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季节性冻结与消融的湖冰是气候变化的重要指示器。本文以兴凯湖为例,基于1979年—2019年的被动微波遥感数据获取了兴凯湖的冻融日期,用2000年—2019年的中等分辨率成像光谱仪MODIS(Moderate-resolution Imaging Spectroradiometer)数据进行了验证,并用气候数据分析了湖冰物候变化的原因。结果表明被动微波与MODIS遥感数据在湖冰物候提取方面具有较好的一致性,也即MODIS的验证结果表明用低频被动微波亮度温度数据获取湖冰物候的方法是可行的,结果也是可靠的。平均而言,兴凯湖湖冰每年11-13左右开始冻结,11-23左右完全冻结,湖冰冻结持续时间9.80 d;次年04-23左右湖冰开始消融,04-30左右湖冰完全消融,消融持续时间8.03 d;湖冰完全封冻时间150.50 d,湖冰覆盖时间168.03 d。过去41 a,兴凯湖开始冻结日期没有明显变化,完全冻结日期平均推后了0.19 d/a,开始消融日期和完全消融日期分别提前了0.16 d/a和0.13 d/a,湖泊完全封冻时间和湖冰覆盖时间分别缩短了12.71 d和2.87 d。湖冰冻结日期推后与风速增大密切相关,消融日期提前和湖冰持续时间缩短与气温升高显著相关。 相似文献
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Alpine lakes on the Tibetan Plateau (TP) are key indicators of climate change and climate variability. The increasing availability of remote sensing techniques with appropriate spatiotemporal resolutions, broad coverage and low costs allows for effective monitoring lake changes on the TP and surroundings and understanding climate change impacts, particularly in remote and inaccessible areas where there are lack of in situ observations. This paper firstly introduces characteristics of Tibetan lakes, and outlines available satellite observation platforms and different remote sensing water-body extraction algorithms. Then, this paper reviews advances in applying remote sensing methods for various lake environment monitoring, including lake surface extent and water level, glacial lake and potential outburst floods, lake ice phenology, geological or geomorphologic evidences of lake basins, with a focus on the trends and magnitudes of lake area and water-level change and their spatially and temporally heterogeneous patterns. Finally we discuss current uncertainties or accuracy of detecting lake area and water-level changes from multi-source satellite data and on-going challenges in mapping characteristics of glacial lakes using remote sensing. Based on previous studies on the relationship between lake variation and climate change, it is inferred that the climate-driven mechanisms of lake variations on the TP still remain unclear and require further research. 相似文献
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准确提取湖泊围网区域的时空分布信息对湖泊的保护和可持续发展具有重要意义。本文以阳澄湖为研究区域,收集该地区1984年—2017年所有的Landsat 5和Landsat 8影像(共计396景),提出了结合光谱和纹理特征的围网提取新算法,同时利用时间序列滤波消除年际间因数据不一致造成的偏差。以高清影像人工解译作为参考,阳澄湖围网提取结果的生产者精度在72.57%—88.53%,用户者精度在79.79%—98.10%,围网面积变化与文献记录吻合。结果表明,阳澄湖围网经历了"无围网期"(1984年—1994年)、"快速增长期"(1994年—1998年)、"巅峰期"(1999年—2002年)、"快速下降期"(2003年—2006年)和"稳定期"(2007年—2017年)5个阶段,最高达到100 km2,目前稳定在30 km2;通过研究围网区植被指数发现,2002年之后围网区浮水植物的种植面积增大;通过对比水质数据发现,2002年至今持续15年的围网拆除并未使阳澄湖恢复到80年代无围网养殖时期的II类水,其水质依然处于Ⅲ—Ⅳ类。因此在湖泊养殖开发过程中,政府应该坚持可持续发展道路,在不破坏湖泊水质的基础上发展湖泊经济。 相似文献
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Parkachik Glacier is located in the Suru sub-basin of the Upper Indus River, Zanskar Himalaya. The Glacier has been analysed using Corona KH-4B (1971), Landsat-TM (1999), field survey (2015), Google EarthTM (2015) and ASTER GDEM (2015) for frontal recession and area changes. Overall, from 1971 to 2015, the Glacier has retreated by 127 ± 0.09 m i.e. (0.75 ± 0.07%) at a rate of 2.9 ± 0.004 ma?1 with a simultaneous decrease in area from 49.5 to 48.8 km2 i.e. 740 ± 0.7 m2 (1.5 ± 0.09%) at a rate of 74 ± 0.7 m2a?1. However, during recent decade (1999–2015), the rate of glacier recession of 3.9 ± 0.004 ma?1 with a corresponding area loss of 500 ± 0.74m2 (1 ± 0.1%) was higher than the retreat rate of 2.3 ± 0.001 ma?1 and an area loss of 240 ± 0.02m2 (0.48 ± 0.08%) during 1971–1999. In the field, the evidences of glacier recession are present in the form of separated dead ice blocks from the main Glacier, recessional dumps/moraines, active ice calving activity and a small proglacial pond/lake at the terminus/snout of the Glacier. However, the recession over the studied period has been very slow and is controlled by its topographic configuration, particularly the large altitudinal range (6030–3620 m), almost northerly aspect and steep slope (average ~ 30°). 相似文献
