Collaborative Research: Four-Dimensional (4D) Investigation of Tropical Waves Using High-Resolution GNSS Radio Occultation from Strateole2 Balloons

合作研究：利用 Strateole2 气球的高分辨率 GNSS 无线电掩星对热带波进行四维 (4D) 研究

• 批准号: 2402728
• 负责人: Jennifer Haase
• 金额: $ 120.13万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-02-15 至 2027-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2402728&HistoricalAwards=false
• 关键词: Collaborative; Research; Four; Dimensional; 4D

This award supports the continued participation of the Principal Investigators (PIs) in the Strateole-2 field campaign, organized by the French space agency (CNES, for Centre National d'Etudes Spatiales) and the Dynamic Meteorology Laboratory at the University of Paris-Saclay. The campaign makes observations of the tropical tropopause layer (TTL), the layer of the atmosphere from roughly 14km to 18km between the tropical troposphere and stratosphere, using balloons designed to float at a constant altitude for flights of up to 3 months. The balloons are launched from the Seychelles and float around the equator at the top of the TTL (18km) or in the lower stratosphere (20km). Strateole-2 was planned as a set of three deployments, a preliminary engineering deployment with 8 balloon flights followed by two science deployments with 20 flights each. The first two deployments took place in 2019 and 2021 and the PIs participated in these deployments using funds from AGS-1642650 and AGS-1642644. The PIs' participation in the third deployment, scheduled to begin in October 2025, is supported here.The PIs' role in Strateole-2 is to build and fly a Radio OCcultation receiver called ROC, which detects the refraction of radio waves transmitted by satellites from the Global Navigation Satellite System (GNSS, which includes the GPS satellites launched by the US). The strength of the refraction can be used to infer atmospheric temperature along the line of sight between ROC and a transmitter satellite, thus ROC can create temperature profiles by tracking a GNSS satellite as it descends to the horizon or rises from below it. Funds from this award are used to build six ROC receivers, manage their field deployment, and collect and analyze the data they generate.The temperature profiles from ROC are of interest because they show temperature fluctuations associated with wave motions in the TTL generated by large areas of tropical convection. One reason these waves are of interest is that they drive the quasi-biennial oscillation (QBO), an alternation between eastward and westward winds in the equatorial stratosphere which begins in the upper stratosphere and descends to the tropopause over the course of roughly two years. The QBO is confined to the tropics but it affects weather and climate around the world. It is well known that the QBO is driven by vertical momentum flux from waves that propagate upward from the TTL, but it is not clear what types of waves, particularly in terms of wavelengths and frequencies, are most important for driving the QBO. Another reason the waves are of interest is that their up-and-down motions are associated with cooling and warming of the ambient air, and cooling induced by rising motions can cause water vapor to freeze into ice particles (a process called deposition). Ice formation matters because it dehydrates air as it enters the stratosphere, thereby regulating the humidity of the stratosphere, and because ice particles form cirrus clouds which affect Earth's climate by trapping outgoing infrared radiation.Work on the wave driving of the QBO focuses on waves with periods of three or four days which were found to be prominent in the previous deployments. The PIs seek to determine the three-dimensional structure of the waves and their intrinsic frequencies, factors which together determine their wave momentum flux and thus their potential importance for QBO driving. The PIs have developed techniques for probing wave structure using the fact that the RO profiles are side-looking from the balloon and measure temperature at successively lower heights with distance from the balloon gondola. The three-dimensional structure of the waves can thus be reconstructed by combining consecutive RO profiles along the balloon flight path.As for cirrus cloud formation, four of the six ROC receivers will be flown with a downward-pointing lidar called BeCOOL, the Balloon-borne Cloud Overshoot Observation Lidar (BeCOOL), developed by a French team. BeCOOL observations of cirrus clouds can be combined with ROC observations of wave-induced temperature fluctuations to determine the extent to which cirrus clouds occur in the cold phases of waves in the TTL.The work has societal value through its connections to weather forecasting. Radio occultation receivers on satellites are an important source of observations used in operational weather prediction and work performed here includes an effort to assimilate ROC observations into weather models and test their value for prediction. The data assimilation and prediction effort involves collaborations with two operational centers. In addition, weather models have difficulty simulating the QBO and its global impacts, thus better understanding of the wave driving of the QBO can contribute to better forecast models. All data from the campaign are made freely available to the global research community and can be used in a variety of ways that go beyond the goals of the campaign. The project also builds the scientific workforce by supporting two graduate students and providing internship opportunities for undergraduates including two students from the Seychelles.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.

