the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Refining the resolution of DUACS along track (level 3) altimeter Sea Level products
Abstract. This paper describes a high-resolution Level-3 (L3) altimeter Data Unification and Altimeter Combination System (DUACS) experimental regional product developed with support from the French space agency (CNES). Deduced from full rate (20 Hz to 40 Hz) Level-2 (L2) altimeter measurements, this product delivers Sea Level Anomalies (SLA) and other essential physical variables with a nearly 1-Km sampling over the North Atlantic 0cean. It allows us to resolve wavelengths from ~35 km to ~55 Km depending on the altimeter considered. This was made possible by recent advances in radar altimeter processing for both Synthetic aperture Radar (SAR) and Low-Resolution Mode (LRM) measurements, and improvements made to different stages of the DUACS processing chain. Firstly, the new adaptive and LR-RMC (Low Resolution with Range Migration Correction) processing techniques were considered for Jason and Sentinel-3 (S3A) respectively. They significantly reduce errors at short wavelengths and, for the adaptive processing, possible land contamination near the coast. Next, up-to-date geophysical and environmental corrections were selected for this production. This includes specific corrections intended to reduce the measurement noise on LRM measurement and thus enhance the observability at short wavelengths. Compared to the 1 Hz product, the observable wavelength reached with the experimental high-resolution product are reduced by up to one third, or up to half in the North-East Atlantic region. The residual noises were optimally filtered from full rate measurements taking into consideration the different observing capabilities of the altimeters processed. A specific data recovery strategy was applied, significantly optimizing the data availability both in the coastal and open ocean. This experimental L3 product is thus better resolved than the conventional 1 Hz product, especially near the coast where it is defined up to ~5 km against ~10 km for the 1 Hz version. The multi-mission cross-calibration processing was also optimized with an improved Long Wavelengths Error (LWE) correction leading to a better consistency between tracks with an 9–15 % reduction of SLA variance at cross-over. The experimental L3 product improves the overall consistency with tide gauge measurements with a reduction of the variance of the SLA differences by 5 and 17 % compared to the 1 Hz product from S3A and Jason-3 (J3) measurements respectively. Primarily intended for regional applications, this product can significantly contribute to improving high resolution numerical model outputs via data assimilation. It also opens new perspectives for a better understanding of regional sea surface dynamics, with an improved representation of the coastal currents and a refined spectral content that reveals the unbalanced signal.
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CEC1: 'Comment on essd-2022-292', Giuseppe M.R. Manzella, 25 Nov 2022
Dear authors,
I must apologize for some delays in the evaluation of your paper on DUACS L3 5Hz experimental altimeter products. Evaluators who have been invited to rate your paper have not responded and this has forced us to a critical assessment of its content
I must say that the paper is of extremely high scientific value, but it proposes an experimental product. In presentation of the article you write that the paper is describing a regional experimental product with specific corrections aimed at reducing noise (lines 24 – 26), improving the long wavelengths error (line 33). The problems derive much more from paragraph 1.2 which explicitly speaks of an innovative and experimental process, as on the other hand results in the link of the products (https://www.aviso.altimetry.fr/en/data/products/sea -surface-height-products/regional/ssalto/duacs-experimental-products.html)
ESSD requires that the methods are validated and consolidated, but the validation of the methods falls outside the ESSD scope. If a criticism is allowed to us, based on past experience, the methods used for developing specific regional products may not be applicable in other regions. It is not within the scope of ESSD to conduct such assessments.
Your very interesting article on methodologies can be successfully submitted to other more suitable journals and I encourage you to do so, due to the interest there is in your field of study.
My personal best regards
Citation: https://doi.org/10.5194/essd-2022-292-CEC1
Status: closed
-
CEC1: 'Comment on essd-2022-292', Giuseppe M.R. Manzella, 25 Nov 2022
Dear authors,
I must apologize for some delays in the evaluation of your paper on DUACS L3 5Hz experimental altimeter products. Evaluators who have been invited to rate your paper have not responded and this has forced us to a critical assessment of its content
I must say that the paper is of extremely high scientific value, but it proposes an experimental product. In presentation of the article you write that the paper is describing a regional experimental product with specific corrections aimed at reducing noise (lines 24 – 26), improving the long wavelengths error (line 33). The problems derive much more from paragraph 1.2 which explicitly speaks of an innovative and experimental process, as on the other hand results in the link of the products (https://www.aviso.altimetry.fr/en/data/products/sea -surface-height-products/regional/ssalto/duacs-experimental-products.html)
ESSD requires that the methods are validated and consolidated, but the validation of the methods falls outside the ESSD scope. If a criticism is allowed to us, based on past experience, the methods used for developing specific regional products may not be applicable in other regions. It is not within the scope of ESSD to conduct such assessments.
Your very interesting article on methodologies can be successfully submitted to other more suitable journals and I encourage you to do so, due to the interest there is in your field of study.
My personal best regards
Citation: https://doi.org/10.5194/essd-2022-292-CEC1
Data sets
SSALTO/DUACS along-track Sea Level Anomalies at 5Hz Experimental products Pujol, M.-I., Dupuy, S., Vergara, O., Sánchez-Román, A., Faugère, Y., Prandi, P., Dabat, M.-L., Dagneaux, Q., Lievin, M., Cadier, E., Dibarboure, G., and Picot, N. https://doi.org/10.24400/527896/a01-2021.003
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