基于GRACE重力卫星的珠江流域大尺度洪水监测

Exploration of large-scale flood monitoring in the Pearl River basin based on GRACE satellites

洪水监测对流域洪水预报预警,防洪工程调度及洪水风险管理至关重要。以珠江流域为研究区,基于重力恢复与气候实验卫星(Gravity Recovery and Climate Experiment,GRACE)数据研究2002年4月—2017年6月陆地水储量异常(terrestrial water storage anomaly,TWSA)的变化情况,并结合全球陆地数据同化系统模拟的TWSA/气温、卫星降雨数据构建广义回归神经网络(general regression neural network,GRNN)模型延长TWSA序列(2000年1月—2018年12月),通过计算洪水潜力指数(flood potential index,FPI)监测大尺度洪水事件。结果表明:(1)五套官方GRACE产品的相关性较强,且GRACE监测的TWSA相对基于水量平衡的估算结果存在1~2个月提前期;(2)基于GRNN模型延长的TWSA与全球陆地数据同化系统模拟值高度相关,说明GRNN模型预测能力较强;(3)使用GRNN模型预测的TWSA数据计算FPI,发现其对流域2008年4—12月发生的大尺度洪水事件起到了较好的监测作用。

Monitoring flood events is essential for early warning,control project scheduling,and risk management.Based on the Gravity Recovery and Climate Experiment(GRACE)satellite data of Apr.2002 to June 2017,this paper studies variations in terrestrial water storage anomaly(TWSA)in the Pearl River basin,and combines the Global Land Data Assimilation Systems(GLDAS)-simulated TWSA,temperature,and rainfall data to construct a generalized regression neural network(GRNN)model to extend the TWSA time series to the time span of Jan.2000 to Dec.2018.A flood potential index(FPI)is calculated to monitor large-scale extreme flood events.Results show that 1)five official GRACE products are highly correlated in this basin,and the TWSA derived from GRACE has a 1-2 month lead time relative to that from water budget.2)The GRNN-extended TWSA for the basin is consistent with that of GLDAS,indicating strong capability of prediction by the GRNN model.3)FPI is,when calculated using the GRNN-predicted TWSA,a good indicator in monitoring the basin’s large-scale flood events of Apr.to Dec.2008.