Waves, Aerosol and Gas Exchange Study (WAGES)

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。一个中心过程是入射的太阳（短波）辐射和出射的红外（长波）辐射与大气，特别是与云的相互作用。由于云的大小、位置和类型的变化，以及随着云滴或冰晶的浓度和大小分布的变化，反射率等性质的强烈变化，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（大面积的低空云层）起着主要作用。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于气泡破裂和被风从浪顶撕裂的喷雾所产生的水滴蒸发而产生的。所产生的水滴的大小和数量，以及由此产生的气溶胶，随着风速、波浪状态、波浪破碎等不同条件的变化而变化很大。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。在这方面有很大的不确定性（10倍），特别是对气候过程最重要的最小气溶胶。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、波浪大小和白顶。研究结果将提高我们对气溶胶产生的理解，并最终改善气候模型中云的表征方式。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；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。虽然二氧化碳被海洋作为一个整体吸收，但在不同的时间和地点，大气和海洋之间的二氧化碳转移可能发生在任何一个方向，这取决于当地空气和水中的气体浓度。转移的速率还取决于风速、海况、波浪破碎等。与气溶胶的产生一样，在不同的条件下，传输速率如何变化存在很大的不确定性（在某些条件下约为2个因素）。大气和海洋之间二氧化碳转移的直接测量，以及气象和波浪条件的直接测量，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。为了理清影响气体和气溶胶通量的所有不同参数的影响，我们需要大量的数据。为了达到这个目的，我们将在世界上最后一艘气象船上使用自动测量系统，这艘船全年都在海上航行，在一个经历各种风浪条件的地区。我们将保持三年的测量。此外，我们将进行三次为期4周的载人巡航，每次我们将部署一个浮标来详细测量波浪破碎，还将从风筝上放飞摄像机，以获得几个小时或更长时间的连续白浪数据。这些数据将使我们能够非常详细地研究驱动通量的过程，它们也将用于验证来自自主波和白浪系统的不太详细的数据，这些数据将连续测量整整三年。

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 is the interaction of 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 to the variation in size, location, and type of cloud, and also 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. 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 different conditions such as wind speed, wave state, wave breaking, 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 much uncertainty in this (a factor of 10), particularly for the smallest aerosols which are the most important for 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 and white-capping under a wide range of different conditions. The results will improve our understanding of aerosol generation, and ultimately the way in which clouds are represented 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 means more infra-red radiation is absorbed, causing a warming of the atmosphere. Although CO2 is absorbed by the oceans as a whole, at different times and places 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 also depends on the wind speed, sea-state, wave breaking etc. As with aerosol production, there are large uncertainties (about a factor of two in some conditions) in how the rate of transfer varies with different conditions. Direct measurements of the transfer of CO2 between the atmosphere and ocean, along with those of the meteorological and wave 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. To untangle the influence of all the different parameters that affect gas and aerosol fluxes we need a great deal of data. To obtain this we will use automatic measuring systems on the world's last weather ship which stays at sea all year round in a region which experiences a wide range of wind and wave conditions. We will maintain the measurements for three years. In addition we will have three manned cruises of 4 weeks each where we will deploy a buoy to make detailed measurements of wave breaking and will also fly a video camera from a kite to obtain continuous whitecap data for periods of a few hours or more. These data will allow us to study the process that drive the fluxes in great detail, and they will also be used to verify the less detailed data from the autonomous wave and whitecap systems which will measure continuously for the whole three years.