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| 1 | 基于Landsat-8的东南极达尔克冰川季节性表面消融信息提取显示文摘冰盖表面消融是气候变化和全球变暖的敏感指示剂。冰雪消融会降低地表反照率进而影响全球能量平衡,表面融水会加剧裂隙的传播,降低冰架稳定性进而影响冰盖物质平衡。当前,高时空分辨率消融区分布数据的缺乏限制了南极冰盖消融发生机理和时空特征的深入探索。围绕南极冰盖大范围消融区(蓝冰、湿雪和融水)的提取研究,提出了一种基于改进的冰雪归一化消融指数(Modified Normalized Difference Water Index Adapted for Ice,MNDWIice)的消融区自动提取方法,采用2016年9月—2017年4月18景30 m分辨率的Landsat-8数据,获取了消融区自动提取的MNDWIice阈值,并以东南极达尔克冰川为例,实现了高空间分辨率的季节性消融信息提取和分析。结果表明:在云和地形阴影干扰较小的情况下,基于Landsat-8反射率数据计算的MNDWIice采用单一阈值(0.136)对消融区的提取精度在67.7%—94.2%之间,平均精度为81.5%;达尔克冰川消融面积、消融区MNDWIice均值表现出明显的季节性时空变化特征;消融发生的时间不晚于Landsat-8数据观测的最早时间(9月7日);消融最早出现和主要分布区在地形下降剧烈的东部接地线处。 | 璩榆桐 程晓 刘岩 | 2020 | 极地研究2020，32，2： | 5 |
| 2 | 基于多遥感产品和地面观测的北极苔原春季返青期特征研究显示文摘北极是气候变化的敏感区,其增温幅度约为全球地表平均增温幅度的两倍.北极苔原由于受到气候变化的影响其生长特征出现明显的年际和季节波动.本研究基于北极苔原区29个地面台站的长期连续观测数据,对2000~2018年遥感归一化植被指数(NDVI)、归一化水分指数(NDWI)和归一化雪指数(NDSI)采用多种拟合方法进行平滑降噪,并提取返青期日期(SOS).同时利用多源地面观测资料,包括通量、物候影像和实地物候记录,对遥感返青期进行验证,探究返青期的时空变化规律及其在不同植物群落的变化特征.结果表明,在研究的站点中,纬度越高,返青期开始时间越晚;纬度每向北增加一度,返青期推迟约3.86天.2000~2018年间,不同的植物群落,返青期的发生时间和年际变化幅度差异大;尽管2000~2018年间研究站点的时间变化趋势并不显著,但不同群落的返青期在2016年之后逐年推迟.高北极植被包括:(1)以莎草/禾草、苔藓为主的北极低矮湿地复合体(5~10cm),(2)稍高的匍匐、半匍匐矮灌木苔原(<15cm);高北极植被的大部分返青期呈延迟趋势.低北极植被包括:(1)以莎草、苔藓、矮灌木为主的湿地复合体(10~40cm),(2)以莎草和矮灌木为主的直立灌木苔原(20~50cm),(3)包含苔原与泰加林的过渡带;大部分的低北极植被返青期无明显趋势. | 郑江珊 徐希燕 贾根锁 吴文瑾 | 2020 | 中国科学:地球科学2020，50，11： | 3 |
| 3 | 全新的Landsat-8 OLI格陵兰遥感影像图显示文摘格陵兰是世界上最大的岛屿, 2/3的国土面积被冰雪覆盖.在全球气候变化的背景下,格陵兰冰盖正在加速融化和流失.为了定量化研究格陵兰冰盖消融的速度及其对全球海平面上升的贡献,格陵兰地区高分辨率遥感影像图是必不可少的研究数据.目前唯一的一套高分辨率格陵兰遥感影像图(LIMG)是由GIMP项目发布的,该数据采用1999~2002年的Landsat 7和Radarsat 1影像拼接完成.由于该数据集过于陈旧,各国研究者迫切需要最新的格陵兰高分辨率遥感影像图开展相关研究.本文在收集2014~2015年229景Landsat 8遥感影像数据的基础上,提出了分段聚类拉伸和最大信息熵自动去云算法,克服了冰雪与裸露地表反射率反差巨大,不同时间获取的卫星图像色差巨大等技术难点,成功绘制了格陵兰岛全岛卫星图像(2014~2015年).目前,该数据集可在http://gffzzfa7b6b0637cf46cbh5vkqpwbx5nuo69p0.ffgz.tsg.suse.edu.cn/greenland Mosaic免费下载. | 陈卓奇 迟肇惠 Karl B.Zinglersen 田颖 王凯加 惠凤鸣 程晓 | 2020 | Science Bulletin2020，65，7： | 2 |
| 4 | Understanding the spring phenology of Arctic tundra using multiple satellite data products and ground observations显示文摘The Arctic is highly sensitive to climate change,and the rise in its near-surface air temperatures has been almost twice the global average.The increased growth of the Arctic tundra and its changing seasonality have been observed,largely in response to the impacts of climate change.In this study,we investigated the temporal and spatial variations of the start of the growing season(SOS)using various remote sensing indices,including Normalized Difference Vegetation Index,Normalized Difference Water Index,and Normalized Difference Snow Index from 2000 to 2018 in Arctic tundra regions.The SOS was derived at 29 sites from ground observations,including CO2 flux data,phenological images,and field records that were used to validate the SOS from remote sensing indices.Our results revealed that the SOS was delayed by approximately 3.86 days per degree of latitude along the northward latitudinal gradient.From 2000 to 2018,the start of the growing season and the interannual variability differed greatly among tundra types.Although the overall trends were not significant from 2000 to 2018,the start of the growing season in different plant communities was consistently delayed after 2016.High Arctic vegetation,including(1)low wetland complexes(5–10 cm)dominated by sedges,grasses,and mosses,and(2)slightly higher prostrate and hemi-prostrate shrubs(<15 cm),experienced a delayed start of the growing season.The start of the growing season of Low Arctic vegetation,comprising(1)wetland complexes(10–40 cm)dominated by sedges,grasses,mosses,and dwarf shrubs,(2)moist tundra(20–50 cm)dominated by tussock cottongrass and dwarf shrubs,and(3)transition zones containing tundra and taiga,displayed no obvious trend. | Jiangshan ZHENG Xiyan XU Gensuo JIA Wenjin WU | 2020 | Science China Earth Sciences2020，63，10： | 1 |
| 5 | 土地覆盖制图的精细尺度转变显示文摘Land cover is the physical evidence on Earth,and land cover maps show the spatial distribution of the different covers on the Earth’s surface as well as the complex interactions among them.After evolving for several decades,land cover mapping has reached a milestone and is currently experiencing a transformation from coarse and moderate scales to much finer scales to provide more precise knowledge on land.This paper reviews the history of land cover mapping,summarizes the key characteristics of this transformation,and highlights the recent advances in urban land cover mapping. | 冯敏 李新 | 2020 | Science Bulletin2020，65，19： | 1 |
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