基于Sentinel-1,2和Landsat 8时序影像的鄱阳湖湿地连续变化监测研究

Consecutive Monitoring of the Poyang Lake Wetland by Integrating Sentinel-2 with Sentinel-1 and Landsat 8 Data

湿地具有季节性特征,高时间分辨率遥感监测能够更为客观精准地认识其时空变化规律。选择季节性变化显著、我国第一大淡水湖生态湿地——鄱阳湖湿地为典型案例,利用Sentinel-1,2和Landsat 8卫星的2017~2019年所有可以获取的不同时相影像,采用随机森林分类(Random Forest,RF)方法,对研究区的湿地进行遥感分类和信息提取,发挥海量遥感影像在湿地宏观连续监测的优势,解析鄱阳湖湿地的年际、年内时空动态变化特征。研究结果表明:Sentinel-2影像为鄱阳湖湿地动态变化监测提供良好的数据基础,随机森林分类总体分类精度高于90%,提取效果具有比较优势。对3 a分类结果进行统计分析,各湿地类型在年内均呈现出动态变化的特点,在每年2月泥滩和草洲面积到达年内最大,水体面积为年内最小;每年6、7月份水域面积达到年内最大,泥滩和草洲面积最小,季节性变化明显;月度时间序列的分类结果,能更准确地说明湿地类型的月度和季度变化。因此,结合Seninel-1,2以及Landsat 8数据,基于RF算法,能及时、有效地对鄱阳湖等季节性变化强烈的湿地进行动态监测,对开展湿地资源高效调查工作具有重要意义。

Wetlands are usually featured by evident seasonality,and thus high temporal-resolution remote sens⁃ing monitoring of their consecutive changes would greatly benefit to more objectively and accurately detecting the characteristics of spatial-temporal changes.The Poyang Lake wetland,as the largest freshwater lake in Chi⁃na,which shows significant intra-annual variability,was selected as the demonstrative case in this study.By collecting all available remote sensing images of Sentinel-1&2 and Landsat-8 from 2017 to 2019 based on the Google Earth Engine platform,we adopted the Random Forest(RF)method to map various types of wetlands of the Poyang Lake.It aims to demonstrate the capacity of Sentinel-2 optical images integrated with Sentinel-1 SAR and Landsat-8 data applicable to monitor wetland variations at both the inter-annual and intra-annual tim⁃escales.Results show that the Sentinel-2 images enable to provide a powerful data base for monitoring the dy⁃namics of Poyang Lake wetland,and the overall classification accuracy was higher than 90%.the areas of the classification results were statistically analyzed in the 3 years,in February of each year,mudflat and vegetation reach the maximum area,while water area is the minimum.In June and July of each year,the water area reaches the largest in the year,while the mudflat and vegetation area is the smallest.All types of wetlands in the Poyang Lake show evidently seasonal changes,and the monthly classification results can more accurately illustrate the intra-annual changes characteristics of various types.Overall,the integration of Seninel-2 data with Sentinel 1 and Landsat-8 images,can effectively monitor the wetland changes at fine timescale,which is crucial for timely and costly management of wetland resources.