鍏抽敭璇�: 娌虫祦姘翠綅, 闆疯揪楂樺害璁�, 娴嬮珮鏁版嵁闆�, 绮惧害璇勪环

Abstract:

The water surface level is essential for the assessment of fresh water resources锛� disaster prevention锛� and highly related to the understanding and response to climate change and its impact on water cycle. With the development of remote sensing technology锛� observation of water level based on satellite platforms provides an alternative way of river water level monitoring featured by automated锛� long-time锛� and low-cost river monitoring solution. The principle锛� characteristics and accuracy of satellite-based river observations are the basis for applications. In this paper锛� the characteristics and accuracy of three major satellite river water level datasets锛� Hydroweb锛� DAHITI锛� GRRATS are summarized verified with in-situ water level measurements from gauge stations in China. Taking water level time series derived from the Jason mission锛� we evaluated the accuracy of different water level retrieval algorithms employed by the three datasets. The global accuracy of the Hydroweb dataset 锛坅verage RMSE 0.70 m锛� is higher than the other two sources 锛坅verage RMSE 1.29 m and 3.21 m for the DAHITI and GRRATS锛夛紝 and that is owing to the usage of a large number of Sentinel-3 observations which are characterized by smaller footprints and Synthetic Aperture Radar 锛圫AR锛� and the on-board tracking system in open-loop. The accuracy of river water level derived from the Sentinel-3 mission 锛坵ith average RMSE of 0.51 m锛� is significantly higher than that of ENVISAT 锛坵ith average RMSE 3.34 m锛� and Jason 锛坵ith average RMSE 1.69 m for Hydroweb and 2.96 m for GRRATS锛�.Generally锛� the three datasets can capture reliable river water level changes at some stations 锛坵ith RMSE < 1.2 m and R² > 0.8锛夛紝 but their performances vary considerably among different stations 锛坵ith RMSE > 2 m for majority of the evaluated stations锛�. Among all the stations锛� the Gaocun virtual station from the DAHITI dataset shows the highest accuracy 锛圧MSE 0.22 m锛�. In addition锛� the variation of river water level in dry and wet seasons and the small lakes锛� ponds and seasonal water around rivers pose significant influences on the accuracy of retrieved water level. This study provides guidance for future applications of relevant data sets锛� and also highlights the challenges of accurate water level retrieval over land surface conditions in China as well as the necessity of algorithm improvement in the future.

Key words: Stage of river, Radar altimetry, Altimetry data set, Accuracy evaluation