Abstract
Abstract. The new dynamic atmospheric correction (DAC) and dry tropospheric (DT) correction derived from the ERA-Interim meteorological reanalysis have been computed for the 1992–2013 altimeter period. Using these new corrections significantly improves sea level estimations for short temporal signals (< 2 months); the impact is stronger if considering old altimeter missions (ERS-1, ERS-2, and Topex/Poseidon), for which DAC_ERA (DAC derived from ERA-Interim meteorological reanalysis) allows reduction of the along-track altimeter sea surface height (SSH) error by more than 3 cm in the Southern Ocean and in some shallow water regions. The impact of DT_ERA (DT derived from ERA-Interim meteorological reanalysis) is also significant in the southern high latitudes for these missions. Concerning more recent missions (Jason-1, Jason-2, and Envisat), results are very similar between ERA-Interim and ECMWF-based corrections: on average for the global ocean, the operational DAC becomes slightly better than DAC_ERA only from the year 2006, likely due to the switch of the operational forcing to a higher spatial resolution. At regional scale, both DACs are similar in the deep ocean but DAC_ERA raises the residual crossovers' variance in some shallow water regions, indicating a slight degradation in the most recent years of the study. In the second decade of altimetry, unexpectedly DT_ERA still gives better results compared to the operational DT. Concerning climate signals, both DAC_ERA and DT_ERA have a low impact on global mean sea level rise (MSL) trends, but they can have a strong impact on long-term regional trends' estimation, up to several millimeters per year locally.
Highlights
Since the 1990s, several altimeter missions have been monitoring the sea level at a global scale
New dynamic atmospheric correction (DAC) and dry tropospheric correction (DT) corrections derived from the ERA-Interim reanalysis have been computed for the entire altimetric period
These corrections have been extensively compared to the operational DAC and DT solutions using long time series of six altimeter missions: ERS-1, ERS-2, TP, Envisat, Jason1, and Jason-2
Summary
Since the 1990s, several altimeter missions have been monitoring the sea level at a global scale. Significant errors remain mostly due to a lack of resolution of the model (in shelf seas and in some deep ocean regions), to remaining bathymetry errors and due to atmospheric forcing field uncertainties (Lamouroux et al, 2006; Lamouroux, 2006; Greenberg et al, 2007). In this context, the main objective of the sea level CCI project (Ablain et al, 2015) was to build improved long-term altimeter sea level data records dedicated to climate studies.
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