Mass Balance Estimation of Dokriani Glacier in Central Indian Himalaya Using Remote Sensing Data

Dokriani Glacier is regarded as one of the important glaciers of Bhagirathi River basin, which fed river Ganges. The length of the glacier is about 4.6 km, and snout elevation is about 4028 m m.s.l. The mass balance of this glacier was calculated using field-based measurements for few years during 1994 to 2000. However, due to remote and poor accessibility, the field-based measurements could not continue; thus, remote sensing-based methods become useful tool to estimate the long-term mass balance of the glacier. In this study, glacier mass balance has been determined using accumulation area ratio (AAR) method. Remote sensing data sets, e.g. Landsat TM, ETM?+?and OLI, have been used to estimate AAR for different years from 1994 to 2014. An attempt has also been made to develop a mathematical relationship between remote sensing-derived AAR and field-observed mass balance data of the glacier. Further, this relationship has been used to estimate mass balance of the glacier for different years using remote sensing-derived AAR. Estimated mass balance was validated from ground-observed mass balance for few years. The field-observed and remote sensing-derived mass balance data are compared and showed high correlation. It has been observed that AAR for the Dokriani Glacier varies from 0.64 to 0.71. Mass balance of the glacier was observed between ??15.54 cm and ??50.95 cm during the study period. The study highlights the application of remote sensing in mass balance study of the glaciers and impact of climate change in glaciers of Central Indian Himalaya.     

基于卫星高度计的冰川物质平衡测量

2003~2009年全球冰川物质平衡量大约为-259 Gt·a~(-1)±28 Gt·a~(-1),冰川高程变化和物质平衡研究一直是冰川研究的重要方面。简要介绍了目前主要用于冰川高程变化研究的卫星高度计数据和冰川高程变化和物质平衡研究的主要方法。不同学者对全球各个主要冰川的物质平衡计算结果显示,全球冰川基本上都是负的物质平衡。随着卫星遥感技术的不断发展,卫星高度计将获得精度更高的全球高程数据,为冰川高程变化和物质平衡提供更多的数据支持。     

Glacier changes using satellite data and effect of climate in Tirungkhad basin located in western Himalaya

Glaciers are widely recognized as key indicators of climate change, and melt water obtained from them is an important source of fresh water and for hydropower generation. Regular monitoring of a large number of Himalayan glaciers is important for improving our knowledge of glacier response to climate change. In the present study, Survey of India topographical maps (1966) and Landsat datasets as ETM+ (2000, 2006) and TM (2011) have been used to study glacier fluctuations in Tirungkhad basin. A deglaciation of 26.1% (29.1?km²) in terms of area from 1966 to 2011 was observed. Lower altitude small glaciers (area?<?1?km²) lost more ice (34%), while glaciers with an area <10?km² lost less (20%). The percentage of change in glacier length was 26% (31.9?km) from 1966 to 2011. The south-facing glaciers showed high percentages of loss. From 2000 to 2011, debris cover has increased by 1.34%. The analysis of the trend in meteorological data collected from Kalpa and Purbani stations was carried out by Mann Kendall non-parametric method. During the last two decades, the mean annual temperature (T_max and T_min) has increased significantly, accompanied with a fall in snow water equivalent (SWE) and rainfall. The increasing trend in temperature and decreasing trend in SWE were significant at 95% confidence level. This observation shows that the warming of the climate is probably one of the major reasons for the glacier change in the basin.     

基于CryoSat-2数据的纳木那尼冰川冰面高程变化方法研究

随着全球气候变暖,中亚地区大部分冰川逐渐变薄。高海拔山地冰川的变化会影响到周边地区的水资源和海平面变化,因此,我们需要高精度的地表高程观测数据来监测冰面高程变化。本文以喜马拉雅山脉西段的纳木那尼冰川为例,基于CryoSat-2卫星雷达高度计SARIn模式数据,修改了伪重复轨平面拟合方法,并计算了从2010年8月至2016年7月的冰面高程变化。纳木那尼冰面平均高程变化率为-0.47±0.44 m/year,整体呈现变薄趋势,与前人文献的结果基本一致,表明CryoSat-2数据在山地冰川使用伪重复轨平面方法估算高程变化有效可行。     

Variation of Snowline and Mass Balance of Glaciers of Warwan and Bhut Basins of Western Himalaya Using Remote Sensing Technique

