RADARSAT影像在土地利用动态监测中的应用

为了改变以往土地管理部门对土地管理的传统方式,节省在常规管理中耗费的大量人力和物力,遥感技术作为新兴发展的科学技术,已应用于动态监测土地利用的变化。本文将具体论述如何利用微波遥感技术监测土地利用的动态变化。     

SAR interferometric coherence analysis for snow cover mapping in the western Himalayan region

Abstract

Information of snow cover (SC) over Himalayan regions is very important for regional climatological and hydrological studies. Precise monitoring of SC in the Himalayan region is essential for water supply to hydropower stations, irrigation requirements, and flood forecasting. Microwave remote sensing has all weather, day and night earth observation capability unlike optical remote sensing. In this study, spaceborne synthetic aperture radar interferometric (InSAR) coherence analysis is used to monitor SC over Himalayan rugged terrain. The feasibility of monitoring SC using synthetic aperture radar (SAR) interferometry depends on the ability to maintain coherence over InSAR pair acquisition time interval. ERS-1/2 InSAR coherence and ENVISAT ASAR InSAR coherence images are analyzed for SC mapping. Data sets of winter and of snow free months of the Himalayan region are taken for interferogram generation. Coherence images of the available data sets show maximum decorrelation in most of the area which indicates massive snowfall in the region in the winter season and melting in the summer. Area showing coherence loss due to decorrelation is mapped as a snow-covered area. The result is validated with field observations of snow depth and it is found that standing snow is inversely related to coherence in the Himalayan region.     

Polarimetric synthetic aperture radar change detection for specific land cover types

This paper presents a supervised polarimetric synthetic aperture radar (PolSAR) change detection method applied to specific land cover types. For each pixel of a PolSAR image, its target scattering vector can be modeled as having a complex multivariate normal distribution. Based on this assumption, the joint distribution of two corresponding vectors in a pair of PolSAR images is derived. Then, a generalized likelihood ratio test statistic for the equality of two likelihood functions of such joint distribution is considered and a maximum likelihood distance measure for specific land cover types is presented. Subsequently, the Kittler and Illingworth minimum error threshold segmentation method is applied to extract the specific changed areas. Experiments on two repeat-pass Radarsat-2 fully polarimetric images of Suzhou, China, demonstrate that the proposed change detection method gives a good performance in determining the specific changed areas in PolSAR images, especially the areas that have changed to water.     

超声激励低渗煤层甲烷增透机理

超声激励增透煤层是一种不受甲烷储层地质条件和气源特性限制,具有普遍应用价值的增采技术.但由于煤岩致密、裂隙发育,煤岩孔隙度存在多尺度效应,受储层介质尺度效应影响的增透促吸机理尚不明确.本文通过CT观测实验和渗透率测定实验,对超声波作用下煤样不同尺度裂隙发展规律进行了分析,对比测定超声作用煤样渗透率变化规律,建立了超声增透煤层甲烷渗透率的修正公式.研究结果表明:CT观测实验很好地证明了超声的机械震碎作用;在声场衰减范围内,煤体损伤和机械震碎作用明显;超声波作用后的煤层渗透率有平均135%～169%的提高.研究工作为超声激励增加煤层的渗透率提供了实验基础.     

Spatiotemporal Variations of Microwave Land Surface Emissivity (MLSE) over China Derived from Four-Year Recalibrated Fengyun 3B MWRI Data

Microwave Land Surface Emissivity (MLSE) over China under both clear and cloudy sky conditions was retrieved using measurements of recalibrated microwave brightness temperatures (Tbs) from Fengyun-3B Microwave Radiation Imager (FY-3B MWRI), combined with cloud properties derived from Himawari-8 Advanced Himawari Imager (AHI) observations. The contributions from cloud particles and atmospheric gases to the upwelling Tbs at the top of atmosphere were calculated and removed in radiative transfer. The MLSEs at horizontal polarizations at 10.65, 18.7, and 36.5 GHz during 7 July 2015 to 30 June 2019 over China showed high values in the southeast vegetated area and low values in the northwest barren, or sparsely vegetated, area. The maximum values were found in the belt area of the Qinling-Taihang Mountains and the eastern edge of the Qinghai-Tibet Plateau, which is highly consistent with MLSEs derived from AMSR-E. It demonstrates that the measurements of FY-3B MWRI Tbs, including its calibration and validation, are reliable, and the retrieval algorithm developed in this study works well. Seasonal variations of MLSE in China are mainly driven by the combined effects of vegetation, rainfall, and snow cover. In tropical and southern forest regions, the seasonal variation of MLSE is small due to the enhancement from vegetation and the suppression from rainfall. In the boreal area, snow causes a significant decrease of MLSE at 36.5 GHz in winter. Meanwhile, the MLSE at lower frequencies experiences less suppression. In the desert region in Xinjiang, increases of MLSEs at all frequencies are observed with increasing snow cover.     

