What has 16 years of Satellite Radar Altimetry given us towards Global monitoring of the Earth’s inland water resources?

The series of satellite radar altimeter missions has now given us more than 16 years of data gathered over the earth’s inland water. However, this incredibly rich database of unique hydrological information is only now beginning to be mined effectively, as researchers increasingly move from accepting the pre-processed range information to retracking the waveform data to optimise the range measurement and generate accurate heights. This paper presents the results of a global analysis of waveform data acquired by ERS-1/2, EnviSat, TOPEX and Jason-1 which demonstrates that only a tiny fraction, as low as 10%, of the potential hydrological information content has been utilised to date. A much greater fraction of overflown inland water targets do have viable waveform data: these results suggest that over perhaps 40 % of the targets useable time series of heights could be derived by more sophisticated reprocessing of the data. Successful recovery of this information will give access to a huge decadal dataset of river and lake heights containing both climatological data and information on the anthropogenic use of inland water resources. Additionally, analysis of the target acquisition and echo characteristics from these missions gives a valuable and unique insight into the response of these complex surfaces to radar altimetry to aid future mission design