无人机机载LiDAR在沿海滩涂大比例尺地形测绘中的应用     

郭春海  张英明  丁忠明 《测绘通报》2019,(9):155-158

以南京市以下长江12.5 m深水航道建设工程中的白茆沙整治建筑物工程的年度监测为例，介绍了利用无人机航摄和机载LiDAR技术进行大比例尺高精度的滩涂地理信息数据采集的关键技术。研究案例表明，采用无人机搭载数码相机和LiDAR联合进行数据采集，在小区域、通行困难地区的高分辨率影像和地面高程数据快速获取方面具有明显优势，为沿海滩涂开发中的工程用图测绘工作提供了一种新的有效快捷的技术手段。  相似文献   

利用GPS-R遥感技术反演植被生物量   总被引：5，自引：3，他引：2  

周晓敏  郑南山  祁云  陈顺 《测绘通报》2018,(1):129-132,137

为了验证利用GPS-R遥感技术反演植被生物量的可行性,分析了GPS反射信号反演植被生物量的原理与方法,通过试验利用干涉复合场数据（ICF）计算出信号反射率,利用已有文献拟合出的信号反射率与植被生物量之间的关系求出生物量,并与遥感技术结果进行了对比。试验结果表明：利用GPS-R遥感技术反演植被生物量是可行的,但是精度还需依靠时间反演模型;GNSS-R反演植被生物量对分析调查区域植被生长和碳排放情况具有重要意义。  相似文献   

非均匀各向异性储层地震AVAZ响应模拟及分析     

韩旭  郭智奇  徐聪  刘财  刘喜武  刘宇巍 《世界地质》2018,37(2):608-619

基于波动理论的各向异性反射率方法能够充分考虑地震波动力学特征。对单界面理论模型、实际非均匀各向异性模型分别进行正演模拟及分析,比较Ruger理论与反射率方法模拟结果的波动力学特征。结果表明,对于界面模型两种方法均能得到相同的计算结果,但对于实际非均匀各向异性介质,基于Ruger理论的算法受时间采样率的影响,而基于波动理论的反射率方法输入实际空间域模型,计算结果不受时间采样率的限制。  相似文献   

Twenty-five years of spectral UV-B measurements over Canada,Europe and Japan: Trends and effects from changes in ozone,aerosols, clouds,and surface reflectivity     

《Comptes Rendus Geoscience》2018,350(7):393-402

Spectral UV records of solar irradiance at stations over Europe, Canada, and Japan were used to study long-term trends at 307.5 nm for a 25-year period, from 1992 to 2016. Ground-based measurements of total ozone, as well as satellite measurements of the Aerosol Index, the Total Cloud Cover and the surface reflectivity were also used in order to attribute the estimated changes of the UV to the corresponding changes of these factors. The present study shows that over the Northern Hemisphere, the long-term changes in UV-B radiation reaching the Earth's surface vary significantly over different locations, and that the main drivers of these variations are changes in aerosols and total ozone. At high latitudes, part of the observed changes may also be attributed to changes in the surface reflectivity. Over Japan, the UV-B irradiance at 307.5 nm has increased significantly by ∼3%/decade during the past 25 years, possibly due to the corresponding significant decrease of its absorption by aerosols. It was found that the greatest part of this increase took place before the mid-2000s. The only European station, over which UV radiation increases significantly, is that of Thessaloniki, Greece. Analysis of the clear-sky irradiance for the particular station shows increasing irradiance at 307.5 nm by ∼3.5%/decade during the entire period of study, with an increasing rate of change during the last decade, possibly again due to the decreasing absorption by aerosols.  相似文献   

Satellite Observations of Reflectivity Maxima above the Freezing Level Induced by Terrain     

Aoqi ZHANG  Weibiao LI  Shumin CHEN  Yilun CHEN  Yunfei FU 《大气科学进展》2021,38(4):627-640

Previous studies have recognized reflectivity maxima above the freezing level(RMAF) within stratiform precipitation over mountain slopes, however, quantitative studies are limited due to the lack of adequate identification criteria. Here, we establish an identification method for RMAF precipitation and apply it to the Tropical Rainfall Measuring Mission(TRMM) Precipitation Radar(PR) observations. Using the TRMM 2A25 product from 1998 to 2013, we show that the RMAF structure in reflectivity profiles can be effectively identified. RMAF exists not only in stratiform precipitation but also in convective precipitation. RMAF frequency is positively correlated with elevation, which is thought to be caused by enhanced updrafts in the middle layers of stratiform precipitation, or in the low to middle layers of convective precipitation over mountains. The average RMAF heights in stratiform and convective precipitation were 1.35 and 2.01 km above the freezing level, respectively, which is lower than previous results. In addition, our results indicate that the RMAF structure increased the echo top height and enhanced precipitation processes above the RMAF height, but it suppressed the downward propagation of ice particles and the near-surface rain rate. Future studies of orographic precipitation should take into account the impact of the RMAF structure and its relevant dynamic triggers.  相似文献   

