Evaluation of new CryoSat-2 measurements over the ocean
Event: 2015 Ocean Surface Topography Science Team Meeting
Session: Regional and Global CAL/VAL for Assembling a Climate Data Record
Presentation type: Type Poster
Contribution: PDF file
CryoSat-2 is a tremendous asset to the oceanographic community, and the exploitation of its data over the ocean represents a welcome additional return for ESA’s investment in a mission whose primary objective is to monitor the cryosphere. The CryoSat Project has approved, in the frame of the CryoSat routine phase, the generation of additional ocean products, which are available since April 2014. Here we present the results of a scientific validation of the Geophysical Ocean Products (GOP), which have consolidated orbits and are available 30 days after acquisition. The validation is performed for the sea surface height (SSH), the significant wave height (SWH), and the wind speed. The performance of the altimeter generally degrades as it gets closer to the coast due to contamination of the altimetric waveforms and/or inadequacy of some of the corrections, therefore it is important that validation be conducted both in the coastal zone and the open ocean. The SSH is validated at the coast against the sea level measured by a set of carefully selected and quality controlled tide gauges. Correlations between SSH and tide gauge records are statistically significant at nearly all stations, though they are spread across a broad range of values from 0.3 to 0.9. Comparisons between Jason-2 and the tide gauges show that CryoSat-2 outperforms Jason-2 at many stations. In the open ocean the SSH is compared globally with the steric heights derived from ARGO temperature and salinity profiles. Correlations between the two quantities are larger than 0.6 at most Argo floats and the mean normalized RMS difference is 40%. As an additional validation test, geostrophic velocities derived from the SSH are compared with the surface velocities from HF radars located along the Australian coast. Regarding the SWH and wind speed, they are both validated against buoy observations. The SWH shows an RMS of 12 cm with virtually zero bias, however the performance of the CryoSat-2 for wind speed is worse with a bias of almost 2 m/s. In addition, the SWH is also compared with Jason-2 observations as well as with the SWH provided by the Wavewatch III model.