Glaciers are natural reservoirs of fresh water in frozen state and sensitive indicators of climate change. Among all the mountainous glaciated regions, glaciers of Himalayas form one of the largest concentrations of ice outside the Polar Regions. Almost all the major rivers of northern India originate from these glaciers and sustain perennial flow. Therefore, in view of the importance and role of the glaciers in sustaining the life on the Earth, monitoring the health of glaciers is necessary. Glacier??s health is monitored in two ways (i) by mapping the change in extent of glaciers (ii) by finding variation in the annual mass balance. This paper has been discussed the later approach for monitoring the health of glaciers of Warwan and Bhut basins. Mass balance of glaciers of these two basins was determined based on the extraction of snow line at the end of ablation season. A series of satellite images of AWiFS sensor were analysed for extraction of snowline on the glaciers for the period of 2005, 2006 and 2007. The snow line at the end of ablation season is used to compute accumulation area ratio (AAR = Accumulation area/Glacier area) for each glacier of basins. An approach based on relationship of AAR to specific mass balance (computed in field) for glaciers of Basapa basin was employed in the present study. Mean of specific mass balance of individual glacier for the year 2005, 2006 and 2007 of Warwan basin was found to be ?ve 0.19?m, ?ve 0.27?m and ?ve 0.2?m respectively. It is 0.05?m, ?ve 0.11?m and ?ve 0.19?m for Bhut basin. The analysis suggests a loss of 4.3 and 0.83?km3 of glacier in the monitoring period of 3?years for Warwan and Bhut basins respectively. The overall results suggest that the glaciers of Warwan basin and Bhut basins have suffered more loss of ice than gain in the monitoring period of 3?years.     

气象卫星多通道信息监测沙尘暴的研究

介绍了利用气象卫星多通道信息监测沙尘暴的原理和方法，并利用此技术方法对2000年3－4月北方沙尘暴过程进行了监测，分析了影响北京地区沙尘暴过程的沙源和可能路径，取得了较好结果。     

FY-2C积雪判识方法研究

介绍了利用FY-2C资料进行积雪判识的原理,在阈值法基础上的辅助因子函数积雪判识方法以及相应的FY-2C积雪判识结果精度验证分析等。一般较为常用的卫星遥感积雪判识方法为简单阈值法,由于其带有一定的随机性,很难客观反映下垫面条件差异对阈值选取的影响。以阈值法为基础,将所使用的主要变量以函数形式表达,以海拔高度、地理位置、季节、土地覆盖类型等作为阈值函数的变量,通过大量采样建立起多种阈值函数,从而实现随时空特点变化的阈值实时计算。该方法用于FY-2C积雪判识,较好地解决了FY-2C全圆盘范围内广大区域不同下垫面类型下的实时积雪监测。通过与NOAA-17人机交互积雪判识结果对比分析,该方法的积雪判识精度可达85%左右。     

Diffusion Source Detection of Volcanic Ash Cloud Using MODIS Satellite Data

The massive volcanic ash cloud not only causes obvious global climate and environmental changes, but also threatens aviation safety under the background of globalization. The diffusion source detection is a key factor in the volcanic ash cloud monitoring and the diffusion research. Taking the Eyjafjallajokull’s volcanic ash cloud on April 19, 2010 in Iceland as an example, based on the analysis of the absorption spectrum characteristics in the thermal infrared spectral range, in this paper, a new diffusion source detection algorithm of volcanic ash cloud combining split window algorithm with SO₂ concentration distribution is proposed from the moderate resolution imaging spectroradiometer (MODIS) satellite remote sensing images; subsequently the ash radiance index (ARI) and absorbing aerosol index (AAI) are applied as contrast to the detection results. The results show that the proposed algorithm can effectively detect the diffusion source of volcanic ash cloud, and has high consistency with the ARI and AAI distributions, and has certain potential applications in improving the detection effect of volcanic ash cloud and prediction accuracy of diffusion model.     

联合卫星测高、GRACE、海洋和气象资料研究南海海水质量变化

首先利用重力恢复与气候实验（gravity recovery and climate experiment,GRACE）卫星重力、卫星测高和海洋温盐数据分析了2003-2012年间南海海水质量的变化特征,进而结合海洋和气象资料探讨了厄尔尼诺和南方涛动（El Ni?o-Southern Oscillation,ENSO）、净淡水通量、海水体积输送和陆地径流在此期间对南中国海海水质量变化的影响。研究结果表明,南海海水质量变化主要受海面净淡水通量和海水体积输送的联合调制影响,周边陆地径流对其影响有限。南海海水质量季节性变化显著,且具有明显的长期增加趋势;ENSO通过改变降水和黑潮自吕宋海峡流入南海的水量影响南海海水质量,使得南海海水质量存在着显著的具有ENSO特征的年际变化。     

中国气象参数建模与仿真在卫星导航中的应用

为了模拟出不同时刻覆盖我国内陆区域的气象数据,基于网格法建立了气象数据模型,并在网格点上分别建立了静态的均值模型和动态的日变化函数模型;从多角度对仿真得到的气象参数与实测数据进行了比较分析,说明了模型的精度情况及其适用范围和适用条件。仿真结果表明,利用该模型模拟的我国绝大部分区域的气象数据接近于实测值,即使是在模型精度相对较低的西藏地区,也可以进一步提高对流层延迟改正计算的精度。因此可为对流层延迟改正模型提供更好地气象数据支持,并最终为提高我国新一代卫星导航精度的应用研究服务。     