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The land use and land cover pattern of a region is a consequence of natural and socio-economic factors and their utilization by man in time and space. In this study, we hypothesized that land use and land cover change patterns in the Lake Chivero catchment, Zimbabwe, were related to its human population dynamics. Using nonparametric correlation coefficients (Spearman’s rho, ρ), we found that bareland, cropland and built-up land had positive relations with human population growth of ρ = 0.7, ρ = 0.9 and ρ = 1, respectively. Grassland/shrubland, water and forest, on the other hand, had a negative relationship with human population growth of ρ = ?0.9, ρ = ?0.7 and ρ = ?0.667, respectively. However, these relationships were only significant (p < 0.05) for cropland, grassland/shrubland and built-up land. Human population dynamics in the Lake Chivero catchment could be one of the major drivers of land use and land cover change in the catchment between 1986 and 2014. 相似文献
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The expected responses of ice sheets to climate warming are growth in the thickness of the inland ice areas and thinning near the margins. In recent decades, researchers have identified glacier acceleration along Antarctic ice sheet coastal margins. However, the study of ice sheet interiors where seasonal accumulation eventually balances ice wastage at the lower elevation is poorly understood. In this paper, the ice sheet elevation change around Dome A region is analyzed from 2002 to 2012 using two million elevation change measurements from EnviSat satellite radar altimeter data covering an area of about 7000 km2. A declining trend of 0.572 ± 1.31 mm/year which means that the Dome A region was in balance during the last decade can be captured. In addition, two obvious changes in accumulation which divide elevation change time series into three independent equilibration stages are also extracted. In order to explain this phenomenon, two speculations related to snowfall and firn compaction are proposed in this paper. 相似文献
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Evidence for Mountain Glacier Changes in Semi-arid Environments based on Remote Sensing Data 总被引：1，自引：0，他引：1
Neamat Karimi Manuchehr Farajzadeh Ali Moridnejad Soodabeh Namdari 《Journal of the Indian Society of Remote Sensing》2014,42(4):801-815
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. 相似文献
10.
Diego Gómez Pablo Salvador Julia Sanz Mikhail Urbazaev José Luis Casanova 《地理信息系统科学与遥感》2020,57(6):813-829
ABSTRACT The climate in southern Iceland has warmed over the last 70 years, resulting in accelerated glacier dynamics at the Solheimajoküll glacier. In this study, we compare glacier terminus locations from 1973 to 2018, to changes in climate across the study area, and we derive ice-surface velocities (2015–2018) from satellite remote-sensing imagery (Sentinel-1) using the offset-tracking method. There have been two regional temperature trends in the study period: cooling (1973–1979) and warming (1980–2018). Our results indicate a time lag of about 20 years between the onset of glacier retreat (?53 m/year since 2000) and the inception of the warming period. Seasonally, the velocity time series suggest acceleration during the summer melt season since 2016, whereas glacier velocities during accumulation months were constant. The highest velocities were observed at high elevations where the ice-surface slope is the steepest. We tested several scenarios to assess the hydrological time response to glacier accelerations, with the highest correlations being found between one and 30 days after the velocity estimates. Monthly correlation analyses indicated inter-annual and intra-annual variability in the glacier dynamics. Additionally, we investigate the linkage between glacier velocities and meltwater outflow parameters as they provide useful information about internal processes in the glacier. Velocity estimates positively correlate with water level and negatively correlate with water conductivity between April and August. There is also a disruption in the correlation trend between water conductivity and ice velocity in June, potentially due to a seasonal release of geothermal water. 相似文献
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Fayma Mushtaq 《国际地球制图》2017,32(10):1090-1104
The present investigation was conducted to analyse the trends in hydrometeorological data to addresses how these trends impacted on the water extent of Wular Lake, Kashmir. Temporal changes in the lake surface area have been analysed, using the Landsat satellite data. The nonparametric Mann–Kendall and Sen’s methods were used to determine trends in hydrometeorological data. In addition, trends in extreme indices of frost days (FD), summer days, days with rainfall > 10 mm (R10), days with rainfall > 20 mm (R20) and dry spell for temperature and precipitation were also analysed. The results suggest an overall decrease in extreme rainfall events, R10 and R20, and annual precipitation pattern with increase in maximum and minimum annual average temperatures. Furthermore, the analysis of extreme temperature events suggests warming trend with increased number of warm days and decreased number of FD. With regard to water extent of the lake, an intense decreasing trend was observed. 相似文献
