Jason-2测高卫星对湖泊水位的监测精度评价

湖泊水位是评估湖泊水量变化的重要指标。本文以洪泽湖、高邮湖及洞庭湖为研究对象,利用集中度的概率密度函数方法(CPDF)来提高Jason-2测高数据精度,分析了降水量与各个湖泊水位变化的相关性,并基于实测水位数据对比评价了Jason-2测高卫星原始GDR数据和CPDF方法处理后的卫星数据的精度。结果表明:①Jason-2原始GDR数据点的分布存在疏密之分,大部分数据分布相对集中,且有一定的周期变化,但评价结果显示精度较差,故原始GDR数据不能直接用于湖泊水位监测;②CPDF方法可以极大提高测高卫星的水位数据精度,洪泽湖与高邮湖的均方根误差分别由1.92 m与1.74 m减少到了0.32 m和0.36 m,相关系数由0.28和0.04提高到了0.85和0.72。对于南北宽度较窄且日水位变化较大的湖泊(如洞庭湖),CPDF方法提高原始GDR结果的精度有限;③洞庭湖降水与水位相关性最强,高邮湖次之,而洪泽湖降水与水位成不显著的负相关,是洪泽湖水利工程对于水位的调节导致了这一结果。本研究对于利用测高卫星获得湖泊水位值,进而对湖泊进行动态监控,特别是在填补资料匮乏地区湖泊水位数据方面具有重要意义。

Evaluation of the Monitoring Accuracy of Lake Water Level by the Jason-2 Altimeter Satellite

As one of the important characteristics of lakes, lake water level is an important indicator for evaluating the change of lake water storage capacity. As a new remote sensing monitoring technology, satellite altimetry technology has played an increasingly important role in monitoring the dynamic changes of lake waters, and has become an effective means for lake research, water resources investigation and wetland protection. This study took Hongze Lake, Gaoyou Lake and Dongting Lake as examples, using the Centralized Probability Density Function method (CPDF) to improve the accuracy of Jason-2 altimetry data, as well as analyze the correlation of precipitation and water level of each lake. Besides, based on the measured water level data we compared the accuracy of the original GDR data of the Jason-2 altimeter satellite and the satellite data processed by the CPDF method. Results show that: (1) The distribution of Jason-2 original GDR data points is sparse, most of the data are relatively concentrated, and there are certain periodic changes, but the evaluation results show poor accuracy, so the original GDR data cannot be directly used for lake water level monitoring. (2) CPDF method can greatly improve the accuracy of the water level data of the altimeter satellite. The evaluation results of Hongze Lake and Gaoyou Lake show that the RMSE decreased from 1.92m and 1.74m to 0.32 m and 0.36m, and the correlation coefficient increased from 0.28 and 0.04 to 0.85 and 0.72, indicating that Jason-2 altimetry data processed by the CPDF method can achieve higher accuracy in lake water level monitoring. However, it is worth noting that for the lake, which is with narrow north-south widths and large changes in daily water levels (such as Dongting Lake), the accuracy of the raw GDR improved by the CPDF method would be limited. (3) The precipitation of Dongting Lake had the strongest correlation with the water level, followed by Gaoyou Lake,the water level changes of Gaoyou Lake and Dongting Lake lag behind the precipitation by about 1 month and 1-2 months respectively. However, the precipitation of Hongze Lake was not significantly negatively correlated with the water level, which is partly due to the adjustment of water level by the Hongze Lake water conservancy project. This study is of great significance for obtaining lake water level values using altimetry satellites, and then for dynamic monitoring of lakes, especially in filling lake water level data in data-poor areas.