Abstract
At each of five fixed locations along the ground tracks of JASON-1 and ENVISAT, a repeat-track analysis of 1-Hz sea surface height (SSH) data has been conducted to assess the performance of waveform retrackers over Lake Baikal in Siberia, Russia. This simple analysis of time series at each point location is needed to minimize the effect of the range correction artifacts in current Geophysical Data Record (GDR) data products of radar altimeters in in-land areas. Using the retracked data available in the GDRs as the baseline, two retrackers are evaluated in terms of the number of valid data points produced and the degree of agreement with in-situ data of water level record. The threshold retrackers that are based on the amplitude of the robust OCOG algorithm (Offset Center of Gravity) are found to perform the best in Lake Baikal.
Highlights
Monitoring the relative lake level changes became possible on a global scale starting with the TOPEX/POSEIDON altimeter mission (Birkett 1995)
The JASON-1 Sensor Geophysical Data Record (GDR) (SGDR) data product provided by the AVISO-CNES Data Center and the ENVISAT MWS data of the European Space Agency were used
The RMS difference of 1-Hz ENVISAT sea surface height (SSH) data from the in situ monthly water level computed for each retracker is 25.6 cm for the GDR ocean, 9.5 cm for the GDR ice1, and 12.1 cm for the 50% TR/OCOG for 36 data points at which all three retrackers produce valid heights, excluding the MLE3-type
Summary
Monitoring the relative lake level changes became possible on a global scale starting with the TOPEX/POSEIDON altimeter mission (Birkett 1995). This remote sensing technology is well validated; the altimeter-monitored data of lakes and reservoirs are available at several websites (Crétaux et al 2011a, b). The geophysical range corrections available in the Geophysical Data Records (GDRs) of ENVISAT and JASON-1 have known problems over inland bodies of water. The test locations of altimeter data were selected near the center of the lake as much as possible to avoid the waveform data contaminated by radar echoes from land reflectors and the loss of lock of onboard trackers near the coasts. The JASON-1 Sensor GDR (SGDR) data product provided by the AVISO-CNES Data Center and the ENVISAT MWS (reprocessed V2.1 SGDR) data of the European Space Agency were used
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