该奖项支持首席研究员 (PI) 继续参与由法国航天局（CNES，国家空间研究中心）和巴黎萨克雷大学动态气象实验室组织的 Strateole-2 实地活动。该活动使用设计为在恒定高度漂浮的气球进行长达 3 个月的飞行，对热带对流层顶层 (TTL) 进行观测，该层是热带对流层和平流层之间约 14 公里至 18 公里的大气层。 气球从塞舌尔发射，在 TTL 顶部（18 公里）或平流层下层（20 公里）围绕赤道漂浮。 Strateole-2 计划分为三项部署，一项是初步工程部署，进行 8 次气球飞行，随后是两项科学部署，每次 20 次飞行。前两次部署于 2019 年和 2021 年进行，PI 使用 AGS-1642650 和 AGS-1642644 的资金参与了这些部署。 此处支持 PI 参与计划于 2025 年 10 月开始的第三次部署。PI 在 Strateole-2 中的作用是建造并飞行名为 ROC 的无线电掩星接收器，该接收器可检测卫星传输的无线电波的折射来自全球导航卫星系统（GNSS，包括美国发射的 GPS 卫星）。 折射的强度可用于推断沿 ROC 和发射卫星之间视线的大气温度，因此 ROC 可以通过跟踪 GNSS 卫星下降到地平线或从地平线以下升起时创建温度剖面。 该奖项的资金用于建造六个 ROC 接收器、管理它们的现场部署以及收集和分析它们生成的数据。ROC 的温度剖面很有趣，因为它们显示了与大面积产生的 TTL 中的波动相关的温度波动。热带对流。 这些波令人感兴趣的一个原因是它们驱动了准两年一次的振荡（QBO），这是赤道平流层中东风和西风的交替，从平流层上层开始，在大约两年的时间内下降到对流层顶。 QBO 仅限于热带地区，但它影响世界各地的天气和气候。 众所周知，QBO 是由从 TTL 向上传播的波的垂直动量通量驱动的，但尚不清楚什么类型的波，特别是波长和频率方面的波，对于驱动 QBO 最重要。 波浪令人感兴趣的另一个原因是它们的上下运动与周围空气的冷却和变暖有关，上升运动引起的冷却会导致水蒸气冻结成冰粒（这一过程称为沉积）。 冰的形成很重要，因为它在进入平流层时使空气脱水，从而调节平流层的湿度，而且因为冰颗粒形成卷云，通过捕获传出的红外辐射影响地球气候。QBO 波驱动的工作重点关注具有以下特征的波：三天或四天的时间在以前的部署中很突出。 PI 旨在确定波浪的三维结构及其固有频率，这些因素共同决定了波浪动量通量，从而确定了它们对 QBO 驱动的潜在重要性。 PI 开发了利用 RO 剖面从气球侧视的事实来探测波浪结构的技术，并测量随着距气球吊篮的距离逐渐降低的高度的温度。 因此，可以通过组合沿气球飞行路径的连续 RO 剖面来重建波浪的三维结构。 至于卷云的形成，六个 ROC 接收器中的四个将使用名为 BeCOOL（气球-法国团队研发的云超调观测激光雷达（BeCOOL）。 BeCOOL 对卷云的观测可以与 ROC 对波浪引起的温度波动的观测相结合，以确定卷云在 TTL 波浪冷阶段出现的程度。这项工作通过与天气预报的联系而具有社会价值。 卫星上的无线电掩星接收器是业务天气预报中使用的重要观测来源，这里进行的工作包括将 ROC 观测结果同化到天气模型中并测试其预测价值。 数据同化和预测工作涉及与两个运营中心的合作。 此外，天气模型难以模拟 QBO 及其全球影响，因此更好地了解 QBO 的波浪驱动有助于建立更好的预报模型。 该活动的所有数据均免费提供给全球研究界，并且可以以超出该活动目标的多种方式使用。 该项目还通过支持两名研究生并为本科生（包括两名来自塞舌尔的学生）提供实习机会来建设科学队伍。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。