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.     

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.     

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.     

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。     

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.     

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。     

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.     

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...     

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.     

利用IRS-P6卫星数据制作遥感影像地图

本文介绍了以IRS-P6卫星数据作为信息源完成大兴安岭林区的遥感影像地图制作的方法, 通过试验初步认识到:利用IRS-P6卫星数据制作遥感影像地图,可以满足1:50000、 1:25000比例尺的平面制图精度要求,在一些专业和专题应用中可以放大到1:15000比例尺使用。     

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.     

LRI与KBR数据检核GRACE-FO卫星精密轨道

GRACE-FO卫星定轨精度直接影响其反演地球重力场,评估检核轨道数据精度是保证重力场反演效果的重要步骤.自该卫星升空以来,已在轨观测近2年6个月,尚未见对各时期卫星轨道的检核分析.针对以上情况,提出了利用LRI与KBR数据检核GRACE-FO卫星精密轨道的方法,引入了基于信噪比确定权重系数的星间距离组合观测量作为参考...     

Water Balance Study for a Basin Integrating Remote Sensing Data and GIS

Water balance of a basin involves estimation of input precipitation, runoff, infiltration and evapotranspiration (ET). Although ET may have large variations over a big basin, it is commonly estimated using a few point measurements and this makes the estimation error prone. Satellite based remote sensing data provides few parameters for estimation of energy fluxes, at the land surface and atmosphere interaction in a distributed manner using the meteorological parameters. These parameters through surface energy balance equation have been used for the estimation of ET in this study. Various spatially distributed variables required for ET estimation; viz. NDVI, surface albedo, surface temperature etc. have been derived using remote sensing and ancillary data for Tapi basin located in western India. Beside this field data such as rainfall, air temperature, relative humidity, sunshine hours etc. have been used. For computation of runoff, Soil Conservation Services (SCS) approach has been considered. Tapi basin up to Ukai dam has been selected as the study area. Satellite data from National Oceanic and Atmospheric Administration (NOAA), Polar Orbiting Environmental Satellite, which carries the Advanced Very High Resolution Radiometer (AVHRR), have been used for preparation of various maps required for runoff and ET analysis. The results of runoff and ET have been compared with observed data for 2 years, 2002–2003 and the results have been found in good agreement with observed data.     

利用多光谱影像检测资源三号卫星平台震颤

卫星平台震颤是影响高分辨率卫星成像质量的因素之一,会引起影像模糊和内部畸变。本文从资源三号卫星多光谱相机的成像特点和多光谱影像配准误差影响因素入手,理论推导和仿真分析了卫星平台震颤对配准误差的影响规律,在此基础上提出了基于多光谱影像高精度密集匹配的平台震颤检测方法和流程,最后利用不同波段、不同时间的成像数据进行试验。试验结果表明资源三号卫星在试验数据成像阶段存在约0.6Hz的平台震颤,且垂轨方向震颤幅值大于沿轨方向,同时引起波段间相同频率周期性配准误差。检测结果为进一步提高资源三号处理精度提供了可能,也为卫星平台震颤源的分析和优化卫星平台设计提供了重要参考依据。     

Impact of Topography on Accuracy of Land Cover Spectral Change Vector Analysis Using AWiFS in Western Himalaya

The present paper discusses the impact of topography on accuracy for land cover classification and “from-to class change using improved spectral change vector analysis suggested by Chen et al. (2003). Two AWiFS sensor images of different dates are used. Double Window Flexible Pace Search (DFPS) is used to estimate threshold of change magnitude for change/no change classes. The topographic corrections show accuracy of 90% (Kappa coefficient 0.7811) for change/no change area as compared to 82% (Kappa coefficient 0.6512) in uncorrected satellite data. Direction cosines of change vector for determining change direction in n-dimensional spectral space is used for image classification with a minimum distance categorizing technique. The results of change detection are compared (i) Improved CVA with conventional two bands CVA and (ii) Improved CVA before and after topographic corrections. The improved CVA with topographic correction consideration using slope match show maximum accuracy of 90% (Kappa coefficient 0.83) as compared to conventional CVA which show maximum accuracy of 82% (Kappa coefficient 0.6624). The overall accuracy of ”from- to class using improved CVA increases from 86% (Kappa coefficient 0.7817) to 90% (Kappa coefficient 0.83) after topographic corrections. The improved CVA with proper topographic corrections is found to be effective for change detection analysis in the rugged Western Himalayan terrain.     

An Assessment of Snow Avalanche Paths and Forest Dynamics Using Ikonos Satellite Data

Abstract

Ikonos panchromatic and multispectral satellite data were acquired in October 2000 and August 2002 for a test area along US Highway 2, the southern border of Glacier National Park (GNP), Montana, USA. The research goals were to map snow avalanche paths and to characterize vegetation patterns in selected paths for longitudinal (i.e., source, track, and runout) and transverse (i.e., inner, flanking, outer) zones as part of a study of forest dynamics and nutrient flux from paths into terrestrial and aquatic systems. In some valleys, as much as 50 percent of the area may be covered by snow avalanche paths, and as such, serve as an important carbon source servicing terrestrial and aquatic ecosystems. Snow avalanches move woody debris down‐slope by snapping, tipping, trimming, and excavating branches, limbs, and trees, and by injuring and scaring trees that remain in‐place. Further, snow avalanches alter the vegetation structure on paths through secondary plant succession of disturbed areas. Contrast and edge enhancements, Normalized Difference Vegetation Index (NDVI), and the Tasseled Cap greenness and wetness transformations were used to examine vegetation patterns in selected paths that were affected by high magnitude snow avalanches during the winter of 2001-2002. Using image transects organized in longitudinal patterns in paths and in forests, and transects arranged in transverse patterns across the sampled paths, the Tasseled Cap transforms (and NDVI values) were plotted and assessed. Preliminary results suggest that NDVI patterns are different for paths and forests, and Tasseled Cap greenness and wetness patterns are different for longitudinal and transverse zones that describe the morphology of snow avalanche paths. The differentiation of paths from the background forest and the characterization of paths by morphometric zones through remote sensing has implications for mapping forest disturbances and dynamics over time and for large geographic areas and for modeling nutrient flux in terrestrial and aquatic systems.