中国气象参数建模与仿真在卫星导航中的应用

为了模拟出不同时刻覆盖我国内陆区域的气象数据,基于网格法建立了气象数据模型,并在网格点上分别建立了静态的均值模型和动态的日变化函数模型;从多角度对仿真得到的气象参数与实测数据进行了比较分析,说明了模型的精度情况及其适用范围和适用条件.仿真结果表明,利用该模型模拟的我国绝大部分区域的气象数据接近于实测值,即使是在模型精度...     

基于GPS的气象卫星数据地理定位精度验证

以天津渤海湾围海造田形成的规则人工基础设施为参照物,对长时间序列的FY-3B星250 m空间分辨率数据的几何定位精度误差进行量化,并在此基础上对几何定位精度进行了分析。研究发现,FY-3B星中分辨率卫星数据的几何定位精度存在较大误差,尚未完全达到1个像元或亚像元级的精度水平。纬度方向误差明显大于经度方向误差,纬度方向的几何定位误差整体在-2～-9个像元,经度方向误差基本处于±3个像元的水平。经度方向误差随时间序列的增加,呈偏西向偏东的发展趋势;纬度方向的几何定位整体偏北,且有向北扩大的趋势。在天顶角小于30°的范围内,经度方向误差并不随天顶角的增加而变化,而纬度方向误差随天顶角增加而缩小,且变化幅度在扩大。研究结果有助于改善FY-3B星中分辨率卫星数据的几何定位精度以及研究目前几何定位模型存在的问题。     

Urban Slum Detection Approaches from High-Resolution Satellite Data Using Statistical and Spectral Based Approaches

This paper proposes a new technique to detect the urban slums from urban buildings using very high resolution data. Many cities in the Global South are facing the development and growth of highly dynamic slum areas, but often lack detailed spatial information. Unlike buildings, vegetation and other features, urban slums lack in their unique spectral signatures. Thus, accurate detection of slums using remote sensing data poses real challenge to researchers and decision-makers. In this work, gray-level co-occurrence matrix, Tamura-based statistical feature extraction and wavelet frame transform-based spectral feature extraction techniques are proposed for detecting the urban slums from urban buildings. The very high resolution data of Madurai city, South India, acquired by Worldview-2 sensor (1.84 m) proved the ability of the proposed approaches to identify urban slums from urban buildings. Experimental results demonstrate that the proposed wavelet frame transform-based approach can generate higher classification accuracy than other approaches.     

应用FY－1B气象卫星监测1991年江淮洪水的研究

本文研究了ＦＹ－１ＢＶＨＲＳＲ的三个可见光通道和一个近红外通道监测１９９１年夏天中国江淮地区洪水的能力。分析该区域不同水体的各个通道的光谱状况表明，ＶＨＲＳＲ第二通道区别水、陆（植被）边界十分显著，ＶＨＲＳＲ第一通道有感应洪水泥沙含量信息的能力，ＶＨＲＳＲ的第三、四通道（海洋通道）则可以获得水深信息。文中针对ＦＹ－１Ｂ的波段的特点设计了几种信息增强方法，从而有效地识别出水陆边界，计算了洪水深度及洪水浑浊度的相对等级，精确地统计出洪水的面积。结果表明ＦＹ－１Ｂ在洪水监测中大有潜力。     

Estimation of Snow Cover Area,Snow Physical Properties and Glacier Classification in Parts of Western Himalayas Using C-Band SAR Data

Snow physical properties, snow cover and glacier facies are important parameters which are used to quantify snowpack characteristics, glacier mass balance and seasonal snow and glacier melt. This study has been done using C-band synthetic aperture radar (SAR) data of Indian radar imaging satellite, radar imaging satellite-1 (RISAT)-1, to estimate the seasonal snow cover and retrieve snow physical properties (snow wetness and snow density), and glacier radar zones or facies classification in parts of North West Himalaya (NWH), India. Additional SAR data used are of Radarsat-2 (RS-2) satellite, which was used for glacier facies classification of Smudra Tapu glacier in Himachal Pradesh. RISAT-1 based snow cover area (SCA) mapping, snow wetness and snow density retrieval and glacier facies classification have been done for the first time in NWH region. SAR-based inversion models were used for finding out wet and dry snow dielectric constant, dry and wet SCA, snow wetness and snow density. RISAT-1 medium resolution scan-SAR mode (MRS) in HV polarization was used for first time in NWH for deriving time series of SCA maps in Beas and Bhagirathi river basins for years 2013–2014. The SAR-based inversion models were implemented separately for RISAT-1 quad pol. FRS2, for wet snow and dry snow permittivity retrieval. Masks for layover and shadow were considered in estimating final snow parameters. The overall accuracy in terms of R² value comes out to be 0.74 for snow wetness and 0.72 for snow density based on the limited ground truth data for subset area of Manali sub-basin of Beas River up to Manali for winter of 2014. Accuracy for SCA was estimated to be 95 % when compared with optical remote sensing based SCA maps with error of ±10 %. The time series data of RISAT-1 MRS and hybrid data in RH/RV mode based decompositions were also used for glacier radar zones classification for Gangotri and Samudra Tapu glaciers. The various glaciers radar zones or facies such as debris covered glacier ice, clean or bare glacier ice radar zone, percolation/refreeze radar zone and wet snow, ice wall etc., were identified. The accuracy of classified maps was estimated using ground truth data collected during 2013 and 2014 glacier field work to Samudra Tapu and Gangotri glaciers and overall accuracy was found to be in range of 82–90 %. This information of various glacier radar zones can be utilized in marking firn line of glaciers, which can be helpful for glacier mass balance studies.     

