TRMM PR雷达与阜阳雷达降水资料的对比研究

选取了1998年与1999年HUBEX观测资料，将TRMM卫星上的星载降雨雷达PR与阜阳的713数字化天气雷达资料在以下3个方面做了比较：(1)强度场的分布；(2)平均反射率廓线；(3)灵敏度。分析、比较结果可知阜阳雷达在探测灵敏度和水平方向的分辨率要高于PR，但由于波束宽度、衰减和资料转化过程计算误差的原因，其远距离处的观测值与真实值有一定偏差。PR波长短，对衰减敏感，尤其是在垂直方向上经过强衰减后，订正值仍偏小。但由于探测方式的不同PR在水平方向上不存在衰减的问题，且其资料分布均匀，因此提出一种用PR     

TRMM PR雷达与阜阳雷达降水资料的对比研究

选取了1998年与1999年HUBEX观测资料，将TRMM卫星上的星载降雨雷达PR与阜阳的713数字化天气雷达资料在以下3个方面做了比较：(1)强度场的分布；(2)平均反射率廓线；(3)灵敏度。分析、比较结果可知阜阳雷达在探测灵敏度和水平方向的分辨率要高于PR，但由于波束宽度、衰减和资料转化过程计算误差的原因，其远距离处的观测值与真实值有一定偏差。PR波长短，对衰减敏感，尤其是在垂直方向上经过强衰减后，订正值仍偏小。但由于探测方式的不同PR在水平方向上不存在衰减的问题，且其资料分布均匀，因此提出一种用PR资料来订正地基雷达资料的方法用以提高地基雷达探测的精确度。     

广东肇庆地区SIR-C森林雷达后向散射特征分析

森林雷达后向散射特征的研究是森林微波遥感应用的重要前提。本文利用不连续树冠森林微波后向散射模型模拟了肇庆地区松树林的雷达后向散射特征,并与从ＳＩＲ－Ｃ图像提取的雷达后向散射特征进行对比,从而分析和探讨了该区松树的雷达后向散射机制。     

中分辨率机载海洋雷达高度计信号处理方法及其实现

该文简要地介绍了海洋雷达高度计的工作原理 ,分析了“全去斜坡”技术在高度计信号处理中的时域和频域的对应关系及其相关的控制技术。研制出了分裂门跟踪和全程搜索软件 ,该软件在飞行实验中获得了成功 ,在国内首次获得了海洋回波曲线。首次提出全程搜索的方法 ,在此基础上提出了“平滑归并”的方法进行数据复合处理 ,进而提高了系统的指标     

中分辨率机载海洋雷达高度计系统分析及接收系统的研制

本文简要介绍了海洋雷达高度计的工作原理，分析了定时抖动、时钟精度及回波中的固有噪声等因素对高度测量造成的影响，讨论了“全去斜坡”等接收系统的关键技术，研制出了中分辨率机载海洋雷达高度计接收系统，并且与发射系统联调取得了成功。系统分辨率达到了５ｎｓ的设计需求。     

海底入射角对多波束反向散射强度的影响及其改正

综合考虑测船姿态、声线弯曲和海底地形对入射角的影响,推导了计算多波束海底入射角的实用模型。根据Lambert法则,改正海底入射角对反向散射强度的影响。实例计算结果表明,所述模型能精确地计算波束在海底的入射角,有效地改正其对反向散射强度的影响。     

The Effect of the Bistatic Scattering Angle on the High-Frequency Radar Cross Sections of the Ocean Surface

High-frequency (HF) bistatic Doppler cross sections of the ocean surface are examined with respect to their dependency on the bistatic angle. Previously derived results which incorporate a pulsed dipole source and two orders of scatter are considered. It is trivially seen that the first-order result has a linear dependence on the cosine of the bistatic angle. The second-order echo accounts for a double scatter of incident radiation from first-order surface waves - the so-called electromagnetic term - and a single scatter from a second-order ocean wave. The latter, generally referred to as the second-order hydrodynamic term because it originates from coupling between first-order ocean waves, predominates the Doppler continuum in most regions of interest. The analysis presented here verifies that in addition to a cosine-dependent reduction in cross section magnitude with increasing bistatic angle, both components of the second-order scatter tend to zero under the condition of near-forward scatter for bistatic HF radar operation. Of course, this imposes practical limitations on the region over which a bistatically configured HF radar system may be used to remotely sense ocean surface parameters.     

