RAPID: Long-term Trends of the Atlantic Interhemispheric SST Gradient in the CMIP5 20th Century Simulations

RAPID：CMIP5 20 世纪模拟中大西洋半球海温梯度的长期趋势

• 批准号: 1126351
• 负责人: John Chiang
• 金额: $ 3.29万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-06-01 至 2012-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1126351&HistoricalAwards=false
• 关键词: RAPID; Long; term; Trends; Atlantic

This is one of 16 Rapid Response (RAPID) projects funded as the result of a Dear Colleague Letter (NSF 11-006) encouraging diagnostic analyses of climate model simulations prepared for the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5). Research conducted in these projects is expected to lead to more detailed model intercomparisons, better understanding of robust model behaviors, and better understanding and quantification of uncertainty in future climate simulations. This project examines the secular trend in the Atlantic interhemispheric sea surface temperature (SST) gradient occuring in 20th century observations and climate model simulations. Observations show a trend in the gradient in which the Southern Hemisphere tropical SSTs warm faster than their Northern Hemisphere counterparts. Previous work using an earlier ensemble of climate model simulations suggested that the SST gradient trend is forced in part, perhaps predominantly, by the radiative effects of anthropogenic sulfate aerosols. The behavior of the SST gradient trend in simulations prepared for the AR5 is of particular interest because the new generation of models incorporates significant advances in the simulation of both direct and indirect effects of aerosols. In this project, research focuses on 1) quantifying the magnitude of the SST gradient trend, and assessing the spread in the trend across the different multimodel ensemble members; 2) attributing the cause of the trend; 3) assessing the role of aerosol indirect effects in determining the magnitude of the trend; 4) determining the relative roles of different aerosol types in forcing the trend, particularly sulfate aerosols and black carbon; and 5) understanding the flattening of the trend in the late 20th century. The primary method for identifying the aerosol radiative contribution to the trend consists of comparisons between model simulations forced with all 20th-century climate forcings (including aerosols) and simulations in which only the 20th century increases in greenhouse gas concentrations are used as forcing.The broader impact of the project lies in its support of the IPCC AR5, which is intended to provide information on climate change and its consequences to decision makers worldwide. The Atlantic SST gradient exerts a significant influence on the climate of the surrounding landmasses, and is implicated in droughts over the Sahel and northeastern Brazil. The extent to which the SST gradient trend is forced by aerosols, and if so which aerosols are most responsible, is thus of great societal relevance to these regions.

这是一封亲爱同事的信 (NSF 11-006) 资助的 16 个快速响应 (RAPID) 项目之一，鼓励对为政府间气候变化专门委员会第五次评估报告 (IPCC AR5) 准备的气候模型模拟进行诊断分析。这些项目中进行的研究预计将导致更详细的模型相互比较，更好地理解稳健的模型行为，以及更好地理解和量化未来气候模拟中的不确定性。 该项目研究了 20 世纪观测和气候模型模拟中出现的大西洋半球间海面温度 (SST) 梯度的长期趋势。观测结果显示，南半球热带海温变暖速度快于北半球热带海温梯度趋势。 先前使用早期气候模型模拟集合的工作表明，海温梯度趋势部分（也许主要）是由人为硫酸盐气溶胶的辐射效应所推动的。为 AR5 准备的模拟中海温梯度趋势的行为特别令人感兴趣，因为新一代模型在模拟气溶胶的直接和间接影响方面取得了重大进展。 在该项目中，研究重点是：1）量化海温梯度趋势的大小，并评估不同多模式集合成员之间趋势的分布； 2）归因趋势的原因； 3) 评估气溶胶间接影响在确定趋势强度方面的作用； 4) 确定不同气溶胶类型在推动趋势方面的相对作用，特别是硫酸盐气溶胶和炭黑； 5) 了解 20 世纪末趋势的扁平化。 识别气溶胶辐射对趋势的贡献的主要方法包括将所有 20 世纪气候强迫（包括气溶胶）的模型模拟与仅使用 20 世纪温室气体浓度增加作为强迫的模拟进行比较。该项目的影响在于它对IPCC AR5的支持，该报告旨在向全世界决策者提供有关气候变化及其后果的信息。大西洋海温梯度对周围陆地的气候产生重大影响，并与萨赫勒和巴西东北部的干旱有关。 因此，海温梯度趋势受气溶胶影响的程度，以及如果是这样的话，哪些气溶胶是最有影响的，因此与这些地区具有很大的社会相关性。