Studies of the Maritime Atmospheric Boundary Layer during DYNAMO

大气边界层（ABL），通常是在大气的最低一两公里处，对热带海洋上空深层对流云的发展有着巨大的影响。麦登-朱利安涛动（MJO）是印度洋上形成的一个大型向东移动的对流区域，ABL在MJO发展中的作用是2011年MJO （DYNAMO）场运动动力学的主要焦点（例如参见1022899和1059899）。该运动从印度洋中部的四个岛屿站和两个船站收集了观测数据。该奖项下的工作使用DYNAMO观测来表征热带海洋ABL的行为及其与底层海洋的相互作用。它还试图确定从岛屿站取得的观测结果在多大程度上受到岛屿效应的影响，而岛屿效应并不代表对广泛对流发展有影响的周围海洋的情况。要检查的ABL属性包括温度、湿度、稳定性、风和云量，特别关注ABL深度的日循环。在运动的密集观测期间，气象气球每三小时发射一次，以评估日周期。PI开发了一种方法，根据部署在岛屿和船上的风廓线仪和无线电声学探测系统（RASS）的连续观测的信噪比来确定ABL的高度。这项技术可以用来填补气球发射之间的空白，并验证气球观测是否捕捉到了ABL深度的完整日循环。在迭戈加西亚岛和研究船Revelle上收集的剖面仪和RASS数据，在相同的纬度和经度10度之间进行比较，以检测岛屿效应。用于该运动的两个岛屿是环礁（第二个是马尔代夫的甘岛），陆地面积最小，但环绕着泻湖，昼夜温度循环相对强烈，这可能影响ABL观测。从Revelle和船上部署的系泊处获得的观测结果用于表征与ABL发展和随后的对流相关的海气相互作用。这项工作具有社会价值，因为MJO以多种方式影响全球天气和气候，包括墨西哥湾飓风的发展和加利福尼亚州的极端降雨事件。MJO对目前的天气预报模式提出了挑战，在这里进行的工作可能会改善MJO及其影响的预报。更具体地说，项目生成可用于模型开发的强制数据集。根据该奖项产生的产品将通过国家大气研究中心的网站公开提供给研究和业务团体。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The atmospheric boundary layer (ABL), typically the lowest kilometer or two of the atmosphere, has an outsized influence on the development of deep convective clouds over the tropical oceans. The role of the ABL in the development of the Madden-Julian Oscillation (MJO), a large eastward moving region of convection that forms over the Indian Ocean, was a primary focus of the 2011 Dynamics of the MJO (DYNAMO) field campaign (see for example awards 1022899 and 1059899). The campaign collected observations from four island stations and two ship stations in the Central Indian Ocean. Work under this award uses the DYNAMO observations to characterize the behavior of the tropical marine ABL and its interactions with the underlying ocean. It also seeks to determine the extent to which observations taken from the island stations are influenced by island effects which do not represent the conditions over the surrounding ocean that matter for the development of widespread convection.ABL properties to be examined include temperature, moisture, stability, winds, and cloudiness, with a particular focus on the diurnal cycle of ABL depth. The diurnal cycle is assessed from weather balloons launches that took place every three hours during the intensive observing period of the campaign. The PI has developed a method to determine the height of the ABL from the signal-to-noise ratio of continuous observations from the wind profiler and Radio Acoustic Sounding System (RASS) deployed on the islands and ships. The technique could prove useful for filling in the gaps between balloon launches and verifying that the balloon observations capture the full diurnal cycle of ABL depth. Profiler and RASS data collected on the island of Diego Garcia and the research vessel Revelle, at the same latitude and separated by 10 degrees longitude, are compared to detect island effects. Two of the islands used for the campaign are atolls (the second is Gan Island in the Maldives), which have minimal land area but surround lagoons with a relatively strong diurnal temperature cycle which might influence ABL observations. Observations taken from the Revelle and moorings deployed from the ship are used to characterize air-sea interactions relevant to ABL development and subsequent convection.The work has societal value due to the many ways in which the MJO affects weather and climate worldwide, including the development of hurricanes in the Gulf of Mexico and extreme rainfall events in California. The MJO presents a challenge to current weather prediction models, and work performed here may lead to improved forecasts of the MJO and its impacts. More specifically, the project generates forcing datasets that can be used for model development. Products generated under this award are made openly available to the research and operational communities through a website at the National Center for Atmospheric Research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.