94/220 GHz星载雷达双波长比对非球形冰晶云参数敏感性分析          下载免费PDF全文

吴举秀  窦芳丽  安大伟  顾瑜  周青  刘伟 《气象学报》2019,77(3):529-540

利用不同形状冰晶的散射特性,获得了非球形冰晶云的94/220 GHz测云雷达双波长比,探讨了非球形冰晶云的双波长比与云内微物理参数的关系,分析了衰减前后的星载雷达反射率因子及双波长比的垂直廓线。结果表明:（1）双波长比可以反映小到0.1 mm中值尺度的冰粒子,对粒子总数、谱的形状参数不敏感,对粒子大小、形状、云衰减较敏感。（2）雷达灵敏度一定时,星载雷达可测云厚与雷达波长、冰含水量（IWC）的垂直分布、云厚及衰减有关;没有进行衰减订正时,双波长比和衰减有关,冰含水量越大,波长越短,衰减越大,双波长比最大值与可探测云厚有关。两部雷达可探测冰含水量为0.001—0.1 g/m3、厚2 km的冰云;当云厚5 km、冰含水量垂直分布在0.001—0.2 g/m3时,云厚的94%基本可以被220 GHz云雷达探测到。（3）如果两部雷达气象方程中用水的介电因子,测量回波强度应进行介电因子的订正后再计算双波长比。   相似文献   

X波段一维扫描有源相控阵天气雷达测试定标方法          下载免费PDF全文

刘黎平  吴翀  汪旭东  葛润生 《应用气象学报》2015,26(2):129-140

该文根据有源相控阵天气雷达的体制特点,参考多普勒天气雷达测试定标方法,提出了一维扫描有源相控阵天气雷达的测试和定标方法,将测试重点放在天馈系统、T/R组件、脉冲压缩、动态范围的测试和定标上,以解决不同观测模式、不同波位的天线增益等参数变化引起的回波强度测量误差问题。测试结果表明:天馈系统在不同观测模式下的天线参数随仰角的变化情况、波束指向的准确度、T/R组件的动态范围等均符合设计要求,回波强度和径向速度定标精度较高。雷达经过测试和定标后,于2014年5—8月分别在安徽定远和四川甘孜进行外场试验,并与附近多普勒天气雷达 (SA) 和C波段双线偏振雷达观测数据进行对比,结果表明:回波强度误差在合理范围内,精细测量、警戒搜索、快速观测3种模式观测的强回波的水平和垂直位置、结构和系统误差均比较一致,数据可靠。  相似文献   

积水沉陷区水体的表观光学特性参数测量与分析     

朱继文  孟祥来  张贺 《地理空间信息》2011,9(3):6-8

通过实际测量试验区的积水沉陷区水深值,了解水体光学特性随水深不同而引起的衰减特征变化,建立水深与光谱特性响应间的关系表达式,确定获取水深信息的最佳波谱范围;揭示了叶绿素、悬浮物质、CDOM等水体组分与水体光谱特征变化的关系,探讨因水体各主要组分变化而引起的水体光谱吸收光谱、散射光谱的变化规律.  相似文献   

X波段双线偏振雷达冰雹识别初步研究   总被引：7，自引：0，他引：7  

苏德斌  马建立  张蔷  吕达仁 《气象》2011,37(10):1228-1232

利用北京市人工影响天气办公室X波段双线偏振雷达2009年4—10月观测的不同降雨类型的资料,统计出下雨天ZH—ZDR的分布特征,给出了ZH-ZDR分布的分段函数表达式,在此基础上定义了X波段双线偏振雷达冰雹识别参量HDR,HDR〉0表示有冰雹,HDR〈0表示无冰雹,并指出电磁波的衰减会影响H_DR识别冰雹的结果。根据实际降雹情况和识别效果对比,结果表明HDR大于零的区域与地面降雹情况基本对应一致。  相似文献   

Relationship between cloud characteristics and radar reflectivity based on aircraft and cloud radar co-observations     

宗蓉  刘黎平  银燕 《大气科学进展》2013,30(5):1275-1286

Cloud properties were investigated based on aircraft and cloud radar co-observation conducted at Yitong, Jilin, Northeast China. The aircraft provided in situ measurements of cloud droplet size distribution, while the millimeter-wavelength cloud radar vertically scanned the same cloud that the aircraft penetrated. The reflectivity factor calculated from aircraft measurements was compared in detail with simultaneous radar observations. The results showed that the two reflectivities were comparable in warm clouds, but in ice cloud there were more differences, which were probably associated with the occurrence of liquid water. The acceptable agreement between reflectivities obtained in water cloud confirmed that it is feasible to derive cloud properties by using aircraft data, and hence for cloud radar to remotely sense cloud properties. Based on the dataset collected in warm clouds, the threshold of reflectivity to diagnose drizzle and cloud particles was studied by analyses of the probability distribution function of reflectivity from cloud particles and drizzle drops. The relationship between reflectivity factor (Z) and cloud liquid water content (LWC) was also derived from data on both cloud particles and drizzle. In comparison with cloud droplets, the relationship for drizzle was blurred by many scatter points and thus was less evident. However, these scatters could be partly removed by filtering out the drop size distribution with a large ratio of reflectivity and large extinction coefficient but small effective radius. Empirical relationships of Z-LWC for both cloud particles and drizzle could then be derived.  相似文献