日本东京大学Toda Masaki团队研究了热带外海面温度变化驱动沃克环流的增强。该项研究成果发表在2024年8月29日出版的《自然—地球科学》上。
据介绍，太平洋沃克环流——热带太平洋纬向翻转环流——以及热带太平洋相关的海表温度分布对全球气候具有重要影响。然而，气候模型的历史模拟未能捕捉到1980年前后观测到的沃克环流的增强。虽然已有观点提出了一些机制来解释观测到的变化，但定量讨论和调和模型—观测差异的线索尚未解决。
研究表明，1980-2020年沃克环流的增强可以用副热带和温带海表温度变化的远程影响来定量解释。这一结论是从气候模拟起搏器试验中得到的，在这些试验中，热带以外的海面温度异常与观测值相符。来自东南太平洋的影响，使得热带太平洋东部变冷，对沃克环流的加强尤为重要。
这种向赤道的影响主要是通过大气及其与海洋的热耦合发生的。结果进一步表明，当前的气候模式在东南太平洋表面温度变化中存在偏差，这可能是无法再现沃克环流趋势的原因。研究结果强调，该地区海气耦合的改善可以更好地预测未来的气候。
附：英文原文
Title: Walker circulation strengthening driven by sea surface temperature changes outside the tropics
Author: Toda, Masaki, Kosaka, Yu, Miyamoto, Ayumu, Watanabe, Masahiro
Issue&Volume: 2024-08-29
Abstract: The Pacific Walker circulation—the tropical Pacific zonal overturning circulation of the atmosphere—and the associated sea surface temperature distribution in the tropical Pacific significantly impact global climate. However, climate model historical simulations cannot capture the observed Walker circulation enhancement since around 1980. Although a number of mechanisms have been proposed to explain the observed change, quantitative discussion and clues for reconciling the model-observation discrepancy have not yet been settled. Here we show that the Walker circulation strengthening between 1980 and 2020 can be quantitatively explained by the remote influence of subtropical and extratropical sea surface temperature changes. This conclusion is obtained from climate model pacemaker experiments in which sea surface temperature anomalies outside the tropics are restored towards observations. Influence from the southeastern Pacific, which cools the eastern tropical Pacific, is especially crucial for the Walker circulation strengthening. This equatorward influence occurs mostly through the atmosphere and its thermal coupling with the ocean. We further show that current generation climate models have biases in southeastern Pacific surface temperature changes, which may cause the failure in reproducing the Walker circulation trend. Our results suggest that improved representation of air–sea coupling in this region could enable better projections of future climate.
DOI: 10.1038/s41561-024-01510-5
Source: https://www.nature.com/articles/s41561-024-01510-5