Abstract Motivated by observations of fine scale vertical shear and its contribution to mixing in the tropical ocean, this study explores the impact of vertical resolution in an ocean model on sea surface temperature in the tropical Pacific Ocean. We conduct two model experiments that differ in the vertical discretization only, with the grid spacing in one being significantly smaller than the other in the upper ocean. We examine the temperature difference between the high and low vertical resolution experiments. We find that the difference in the upper-most layer is positive in the equatorial cold tongue and negative along the South American coast, thus reducing the commonly seen cool and warm biases in the two regions, respectively. The change in the structure of the vertical diffusivity, as determined by the K-profile parametrization, is identified as the primary cause in reducing the biases. In the central equatorial Pacific, the change in the vertical diffusivity from low to high vertical resolution in the upper pycnocline results in a positive temperature difference that propagates eastward as an equatorial Kelvin wave, rising to the sea surface in the central and eastern regions to increase the sea surface temperature there. In the far eastern equatorial Pacific, the change in the vertical diffusivity in the lower pycnocline produces a negative temperature difference that propagates poleward as coastal Kelvin waves along the west coast of the American continent, outcropping along the South American coast to reduce the sea surface temperature there. The high vertical resolution experiment captures much of the small-scale vertical velocity shear and resolves the fine details of the stratification in the upper ocean. Our analysis suggests that the shear-generated turbulence is the primary contributor to the change in the vertical diffusivity in the central region whereas stratification is the dominant factor in the far eastern region.

中文翻译：

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热带太平洋模式中垂直分辨率对减少海面温度偏差的影响

摘要 受细尺度垂直切变观测及其对热带海洋混合作用的影响，本研究探讨了海洋模式中垂直分辨率对热带太平洋海面温度的影响。我们进行了两个模型实验，它们仅在垂直离散化方面有所不同，其中一个的网格间距明显小于上层海洋的另一个。我们检查了高和低垂直分辨率实验之间的温差。我们发现赤道冷舌的最上层差异为正，南美沿岸为负，从而分别减少了两个地区常见的冷暖偏差。由 K 剖面参数化确定的垂直扩散率结构的变化，被确定为减少偏差的主要原因。在赤道中太平洋，上密云斜层的垂直扩散率由低到高的垂直分辨率变化导致正温差作为赤道开尔文波向东传播，在中东部地区上升到海面增加那里的海面温度。在远东赤道太平洋，下部火山口垂直扩散率的变化产生负温差，以沿海开尔文波的形式沿美洲大陆西海岸向极地传播，沿南美洲海岸出露以降低海面温度那里。高垂直分辨率实验捕获了大部分小尺度垂直速度切变并解析了上层海洋分层的精细细节。我们的分析表明，剪切产生的湍流是中部地区垂直扩散率变化的主要因素，而分层是远东地区的主要因素。