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Arshad Amin Shahab Fazal Ahmad Mujtaba Sudhir Kumar Singh 《Journal of the Indian Society of Remote Sensing》2014,42(1):119-128
The present study focuses on the growing human needs which drive the native boatmen of the Kashmir valley (Hanjis) that bring the interchanges of land use/cover classes in Dal lake and its environs of Srinagar city. Further to assesses the effects of land transformation on lake water quality. The results suggested that the significant land use changes have been occurred during the past of 30 years (1981–2011). Besides this, interchange of land has taken place between different land uses classes, which has resulted into lake water pollution due the addition of various nutrients/pollutant discharged from Hanjis activities. The study concludes that the land transformation has converted the once fresh water lake much deteriorated pond. 相似文献
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《International Journal of Digital Earth》2013,6(6):534-549
The Qinghai-Tibetan Plateau plays an important role in global climate and environmental change and holds the largest lake area in China, with a total surface area of 36,900 km2. The expansion and shrinkage of these lakes are critical to the water cycle and ecological and environmental systems across the plateau. In this paper, surface areas of major lakes within the plateau were extracted based on a topographic map from 1970, and Landsat MSS, TM and ETM+ satellite images from the 1970s to 2008. Then, a multivariate correlation analysis was conducted to examine the relationship between the changes in lake surface areas and the changes in climatic variables including temperature, precipitation, evaporation, and sunshine duration. Initial results suggest that the variations in lake surface areas within the plateau are closely related to the warming, humidified climate transition in recent years such as the rise of air temperature and the increase in precipitation. In particular, the rising temperature accelerates melting of glaciers and perennial snow cover and triggers permafrost degradation, and leads to the expansion of most lakes across the plateau. In addition, different distributions and types of permafrost may cause different lake variations in the southern Tibetan Plateau. 相似文献
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B. P. Rathore S. K. Singh Purnesh Jani I. M. Bahuguna Rupal Brahmbhatt A. S. Rajawat S. S. Randhawa Anjana Vyas 《Journal of the Indian Society of Remote Sensing》2018,46(9):1497-1506
Monitoring of seasonal snow cover is important for many applications such as melt runoff estimation, climate change studies and strategic requirements. Contribution of seasonal snow melt runoff of Chenab River is significant and important to meet hydrological requirement at foothills. Seasonal snow cover of Chandra, Bhaga, Miyar, Bhut, Warwan and Ravi, six major tributaries of Chenab River, becomes crucial to assess the water availability. In addition, altitudinal distribution of snow cover significantly influences the melt runoff which is highly sensitive to minor variations in atmospheric temperature. In this investigation, remote sensing based Normalized Difference Snow Index technique has been used to generate 10 daily snow cover product. Snow cover monitoring of all the sub-basins were carried out for 10 years from 2004–2005 to 2013–2014 during hydrological year (October to June) using Advanced Wide Field Sensor (AWiFS) of Indian remote sensing satellite (IRS). Accumulation and ablation patterns of snow cover have also been analyzed for the six sub-basins. Accumulation and ablation pattern of snow cover, from 2004 to 2014 which shows slightly increasing trend for all the sub-basins. Meteorological data of Kelong at Bhaga sub-basin was also analysed. Average monthly snow line altitude was estimated for all the sub-basins using hypsographic curve. Chandra and Bhaga sub-basins are at higher altitude and Ravi sub-basin is at lower altitude. It was also observed that areal extent of snow reaches to lower altitude during last 5 years, particularly in Ravi sub-basin. 相似文献
