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The Altimetric Wet Tropospheric Correction: Progress since the ERS-1 mission

Laurence Eymard(1) and Estelle Obligis(2)

(1) LOCEAN-IPSL, 4 place Jussieu, 75005 Paris, France
(2) CLS, 8-10 rue Hermes, 31520 Ramonville Saint Agne, France

Abstract

In order to correct the altimeter range for water vapor path delay over ocean, a microwave radiometer has been embarked on the spacecraft since the early 90?s. As any error in the wet tropospheric correction directly impacts the sea level determination, the constraints on the quality and stability of the radiometer products are particularly stringent. In this paper, we present the improvements performed since the ERS-1 mission, the remaining limitations, and the perspectives for the improvement of the wet tropospheric correction for the future altimetry missions. New technologies like the in-flight calibration using injection noise diodes have been used (Jason/JMR). But recent improvements mainly concern the processing of the radiometer measurements at both level 1 (calculation of the brightness temperature) and level 2 (wet tropospheric correction retrieval). Nowadays, the sea level rise is estimated at the mm/year level, so new methods have been developed to detect any drift in order to correct it and so to provide stable products.

Despite the numerous progress achievements made since the launch of ERS1, the uncertainty on the wet tropospheric correction is still today around 1 cm rms and remains a significant contribution in the global uncertainty on the sea level estimation. For the future altimetry missions, the wet tropospheric correction would have to fulfill new constraints on accuracy and spatial resolution. We think that only the combination between new instruments (scanning instruments, higher frequencies, ?) combined with high quality meteorological models should allow to reach this goal.

 

Workshop presentation

Full paper

 

                 Last modified: 07.10.03