Collaborative Research: Investigating Thermal Structure, Dynamics, and Dehydration in the Tropical Tropopause Layer with Fiber Optic Temperature Profiling from Strateole-2 Balloons

合作研究：利用 Strateole-2 气球的光纤温度剖面研究热带对流层顶层的热结构、动力学和脱水

• 批准号: 1642246
• 负责人: M Joan Alexander
• 金额: $ 13.68万
• 依托单位: NorthWest Research Associates, Incorporated
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-02-01 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1642246&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Thermal; Structure

The tropical tropopause layer (TTL) is transition zone between the troposphere (the domain of clouds, precipitation, and weather systems) and the stratosphere (the cold and dry region above it which contains the ozone layer). The TTL extends from about 14 to 18.5km over the tropics and is above the tops of all but the tallest convective clouds. It often contains thin cirrus clouds which, though difficult to see, play an outsized role in trapping outgoing radiation and thus warming the troposphere. It is sometimes called the "gateway to the stratosphere" because most of the water vapor in the stratosphere, and many other stratospheric constituents, enter the stratosphere by moving upward through the TTL. The stratosphere is extremely dry compared to the troposphere, but stratospheric water vapor is of interest because it has an important greenhouse effect and can lead to the formation of polar stratospheric clouds which play a role in ozone hole formation.Work under this project seeks to improve understanding of the TTL by developing and deploying a temperature profiler as part of a long-duration ballooning campaign. The profiler, with the acronym FLOATS (Fiber-optic Laser Operated Atmospheric Temperature Sensor), measures temperature along a fiber optic cable 2km long which is suspended below a balloon gondola. FLOATS works by injecting laser light into a fiber optic cable and sensing Raman backscattered light. It can measure temperature with 0.3K precision and a vertical resolution of 3m, generating a profile every two to five minutes. A proof-of-concept prototype was developed under an EAGER award, AGS-1419932. FLOATS is deployed as part of the Strateole-2 field campaign organized by the Centre National d'Etudes Spatiales (CNES), the French Space Agency, and the Laboratoire de Meteorologie Dynamic (LMD) of the University of Paris-Saclay. Strateole-2 is a five-year campaign, with a small validation deployment in 2018 and full science deployments in 2020-2021 and 2022-2023. Balloons are launched from the Seychelles (about 5S in the Indian Ocean), with the expectation that each balloon will circle the earth for up to 90 days and observe the TTL between 20S and 15N. This award supports US participation in the validation campaign and the first full science deployment, along with post-campaign analysis. It is one of three awards made to US PIs for participation in Strateole-2, the full set being AGS-1643022, AGS-1642277/1642246, and AGS-1642650/1653644.The FLOATS measurements are used to address three scientific objectives, all of which use temperature variations along the fiber optic cable to examine the behavior of gravity waves (wave motions in the air in which buoyancy provides the restoring force). The first is the depression of the cold point tropopause (CPT) temperature by vertically propagating gravity waves, which is a key factor in determining how much water vapor enters the stratosphere through the TTL. If condensation or sublimation occurs when relative humidity reaches 100%, then the amount of water vapor entering the stratosphere should not exceed the amount corresponding to 100% relative humidity at the CPT temperature. Earlier work by one of the PIs and others suggests that wave-induced CPT temperature depression could be significant, and an increase in wave activity could be responsible for a substantial portion of the decrease in CPT temperature and stratospheric water vapor believed to have occurred in the first decade of the 21st century. The second science objective is to understand the role of gravity waves in producing cirrus clouds in the TTL. The problem is complementary to stratospheric dehydration produced by temperature depression, as water vapor prevented from entering the stratosphere by colder temperatures instead freezes out to form cirrus ice particles.The third objective is to measure the vertical momentum flux associated with the waves. These waves are critical for the stratospheric quasi-biennial oscillation (QBO), which can influence the skill of long-range weather forecasts. Momentum flux would be estimated by combining FLOATS measurements (which give wave amplitude, vertical wavelength, and phase speed) with additional measurement taken on the balloon gondola including wave-induced directional displacement inferred from GPS positioning.The work has scientific broader impacts due to the value of the observations for addressing a variety of questions regarding TTL processes and the stratospheric QBO. In particular, wave momentum flux data is of value for developing gravity wave parameterizations for use in improving numerical models used for weather forecasting. FLOATS observations will be made available to the research community from servers at the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder, so that they can be freely examined by the research community. In addition, the project constitutes a demonstration of a novel technology for meteorological observations which could have a wide array of scientific applications. Beyond these considerations, the project supports a postdoctoral research associate, thereby developing the future scientific workforce in this research area.

