There are a large number of lakes,rivers,and other natural water bodies distributed in the permafrost area of the Qinghai-Tibet Plateau(QTP).The changes in water bodies will affect the distribution of water resources ...There are a large number of lakes,rivers,and other natural water bodies distributed in the permafrost area of the Qinghai-Tibet Plateau(QTP).The changes in water bodies will affect the distribution of water resources in sur-rounding areas and downstream areas,resulting in environmental impact and bringing potential flood disasters,which will induce more serious issues and problems in alpine and high-altitude areas with a fragile habitat(such as the QTP in China).Generally,effective,reasonable,and scientific monitoring of large-scale water bodies can not only document the changes in water bodies intuitively,but also provide important theoretical reference for subsequent environmental impact prediction,and disaster prevention and mitigation in due course of time.The large-scale water extraction technology derived from the optical remote sensing(RS)image is seriously affected by clouds,bringing about large differences among the extracted water result products.Synthetic aperture radar(SAR)RS technology has the unique advantage characteristics of all-weather,all-day,strong penetration,and not being affected by clouds,which is hopeful in extracting water body data,especially for days with cloudy weather.The data extraction of large-scale water bodies based on SAR images can effectively avoid the errors caused by clouds that become prevalent at present.In this paper,the Hoh Xil Salt Lake on the QTP and its surrounding five lakes are taken as the research objects.The 2-scene Sentinel-1 SAR image data covering the whole area on 22 August 2022 was used to verify the feasibility of extracting water body data in permafrost zones.Furthermore,on 22 August 2022,the wealth here was cloudy,which made the optical RS images,e.g.,Sentinel-2 images full of clouds.The results show that:using the Sentinel-1 image and threshold segmentation method to extract water body data is efficient and effective with excellent results in permafrost areas.Concretely,the Sentinel-1 dual-polarized water index(SDWI),calculated by combining dual vertical–vertical(VV)polarized and verti-cal–horizontal(VH)polarized data is a useful index for water extraction and the result is better than each of the VV or VH polarized images.展开更多
As one of the areas with numerous lakes on the Tibetan Plateau, the Hoh Xil region plays an extremely important role in the fragile plateau eco-environment. Based on topographic maps in the 1970s and Landsat TM/ETM＋ ...As one of the areas with numerous lakes on the Tibetan Plateau, the Hoh Xil region plays an extremely important role in the fragile plateau eco-environment. Based on topographic maps in the 1970s and Landsat TM/ETM＋ remote sensing images iin the 1990s and the period from 2000 to 2011, the data of 83 lakes with an area above 10 km2 each were obtained by digitization method and artificial visual interpretation technology, and the causes for lake variations were also analyzed. Some conclusions can be drawn as follows. （1） From the 1970s to 2011, the lakes in the Hoh Xil region firstly shrank and then expanded, in particular, the area of lakes generally decreased during the 1970s-1990s. Then the lakes expanded from the 1990s to 2000 and the area was slightly higher than that in the 1970s. The area of lakes dramatically increased after 2000. （2） From 2000 to 2011, the lakes with different area ranks in the Hoh Xil region showed an overall expansion trend. Meanwhile, some regional differences were also discovered. Most of the lakes expanded and were widely distributed in the northern, central and western parts of the region. Some lakes were merged together or overflowed due to their rapid expansion. A small number of lakes with the trend of area decrease or strong fluctuation were scattered in the central and southern parts of the study area. And their variations were related to their own supply conditions or hydraulic connection with the downstream lakes or rivers. （3） The increase in precipitation was the dominant factor resulting in the expansion of lakes in the Hoh Xil region. The secondary factor was the increase in meltwater from glaciers and frozen soil due to climate warming.展开更多
通过对可可西里库赛湖KS-2006孔矿物组合的分析表明:库赛湖沉积的碳酸盐为以文石为主的自生碳酸盐,其含量的高低能够指示温度的变化;盐类矿物只是在2150 cal aBP以来才出现,表明湖水盐度增高,与此同时,石英含量的持续增高可能同冷干气...通过对可可西里库赛湖KS-2006孔矿物组合的分析表明:库赛湖沉积的碳酸盐为以文石为主的自生碳酸盐,其含量的高低能够指示温度的变化;盐类矿物只是在2150 cal aBP以来才出现,表明湖水盐度增高,与此同时,石英含量的持续增高可能同冷干气候条件下该区风成活动的加强有关.青藏高原北部晚全新世的气候环境演化过程为:3770-2550 cal aBP期间气候条件整体较为温暖;2550-2150 cal aBP期间,气温缓慢下降有变冷的趋势;约2150 cal aBP至今,气候迅速转冷,湖区湿度降低,湖水盐度增高,风成活动加强,但900-700 cal aBP期间,为明显的温暖时期.展开更多
探究基于高分六号水体提取模型,能为水体监测提供新的数据源和技术支撑。首先,基于卓乃湖的高分六号WFV数据分析水体与其他地物反射率的差异,从而构建了一种新的水体指数——红边水体指数(read side water index,RSWI);然后,利用混淆矩...探究基于高分六号水体提取模型,能为水体监测提供新的数据源和技术支撑。首先,基于卓乃湖的高分六号WFV数据分析水体与其他地物反射率的差异,从而构建了一种新的水体指数——红边水体指数(read side water index,RSWI);然后,利用混淆矩阵生成的总体精度和Kappa系数,分别与归一化差异水体指数、改进的阴影水体指数和单波段阈值法进行了对比精度检验;最后,选取可可西里地区不同类型面积大于100 km^(2)的6个典型湖泊进行普适性分析。结果表明:与其他方法相比,RSWI和近红外波段构成的决策树模型有效消除了湖底沉积物对水体的影响,更完整地提取浅水区水体,总体精度达93.78%,Kappa系数为0.87;另外,RSWI水体模型对不同类型的湖泊具有较好的稳定性和普适性。展开更多
基金funded by the Second Tibetan Plateau Scientific Expedition and Research(STEP)program,grant number 2019QZKK0905the National Natural Science Foundation of China,grant number 42272339,42201162,42101121the Research Project of the State Key Laboratory of Frozen Soils Engineering,grant number SKLFSE-ZQ-58,SKLFSE-ZT-202203,SKLFSE-ZY-20.
