Collaborative Research: Measuring Air-Sea Gas Exchange in High Winds for Improvement of Physics-Based Air-Sea Transfer Parameterizations

合作研究：测量强风中的海气交换，以改进基于物理的海气传输参数化

• 批准号: 1036062
• 负责人: Barry Huebert
• 金额: $ 83.7万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-10-01 至 2015-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1036062&HistoricalAwards=false
• 关键词: Collaborative; Research; Measuring; Air; Sea

Predicting future climate requires, among other factors, accurate estimates of the atmospheric concentration of carbon dioxide and other greenhouse gases and an understanding of the feedbacks between atmospheric radiative processes and surface ocean biogeochemistry. In this context, of particular interest to climate modeling is an understanding of the exchange of gases (like carbon dioxide and dimethylsufide, DMS) between the atmosphere and ocean surface. DMS is a contributor to secondary aerosol and cloud condensation nuclei production. Numerous physical processes are responsible for gas exchange, including momentum transfer to the ocean surface from wind shear, transfer of momentum directly to waves via pressure differential across the wave face (form drag), breaking waves which generate bubbles of air forced into the water column, near-surface biogeochemical processes which modify surface tension and water column thermal stability, gas species chemical properties, etc. In order to parameterize air-sea gas exchange for application in climate models, it is crucial to understand which of these processes are important under specific environmental conditions. Recent experimental work has shown that simple parameterizations based solely on wind speed are not adequate to describe the gas transfer, and this is particularly true at the higher wind regimes where breaking wave processes dominate the gas exchange. For example, observations have shown that gas transfer from bubbles is enhanced for less soluble gases, and theory suggests that form drag becomes increasingly important at high winds; this effect will modulate the water-side mixing from tangential shear transfer. This realization has led to the development of a new air-sea gas transfer parameterization which expresses the exchange in terms of the forcing physical processes. However, the parameterization has not been tested at higher wind regimes where the bulk of the globally-integrated transfer occurs. A four-year effort will be undertaken which includes two cruises on ships-of-opportunity and one dedicated cruise with the intention of investigating air-sea gas transfer across a range of wind speeds (the dedicated cruise will focus on high winds), a range of gas solubility (e.g., DMS, carbon dioxide, acetone, carbon monoxide, sulfur dioxide), and a range of wave states (control on fetch and distribution of wind stress between tangential and form drag components) and wave breaking (bubble processes).The results from the experimental work will be used to further develop the new gas transfer parameterization which is applicable in larger scale climate models that include the effects of air-sea gas transfer. This potentially leads to better predictions of future climate, and these projections will be of significant value to society and policy decision makers. The project will include scientist participation in workshops focused on providing local earth science teachers with tools necessary to understand and communicate climate science to their elementary and high school students. Scientist lectures will be teleconferenced to remote sites, and the project contribution to the workshops will include imparting knowledge about connections between observations and models, as well as assisting teachers in understanding the limitations and strengths of models in predicting climate.

除其他因素外，预测未来气候需要准确估计二氧化碳和其他温室气体在大气中的浓度，并了解大气辐射过程与表层海洋生态地球化学之间的反馈。在这种情况下，对气候建模特别感兴趣的是对大气和海洋表面之间的气体（如二氧化碳和二甲基硫醚，DMS）交换的理解。DMS是二次气溶胶和云凝结核产生的贡献者。气体交换的物理过程有很多，包括风切变向海面的动量传递，通过波面压差直接向波浪的动量传递（形成拖曳），产生被迫进入水柱的气泡的破碎波浪，改变表面张力和水柱热稳定性的近地表地球化学过程，气体种类化学性质，为了将海气交换参数化以应用于气候模式，关键是要了解这些过程中哪些在特定环境条件下是重要的。最近的实验工作表明，单纯基于风速的简单参数化不足以描述气体传输，这是特别真实的，在较高的风状态下，破碎波过程占主导地位的气体交换。例如，观测表明，气泡中的气体传输对于溶解度较低的气体来说是增强的，并且理论表明形状阻力在强风下变得越来越重要;这种效应将调节切向剪切传输的水侧混合。这一认识导致了一个新的海气输送参数化的发展，表示交换的强迫物理过程。然而，参数化还没有在更高的风况下进行测试，其中大部分的全球综合传输发生。将进行为期四年的努力，其中包括两次机会船巡航和一次专门巡航，目的是调查不同风速范围内的海气转移（专门巡航将侧重于强风），一系列气体溶解度（例如，DMS，二氧化碳，丙酮，一氧化碳，二氧化硫），和一系列的波状态（控制风应力之间的切向和形状阻力分量的获取和分布）和波浪破碎（气泡过程）。实验工作的结果将被用来进一步开发新的气体传输参数化，适用于更大规模的气候模式，包括空气-海洋气体传输的影响。这可能会导致更好地预测未来的气候，这些预测将对社会和政策决策者具有重要价值。该项目将包括科学家参加讲习班，重点是为当地地球科学教师提供必要的工具，使他们能够理解气候科学并向小学和高中学生进行交流。科学家的讲座将在偏远地点举行，项目对讲习班的贡献将包括传授关于观测与模型之间联系的知识，以及协助教师了解模型在预测气候方面的局限性和优势。