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AGS-PRF Coupling Between Regional Climate Feedbacks and Large-Scale Circulation in a Hierarchy of Models

模型层次结构中区域气候反馈与大尺度环流之间的 AGS-PRF 耦合

基本信息

批准号：
1524569
负责人：
Nicole Feldl
金额：
$ 8.6万
依托单位：
Feldl Nicole
依托单位国家：
美国
项目类别：
Fellowship Award
财政年份：
2015
资助国家：
美国
起止时间：
2015-07-01 至 2016-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1524569&HistoricalAwards=false
关键词：
AGS PRF Coupling Between Regional

项目摘要

Climate change due to increased greenhouse gas concentration is generally referred to as global warming, and the sensitivity of climate to greenhouse gas increases is measured by the increase in global mean temperature for a given uniform increase in greenhouse gas concentrations. Yet the feedback processes which determine climate sensitivity show substantial geographical dependencies, for example the albedo feedbacks associated with ice and snow are largely confined to colder high latitude regions, while cloud and water vapor feedbacks are strongest in the subtropics. The response of climate to uniform external forcing also shows strong geographical dependence, with important consequences for human and natural systems. But the spatial pattern of the response does not match the spatial pattern of the feedbacks, as atmospheric and oceanic circulation are effective in redistributing the excess energy introduced to the system by the regional feedbacks. Moreover, robust changes in atmospheric circulation are found in climate change simulations, presumably caused by the feedbacks and external forcing, but they may in turn have substantial effects on the feedbacks.This award supports the PI to conduct postdoctoral research to understand the interplay of regional climate feedbacks, energy transport, and atmospheric stability and circulation dynamics in determining the regional response of the climate system to external forcing. The specific focus of the work is on climate feedbacks and climate change in the tropics and subtropics and how they relate to changes in the strength of the Hadley cell, the overturning circulation in which air rises in the rainy intertropical convergence zone and subsides in the dry subtropics. The PI and her colleagues have developed a diagnostic equation in which fractional changes in the strength of the Hadley cell can be decomposed into contributions from all of the factors mentioned above. The diagnostic analysis is applied to a set of climate simulations archived for the Climate Model Intercomparison Project version 5 (CMIP5) for which the climate feedbacks can be quantified. One question to be addressed is why model simulations tend to show a decrease in the strength of the Hadley simulation as climate warms, and another is whether model-to-model differences in the Hadley cell response can be related to differences in feedbacks and other factors. This analysis will be supplemented by experiments with a hierarchy of models at various stages of complexity, to examine causal relationships between changes in the Hadley cell and the feedbacks and energy transports.The work has important broader impacts given the substantial social and ecological impacts of climate change in the tropics and subtropics. The results of this work may be valuable for understanding the behavior of model simulations of future climate change, in particular for understanding and reducing uncertainty in climate model projections, and for deciding which aspects of simulations are likely to prove most reliable. In addition, the project has an educational component in which the PI will develop educational materials to provide undergraduate students with a rigorous foundation in climate feedback analysis. The materials include hands-on exercises using a simple energy balance model written in Python, which will be made available online.

由温室气体浓度增加引起的气候变化通常被称为全球变暖，气候对温室气体增加的敏感性是用给定温室气体浓度均匀增加时全球平均温度的增加来衡量的。然而，决定气候敏感性的反馈过程显示出大量的地理依赖性，例如，与冰雪有关的反照率反馈主要局限于较冷的高纬度地区，而云和水蒸气反馈在亚热带最强。气候对均匀的外部强迫的响应也显示出强烈的地理依赖性，对人类和自然系统产生重要影响。但是响应的空间格局与反馈的空间格局并不匹配，因为大气和海洋环流可以有效地重新分配由区域反馈引入系统的多余能量。此外，在气候变化模拟中发现大气环流的强劲变化，可能是由反馈和外部强迫引起的，但它们反过来可能对反馈产生实质性影响。该奖项支持PI开展博士后研究，以了解区域气候反馈、能量输送、大气稳定性和环流动力学之间的相互作用，从而确定气候系统对外部强迫的区域响应。这项工作的具体重点是热带和亚热带的气候反馈和气候变化，以及它们与哈德利环流强度变化的关系。哈德利环流是一种翻转环流，在这种环流中，空气在多雨的热带辐合带上升，在干燥的亚热带下降。PI和她的同事已经开发了一个诊断方程，其中哈德利细胞强度的微小变化可以分解为上述所有因素的贡献。将诊断分析应用于气候模式比较项目第5版（CMIP5）存档的一组气候模拟，其中气候反馈可以量化。需要解决的一个问题是，为什么随着气候变暖，模型模拟往往会显示哈德利模拟的强度下降，另一个问题是，模型与模型之间哈德利细胞反应的差异是否与反馈和其他因素的差异有关。这一分析将通过在不同复杂阶段的模型层次的实验加以补充，以检验哈德利细胞的变化与反馈和能量传输之间的因果关系。鉴于热带和亚热带气候变化对社会和生态的重大影响，这项工作具有重要的广泛影响。这项工作的结果对于理解模式模拟未来气候变化的行为，特别是对于理解和减少气候模式预估中的不确定性，以及对于决定模拟的哪些方面可能被证明是最可靠的，可能是有价值的。此外，该项目还有一个教育组成部分，PI将编写教育材料，为本科生提供气候反馈分析的严格基础。这些材料包括使用Python编写的简单能量平衡模型的动手练习，该模型将在网上提供。