A comparison of ocean topography derived from the Shuttle Laser Altimeter-01 and TOPEX/POSEIDON

To assess the utility of laser altimetry for studies in dynamical oceanography, the authors present a comparison of the Shuttle Laser Altimeter (SLA)-01 and the TOPEX/POSEIDON (T/P) radar altimeter on global and regional scales. They compare all ~1.1 million SLA-01 range measurements over the oceans to the CSRMSS95 gridded mean sea surface model and find the overall root mean square (RMS) difference to be 2.33 m. The misfit was improved significantly by removing the mean and trend from individual SLA-01 profiles, often resulting in RMS differences less than 1 m. They also show that in regions where sea surface height varies dramatically over relatively short horizontal scales such as across major subduction zones, SLA-01 as capable of resolving rapid changes in sea surface height. Finally, they examine a number of coastal zones and illustrate SLA-01´s ability to track continuously across the land-sea interface, even in regions of dramatic coastal topography. The dominant sources of radial error in the SLA-01 data are time-interval unit (TIU) error (±0.75 m) and radial orbit error (1 m RMS). Therefore, limitations of the SLA-01 data set are caused primarily by system constraints as opposed to instrumentation error. Their results indicate that future laser altimeters will provide valuable information regarding ocean topography. In particular, laser altimetry data can be used to supplement orbiting microwave ranging systems in coastal areas where such sensors are incapable of maintaining lock across the continent-ocean transition