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，预测未来气候还需要准确估计大气中二氧化碳和其他温室气体的浓度，并了解大气辐射过程和表面海洋生物地球化学之间的反馈。在这种情况下，气候建模特别感兴趣的是了解大气和海洋表面之间的气体交换（例如二氧化碳和二甲硫醚，DMS）。 DMS 是二次气溶胶和云凝结核产生的贡献者。许多物理过程负责气体交换，包括从风切变到海洋表面的动量传递、通过波面压差（形成阻力）将动量直接传递到波浪、破碎波浪产生被迫进入水柱的空气气泡、近地表生物地球化学过程，这些过程会改变表面张力和水柱热稳定性、气体种类化学性质等。为了参数化空气-海洋气体交换以应用于气候模型，了解这些过程中哪些过程在以下情况下是重要的至关重要：具体的环境条件。最近的实验工作表明，仅基于风速的简单参数化不足以描述气体传递，在破碎波过程主导气体交换的较高风况下尤其如此。例如，观察表明，对于溶解度较低的气体，气泡中的气体转移会增强，并且理论表明，在强风下，形状阻力变得越来越重要；这种效应将调节切向剪切传递的水侧混合。这种认识导致了新的空气-海洋气体传递参数化的发展，该参数化用强迫物理过程来表达交换。然而，参数化尚未在发生大部分全球整合传输的较高风况下进行测试。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用巡航，旨在调查不同风速范围内的空气-海洋气体转移（专用巡航将重点关注强风），气体溶解度范围（例如，DMS、二氧化碳、丙酮、一氧化碳、二氧化硫），以及一系列波态（控制切向阻力分量和形状阻力分量之间风应力的获取和分布）和波浪破碎（气泡）实验工作的结果将用于进一步开发新的气体传输参数化，该参数化适用于包括空气-海洋气体传输影响的更大规模气候模型。这可能会导致对未来气候的更好预测，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与研讨会，重点是为当地地球科学教师提供理解气候科学并向中小学生传达气候科学所需的工具。科学家讲座将在远程地点进行电话会议，项目对研讨会的贡献将包括传授有关观测和模型之间联系的知识，以及帮助教师了解模型在预测气候方面的局限性和优势。