热带对流层顶层(TTL)是对流层(云、降水和天气系统的区域)和平流层(其上方包含臭氧层的寒冷干燥地区)之间的过渡区。TTL在热带地区延伸约14至18.5公里，位于除最高对流云之外的所有云层的顶部。它经常包含薄薄的卷云，虽然很难看到，但在捕获传出的辐射从而使对流层变暖方面发挥着巨大的作用。它有时被称为“通向平流层的门户”，因为平流层中的大部分水蒸气和许多其他平流层成分通过TTL向上移动进入平流层。与对流层相比，平流层非常干燥，但平流层的水蒸气引起了人们的兴趣，因为它具有重要的温室效应，并可能导致极地平流层云的形成，从而在臭氧空洞的形成中发挥作用。该项目的工作旨在通过开发和部署温度廓线仪来提高对TTL的理解，作为长期气球运动的一部分。该测温仪的首字母缩写为Floats(光纤激光操作大气温度传感器)，它沿着悬挂在气球吊车下方的2公里长的光纤电缆测量温度。Floats的工作原理是将激光注入光缆，并感应拉曼背向散射光。它可以测量0.3K精度的温度，垂直分辨率为3米，每两到五分钟生成一次轮廓。一个概念验证原型是在一个热切的奖项--AGS-1419932下开发的。花车是国家空间研究中心、法国航天局和巴黎萨克莱大学气象动力学实验室组织的Strateole-2实地活动的一部分。Strateole-2是一项为期五年的计划，2018年进行小规模验证部署，2020-2021年和2022-2023年进行全面科学部署。气球是从塞舌尔群岛(印度洋约为5S)发射的，预计每个气球将绕地球90天，并在20至15 N之间观测TTL。该奖项支持美国参与验证活动和第一次全面的科学部署，以及活动后分析。它是颁发给美国PI的参与第二层的三个奖项之一，全套奖项是AGS-1643022、AGS-1642277/1642246和AGS-1642650/1653644。浮标测量用于实现三个科学目标，所有这些目标都使用光缆上的温度变化来检查重力波(空气中的波动，浮力提供恢复力)的行为。首先是通过垂直传播重力波降低冷点对流层顶(CPT)温度，这是决定有多少水蒸气通过TTL进入平流层的关键因素。如果相对湿度达到100%时发生冷凝或升华，则进入平流层的水蒸气的量不应超过CPT温度下对应的100%相对湿度的量。其中一位PI和其他人的早期工作表明，波浪诱导的CPT温度下降可能是显著的，波活动的增加可能是CPT温度和平流层水汽下降的主要原因，据信发生在21世纪的头十年。第二个科学目标是了解重力波在TTL中产生卷云的作用。这个问题是对温度降低造成的平流层脱水的补充，因为较低的温度阻止了水蒸气进入平流层，而是冻结形成卷云冰粒。第三个目标是测量与波浪相关的垂直动量通量。这些波动对平流层准两年振荡(QBO)是至关重要的，它可以影响长期天气预报的技巧。动量通量将通过浮标测量(给出波幅、垂直波长和相速度)和气球吊车上的附加测量(包括由GPS定位推断的波浪诱导的方向位移)来估计。由于观测对于解决关于TTL过程和平流层QBO的各种问题的价值，这项工作具有科学上更广泛的影响。特别值得一提的是，波动量通量资料对于发展重力波参数，用于改进用于天气预报的数值模式是有价值的。浮标观测将通过科罗拉多大学博尔德大学大气和空间物理实验室的服务器向研究界提供，以便研究界可以自由检查。此外，该项目还展示了一种可广泛应用于科学领域的气象观测新技术。除了这些考虑之外，该项目还支持一名博士后研究助理，从而培养这一研究领域未来的科学队伍。

项目成果

First Super‐Pressure Balloon‐Borne Fine‐Vertical‐Scale Profiles in the Upper TTL: Impacts of Atmospheric Waves on Cirrus Clouds and the QBO

第一个超压气球 - TTL 上部的精细 - 垂直 - 尺度剖面：大气波对卷云和 QBO 的影响

• DOI: 10.1029/2021gl097596
• 发表时间: 2022
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Bramberger, Martina;Alexander, M. Joan;Davis, Sean;Podglajen, Aurelien;Hertzog, Albert;Kalnajs, Lars;Deshler, Terry;Goetz, J. Douglas;Khaykin, Sergey
• 通讯作者: Khaykin, Sergey

Balloon‐Borne Observations of Short Vertical Wavelength Gravity Waves and Interaction With QBO Winds

• DOI: 10.1029/2020jd032779
• 发表时间: 2020-08
• 期刊: Journal of Geophysical Research: Atmospheres
• 作者: R. Vincent;M. Alexander

Tropical Wave Observations From the Reel‐Down Atmospheric Temperature Sensor (RATS) in the Lowermost Stratosphere During Strateole‐2

平流层最低层 ReelDown 大气温度传感器 (RATS) 的热带波观测 —2

• DOI: 10.1029/2023gl104711
• 发表时间: 2023
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Bramberger, Martina;Goetz, Doug;Alexander, M. Joan;Kalnajs, Lars;Hertzog, Albert;Podglajen, Aurelien
• 通讯作者: Podglajen, Aurelien

Around the World in 84 Days

• DOI: 10.1029/2018eo091907
• 发表时间: 2018-03
• 期刊: Eos
• 作者: J. Haase;M. Alexander;A. Hertzog;L. Kalnajs;T. Deshler;S. Davis;R. Plougonven;P. Cocquerez;Stéphanie Venel