COMBINATION OF ENVISAT, CRYOSAT-2 AND SARAL/ALTIKA MEASUREMENTS FOR ESTIMATING WATER LEVEL VARIATIONS OF LAKES

摘要

The estimation of lake water level variations with satellite altimetry is a challenging task because the majority of altimeter waveforms of smaller lakes are contaminated by land. The main goal of this study is the determination of improved long-term water level time series of lakes by combining Envisat, CryoSat-2 and SARAL/AltiKa altimeter measurements in an optimal way. While Envisat and SARAL/AltiKa carry classical pulse-limited radar altimeters on board, CryoSat-2 carries a Delay-Doppler/SAR altimeter on board which allows to exploit the full Doppler bandwidth. Depending on the observation technique and surface conditions the altimeter waveforms vary from specular over land to multi peaks at the land/water transition and brown-like in the center of the lake. In a first step, we develop a new processing strategy for CryoSat-2 SAR data over lakes based on waveform classification, waveform retracking and outlier rejection. The results are validated with water level time series derived from classical altimeter missions and in-situ gauging data. For more detailed information please read the upcoming publication [1]. These new findings can be adopted to the new Sentinel-3 products.