Collaborative Research: Characterizing Atmospheric Tropical-waves of the Lower Stratosphere with Reel-down Atmospheric Temperature Sensing for Strateole-2--RATS Chasing CATS!

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（LMD）组织的Strateole-2实地活动。该活动使用设计为在恒定高度漂浮长达3个月的气球，对热带对流层顶层（TTL）进行观测，TTL是热带对流层和平流层之间大约14公里至18公里的大气层层。这些气球从塞舌尔发射，漂浮在TTL顶部上方的赤道附近，或者在海拔近20公里的平流层低处。stratole -2计划分为三次部署，一次是初步的工程部署，有8次气球飞行，然后是两次科学部署，每次飞行20次。前两次部署分别于2019年和2021年进行，通过AGS-1642277提供了pi参与这些部署的资金。第三次部署计划于2025年10月开始。这里提供的资金支持开发和部署一种缩写为RATS的新仪器，即卷轴式大气温度传感器。粗略地说，RATS是一个温度计，它被一根长绳拴在一个气球贡多拉下面，气球贡多拉下面有第二个温度计。两个温度计之间的温差可以用来探测重力波，大气波类似于海洋表面波，只是它们既可以垂直传播，也可以水平传播。RATS可以探测重力波，因为重力波的上下运动会引起变冷或变暖，因此两个适当分开的温度计之间的温差可以记录波的通过。提案的标题是指使用RATS温度计来表征平流层下层的大气热带波。这项工作的动机来自于重力波在驱动准两年振荡（QBO）中的作用，即赤道上空纬向风向的逆转，始于平流层上层，下降到对流层顶，持续时间略长于两年。QBO对亚季节天气预报很重要，因为它与影响全球天气的气候变化模式有关。用于天气预报的模型很难捕捉到QBO，部分原因是驱动QBO的波的波长比典型的模型网格间隔要小，尤其是在垂直方向上。RATS可以探测到垂直波长为两个温度计之间距离的2到30倍的波，该距离被设置为200米或300米，以捕获400米至6公里或600米至9公里的波长。较长的波长可以通过操作模式分辨出来，从而与模式输出进行比较，而较短的波长则无法分辨。该合同涵盖了RATS硬件的开发，其中包括包含温度计（由CNES开发）和RS41无线电探空传感器模块（来自维萨拉）的下测单元（LMU），用于测量温度、湿度和压力，以及用于确定位置的GPS接收器。LMU通过一个线轴和滑轮系统来升降，该系统允许LMU在发射时停靠在贡多拉上，并在气球到达飞行高度时卷筒下降。贡多拉装有第二个温度计、气压计和GPS接收器。考虑到通过改进QBO的波浪驱动表现来更好地进行长期天气预测的前景，这项工作具有社会利益。stratole -2野外战役涉及与两个作战天气预报中心的合作，从而提供了从研究到作战的联系。所有现场活动数据提供给全球研究界，以追求TTL物理和动力学的其他研究课题。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。

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 Laboratory for Dynamic Meteorology (LMD) 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 just above the top of the TTL or in the lower stratosphere at an altitude near 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 funds for the PIs' participation in these deployments were provided through AGS-1642277. The third deployment is scheduled to begin in October 2025.Funds provided here support the development and deployment of a new instrument with the acronym RATS, for Reel-down Atmospheric Temperature Sensor. Roughly speaking RATS is a thermometer lowered on a long tether below a balloon gondola which contains a second thermometer. The difference in temperature between the two thermometers can be used to detect gravity waves, atmospheric waves similar to ocean surface waves only they can propagate vertically as well as horizontally. RATS can detect gravity waves because the up and down motions of the waves cause cooling and warming, thus the difference in temperature between two appropriately separated thermometers can record the passage of a wave. The title of the proposal refers to the use of the RATS thermometers for the Characterization of Atmospheric Tropical waves of the lower Stratosphere (CATS).Motivation for the work comes from the role of gravity waves in driving the Quasi-Biennial Oscillation (QBO), the reversal in zonal wind direction over the equator that begins in the upper stratosphere and descends to the tropopause over a period slightly longer than two years. The QBO matters for subseasonal weather prediction because it has been linked to modes of climate variability that influence weather around the world. Models used for weather prediction have difficulty capturing the QBO, in part because the waves that drive it have wavelengths that are smaller than typical model grid spacings, particularly in the vertical. RATS can detect waves with vertical wavelengths between 2 and 30 times the distance between the two thermometers, which is set to either 200m or 300m to capture wavelengths from 400m to 6km or 600m to 9km. The longer wavelengths can be resolved by operational models and thus compared with the model output while the shorter ones are unresolved.The award covers the development of the RATS hardware, which includes a Lower Measuring Unit (LMU) containing a thermometer (developed by CNES) along with an RS41 radiosonde sensor module (from Vaisala) to measures temperature, humidity, and pressure, and a GPS receiver for determining position. The LMU is raised and lowered using a spool and pulley system that allows it to be docked to the gondola for launch and reeled down when the balloon reaches its flight altitude. The gondola contains a second thermometer along with a barometer and GPS receiver.The work is of societal interest given the prospects for better long-range weather predictions through improved representation of the wave driving of the QBO. The Strateole-2 field campaign involves collaborations with two operational weather prediction centers, thereby providing a connection from research to operations. All field campaign data is made available to the global research community to pursue additional research topics on TTL physics and dynamics.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.