Collaborative Research: Process Mechanics of Cloudiness Transitions in Subtropical Marine Boundary Layers

合作研究：副热带海洋边界层云量转变的过程机制

• 批准号: 2323067
• 负责人: Jui-Yuan Chiu
• 金额: $ 53.27万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-15 至 2026-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2323067&HistoricalAwards=false
• 关键词: Collaborative; Research; Process; Mechanics; Cloudiness

Clouds are one of the key components of the climate system because they influence the amount of sunlight that reaches the Earth’s surface and the amount of energy that the Earth radiates back to space. The most prominent clouds on the planet are thin layered clouds in the lower atmosphere over the oceans, which are known collectively as marine stratocumulus. The climate system is particularly sensitive to the coverage of marine stratocumulus clouds because they reflect almost all the incoming sunlight that would otherwise reach and warm the ocean surface. As marine stratocumuli in the mid-latitudes move south toward the tropics, the ocean surface beneath them warms and they undergo a structural transition that leads to breaks in the clouds. The location, and the details of this transition significantly impact the over-ocean energy budget. While some of the physical mechanisms that determine when and how the marine stratocumulus evolves into a more broken state are known, weather forecast and climate models, which are of societal importance, do not accurately reproduce these cloud structural transitions. This is primarily because the complicated combination of physical processes that produce these transitions are not fully understood. Marine stratocumulus transitions over the Eastern North Atlantic (ENA) are of particular importance because cloud cover over this region has decreased over the past 30-years and the ENA lies downstream of a rapidly warming Arctic. In addition, ocean circulations in the region are known to be sensitive to the input of meltwater as Arctic ice coverage declines. To facilitate a deeper understanding of processes and interactions responsible for marine stratocumulus transitions, the focus of this research is to investigate and understand the shifting balance of driving forces in various transition stages. These stages include transitions between patches of single layer stratocumulus, patches of cumulus, and hybrid regions containing coexisting stratocumulus and cumulus, a structure often referred to as “cumulus-coupled” stratocumulus. Cumulus-coupled stratocumulus present in two configurations: one in which small, random cumulus rise into stratocumulus and another in which the cumulus exhibits extensive mesoscale organization covering tens of kilometers, a configuration referred to as Marine Boundary Layer Convective Complexes (MBLCC). This project capitalizes on modern high-resolution computer simulations and a newly developed causal framework in which key drivers for stratocumulus cloud transitions will be used to build causal webs, illustrating the pathways of underlying processes and interactions. This new framework works for nonlinear systems, and importantly, allows multiple variables to work in concert, beyond concentrating only on independent influences of variables. Research results from this project are expected to address current shortcomings in model representations of marine stratocumulus in models of all types and to provide a new mantra for diagnosing interactions in other atmospheric systems.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.

云是气候系统的关键组成部分之一，因为它们影响到达地球表面的阳光量以及地球辐射回太空的能量。地球上最突出的云是低层的薄层云。海洋上空的大气，统称为海洋层积云。气候系统对海洋层积云的覆盖特别敏感，因为它们反射了几乎所有原本会到达并温暖海洋表面的入射阳光。中纬度地区的层积云向南移动到热带地区，其下方的海洋表面变暖，并且它们经历结构转变，导致云层破裂，而这种转变的细节会极大地影响海洋上空的能量预算。虽然确定海洋层积云何时以及如何演化为更破碎状态的一些物理机制是已知的，但具有社会重要性的天气预报和气候模型并不能准确地再现这些云结构转变，这主要是因为复杂的云结构转变。的组合产生这些转变的物理过程尚未完全了解，北大西洋东部 (ENA) 的海洋层积云转变尤为重要，因为该地区的云量在过去 30 年来有所减少，而且 ENA 位于快速变暖的北极下游。此外，随着北极冰盖面积的减少，该地区的海洋环流对融水的输入很敏感，为了促进对海洋层积云转变的过程和相互作用的更深入了解，本研究的重点是调查和研究。了解各个过渡阶段驱动力的变化平衡。这些阶段包括单层层积云斑块、积云斑块以及包含共存层积云和积云的混合区域（通常称为“积云耦合”层积云）之间的过渡。 -耦合层积云以两种形态存在：一种是小的、随机的积云上升为层积云，另一种是积云展示了覆盖数十公里的广泛中尺度组织，这种配置被称为海洋边界层对流复合体（MBLCC），该项目利用现代高分辨率计算机模拟和新开发的因果框架，其中将使用层积云转变的关键驱动因素。建立因果网络，说明潜在过程和相互作用的路径，这个新框架适用于非线性系统，重要的是，它允许多个变量协同工作，而不仅仅是集中于独立影响。该项目的研究成果预计将解决目前所有类型模型中海洋层积云模型表示的缺陷，并为诊断其他大气系统中的相互作用提供新的方法。该奖项反映了 NSF 的法定使命，并被认为是值得的。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来提供支持。