卫星重力梯度测量数据的粗差探测

分别讨论了阈值法、Dixon检验法和小波算法应用于卫星重力梯度数据粗差探测的效果。为了克服这3种单一粗差探测方法的不足,提出了卫星重力梯度数据的粗差探测组合方案,即联合Dixon检验和小波算法,以及联合Dixon检验、阈值法和小波算法的组合方案。模拟结果表明,两种组合方案均能有效改善粗差探测的效果。     

Glacier surface characteristics derivation and monitoring using Hyperspectral datasets: a case study of Gepang Gath glacier,Western Himalaya

Mountain Glaciers are natural resources of fresh water and these affect the stream flow of the rivers, regional climate and further global climate. Observed trends and projected future evolutions of climate and Cryospheric variables clearly suggest a need to monitor these changes. Accordingly, the article presents the glacier features mapping using Hyperspectral remote sensing imagery. A freely available Hyperion satellite imagery acquired over Gepang Gath glacier in Himachal Pradesh, India is used for the study. Each class is identified based on their surface characteristics of spectral reflectance properties. Identification is simplified by demarcating the study glacier into accumulation and ablation areas through snowline. Accumulation area is characterized with high reflectance clean snow/ice and reduced moderate reflectance Snow/firn. The identification of classes in Hyperion imagery is validated using the spectral library from USGS and ASTER, and field spectra obtained from literature.     

基于BJ -1小卫星遥感数据的矿区土地覆盖变化检测

为了评价利用北京一号小卫星(BJ-I)遥感数据监测煤矿区土地利用/地表覆盖变化的效果,针对其数据特点,选择基于图像信息运算和图像信息变换的直接变化检洲法以及分类后比较法,对徐州东矿区2007～2008年土地利用/地表覆盖变化情况进行检测,以对比、评价各种方法在土地利用/地表覆盖变化检测中的应用效果和BJ -1数据的适用...     

Evidence for Mountain Glacier Changes in Semi-arid Environments based on Remote Sensing Data

Countries like Iran, which are geographically situated in a rather arid and warm regions, will suffer more from global warming than countries located in humid and semi-humid regions. In such environments, analyzing the variations of mountain glaciers can reveal several aspects of climate change patterns more efficiently in comparison to the other geo-indicators. The present study reports some evidence of changes for Alamkouh glacier between 1955 and 2010 based on several mediums to high-resolution satellite images. Considering that most part of the Alamkouh glacier is covered by debris and delineating its actual area is not possible, planimetric change analysis was restricted to the clean-ice regions. The object-oriented classification approach was used to estimate the clean ice areas. This technique takes into account the shapes of the features along with their spectral patterns. Results revealed that clean ice regions of Alamkouh glacier shrank since 1955 with an overall area reduction of about 59 %. Although the general observed trend is a clean ice area reduction, some advancement was detected over the period from 2000 to 2010. During 1992–2000, the maximum reduction in the clean ice area was observed (0.08 km².a^?1). However, clean ice area of the case study has partially increased about 0.028 km².a^?1 from 2000 to 2010. Supra-glacial lake change analysis illustrated that at the surface of the glacier, lakes have been enlarged remarkably in the past 55 years (about 4.75 times greater). In addition, clean ice area and the surface area of supra-glacial lakes oscillated in compliance with each other. The findings revealed that the maximum expansion of supra-glacial lake occurred during 1992–2000, which demonstrate the glacier maximum reduction during this period. This shrinkage in the Alamkouh glacier caused an extensive glacial lake outburst flood in Jun 2011. The results of this study agree with documented changes in other mountain glaciers located in arid and semi-arid environments and they also confirm the application of mountain glaciers in climate variations monitoring over such regions.