Understanding the Influence of Climate Change on Temperature Persistence

温室气体排放造成的各种气候影响超出了全球气温升高的范围，其中许多影响，如热浪和极端降雨频率的增加，都得到了充分的认识。该奖项的工作考察了全球变暖的一个尚未被广泛认识的后果：地表温度短期波动持续更长时间的趋势。在20世纪最后20年和21世纪气候变化模拟的比较中，这种影响已经被看到，地表温度异常的5天持续性增加了50%。虽然到目前为止还没有在观测记录中确定该信号，但它是利用共同体地球系统模型(CESM)进行的一大批模型模拟的一个稳健特征，并且可以在该模型的各种简化配置中再现。持续性增加的模式很耐人寻味，因为它在海洋上比陆地上更突出，尽管它延伸到澳大利亚、中国东部和加拿大西部。该奖项的工作试图从一个概念模型的角度来理解持续性的变化，在这个概念模型中，温度波动是由随机强迫引起的，并通过线性松弛来衰减。在这个模型中，持续时间的增加是由于有效热容的增加，随机强迫的变红，或者控制松弛的阻尼过程的减少。这项工作遵循两个流派，其中一个流派审查了气候模式对比项目(CMIP)的再分析产品和模拟，特别是多模式大型集合档案。另一股流包括使用共同体大气模式(CAM)的数值试验，该模式是CESM的大气成分模式。一些实验涉及禁用相关反馈的技术，例如“云锁定”和在辐射法规中规定水蒸气。该项目利用了作为CESM代码库一部分的模型层次结构。这项工作具有社会意义，因为它有助于我们了解气候变化如何影响极端温度事件的持续性，而此类事件的影响关键取决于它们的持续时间。研究小组还向当地公立学校进行外联，为教师和学生提供一系列关于气候科学的外联讲座。此外，该项目还为两名研究生提供支持和培训。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Greenhouse gas emissions cause a variety of climatic effects which go beyond increasing global temperature and many of these, such as increases in the frequency of heat waves and extreme rainfall, are well recognized. Work under this award examines a consequence of global warming that has not been widely appreciated: the tendency for short-term surface temperature fluctuations to persist for longer periods of time. The effect has been seen in comparisons between the last two decades of the 20th and 21st centuries in climate change simulations, with increases of up to 50% in the 5-day persistence of surface temperature anomalies. While the signal has not been identified in the observed record to date it is a robust feature of simulations across a large ensemble of model simulations performed with the Community Earth System Model (CESM) and can be reproduced in a variety of simplified configurations of the model. The pattern of the persistence increase is intriguing as it is more prominent over the oceans than over land, although it extends over Australia, eastern China, and western Canada.Work under this award seeks to understand the change in persistence in terms of a conceptual model in which temperature fluctuations arise from random forcing and decay through linear relaxation. In this model an increase in persistence results from an increase in effective heat capacity, reddening of the stochastic forcing, or a decrease in the damping processes that control relaxation. The work follows two streams, one of which examines reanalysis products and simulations from the Climate Model Intercomparison Project (CMIP), particular the multi-model large ensemble archive. The other stream consists of numerical experiments using the Community Atmosphere Model (CAM, the atmospheric component model of CESM). Some experiments involve techniques to disable relevant feedbacks, for instance "cloud locking" and prescribing water vapor in the radiation code. The project takes advantage of the model hierarchy available as part of the CESM code base.The work has societal relevance as its serves to inform our understanding of how climate change influences the persistence of extreme temperature events, and the impacts of such events depends critically on their duration. The research team also conducts outreach to local public schools, providing a series of outreach lectures on climate science to teachers and students. In addition, the project provides support and training to two graduate students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.