Collaborative Research: An Observational and Modeling Study of Spring Onset in the Northern Hemisphere Circulation

春季开始(即从冬季向春季的年度过渡)及其年际变化是区域气候的重要组成部分。这两个特征通过对流层中云、海冰、气温和臭氧的变化影响水文循环，从而影响人类、植被生长和生态系统生产力。最近的观测研究表明，春季开始与平流层最终变暖(SFW)密切相关。过去的数值研究也表明，春季开始的年际变化与SFW事件时间的伴随变化有很强的耦合。PIS对SFW事件的关注为研究春季开始的物理和可预测性以及影响区域气候及其变异性的平流层-对流层动力耦合提供了研究环境。智力优势：PI将使用天气和动态观测诊断以及理想化建模研究的混合。首先，将利用观测对春天的到来进行彻底的现象学描述。然后，复合观测场将被用来解决春季开始时的各种基本动力学问题。在唯象描述和探索性线性模式计算的指导下，将进行几个数值试验来研究春季开始时的平流层-对流层耦合。这项工作的完成将为以下方面提供新的见解：1.波-均流相互作用对春季开始演化的影响，2.平流层在春季开始中的作用，3.对流层气候显著变化和可预测性的物理机制。更广泛的影响：该研究为理解和解释与春季开始相关的区域气候变化提供了一个动力学框架。这将对区域气候预测产生重要影响。这项研究促进了两所大学之间的合作，填补了对流层和平流层研究界之间的空白，并可能导致对春季开始及其受SFW事件调制的全面研究。

The spring onset (i.e., yearly transition from winter to spring) and its interannual variability are important components of regional climate. These two features influence the hydrological cycle, through variations in clouds, sea ice, air temperature and ozone in the troposphere affecting humanity, vegetation growth, and ecosystem productivity. Recent observational studies have indicated that spring onset is strongly linked to stratospheric final warming (SFW). Past numerical studies have also indicated that the interannual variability in spring onset is strongly coupled to concomitant variations in the timing of the SFW events. The PIs' focus on SFW events provides a research setting for studying the physics and predictability of spring onset along with stratosphere-troposphere dynamical coupling that influences regional climate and its variability. Intellectual merit: The PIs will use a blend of synoptic and dynamic observational diagnoses and idealized modeling studies. First, a thorough phenomenological characterization of spring onset will be developed using observations. Then, the composite observational fields will be used to address various fundamental dynamical questions for spring onset. Guided by the phenomenological characterization and exploratory linear model calculations, several numerical experiments will be carried out to study stratosphere-troposphere coupling during spring onset. Completion of this work will offer new insights into:1. Effects of wave-mean flow interactions on the evolution of spring onset,2. Roles of the stratosphere in spring onset,3. Physical mechanisms responsible for noted changes in tropospheric climate and predictability.Broader impacts: The research provides a dynamical framework for understanding and interpreting regional climate changes associated with spring onset. It will have important implications for regional climate predictions. The research fosters collaboration between two universities and fills in gaps between tropospheric and stratospheric research communities and may lead to a comprehensive study of spring onset and its modulations by SFW events.