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Jeffrey A. VanLooy 《国际地球制图》2013,28(3):167-181
Advanced space-borne thermal emission and reflection radiometer imagery and Digital Elevation Models were used to analyse surface elevation changes of six glaciers in Northern Labrador. Results indicate an average surface thinning of0.94 ± 0.49 m y?1 (water equivalent) between 2000 and 2009. Three glaciers had an average elevation change of ?1.16 ± 0.55 m y?1 (water equivalent) whichis three times the thinning rate found in a study from 1981 to 1983 ?0.36 ± 0.10 m y?1 water equivalent). Analysis of surface characteristics in relation to elevation changes shows expected results of rapid thinning in bare ice areas and near zero change in accumulation areas. Debris covered areas of three glaciers show expected results of moderate thinning, but three other glaciers indicate high rates of thinning. Variability in thinning rates suggests possible influences in the type ofdebris and/or variations in climate such as increased rainfall. 相似文献
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Kamleshan Pillay Naeem Hoosen Agjee Srinivasan Pillay 《Journal of the Indian Society of Remote Sensing》2014,42(1):51-60
Land is the basic resource that is needed by man in order to survive: It provides humans with living space, nutrition and energy resources. The rapid growth of the human population, climate change and pollution on a catastrophic scale has caused the quality of land resources to be compromised. Remote sensing is a useful tool in land cover change detection providing information to decision makers. The aim of this study was to evaluate land cover changes in the Mtunzini area in South Africa over the past 18 years; determine why changes have occurred and predict land cover patterns for future years. In this study a supervised classification was used to detect land cover classes of the Mtunzini area from 1992 to 2009 using four Landsat images in the time series analysis. The supervised classification had an accuracy of 80.80 % which was used to model land cover changes. Commercial sugar cane and forest plantation classes increased throughout the time series. It was estimated in the modelling procedure that bushland (42.11 %) and bare soil (35 %) would be changed to commercial sugar cane. This is indicative of the expanding agriculture sector in Mtunzini. Natural vegetation is predicted to be disturbed: 18 % of bushland and 15.07 % of dense bush are expected to be replaced by rural dwellings. This is owing to a potential increase in the rural population and a reduced local economic growth. This study highlights the need for increased vigilance of the forestry industry and commercial sugar cane farms which may be encroaching on natural vegetation and livelihoods of local residents. Strategic planning and proper management of natural vegetation types is needed as these land cover types are decreasing rapidly. 相似文献
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Green-leaf phenology describes the development of vegetation throughout a growing season and greatly affects the interaction between climate and the biosphere. Remote sensing is a valuable tool to characterize phenology over large areas but doing at fine- to medium resolution (e.g., with Landsat data) is difficult because of low numbers of cloud-free images in a single year. One way to overcome data availability limitations is to merge multi-year imagery into one time series, but this requires accounting for phenological differences among years. Here we present a new approach that employed a time series of a MODIS vegetation index data to quantify interannual differences in phenology, and Dynamic Time Warping (DTW) to re-align multi-year Landsat images to a common phenology that eliminates year-to-year phenological differences. This allowed us to estimate annual phenology curves from Landsat between 2002 and 2012 from which we extracted key phenological dates in a Monte-Carlo simulation design, including green-up (GU), start-of-season (SoS), maturity (Mat), senescence (Sen), end-of-season (EoS) and dormancy (Dorm). We tested our approach in eight locations across the United States that represented forests of different types and without signs of recent forest disturbance. We compared