Upper-ocean cooling rate of the South China Sea in response to extreme cold surges and weak cold-air invasions

Abstract

Cold-surge events can lead to temperature drops and strong winds, which then leads to upper-ocean cooling and deepening of the mixed-layer depth, as illustrated in previous studies. In this study, based on the temperature drop of Shanwei meteorological station, two extreme cold surges and five weak cold invasions in the South China Sea are simulated using an ocean–atmosphere coupled model to investigate their different impacts on the upper-ocean temperature. The diffusion term contributes to the difference in temperature tendency of the upper 20 m, while the advection term contributes to the positive difference from 20 to 80 m of the offshore region and negative difference from 80 to 160 m. In addition, the significant differences are attributed primarily to the influence of the upper-ocean temperature gradient, which subsequently impacts the advection term and results in notable differences in temperature tendency at depths from 80 to 160 m.

摘要

前人的研究揭示了寒潮事件导致近地气温下降和强风, 也导致上层海洋冷却和混合层深度加深. 本研究根据汕尾气象站的气温变化, 并利用海气耦合模型模拟了南海的两次极端寒流和五次弱冷空气入侵, 研究它们对上层海洋温度变化的不同影响. 研究结果说明了扩散项对上层20米的温度变化差异的贡献, 平流项是导致20至80米的正温度变化差异的主要原因, 平流项也导致80至160米的负温度变化差异. 此外, 这种显著差异主要归因于上层海洋温度梯度的影响, 进而影响平流项, 使80至160米深度的温度变化存在显著差异.