Study on Regional Variations of Aerosol Loading Using Long Term Satellite Data Over Indian Region

Satellite-based measurements of aerosols are one of the most effective ways to understand the role of aerosols in climate in terms of spatial and temporal variability. In the present study, we attempted to analyse spatial and temporal variations of satellite derived aerosol optical depth (AOD) over Indian region using moderate resolution imaging spectrometer over a period of 2001–2011. Due to its vast spatial extent, Indian region and adjacent oceanic regions are divided into different zones for analysis. The land mass is sub divided into five different zones such as Indo Gangetic Plain (IGP), Indian mainland, North Eastern India (NE), South India-1 (SI-1), South India-2 (SI-2). Oceanic areas are divided into Arabian Sea and Bay of Bengal. Arabian Sea is further divided as three zones viz. Northern AS (NAS), Central AS (CAS) and Eastern AS (EAS) zones. Bay of Bengal is divided as North BoB (NBoB), West BoB (WBoB), Central BoB (CBoB), and East BoB (EBoB). The study revealed that among all the land regions, IGP showed the highest peak AOD value (0.52 ± 0.17) while SI-2 showed the lower values of AOD in all the months compared to all India average. The maximum AOD is observed during premonsoon season for all regions. During the winter, average AOD levels were substantially lower than the summer averages. Peak of aerosol loading (0.35 ± 0.159) is observed in March over NE region, whereas in all other regions, peak is observed during May. Frequency distribution of long term AOD (<0.2, 0.3–0.5, >0.5) shows a shift of frequency distribution of AOD from <0.3 to 0.3–0.5 during the study period in all regions except IGP. In IGP shift of frequency of AOD values occurs from 0.3–0.5 to >0.5. Oceanic areas also shows seasonal variation of AOD. Over Arabian Sea, high AOD values with greater variations were observed in summer monsoon season while in Bay of Bengal it is observed during winter monsoon. This is due to the high wind speed prevailing in Arabian Sea during monsoon season which results in production of more sea salt aerosol. Highest AOD values are observed over NAS during monsoon season and over NBOB during winter season. Lowest AOD values with its lower variations observed in both the central region of Arabian Sea and Bay of Bengal.     

Measurement of the Wind Vector Over Sea by an Airborne Radar Altimeter Using an Antenna Characterized by Different Beamwidth in the Vertical and Horizontal Planes

In this letter, a possibility of recovering the wind vector over sea using an airborne radar altimeter in a short-pulse scatterometer mode is discussed. The nadir-looking wide-beam antenna, with the modified beam shape forming an ellipse footprint, is assumed for the purpose of analysis. Simultaneous range Doppler discrimination techniques are also used and a measuring algorithm of the sea-surface wind speed and direction is proposed.     

联合卫星测高和海洋物理数据计算近海稳态海面地形的可行性分析

在系统论的指导下 ,以测量平差中一个浅显的例子作对比 ,巧妙地阐述了联合卫星测高和海洋物理数据计算近海稳态海面地形的可行性 ,进而将可行的计算方案归结为具有本质联系的三类。     

利用TOPEX/Poseidon和Jason-1高度计数据提取中国南海潮汐信息

基于TOPEX/Poseidon和Jason-1卫星高度计16 a原始轨道、6 a变轨轨道数据,利用同步观测期间测高数据计算中国南海海域的系统偏差,生成基于TOPEX/Poseidon高度计平均海面的统一潮高时间序列,按纬差0.1°间隔提取原始轨道2 184个正常点和变轨轨道1 626个正常点,分别对原始轨道、变轨轨道逐正常点进行调和分析及响应分析,各得到8个分潮（Q₁、O₁、P₁、K₁、N₂、M₂、S₂和K₂）调和常数。利用交叉点处升轨、降轨不符值评估潮汐参数的稳定性,结果表明,变轨轨道交叉点处误差相对较大,多分潮总体综合预报误差RSS值为7.28 cm。通过与全球海潮模型比较表明,该结果与海潮模型在中国南海开阔海域精度表现一致,在半封闭浅水海域差异较大;与验潮站结果进行比较发现,受中国南海复杂的潮波系统、与测高星下点距离等因素影响,中国南海北部海域RSS值较大,海潮模型结果在M₂分潮单分潮预报中误差RMS值较大,为13.64 cm,其余分潮均在10 cm内。     