氯化钯作基体改进剂石墨炉原子吸收光谱法测定土壤中的铍

铍是一种对人体有害的金属元素,土壤中铍的测定目前尚无国家标准方法.本文采用盐酸-硝酸-氢氟酸体系微波消解、石墨炉原子吸收光谱法测定土壤样品中的铍,实验了钯、硝酸铝、硝酸镁、钙盐的增敏效果.结果表明,以氯化钯为基体改进剂,灰化温度和原子化温度分别提高到1100℃和2650℃,原子化峰形尖锐,背景吸收很小,提高了测定灵敏度;其他三种基体改进剂虽然也能提高测定灵敏度,但背景吸收较大.采用优化的实验条件,Fe、Mg、K、Na、Ca、Ti、Cu、Ba、Mn、Zn、Pb、Sr等共存元素对测定不产生干扰.铍的浓度在0 ～4.00 μg/L范围内线性良好,方法检出限为0.01 μg/g,精密度(RSD,n=6)为3.5％ ～6.7％,实际土壤样品的加标回收率为84.0％ ～ 113.0％,土壤国家标准物质的测定值在标准值的误差范围内.本法与萃取光度法、电感耦合等离子体发射光谱/质谱法相比,操作简便,分析成本较低.     

全反射X射线荧光光谱法同时测定复混肥料中钒铬锰铁镍铜锌铅

样品经硝酸微波消解,以镓为内标,采用全反射X射线荧光光谱法(TXRF)同时测定复混肥料中的钒、铬、锰、铁、镍、铜、锌、铅,方法检出限从铅的1.0μg/g到钒的7.0μg/g,精密度(RSD)铬为2.5%,铅为16%,除铅以外,其余元素的RSD均小于10%;方法回收率为80%～120%,Pb的回收率略低主要是由于化肥中As Kα谱线对Pb Lα谱线的干扰导致测定结果偏低。用TXRF和电感耦合等离子体发射光谱法(ICP-AES)测定不同复混肥料中各元素的含量,经统计检验,两种方法测定结果在95%置信区间内无显著性差异。对于金属元素含量较高的样品,TXRF法测定结果的相对标准偏差小于ICP-AES法。对于不同的复混肥料,在微量、痕量元素检测范围内,TXRF法具有较高的准确度和适用性,仪器使用和维护成本低,方法快速准确。     

积水沉陷区水体的表观光学特性参数测量与分析

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.     

电线积冰物理过程与数值模拟研究进展

电线积冰对人们的日常生活、电力系统、通信系统等造成了巨大的影响,人们越来越关注电线积冰的形成条件及物理过程,包括气象条件、气流动力学、液滴运动轨迹以及热力学过程。通过外场观测、室内实验和数值模拟研究的不断开展,揭示出电线积冰质量增长过程决定于云降水粒子谱分布、碰撞效率、黏性率、冻结率、碰撞速度和角度等微物理参数,这些参数又受控于降水率、云雾含水量、温度、湿度、风向、风速等宏观气象条件。通过数值模式已可进行电线积冰量和积冰持续时间的定量研究和预测,进而在开发垂冰模式和形态模式等方面也取得了新的进展。在总结过去60多年来电线积冰物理机制和数值模拟研究主要成果的基础上,对开展进一步的深入研究进行了展望。     

利用MSU序列研究高空大气温度变化的进展

美国NOAA卫星上搭载的微波大气探测仪MSU以及后续继承改进仪器AMSU,自1978年投入运行以来,已经积累了超过30年的全球大气温度的观测资料。近年来,国外学者通过仪器定标误差订正、卫星轨道衰减订正、观测时间差异导致的温度日变化订正、仪器间的相互定标处理等技术,发现并剔除了一些影响较大的非气候因素,提高了该序列资料的质量,并用于全球气候变化研究,特别是对流层和平流层近30年的温度变化研究,研究结果是对常规地面和探空资料分析结果的重要补充。本文对目前国际上3种常用的MSU序列资料集的定标误差、偏差订正和不同卫星上仪器观测序列的一致化处理方法进行了综合介绍,并比较分析了3种资料用于30年高空大气温度变化趋势分析的异同。