Organization of Tropical East Pacific Convection (OTREC) - Post-Campaign Analysis

该奖项支持对热带东太平洋对流组织(OTREC)实地活动期间收集的观测数据进行分析。该活动旨在研究赤道东太平洋和加勒比西南部邻近但不同区域的热带对流云及其相关强降雨的形成和发展，以及它们在中美洲和哥伦比亚中间部分的演变。该运动还审议了东风波的产生和演变，即每周在加勒比和东太平洋发生的向西移动的大气大扰动(波长约为2 000公里)。这项活动部署在哥斯达黎加西部，于2019年8月至10月进行，由国家大气研究中心维护的湾流V号研究飞机进行了22次飞行。飞机在约4万英尺的高空飞行，使用落差探测仪和W波段雷达对云层和大气条件进行观测。投放探测仪包含与标准天气气球相同的仪器套装，只是用一个小降落伞从飞机上投放。雷达确定云的性质，包括冰粒和液滴的浓度，并使用多普勒频移来测量云的上升气流和下降气流速度。通过在哥斯达黎加和哥伦比亚地面站点收集的观测数据，扩大了飞机抽样工作。该项目继续开展该运动，以查明导致热带深层对流发展的机制。许多工作都致力于分析对流区的垂直质量通量分布，特别是云中上升运动是发生在对流层中下部还是在对流层上部。这项工作是由主要研究人员和其他人发展的热带对流理论推动的，该理论强调了底-重垂直质量通量廓线与暴雨之间的联系，以及大气稳定性与水分含量之间的反向关系。这里的工作决定了该理论在多大程度上适用于所有OTREC研究区域，尽管它们的海洋表面温度和其他条件不同。该项目还考虑了在东太平洋发现的东风波是在当地形成的，还是在西非形成后传播到大西洋的东风波。其他工作考虑了马登-朱利安振荡(MJO)对运动期间观察到的对流的影响，这是一种大范围的局部性天气模式。MJO在活动期间引起了低层风向的转移，风向转移对对流的影响尚不清楚。最后，这项研究包括与欧洲中期天气预报中心合作，评估OTREC研究区域的天气预报，以及与哥伦比亚国立大学的同事合作，他们将地面观测和区域专业知识带到该项目中。由于热带对流对全球天气和气候的重要性，这项工作具有社会利益。考虑到东风波产生飓风的趋势，东风波对天气预报特别感兴趣。因此，更好地了解热带对流和东风波对于改进天气和气候模式以及帮助决策者预测气候多变和变化可能产生的后果是有意义的。这项工作还通过上述合作促进了大气科学方面的国际合作。主要调查人员通过公开讲座、为高中科学教师开设的“天气科学”课程以及与K-12学生的互动来进行教育和推广。该项目为一名研究生和一名本科生提供支持和培训。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This award supports analysis of observations collected during the Organization of Tropical East Pacific Convection (OTREC) field campaign. The campaign was designed to study the formation and development of tropical convective clouds and associated heavy rainfall in the adjacent but distinct regions of the eastern equatorial Pacific and the southwest Caribbean, along with their evolution over the intervening portions of Central America and Colombia. The campaign also considered the genesis and evolution of easterly waves, large westward-moving atmospheric disturbances (wavelengths of about 2,000 km) which occur on a weekly basis in the Caribbean and eastern Pacific. The campaign deployment, based in western Costa Rica, took place from August to October 2019 and featured 22 flights of the Gulfstream V research aircraft maintained by the National Center for Atmospheric Research. The aircraft flew at about 40,000 feet using dropsondes and a W-band radar to make observations of clouds and atmospheric conditions. Dropsondes contain the same instrument package as standard weather balloons, only dropped from the aircraft with a small parachute. The radar determines cloud properties including the concentrations of ice particles and liquid droplets, and uses Doppler shift to measure cloud updraft and downdraft speeds. The aircraft sampling was augmented by observations collected at ground sites in Costa Rica and Colombia.This project continues the campaign's effort to identify the mechanisms that lead to the development of deep tropical convection. Much of the work is devoted to analysis of vertical mass flux profiles in convecting regions, in paticular whether rising motions in clouds occur in the lower to middle troposphere or the upper troposphere. The work is motivated by a theory of tropical convection developed by the Principle Investigators and others which emphasizes the association between bottom-heavy vertical mass flux profiles and heavy rainfall, as well as an inverse relationship between atmospheric stability and moisture content. Work here determines the extent to which the theory applies to all the OTREC study regions despite their differences in sea surface temperature and other conditions. The project also considers whether easterly waves found in the eastern Pacific form locally or if they are the same easterly waves seen propagating across the Atlantic after forming in West Africa. Additional work considers the impact of the Madden-Julian Oscillation (MJO), a large-scale topical weather pattern, on convection observed during the campaign. The MJO caused a shift in low-level wind direction during the campaign and the effects of the wind shift on convection are not yet clear. Finally, the research includes collaborations with the European Centre for Medium-range Weather Forecasts to evaluate weather forecasts in the OTREC study area, and with colleagues at the National University of Colombia who bring surface-based observations and regional expertise to the project.The work is of societal interest due to the importance of tropical convection for weather and climate across the globe. Easterly waves are of particular interest for weather forecasting given their tendency to spawn hurricanes. Better understanding of tropical convection and easterly waves is thus of interest for the improvement of weather and climate models and for helping decision makers anticipate the likely consequences of climate variability and change. The work also promotes international collaboration in atmospheric science through the collaborations mentioned above. The Principle Investigators pursue education and outreach through public lectures, a class on the "Science of Weather" for high school science teachers, and interactions with K-12 students. The project provides support and training to a graduate student and an undergraduate.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.