Seasonal cycles of lakes on the Tibetan Plateau detected by Sentinel-1 SAR data
Seasonal cycles of lakes on the Tibetan Plateau detected by Sentinel-1 SAR data
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Sentinel-1 SAR数据探测青藏高原湖泊季节变化
DOI：
10.1016/j.scitotenv.2019.135563
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发表时间：
2020
影响因子：
9.8
通讯作者：
Zhu Tingting
中科院分区：
文献类型：
--
作者：
Zhang Yu;Zhang Guoqing;Zhu Tingting
利用20世纪70年代以来的Landsat系列卫星资料，可以观测到青藏高原湖泊的长期演变。然而，由于常用的光学图像的高云污染，TP上的湖泊的季节性周期很少受到关注。在这项研究中，第一次，使用哨兵-1合成孔径雷达（SAR）数据与高重复周期的TP上的湖泊的季节性周期检测。总共获得了约6000个1级场景，覆盖了研究区域内的所有大型湖泊（>50 km 2）。图像提取条带图（SM）和干涉宽测绘带（IW）模式，具有40米的距离和方位角方向的像素间距。使用本研究开发的算法从Sentinel-1数据中提取的湖泊边界与2015年相应的Landsat图像中描绘的湖泊岸线，湖泊轮廓和青海湖湖泊水位的现场测量结果吻合良好。经过分析，它被发现，湖泊的季节性周期表现出截然不同的模式在TP。例如，大型湖泊（>100平方公里）在8月至9月达到峰值，而面积为50-100平方公里的湖泊在6月至7月上旬达到峰值。内流湖的季节周期的峰值比那些外流湖的平坦的山峰更明显，冰川补给的湖泊与额外的水供应表现出延迟的高峰，在其季节周期相对于那些非冰川补给的湖泊。大尺度大气环流系统，如西风带，印度夏季风，过渡之间，东亚夏季风，也被发现影响湖泊的季节性循环。这项研究的结果表明，哨兵-1合成孔径雷达数据是一个强大的工具，可用于填补空白，在年度内湖泊观测。
The long-term evolution of lakes on the Tibetan Plateau (TP) could be observed from Landsat series of satellite data since the 1970s. However, the seasonal cycles of lakes on the TP have received little attention due to high cloud contamination of the commonly-used optical images. In this study, for the first time, the seasonal cycle of lakes on the TP was detected using Sentinel-1 Synthetic Aperture Radar (SAR) data with a high repeat cycle. A total of approximately 6000 Level-1 scenes were obtained that covered all large lakes (>50 km2) in the study area. The images were extracted from stripmap (SM) and interferometric wide swath (IW) modes that had a pixel spacing of 40 m in the range and azimuth directions. The lake boundaries extracted from Sentinel-1 data using the algorithm developed in this study were in good agreement with in-situ measurements of lake shoreline, lake outlines delineated from the corresponding Landsat images in 2015 and lake levels for Qinghai Lake. Upon analysis, it was found that the seasonal cycles of lakes exhibited drastically different patterns across the TP. For example, large size lakes (>100 km2) reached their peaks in August–September while lakes with areas of 50–100 km2reached their peaks in early June–July. The peaks of seasonal cycles for endorheic lakes were more pronounced than those for exorheic lakes with flat peaks, and glacier-fed lakes with additional supplies of water exhibited delayed peaks in their seasonal cycles relative to those of non-glacier-fed lakes. Large-scale atmospheric circulation systems, such as the westerlies, Indian summer monsoon, transition in between, and East Asian summer monsoon, were also found to affect the seasonal cycles of lakes. The results of this study suggest that Sentinel-1 SAR data are a powerful tool that can be used to fill gaps in intra-annual lake observations.