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.

预测未来气候，除其他因素外，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与海洋表面生物地球化学之间的反馈。在这种情况下，气候模型特别感兴趣的是了解大气和海洋表面之间的气体交换（如二氧化碳和二甲硫化物）。DMS对二次气溶胶和云凝结核的产生有贡献。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，通过波面压差直接将动量传递给波浪（形成阻力），破碎的波浪产生气泡，迫使进入水柱，近地表生物地球化学过程，改变表面张力和水柱热稳定性，气体种类的化学性质等。为了参数化海气交换以用于气候模式，了解在特定环境条件下哪些过程是重要的是至关重要的。最近的实验工作表明，仅仅基于风速的简单参数化不足以描述气体传递，特别是在破碎波过程主导气体交换的较高风力条件下。例如，观察表明，气泡中的气体转移对于不溶性气体会增强，理论表明，在大风中，形式阻力变得越来越重要；这种效应将调节切向剪切转移引起的水侧混合。这一认识导致了一种新的海气传递参数化的发展，该参数化用强迫物理过程来表示交换。然而，参数化还没有在更高的风区进行测试，在那里大部分的全球综合传输发生。一项为期四年的工作将进行，其中包括两次在机遇船上的巡航和一次专门的巡航，目的是调查在一系列风速下的海气转移（专门的巡航将侧重于大风），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），以及一系列波浪状态（对取风和切向和形阻力分量之间风应力分布的控制）和波浪破碎（气泡过程）。实验工作的结果将用于进一步发展新的气体传输参数化，该参数化适用于包括海气传输影响的更大尺度气候模式。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制定者具有重要价值。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，以便向他们的小学生和中学生了解和传播气候科学。科学家讲座将通过远程会议传送到偏远地点，项目对讲习班的贡献将包括传授关于观测和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。