Can we improve the representation of modeled ocean mixed layer by assimilating surface-only satellite-derived data? A case study for the tropical Pacific during the 1997-1998 El Nino
Can we improve the representation of modeled ocean mixed layer by assimilating surface-only satellite-derived data? A case study for the tropical Pacific during the 1997-1998 El Nino
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DOI：
10.1029/2002jc001603
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发表时间：
2003-06
影响因子：
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通讯作者：
F. Durand;L. Gourdeau;T. Delcroix;J. Verron
中科院分区：
文献类型：
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作者：
F. Durand;L. Gourdeau;T. Delcroix;J. Verron
[1]在热带海洋中，密度混合层确实影响海洋-大气的相互作用，这一特征是厄尔尼诺-南方涛动（ENSO）现象等高能气候事件发展的根本。这项工作的目的是利用现有的海表温度（SST）和速度以及未来的海表盐度（SSS）卫星派生的数据同化这些数据在一个原始方程模型，以改善模拟的混合层。由于卫星SSS数据还不可用，为了更好地分析同化是如何工作的，我们在一个使同化与真实的实验结论一致的背景下进行了孪生实验。两个模拟使用不同的强迫被用于实验。它们的误差与任何模拟和真实的观测之间的误差相当。同化方案是SEEK滤波器的自适应版本[Pham等人，1998]容易用于同化真实的数据。利用1997-1998年ENSO事件进行同化试验，分析了实际混合层的主要特征。特别是考虑到SSS、SST、混合层深度和障碍层厚度的相关性，卫星数据证明有助于更好地模拟海洋混合层。为了控制纬向赤道流，特别需要速度数据。有趣的是，同化的表面只有数据仍然工作良好的混合层以下，和一些改进是可检测的障碍层厚度方面，即使达到了同化方案的限制。
[1] In the tropical oceans the density mixed layer does influence the ocean-atmosphere interactions, a feature that is fundamental to the development of energetic climatic events such as the El Nino-Southern Oscillation (ENSO) phenomenon. The aim of this work is to take advantage of existing sea surface temperature (SST) and velocity together with future sea surface salinity (SSS) satellite-derived data by assimilating these data in a primitive equation model in order to improve the modeled mixed layer. As satellite SSS data are not yet available, and to better analyze how assimilation works, we performed twin experiments in a context that renders assimilation conclusive with regard to real experiment. Two simulations using different forcing were used for the experiments. They have errors that are comparable to the ones between any simulation and real observations. The assimilation scheme is an adaptive version of the SEEK filter [Pham et al., 1998] readily usable for assimilating real data. An assimilation experiment was conducted covering the 1997–1998 ENSO event to analyze the main characteristics of the actual mixed layer. Looking in particular at the relevance of SSS, SST, mixed layer depth, and barrier layer thickness, satellite-derived data prove to be useful to better simulate the oceanic mixed layer. Velocity data are specially needed to control the zonal equatorial current. Interestingly, assimilation of surface-only data still worked well below the mixed layer, and some improvements were detectable in terms of barrier layer thickness, even though the limit of the assimilation scheme was reached.