Landsat-based phenological transition dates to those derived from MODIS and ground-based camera data from the PhenoCam-network. The Landsat and MODIS comparison showed strong agreement. Dates of green-up, start-of-season and maturity were highly correlated (r 0.86-0.95), as were senescence and end-of-season dates (r > 0.85) and dormancy (r > 0.75). Agreement between the Landsat and PhenoCam was generally lower, but correlation coefficients still exceeded 0.8 for all dates. In addition, because of the high data density in the new Landsat time series, the confidence intervals of the estimated keydates were substantially lower than in case of MODIS and PhenoCam. Our study thus suggests that by exploiting multi-year Landsat imagery and calibrating it with MODIS data it is possible to describe green-leaf phenology at much finer spatial resolution than previously possible, highlighting the potential for fine scale phenology maps using the rich Landsat data archive over large areas. 相似文献
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草型湖泊总悬浮物浓度和浊度遥感监测 总被引：1，自引：0，他引：1
草型湖泊水质遥感监测中水生植物会造成“水体—水生植物”混合像元问题，针对因混合像元导致草型湖泊水生植物覆盖区域水质难以直接利用遥感监测的问题，本文以草型湖泊微山湖为研究对象，提出定性和定量相结合的总悬浮物浓度和浊度分区监测方法，实现微山湖水体总悬浮物浓度和浊度的时空变化监测。基于获取的2014年7月—2015年6月覆盖微山湖的多期高分一号（GF-1） WFV和HJ-1A/1B CCD影像，利用归一化水体指数将微山湖区分为水生植物覆盖区和水体区。针对水生植物覆盖区，利用时序MODIS NDVI数据获取微山湖主要水生植物的时谱曲线，识别不同水生植物的物候特征；基于不同物候期内的水生植物对总悬浮物浓度和浊度的指示作用，对微山湖水生植物覆盖区水体总悬浮物浓度和浊度进行定性监测。针对水体区，分别构建水体总悬浮物浓度和浊度的单波段/波段比值模型和偏最小二乘模型，定量反演微山湖水体区总悬浮物浓度和浊度。研究结果表明，微山湖中水生植物以光叶眼子菜、穗花狐尾藻和菹草等沉水植物为主，其中光叶眼子菜/穗花狐尾藻和菹草的空间分布和物候特征存在明显差异，不同水生植物在不同物候期内对水质具有不同的指示作用；微山湖水体总悬浮物浓度和浊度具有显著的空间变异性，基于定性和定量相结合的方法可以有效监测微山湖水体总悬浮物浓度和浊度的时空变化规律。本文提出的定性和定量相结合的监测方法为草型湖泊水质监测的业务化应用提供了新思路。 相似文献
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Snow effects on alpine vegetation in the Qinghai-Tibetan Plateau 总被引：1，自引：0，他引：1
《International Journal of Digital Earth》2013,6(1):58-75
Understanding the relationships between snow and vegetation is important for interpretation of the responses of alpine ecosystems to climate changes. The Qinghai-Tibetan Plateau is regarded as an ideal area due to its undisturbed features with low population and relatively high snow cover. We used 500 m Moderate Resolution Imaging Spectroradiometer (MODIS) datasets during 2001–2010 to examine the snow–vegetation relationships, specifically, (1) the influence of snow melting date on vegetation green-up date and (2) the effects of snow cover duration on vegetation greenness. The results showed that the alpine vegetation responded strongly to snow phenology (i.e., snow melting date and snow cover duration) over large areas of the Qinghai-Tibetan Plateau. Snow melting date and vegetation green-up date were significantly correlated (p < 0.1) in 39.9% of meadow areas (accounting for 26.2% of vegetated areas) and 36.7% of steppe areas (28.1% of vegetated areas). Vegetation growth was influenced by different seasonal snow cover durations (SCDs) in different regions. Generally, the December–February and March–May SCDs played a significantly role in vegetation growth, both positively and negatively, depending on different water source regions. Snow's positive impact on vegetation was larger than the negative impact. 相似文献
20.
Applying remote sensing techniques to develop the retrieval models and further to obtain the spatiotemporal information of water quality parameters is necessary for understanding, managing, and protecting lake ecosystems. This study aimed to calibrate and validate the retrieval models for estimating the concentrations of chlorophyll a (CCHL), suspended particulate matter (CSPM), and dissolved organic carbon (CDOC) with the in situ hyperspectral measurements in Poyang Lake, China in 2010 and 2011. The model calibration and validation results indicated that: (1) for CCHL retrieval, significantly strong and moderate correlations existed between the measured and estimated values (with the correlation coefficient r = 0.92 and r = 0.76) using the exponential model and the three-band model, respectively, with biased estimation observed for the exponential model; (2) for retrieving CSPM, there was a strong correlation between the measured and estimated values (r = 0.95) using the exponential model; and (3) no significant correlation between measured and estimated CDOC values was found with our developed models. More work is needed to allow the water quality of Poyang Lake to be accurately and steadily estimated, especially for CCHL and CDOC. 相似文献