Ocean reanalysis products are routinely employed as reality checks in model evaluations and for process studies. This is especially so for critical regions such as the equatorial cold tongue (ECT) in the eastern equatorial Pacific where models suffer a chronic cold bias. ECT is a major player in the Pacific equatorial zonal sea surface temperature (SST) gradient (Δ_EWSST) that has a significant impact on oceanic heat uptake and thus global climate. Hence, we investigate the reliability of three ocean reanalysis products for surface flux and ocean dynamic controls on Δ_EWSST and Niño3.4 SST trends. We infer that while Niño3.4 SST trends are positive in all products, the signs of Δ_EWSST trends do not agree with each other because initial conditions likely play a big role in their evolution. However, for Δ_EWSST trends, the effect of initial conditions gets canceled out to some extent. Mixed layer heat budget and trends in ocean dynamic features such as tropical and subtropical cells, equatorial undercurrent, and subsurface temperatures are also diagnosed. We show that two reanalysis products that show a strengthening of Δ_EWSST have contradicting trends in their surface heat flux and ocean dynamic contributions. This suggests that without accurate surface heat and momentum fluxes, data assimilation techniques may produce an east–west trend that is inconsistent among each other. Reanalysis products must address these issues considering the importance of this gradient.

中文翻译：

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重新分析产品中横跨赤道太平洋的大气-海洋动力学和年代际纬向海温梯度趋势不一致

海洋再分析产品通常在模型评估和过程研究中用作现实检查。对于诸如赤道东太平洋的赤道冷舌（ECT）等关键区域，其模型遭受长期的冷偏差尤其如此。ECT是太平洋赤道纬向海表温度（SST）梯度（_ΔEW SST）的主要参与者，该梯度对海洋的热量吸收以及全球气候具有重大影响。因此，我们研究了三种海洋再分析产品上Δ表面通量和海洋动力控制可靠度_EW SST和Niño3.4SST趋势。我们推断，而SSTNiño3.4的趋势是在所有产品中积极，Δ的迹象_EWSST趋势彼此不一致，因为初始条件可能在其演变中发挥重要作用。但是，对于_ΔEW SST趋势，初始条件的影响在某种程度上被抵消了。还可以诊断出混合层热量收支和海洋动态特征（例如热带和亚热带细胞，赤道暗流和地下温度）的趋势。我们发现，显示出加强Δ的两个再分析产品_EW海表温度在其表面热通量和海洋动力贡献方面存在相反的趋势。这表明，如果没有准确的地表热和动量通量，数据同化技术可能会产生东西方向不一致的东西向趋势。考虑到此梯度的重要性，重新分析产品必须解决这些问题。