Analyses of altimetry errors using Argo and GRACE data

• Published in: Ocean science 2016-01, Vol.12 (1), p.1
• Main Authors: Legeais, J.-F, Prandi, P, Ablain, M, Guinehut, S
• Format: Article
• Language: English
• Subjects: Analysis; Salinity
• ISSN: 1812-0784; 1812-0792

This study presents the evaluation of the performances of satellite altimeter missions by comparing the altimeter sea surface heights with in-situ dynamic heights derived from vertical temperature and salinity profiles measured by Argo floats. This external assessment method contributes to altimeter Calibration and Validation analyses that cover a wide range of activities. Among them, our approach focuses on the detection of altimeter drift and the estimation of the impact of new altimeter standards that requires an independent reference. The methodology and the Argo data used are first described and altimeter validation activities are then illustrated with some examples, separating the analyses of the long-term evolution of the mean sea level and its variability, at global and regional scales and results obtained via relative and absolute comparisons. The latter requires the use of the ocean mass contribution to the sea level derived from GRACE measurements. Our analyses are related to different subjects ranging from the estimation of the global mean sea level trend to the validation of multi-missions altimeter products as well as the assess ment of orbit solutions. Even if this approach contributes to the altimeter quality assessment, the differences between two versions of altimeter standards are getting smaller and smaller and it is thus more difficult to detect their impact. It is therefore essential to characterize the errors of the method, which is illustrated with the results of sensitivity analyses to different parameters. This provides an estimation of the robustness of the method and the characterization of associated errors. The results also allow us to draw some recommendations to the Argo community regarding the maintenance of the in-situ network.