Zhou,H., Yuan, D.-L., Yang, L.-N., Li, X., Dewar, W, 2017: Decadal Variability of the Meridional Geostrophic Transport in the Upper Tropical North Pacific Ocean

Title: Decadal Variability of the Meridional Geostrophic Transport in the Upper Tropical North Pacific Ocean

Authors: Zhou,H., Yuan, D.-L., Yang, L.-N., Li, X.,  Dewar, W

Journal: American Meteorological Society

Received: 27 September 2017

Abstract:

The meridional geostrophic transport (MGT) in the interior tropical North Pacific Ocean is estimated based on global ocean heat and salt content data. The decadal variations of the zonally and vertically integrated MGT in the tropical North Pacific Ocean are found to precede the Pacific decadal oscillation (PDO) by 1–3 years. The dynamics of the MGT are analyzed based on Sverdrup theory. It is found that the total meridional transport variability (MGT plus Ekman) is dominated by the MGT variability having positive correlations with the PDO index. The Sverdrup transports differ from the total meridional transport significantly and have insignificant correlations with PDO index, suggesting that the MGT variability is not controlled by the Sverdrup dynamics. In comparison, the simulated meridional transport variability in the models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and the Ocean General Circulation Model for the Earth Simulator are dominated by the Sverdrup transports, having insignificant correlations with the simulated PDO indices. The comparison suggests that the non-Sverdrup component in the MGT is important for the predictability of PDO and that significant deficiencies exist in these models in simulating a realistic structure of the tropical ocean gyre variability and predicting the decadal climate variations associated with it.

Keywords: Climate models; General circulation models; Model evaluation/performance; Decadal variability; Interdecadal variability; Pacific decadal oscillation

热带北太平洋上层经向地转输运年代际变异及其对PDO可预报性

题目：热带北太平洋上层经向地转输运年代际变异及其对PDO可预报性

作者：周慧，袁东亮，李翔，威廉姆·杜瓦

接收期刊：American Meteorological Society

接收日期：2017年9月27日

摘要：

研究表明，太平洋年代际震荡（PDO）源于海洋和大气多个物理过程的相互作用，其中北太平洋环流变异在其中起着重要的作用。在年代际时间尺度上，海洋环流的动力机制由表层艾克曼抽吸产生的海洋经向运动决定。所以，海洋的经向输运年代际变异对热带太平洋年代际变异起着举足轻重的作用。传统上，我们对海洋平均经向输运的认识主要是基于Sverdrup理论，这一理论建立在线性动力学基础上。对海洋经向输运及其变异的成功模拟是现代气候系统模式进行年代际气候预测及研究的关键，而目前气候模式中海洋大多是粗分辨率（纬向分辨率>1度），因此它们对海洋环流的模拟本质上是与Sverdrup理论吻合的。因此，了解实际海洋中海洋经向输运的年代际变异特征及其规律，评估Sverdrup理论在刻画北太平洋经向输运的年代际变异的代表性，对气候年代际变异研究及其预测具有重要意义。本文主要通过分析62年历史水文资料，揭示热带太平洋经向地转输运（MGT）的年代际变异特征，发现MGT在超前PDO指数1-3年具有显著相关，表明其对北太平洋年代际变异具有可预报性。热带太平洋增强（减弱）的经向输运有利于产生PDO正（负）位相，表明热带充放电机制是导致热带太平洋经向输运对PDO有可预报性的主要机制。而热带北太平洋Sverdrup输运对PDO不具有可预报性，目前主要的气候模式（如CMIP5）及高分辨率海洋模式OFES因其动力机制主要受Sverdrup理论控制也未能模拟出MGT对PDO的可预报性。因此，热带北太平洋非线性过程的模拟是气候模式成功模拟年代际变异的关键。