What Causes the Tropical Atlantic SST Bias in CCSM3?

目前的大气-海洋耦合气候模式不能再现热带大西洋海表温度（SST）的年周期，因此没有技能来模拟或预测热带大西洋气候变率。该项目旨在分析国家大气研究中心（NCAR）社区气候系统模式版本3（CCSM 3）和版本3.5的混合层热量收支，以确定有助于这种SST偏差的过程和/或参数化。调查人员将在三个关键区域研究当地海洋动力学的可能作用（东南大西洋、赤道大西洋东部和中部以及热带北大西洋），并确定和量化外部影响，目的是了解当地的大气-海洋反馈过程是否以及如何放大远程信号。具体来说，研究人员将进行一些CCSM 3（3.5）包括（a）固定SST的动力大气试验;（B）固定表面通量的动力海洋试验;（c）完全耦合的大气-海洋试验;（d）区域通量调整的大气-海洋耦合试验。比较这些模式运行沿着与观测数据将提供一些有用的见解的固有偏差在海洋和大气成分的CCSM，以及如果和如何这种偏差被传输到偏远地区和/或本地放大通过耦合过程。通过用CCSM 3（3.5）检验假设，这项研究将增加和完善我们对影响赤道大西洋SST的过程及其在热带大西洋气候变率中更广泛的参与的理解。这项工作的成果将被纳入气候模型，有可能提高对热带大西洋变率的理解，提高季节到十年气候预测技能，这将有利于热带大西洋周围的社会。

Current atmosphere-ocean coupled climate models cannot reproduce the annual cycle of tropical Atlantic sea surface temperatures (SSTs) and thus do not have a skill to simulate or to forecast the tropical Atlantic climate variability. This project seeks to analyze the mixed layer heat budget of the National Center for Atmospheric Resesarch (NCAR) community climate system model version 3 (CCSM3) and version 3.5 to identify processes and/or parameterizations that contribute to this SST bias. The investigators will examine the possible role of local ocean dynamics in three key regions (southeastern Atlantic Ocean, eastern and central equatorial Atlantic Ocean, and tropical North Atlantic Ocean), and determine and quantify the external influences, with the goal of understanding if and how local atmosphere-ocean feedback processes amplify the remote signals.Specifically the investigators will perform some CCSM3(3.5) experiments by including (a) dynamic atmosphere with fixed SST run; (b) dynamic ocean with fixed surface flux run; (c) fully coupled atmosphere-ocean run; (d) coupled atmosphere-ocean runs with the regional flux-adjustment. Comparison of these model runs along with the observational data will provide some useful insights on the inherent biases in the ocean and atmospheric components of CCSM, and if and how such biases are transmitted to remote regions and/or locally amplified through the coupling processes. Through testing hypotheses with CCSM3(3.5), this study will increase and refine our understanding of the processes that affect the equatorial Atlantic SST and their broader involvement in tropical Atlantic climate variability. The outcome of the work will be merged into climate models, potentially improving understanding of tropical Atlantic variability and enhancing seasonal-to-decadal climate prediction skill, which will benefit society surrounding the tropical Atlantic.