Benefit of a second calibration phase to estimate the relative global
and regional mean sea level drifts between Jason-3 and Sentinel-6a
Abstract
The originality of this study is to propose a new calibration method
based on two calibration phases between Jason-3 and Sentinel-6A (S6A) to
better estimate the relative global and regional mean sea level drifts
between the two missions. To date, a first calibration phase of
approximately 12 months is planned from January 15, 2021, to December
31, 2021, when both satellites will be on the same orbit spaced out by
approximately 30 seconds. This calibration will allow for a very
accurate assessment of the GMSL bias between Jason-3 and S6A (less than
0.5 mm, see Zawadzki and Ablain, 2016). A second calibration phase
after a few years would reduce the uncertainty levels of the GMSL
(global mean seal level) drift estimate. The uncertainty would be low
enough to detect any drift detrimental to the stability of the current
GMSL record. It would indeed be possible to evaluate the stability
between the two satellites with an accuracy at least 3 times better at
the global scale than with the most accurate method to date. At regional
scales, the second calibration phases would provide regional MSL drift
estimates with very good precision. This study also shows that the time
spent between the two calibration phases is significantly more sensitive
than the length of the second calibration phase for the reduction in
uncertainties. Finally, a possible scenario proposed by this study would
consist of carrying out the beginning of the second calibration phase
approximately 1.5-2 years after the first and for a duration of 3-4
months. This calibration would allow the detection of a relative GMSL
drift of approximately 0.15 mm/yr and 0.4-0.5 mm/yr at oceanic basin
scales (2000-4000 km).