasma density by applying a spherical scattering model. We use three methods to validate our model. First, we compare the maximum plasma densities determined from the spherical solution using 30 head echoes detected simultaneously at VHF and UHF. Second, we use a head echo detected simultaneously at VHF, UHF and L-band to compare plasma densities at all frequencies. Finally, we apply our spherical solution to 723 VHF head echoes and calculate plasma density, line density and meteoroid mass in order to compare these values with those obtained from a meteoroid ablation and ionization model. In all three comparisons, our results show that the spherical solution produces consistent results across a wide frequency range and agrees well with the single-body ablation model.  相似文献   

流星雷达测距精度的改进     

Yang Kejun  Wang Yahong 《时间频率学报》1995,(1)

针对目前流星雷达测距误差大的问题，本文提出了提高流星雷达测距精度的新方法，即提高采样速率，用相关分析确定回波脉冲参考点的方法。该方法使流星雷达的测距精度提高一个数量级，测距误差降到±１４ｍ，使流星雷达不仅可以用来观测研究流星，还可用于监测飞机、火箭的飞行等，扩大流星雷达的应用。  相似文献   

用雷达回波资料识别雹云的最新进展     

李祚泳  刘少侬  邓新民  张辉军 《成都信息工程学院学报》1993,(1)

本文评述了当前国内外利用雷达回波资料识别雹云的现状,着重介绍了笔者近年来利用雷达回波资料建立雹云识别模式的研究工作,并展望了雹云识别的未来发展前景。  相似文献   

双极化天气雷达方程     

董豹  王贤勤 《成都信息工程学院学报》1996,(3)

在回转椭球状降水粒子的假设下求出了降水粒子的散射截面，并且考虑了粒子轴线铅垂和随机取向两种重要的典型情况；推导了双极化雷达的回波方程以及降雨量公式。该方程除包含降水粒子的信息外，关于雷达与降水粒子间的几何关系都以雷达天线仰角及雷达与降水粒子间的距离表示，同时还考虑了地球的球面效应和大气折射效应。由于采用了并矢方法，使推导简捷明了  相似文献   

江西强雷电天气形势场及雷达回波特征分析     

何文  夏文梅  马中元  钟思奕  段和平 《气象科学》2018,38(5):699-706

利用常规天气资料、地面观测资料、江西WebGIS雷达拼图和雷电监测资料,对2014—2016年江西出现的22次强雷电天气过程进行统计和对比分析。结果表明:江西强雷电天气易出现在赣北北部、南昌附近、上饶地区和吉安西部等区域;强雷电天气出现的环境背景场可分为副热带高压边缘型、副热带高压控制型、低涡切变型和台风外围型,最显著的特征是中高空经常伴有干冷舌侵入低层暖湿区;多项对流指数可以预测出现强雷电天气的可能性;雷达回波和雷电强度关系密切,回波类型以带状和块状为主;雷电强度和雷达回波强度有很好的对应关系,但产生强雷电的回波要具备强度大于50 dBz、强回波中心密实、强回波边缘梯度大等条件。  相似文献   

RPGCA程序的改进          下载免费PDF全文

田程 《中低纬山地气象》2018,42(6):74-77

RPGCA程序负责将CINRAD/CD型雷达的archive基数据标准化命名后压缩上传,此数据是新一代天气雷达站的业务考核内容,同时也是雷达拼图、GR2等短临预报软件的必要数据。但实际使用下来发现RPGCA程序有传输时效性不高,系统资源占用较大等弊端。因此,本站使用C#开发了RPGCA改进版,此改进版不仅具有RPGCA程序的所有功能,并且改进了原版的弊端,同时增加了一些实用功能,提高了数据上传的时效性和稳定性。  相似文献   

定量测量降水量的回波结构自适应算法研究          下载免费PDF全文

魏鸣  宋羽轩  张蕾 《大气科学学报》2018,41(5):676-683

为提高临近预报中对流性降水估测的准确性,分析了统计法估算降水的局限性。依据降水物理机制和降水回波结构,研究雷达反射率因子定量测量降水量(QPE-Qualitative Precipitation Estimate)的自适应算法,旨在减少由于雨滴谱变化导致的Z-I关系不稳定所引起的降水量测量误差。同时考虑组合反射率因子RC和垂直液态水含量VIL两个参量对降水的影响,建立适于城市区域的动态自适应的Z-I关系,改进对强降水严重低估的问题。  相似文献   

Where do planes fly past overhead? Determining departure and arrival routes from radar traces     

《Applied geography (Sevenoaks, England)》2017

This paper questions the main techniques of mapping in the context of aircraft noise in the vicinity of airports, and compares these techniques in terms of their purpose, benefits and limitations. Then the paper describes a method to summarise radar traces of a given air transport departure or arrival route into a median route and its envelope containing 80% of flights. This makes it possible to map global and easy-to-read maps of current air procedures around airports based on actual pathways flown by the aircraft. It also makes it possible to investigate the impact of change in aeronautical procedures on the actual geography of air routes around airports. Such maps complement noise contour maps and offer a good basis for debating aeronautical procedures at airports whose operations expose the population to noise.  相似文献   

EnSRF雷达资料同化对一次强对流天气模拟的影响研究   总被引：2，自引：2，他引：0  

黄丹莲  高士博  闵锦忠 《气象科学》2017,37(5):567-578

利用ARPS(Advanced Regional Prediction System)模式和具有流依赖背景误差协方差的集合均方根滤波(Ensemble Square Root Filter,简称En SRF)方法,通过同化多部多普勒雷达资料,对2013年6月23日的强对流天气过程进行了研究。首先对比同化试验和观测的组合反射率因子,检验了同化效果。通过计算均方根误差和离散度,进一步定量评估了同化结果。再对比模式变量,综合分析了En SRF雷达资料同化对模式热力、动力、湿度和微物理量等变量的影响。最后对集合平均场进行1 km的高分辨率数值模拟。结果表明:En SRF能够同化出与观测类似的对流系统,且减弱了南北部的虚假回波。径向风和反射率因子的均方根误差明显减少。En SRF雷达同化能够明显优化模式的初始场,同化试验的回波在垂直方向上范围增加,强度偏弱。在强对流区域,低层的冷池温度最多降低6 K,相对湿度最多增加30%。对流区域的雨水、冰晶和雪的混合比均有明显增加。模拟发现同化试验能够较好地模拟出对流系统的结构和位置。  相似文献