Air-Sea Interaction and Sea-spray in Typhoons (ASIST)

海洋和大气之间的热量和水分交换取决于低层大气中的湍流混合;这在很大程度上取决于风速。在非常高的风速下，海面被破碎的波浪、白浪和浪花所控制。由于湍流运动而飘到低层大气中的水滴将与周围的空气发生两次相互作用。首先，如果它们与空气处于不同的温度，它们将冷却或加热，直到它们的温度与空气的温度相匹配;其次，它们将开始蒸发，为空气提供水蒸气。蒸发需要能量，其最初通过液滴的冷却获得，然后将热量从空气传递到液滴。这些过程的最终结果是海洋和地面以上一定高度的空气之间的热量和水分转移。在天气预报和气候模式中使用的热湿交换的简化数学描述假设所有的热湿交换都发生在地表，因此它们可能在高风速下提供错误的值。在海上严重风暴条件下进行适当测量的困难意味着，可用于评估所产生的喷雾是否实际上具有重大影响的测量很少。理论研究强烈反对这种效应的重要性。在这项研究中，我们将仪器自主浮标，专门设计用于在极端条件下工作，以测量大气和海洋之间的热，水分，动量和海水喷雾的湍流交换，沿着测量波浪状态，海洋表层的湍流，波浪破碎的程度，以及海洋和大气表层的平均条件。所获得的数据将用于评估海气交换，并确定海洋喷雾对热量和水分总交换的贡献。测量结果还将用于更好地确定大风下海上喷雾气溶胶生成率，以及波浪状态对生成率的影响，这两个方面的定义都很差。提高对海气相互作用的认识对于大风条件尤为重要，因为飓风和台风等严重风暴的发展和轨迹严重依赖于热量和水分输入以及表面的摩擦阻力。这项研究最终将改进对强热带风暴的预测。这项研究将与佛罗里达的迈阿密大学密切合作进行，该大学负责操作浮标进行测量。这些浮标将于2010年6月在东海/南海部署，并于2010年10月收回。

The exchange of heat and moisture between the ocean and atmosphere depends upon turbulent mixing in the lower atmosphere; this depends strongly on the wind speed. At very high wind speeds the sea surface becomes dominated by breaking waves, whitecaps, and sea spray. The water droplets lofted into the lower atmosphere by turbulent air motions will undergo two interactions with the air around them. First, if they are at a different temperature from the air, they will cool or warm until their temperature matches that of the air; secondly, they will start to evaporate, contributing water vapour to the air. Evaporation requires energy, which is obtained initially by a cooling of the droplet, and then a transfer of heat from the air to the droplet. The net result of these processes is a transfer of heat and moisture between ocean and air at some altitude above the surface. The simplified mathematical descriptions of of heat and moisture exchange used within weather forecast and climate models assume that all the heat and moisture exchange takes place at the surface, thus they may provide the wrong values at high wind speeds. The difficulty of making appropriate measurements under severe storm conditions at sea means that there are very few measurements available with which to evaluate whether the spray generated actually has a significant impact or not. Theoretical studies disagree strongly about the importance of the effect. In this study we will instrument autonomous buoys, specifically designed to operate in extreme conditions, to measure the turbulent exchange of heat, moisture, momentum, and sea-spray between the atmosphere and ocean, along measurements of wave state, turbulence in the surface layer of the ocean, the extent of wave breaking, and mean conditions in the surface layers of the ocean and atmosphere. The data obtained will be used to evaluate the air-sea exchange, and determine the contribution of the sea spray to the total exchange of heat and moisture. The measurements will also be used to better define the rate of sea-spray aerosol generation under high winds, and the influence of wave state on the production rate, both of which are poorly defined. Improving understanding of air-sea interaction is particularly important for high wind conditions, because the development and track of severe storms - hurricanes and typhoons - is critically dependent on the heat and moisture input and frictional drag at the surface. This study will ultimately lead to improved prediction of severe tropical storms. The study will be carried out in close collaboration with the University of Miami, Florida, who operate the buoys from which the measurements will be made. The buoys will be deployed in the East/South China Sea in June 2010 and recovered during October 2010.