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.

中文翻译：

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细化DUACS沿轨道（3级）高度计海平面产品的分辨率

摘要。本文介绍了在法国航天局 (CNES) 的支持下开发的高分辨率 Level-3 (L3) 高度计数据统一和高度计组合系统 (DUACS) 实验性区域产品。该产品从全速率（20 Hz 至 40 Hz）Level-2 (L2) 高度计测量结果推导出来，可在北大西洋 0cean 上空近 1 公里的采样范围内提供海平面异常 (SLA) 和其他基本物理变量。它使我们能够根据所考虑的高度计来解析约 35 公里到约 55 公里的波长。这得益于合成孔径雷达 (SAR) 和低分辨率模式 (LRM) 测量的雷达高度计处理的最新进展，以及对 DUACS 处理链不同阶段的改进。首先，Jason 和 Sentinel-3 (S3A) 分别考虑了新的自适应和 LR-RMC（具有距离偏移校正的低分辨率）处理技术。它们显着减少了短波长的误差，并且对于自适应处理，海岸附近可能的土地污染。接下来，为这次生产选择了最新的地球物理和环境修正。这包括旨在减少 LRM 测量中的测量噪声的特定校正，从而增强短波长的可观测性。与 1 Hz 产品相比，实验高分辨率产品达到的可观测波长减少了多达三分之一，或在东北大西洋地区减少了一半。考虑到处理的高度计的不同观测能力，从全速率测量中优化过滤残余噪声。应用了特定的数据恢复策略，显着优化了沿海和公海的数据可用性。因此，这种实验性 L3 产品比传统的 1 Hz 产品具有更好的分辨率，特别是在海岸附近，它被定义为 ~5 公里，而 1 Hz 版本则为 ~10 公里。多任务交叉校准处理也通过改进的长波长误差 (LWE) 校正进行了优化，从而使轨道之间的一致性更好，交叉时的 SLA 方差减少了 9-15%。与 S3A 和 Jason-3 (J3) 测量的 1 Hz 产品相比，实验 L3 产品提高了与潮位计测量的整体一致性，SLA 差异的方差分别减少了 5% 和 17%。该产品主要用于区域应用，可通过数据同化显着提高高分辨率数值模型输出。它还为更好地理解区域海面动力学开辟了新的视角，改进了海岸洋流的表现形式和揭示了不平衡信号的精细光谱内容。该产品可以通过数据同化显着有助于提高高分辨率数值模型的输出。它还为更好地理解区域海面动力学开辟了新的视角，改进了海岸洋流的表现形式和揭示了不平衡信号的精细光谱内容。该产品可以通过数据同化显着有助于提高高分辨率数值模型的输出。它还为更好地理解区域海面动力学开辟了新的视角，改进了海岸洋流的表现形式和揭示了不平衡信号的精细光谱内容。