Understanding Causes of Climate Model Biases in the Southeastern Tropical Atlantic

了解热带大西洋东南部气候模型偏差的原因

• 批准号: 1334707
• 负责人: Ping Chang
• 金额: $ 79.63万
• 依托单位: Texas A&M University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1334707&HistoricalAwards=false
• 关键词: Understanding; Causes; Climate; Model; Biases

Recent studies have revealed that among all the tropical oceans, the Atlantic has experienced the most pronounced warming trend over the 20th century. Many extreme climate events are influenced by oceanic conditions over the Atlantic. It is therefore imperative to have accurate simulations of the Atlantic Ocean climate to be able to make credible projections of future climate in the surrounding continental regions. Unfortunately, current-generation models, including those used by the Intergovernmental Panel on Climate Change (IPCC), exhibit severe biases in their simulations of tropical Atlantic climate. An infamous example is a persistent warm sea surface temperature bias of at least 6°C off the coast of Namibia and Angola. This research aims at investigating the causes of this bias which will ultimately lead to major improvements in the simulation and projection of future climate changes within the Atlantic sector.Intellectual Merit: This project will explore oceanic and atmospheric biases, as well as amplification of biases from the coupled ocean-atmosphere system. The sources of oceanic biases will be analyzed and identified from oceanic observations, ocean reanalysis products, IPCC model simulations, and eddy resolving regional ocean simulations. Similarly, atmospheric biases will be evaluated using atmospheric reanalysis data and convection-resolving regional atmospheric model simulations. The role of ocean-atmosphere interactions in amplifying the oceanic or atmospheric biases will be examined from high-resolution coupled regional climate model (CRCM) simulations. The use of high-resolution (up to 3 km) regional climate models will allow processes such as oceanic mesoscale eddies, fronts and upwelling dynamics off the west coast of southern Africa, as well as atmospheric convection and steep orography effects, and thus will minimize model systematic errors due to uncertainties associated with parameterizations of subgrid-scale processes. This modeling approach will isolate sources of the biases from other ocean basins and will help to pinpoint the causes of the biases within the Atlantic basin. The study will utilize an array of fine temporal and spatial resolution data sets produced by recent intense observational programs within the Atlantic sector. Furthermore, the project will coincide with the launch of two major European research projects in the study region: a German project "Southwest African Coastal Upwelling System and Benguela Niño" (SACUS) led by Brandt, and an EU project "Enhancing prediction of tropical Atlantic climate and its impacts" (PREFACE) led by Keenlyside. Both of these projects will generate new arrays of observations along the southern Africa coast. Close collaboration with the European colleagues will allow their new observations to be combined with US-based detailed modeling that will likely lead to new breakthroughs in solving tropical Atlantic bias problems.Broader Impacts: This research will enhance our understanding of the uncertainties in projecting impacts of global climate change in the Atlantic region, which has enormous socio-economic implications for countries in the region. The CRCM is being developed within the framework of the Coupler (CPL7) software that is part of the National Center for Atmospheric Research Community Earth System Model (CESM). This framework allows easy transfer of parameterizations between CESM and the CRCM, and potential partial coupling between the CESM and the CRCM. We envision that the CRCM will become a community-modeling tool and be made available to the broader climate research community. Findings from this study on reducing climate model biases will feedback to community model development activities. The project will support one graduate student and one postdoc at Texas A&M University (TAMU) and provide valuable professional development for all young scientists involved, including Co-PI Patricola.

最近的研究表明，在所有热带海洋中，大西洋在20世纪经历了最明显的变暖趋势，因此对大西洋进行准确的模拟势在必行。不幸的是，当前的模型，包括政府间气候变化专门委员会（IPCC）使用的模型，在模拟热带大西洋气候时表现出严重的偏差。臭名昭著的例子是一个持久的纳米比亚和安哥拉海岸附近温暖的海面温度偏差至少为 6°C 这项研究旨在调查这种偏差的原因，最终将导致大西洋区域未来气候变化的模拟和预测的重大改进。智力优势：该项目将探索海洋和大气偏差，以及海洋-大气耦合系统偏差的放大。将从海洋观测、海洋再分析产品、IPCC模型中分析和识别海洋偏差的来源。模拟和涡流解析区域海洋模拟将使用大气再分析数据和对流解析区域大气模型模拟进行类似的评估。海洋-大气相互作用在放大海洋或大气偏差中的作用将被检查。耦合区域气候模型（CRCM）模拟的使用高分辨率（高达3公里）区域气候模型将允许诸如海洋中尺度涡流、锋面和上升流动力学等过程。南部非洲西海岸，以及大气对流和陡峭地形效应，因此将最大限度地减少由于与次网格尺度过程参数化相关的不确定性而导致的模型系统误差，这种建模方法将隔离来自其他海洋盆地和区域的偏差来源。该研究将有助于查明大西洋盆地内偏差的原因，该研究将利用大西洋区域近期密集观测计划产生的一系列精细时间和空间分辨率数据集。此外，该项目将与两个项目同时启动。欧洲主要研究项目研究区域：由 Brandt 领导的德国项目“西南非洲沿海上升流系统和本格拉尼诺”（SACUS），以及由 Keenlyside 领导的欧盟项目“加强热带大西洋气候及其影响的预测”（PREFACE）。将在南部非洲海岸产生新的观测结果，与欧洲同事的密切合作将使他们的新观测结果与美国的详细模型相结合，这可能会在解决热带大西洋偏差问题上取得新的突破。影响：这项研究将增强我们对预测全球气候变化对大西洋地区影响的不确定性的理解，这对该地区的国家具有巨大的社会经济影响。CRCM 正在耦合器 (CPL7) 的框架内制定。该软件是国家大气研究中心社区地球系统模型（CESM）的一部分，该框架允许在CESM和CRCM之间轻松传输参数，以及CESM和CRCM之间的潜在部分耦合。将成为一个社区建模工具，并提供给更广泛的气候研究社区。这项关于减少气候模型偏差的研究结果将反馈给社区模型开发活动。该项目将为德克萨斯农工大学的一名研究生和一名博士后提供支持。 TAMU）并为所有参与其中的年轻科学家（包括 Co-PI Patricola）提供有价值的专业发展。