基于雷达和高光谱数据的表层土壤水分反演研究

正土壤水分是地表能量平衡和水分循环的关键参数,区域尺度表层(0~5cm)土壤水分的获取也一直是定量遥感研究的重点和难点之一。本论文充分考虑了全极化雷达和高光谱数据的特点,开展综合利用全极化雷达和高光谱数据直接定量反演表层土壤水分的模型研究。主要研究内容如下:     

利用数据分解与合成法实现基于XML的空间数据转换

基于XML的互操作、开放式环境和空间数据传输格式,设计了WebGIS服务组件,首次提出利用数据分解与合成法实现基于XML的数据转换。实验结果表明,用户可以直接访问通过这种方法实现的基于XML的空间数据。     

应用NOAA/AVHRR数据测算局地水稻种植面积方法研究

本文采用在模糊监督分类中增加迭代过程的方法－－模糊监督分类一迭代法,在分解混合像元的基础上,利用ＡＶＨＲＲ数据求算水稻种植面积。根据稻田与旱地存在温度差异的特点,在分析ＡＶＨＲＲ数据统计特征的基础上,增加了第３和４两通道参加模糊监督分类,从而增加了分类橡元值矢量维数,增强了对水稻的鉴别能力。反采用的迭代法是收敛具有效的,经本方法输出的水稻种植面积百分含量图与实际水稻分布十分吻合,测算出的面积值与Ｔ     

狭长区域GNSS控制网数据处理方法研究

针对狭长区域GNSS控制网边长差异较大的问题,本文通过划分子网来降低数据处理的难度,从基线处理和网平差两个方面,分析了系统误差来源,研究了基准处理中卫星轨道误差、对流层误差以及网平差中位置、尺度、方位和时间演变基准误差的改正方法,形成了一套高精度数据处理方案。基于该方法,对三峡库区GPS滑坡监测网的实测数据进行了分析与处理,获得了高精度的处理结果,本研究对狭长区域GNSS控制网的建立具有借鉴意义和指导作用。     

Effect of Forest Fire on Snow Reflectance in Uttarakhand Region: An Analysis Using AWiFS and INSAT-3D Data

In the summer of 2016, fire broke out in the forests of Uttarakhand state. The effect of forest fire was thought to have severe impact on nearby glaciated region in terms of faster melting. It is understood that contamination and heat enhance the snowmelt, which reduces the reflectance in different part of EM spectrum. In order to assess the effect, AWiFS and IMAGER data from Resourcesat-1 and INSAT-3D, respectively, for the months of April and May of the years 2012, 2013, 2014 and 2016 were used to compare the reflectance of snow. It was observed that pre- and post-fire data of 2016 show drop in reflectance in comparison with earlier years. The change in reflectance for locations near to forest fire was significantly high in comparison with previous year images, whereas far-away locations did not show much change. This drastic drop may be attributed to deposition of black carbon on nearby locations in snow-covered area. AWS data of nearby Joshimath observatory were also analysed to avoid any anomalous change in temperature for the same duration.     

短期潮汐潮流数据的正交潮响应分析研究

论证并试验证明了正交潮响应分析对潮汐潮流数据的时间长度的要求,得出理论最短数据时间长度为2 d;但对于实测数据,要求在以全日潮为主的海区需7 d以上数据,在以半日潮为主的海区需10 d以上。对于一天到几天的数据,通过引入比例关系和改变模型中Δτ的取值,实现了对数据的建模分析。经对中国12个主要验潮站连续366 d数据的试验验证,短期与长期(1 a)数据分析结果相近,而与准调和分析相比较,正交潮响应分析具有较高的精度,且不存在良好天文观测日期的选择问题。     

利用等高线数据提取山脊(谷)线算法研究

在对现有的山脊线和山谷线自动提取算法进行分析比较的基础上,提出一种简单实用的自动提取山脊线和山谷线算法。实验结果表明,用本文方法所提取的山脊线和山谷线与实际地形相符合。     

本体论在城乡一体化土地调查数据组织中的应用研究

随着城乡一体化进程的深入,早期应用于土地调查、区别城市和农村地域所设计的两套系统已无法满足土地调查的需要。针对原有两套系统所出现的数据难以相互融合的问题,探讨了基于本体论来进行城乡一体化土地调查数据组织的思路,提出了本体论的几个概念与城乡一体化土地调查的对应关系,并讨论了如何建立本体以及利用本体的特点来解决土地调查数据的系统整合问题。