Field Observations of Sea Spray, Gas Fluxes and Whitecaps (SEASAW)

人们普遍认为人类活动正在导致全球气候的变化；然而，由于气候系统的复杂性和所涉及的相互作用过程的数量，这些变化的程度还远远不能确定。所有气候研究的一个中心过程是辐射/入射的太阳（短波）辐射和传出的红外（长波）辐射/与大气，特别是与云的相互作用。由于云的范围、位置和类型的变化，以及反射率等性质随着云滴或冰晶的浓度和大小分布的变化而发生的强烈变化，云在辐射平衡中呈现出很大的变异性和不确定性。海洋层积云/大面积的低层云/在全球辐射平衡中起主要作用。云滴的大小和数量在很大程度上取决于可形成云滴的气溶胶颗粒的数量。海盐气溶胶是这种凝结核的主要来源。海盐气溶胶的产生是由气泡破裂产生的水滴和被风从浪顶撕裂的喷雾蒸发而产生的。产生的液滴的大小和数量，以及由此产生的气溶胶，随风速、波浪状态、浮游生物产生的表面膜的存在等条件而有很大变化。为了准确地表示海洋云，从而在气候模型中得到正确的辐射平衡，我们必须首先确定在任何给定条件下产生的气溶胶的数量和大小。这方面存在相当大的不确定性，特别是对于与气候过程最相关的最小气溶胶。本项目将测量不同条件下在地表附近产生并向上输送到大气中的不同大小的气溶胶的数量，以及风速、波浪大小、白顶和热量和水分的传递。在离海面很近的地方对气溶胶进行测量，将使气溶胶产生事件与个别破浪直接相关。这些结果将用于提高我们对气溶胶产生的理解，并最终提高气候模式中云表示的保真度。模拟未来气候的另一个主要不确定性是二氧化碳在大气和海洋之间转移的速度。二氧化碳吸收红外辐射；由于化石燃料的燃烧，大气中二氧化碳的增加意味着更多的红外辐射被吸收，导致大气变暖。观测到的大气中二氧化碳的增加比考虑到燃料燃烧量可能预期的要少。这在很大程度上是由于海洋对二氧化碳的吸收。虽然二氧化碳被海洋作为一个整体吸收，但在区域尺度上，大气和海洋之间的二氧化碳转移可以朝任何一个方向发生，这取决于当地空气和水中气体的浓度。传输速率还取决于风速、气泡形成、海况和表面薄膜。与气溶胶的产生一样，在某些条件下，传输速率如何随条件而变化存在很大的不确定性。大气和海洋之间二氧化碳转移的直接测量，以及气象和海洋条件的直接测量，将用于减少二氧化碳转移参数化的不确定性。这将有助于改进长期气候模型。

It is widely accepted that the activities of mankind are leading to changes in global climate; however, the extent of those changes is far from certain due to the complexity of the climate system and the number of interacting processes involved. A central process in all climate studies is the interaction of radiation / incoming solar (shortwave) radiation, and outgoing infra-red (longwave) radiation / with the atmosphere and in particular with clouds. Clouds present a large source of variability, and uncertainty, in the radiative balance due both to the variation in extent, location, and type of cloud, and to the strong variation in properties such as reflectivity with changes in the concentration and size distribution of cloud droplets or ice crystals. Marine stratocumulus clouds / extensive sheets of low level clouds / play a major role in the global radiation balance. The size and number of their cloud droplets depends strongly on the number of aerosol particles available for droplets to form on. Sea-salt aerosol are a major source of such condensation nuclei. The generation of sea salt aerosol occurs through evaporation of water droplets generated by bubble bursting and spray torn from wave tops by the wind. The size and number of droplets produced, and hence of the aerosol produced, varies greatly with conditions: wind speed, wave state, the presence of surface films produced by plankton, etc. In order to accurately represent marine clouds, and so get the radiation balance correct in climate models, we must first determine how much aerosol and of what size, is generated under any given conditions. There is considerable uncertainty in this, particularly for the smallest aerosol, which are most relevant to climate processes. This project will measure the amount of aerosol at different sizes generated near the surface and transported upwards into the atmosphere, along with the wind speed, wave size, white-capping, and heat and moisture transfers under a wide range of different conditions. Measurements of aerosol very close to the sea surface will enable aerosol generation events to be related directly to individual breaking waves. The results will be used to improve our understanding of aerosol generation, and ultimately the fidelity of cloud representation within climate models. Another major uncertainty in modelling the future climate is the rate at which CO2 is transferred between the atmosphere and the oceans. CO2 absorbs infra-red radiation; an increase in CO2 in the atmosphere due to the burning of fossil fuels means more infra-red radiation is absorbed, causing a warming of the atmosphere. The observed increase in CO2 in the atmosphere is less than might be expected given the amount of fuel burnt. This is due in large part to the absorption of CO2 by the oceans. Although CO2 is absorbed by the oceans as a whole, on regional scales the transfer of CO2 between the atmosphere and ocean can occur in either direction, depending upon the local concentrations of the gas in the air and water. The rate of the transfer depends also on the wind speed, bubble formation, sea-state, and surface films. As with aerosol production, there are large uncertainties in how the rate of transfer varies with conditions / by a factor of two or more under some conditions. Direct measurements of the transfer of CO2 between the atmosphere and ocean, along with those of the meteorological and ocean conditions, will be used to reduce the uncertainty in the parameterization of CO2 transfer. This will in turn allow improvements to long term climate models.