利用星载GNSS-R相干信号探测南亚洪水

Flood Detection of South Asia Using Spaceborne GNSS-R Coherent Signals

洪水监测不仅在防洪减灾中发挥着重要作用,而且对了解洪水的时空演变以及洪灾的预报、预警具有重大的实际意义。全球导航卫星系统反射(global navigation satellite system-reflectometry,GNSS-R)测量的出现为洪水监测提供了一种新的解决方案。首先介绍了一种基于旋风全球导航卫星系统(cyclone global navigation satellite system,CYGNSS)原始计数时延多普勒图(delay-Doppler map,DDM)的相干信号探测方法;然后利用星载GNSS-R信号对洪水的敏感性,分析了南亚洪水发生前后的空间范围和时间序列变化;最后与地表反射率监测洪水的方法进行比较分析。结果表明,在旱季,两种方法与土壤湿度主被动探测卫星(soil moisture active passive,SMAP)的监测范围基本相似;而在雨季,地表反射率的探测范围比SMAP卫星探测范围约大6.69%,功率比的探测范围比SMAP卫星约小3.6%。因此,所提方法比地表反射率更加准确,且该方法无需考虑地表特征等对非相干散射功率的影响,是一种简单有效的洪水探测方法。

Objectives:Flood monitoring not only plays an important role in flood prevention and mitigation,but also provides support for understanding the temporal and spatial evolution of floods and forecasting and warning.The global navigation satellite system-reflectometry(GNSS-R)measurement provides a new solution for flood monitoring.Methods:Firstly,we introduce a coherent signal detection method based on CYGNSS(cyclone global navigation satellite system)raw counts delay-Doppler map(DDM),and then analyze the changes of spatial range and time series before and after flood in South Asia are analyzed,based on the sensitivity of spaceborne GNSS-R signals to floods.Results:Research results show that,compared with the flood detection results of soil moisture active passive(SMAP),the monitoring range of the two methods in the dry season is similar.While in the rainy season,the detection range of the surface reflectivity is larger about 6.69%,and the detection range of the power ratio is smaller about 3.6%.Conclusions:The proposed method of using GNSS-R coherent signals to detect floods is more accurate than the surface reflectivity,and this method does not have to consider the influence of surface characteristics on the incoherent scattering power.It is a simple and effective method for flood detection.