文摘There are a large number of lakes,rivers,and other natural water bodies distributed in the permafrost area of the Qinghai-Tibet Plateau(QTP).The changes in water bodies will affect the distribution of water resources in sur-rounding areas and downstream areas,resulting in environmental impact and bringing potential flood disasters,which will induce more serious issues and problems in alpine and high-altitude areas with a fragile habitat(such as the QTP in China).Generally,effective,reasonable,and scientific monitoring of large-scale water bodies can not only document the changes in water bodies intuitively,but also provide important theoretical reference for subsequent environmental impact prediction,and disaster prevention and mitigation in due course of time.The large-scale water extraction technology derived from the optical remote sensing(RS)image is seriously affected by clouds,bringing about large differences among the extracted water result products.Synthetic aperture radar(SAR)RS technology has the unique advantage characteristics of all-weather,all-day,strong penetration,and not being affected by clouds,which is hopeful in extracting water body data,especially for days with cloudy weather.The data extraction of large-scale water bodies based on SAR images can effectively avoid the errors caused by clouds that become prevalent at present.In this paper,the Hoh Xil Salt Lake on the QTP and its surrounding five lakes are taken as the research objects.The 2-scene Sentinel-1 SAR image data covering the whole area on 22 August 2022 was used to verify the feasibility of extracting water body data in permafrost zones.Furthermore,on 22 August 2022,the wealth here was cloudy,which made the optical RS images,e.g.,Sentinel-2 images full of clouds.The results show that:using the Sentinel-1 image and threshold segmentation method to extract water body data is efficient and effective with excellent results in permafrost areas.Concretely,the Sentinel-1 dual-polarized water index(SDWI),calculated by combining dual vertical–vertical(VV)polarized and verti-cal–horizontal(VH)polarized data is a useful index for water extraction and the result is better than each of the VV or VH polarized images.
基金National Science-technology Support Plan Project, No.2012BAC 19B07 National Natural Science Foundation of China, No.41071044+2 种基金 No.41261016 No.41190084 Youth Teacher Scientific Capability Promoting Project of Northwest Normal University, No.NWNU-LKQN- 10-35
文摘As one of the areas with numerous lakes on the Tibetan Plateau, the Hoh Xil region plays an extremely important role in the fragile plateau eco-environment. Based on topographic maps in the 1970s and Landsat TM/ETM＋ remote sensing images iin the 1990s and the period from 2000 to 2011, the data of 83 lakes with an area above 10 km2 each were obtained by digitization method and artificial visual interpretation technology, and the causes for lake variations were also analyzed. Some conclusions can be drawn as follows. （1） From the 1970s to 2011, the lakes in the Hoh Xil region firstly shrank and then expanded, in particular, the area of lakes generally decreased during the 1970s-1990s. Then the lakes expanded from the 1990s to 2000 and the area was slightly higher than that in the 1970s. The area of lakes dramatically increased after 2000. （2） From 2000 to 2011, the lakes with different area ranks in the Hoh Xil region showed an overall expansion trend. Meanwhile, some regional differences were also discovered. Most of the lakes expanded and were widely distributed in the northern, central and western parts of the region. Some lakes were merged together or overflowed due to their rapid expansion. A small number of lakes with the trend of area decrease or strong fluctuation were scattered in the central and southern parts of the study area. And their variations were related to their own supply conditions or hydraulic connection with the downstream lakes or rivers. （3） The increase in precipitation was the dominant factor resulting in the expansion of lakes in the Hoh Xil region. The secondary factor was the increase in meltwater from glaciers and frozen soil due to climate warming.
文摘通过对可可西里库赛湖KS-2006孔矿物组合的分析表明:库赛湖沉积的碳酸盐为以文石为主的自生碳酸盐,其含量的高低能够指示温度的变化;盐类矿物只是在2150 cal aBP以来才出现,表明湖水盐度增高,与此同时,石英含量的持续增高可能同冷干气候条件下该区风成活动的加强有关.青藏高原北部晚全新世的气候环境演化过程为:3770-2550 cal aBP期间气候条件整体较为温暖;2550-2150 cal aBP期间,气温缓慢下降有变冷的趋势;约2150 cal aBP至今,气候迅速转冷,湖区湿度降低,湖水盐度增高,风成活动加强,但900-700 cal aBP期间,为明显的温暖时期.
文摘探究基于高分六号水体提取模型,能为水体监测提供新的数据源和技术支撑。首先,基于卓乃湖的高分六号WFV数据分析水体与其他地物反射率的差异,从而构建了一种新的水体指数——红边水体指数(read side water index,RSWI);然后,利用混淆矩阵生成的总体精度和Kappa系数,分别与归一化差异水体指数、改进的阴影水体指数和单波段阈值法进行了对比精度检验;最后,选取可可西里地区不同类型面积大于100 km^(2)的6个典型湖泊进行普适性分析。结果表明:与其他方法相比,RSWI和近红外波段构成的决策树模型有效消除了湖底沉积物对水体的影响,更完整地提取浅水区水体,总体精度达93.78%,Kappa系数为0.87;另外,RSWI水体模型对不同类型的湖泊具有较好的稳定性和普适性。
