Convection and Balanced Tropical Dynamics

本项目研究热带对流的基本动力学，热带对流是指在热带积云中发现的与强降水有关的翻转运动，它通过这种动力学与它所处的大尺度水平大气环流相互作用。 这项工作的重点是非洲东风波（AEW）内对流的演变，波长为2，000至2，500公里的热带波扰动，起源于西非，向西传播到北方热带大西洋。 AEW特别令人感兴趣，因为它们在热带风暴和飓风的形成中起着关键作用。 这项工作是基于初步的调查结果，提出了一系列的气象关系，可以导致大雨的发展。 一个是对流层中层（比如600毫巴）的气旋性涡度（衡量气旋旋转或水平环流切变的强度）可以在该层以上产生较暖的温度，在该层以下产生较冷的温度，从而减少该层周围的潮湿对流不稳定性。 这种对流层中部不稳定性的减少导致积云中底部重的质量通量分布，其中大多数云内的上升运动发生在对流层的中低层。 底部重的质量通量分布又导致对流从对流区域输出静态能量的效率降低，这需要更强的对流来维持能量输出。 与此同时，较低的不稳定性导致对流区域通过称为水分准平衡的过程增湿（部分来自AGS-1148594的研究结果），因此，增加的水分和更剧烈的翻转运动都有助于加强降雨。 初步工作表明，这些关系进行了现场活动数据T-PARC/TCS-08（Thorpex太平洋亚洲区域运动/热带气旋运动实验）和PREDICT（热带地区云系的预低气压调查）。 在这里进行的工作进一步测试和探索的因果关系链，从中层涡度对流降水的建议，并考虑机制，通过更有力的对流反过来影响中层涡度和大尺度环流。 这项工作是通过检查观测数据，包括从现场活动，卫星和再分析产品的数据，并构建简单的模型，代表假设的relationships.As上面提到的，过程导致发展的对流降水在AEW是实际的，以及科学的兴趣，因为它们可以导致登陆大西洋飓风。 更具体地说，这项工作侧重于热带风暴形成的早期阶段，这是热带气旋预报中最困难的挑战之一。 该项目还促进了国际科学合作，因为它涉及与智利和克罗地亚的合作者合作，并且工作是在西班牙裔服务机构进行的。 此外，该项目还为一名研究生和一名本科生暑期实习生提供支持和培训，从而为这一研究领域的未来劳动力提供支持。

This project studies the fundamental dynamics through which tropical convection, meaning the overturning motion found in tropical cumulus clouds and associated with intense precipitation, interacts with the larger-scale horizontal atmospheric circulation in which it is embedded. The work focuses on the evolution of convection within African easterly waves (AEWs), tropical waves disturbances with wavelengths of 2,000 to 2,500km which originate over West Africa and propagate westward over the northern tropical Atlantic. AEWs are of particular interest as they play a key role in the formation of tropical storms and hurricanes. The work is based on preliminary findings suggesting a chain of meteorological relationships that can lead to the development of heavy rain. One is that cyclonic vorticity (a measure of the strength of cyclonic rotation or shear in the horizontal circulation) at a mid-tropospheric level (say 600mb) can produce warmer temperatures above and colder temperatures below that level, reducing moist convective instability around the level. This reduction in mid-tropospheric instability leads to a bottom-heavy mass flux profile in the cumulus clouds, in which most of the ascending motions within the clouds occur at low to middle levels of the troposphere. The bottom-heavy mass flux profile in turn leads to a reduction in the efficiency of convection for exporting static energy from the convecting region, which requires stronger convection to maintain the energy export. Meanwhile, lower instability leads to moistening of the convecting region through a process referred to as moisture quasi-equilibrium (a result derived in part from research under AGS-1148594), so that both enhanced moisture and more vigorous overturning motions contribute to intensification of rainfall. Preliminary work suggesting these relationships was performed using field campaign data from T-PARC/TCS-08 (Thorpex Pacific Asian Regional Campaign/Tropical Cyclone Motion experiment) and PREDICT (Pre-Depression Investigation of Cloud Systems in the Tropics). Work performed here further tests and explores the proposed chain of causality from mid-level vorticity to convective precipitation, and also considers mechanisms through which more vigorous convection in turn affects the mid-level vorticity and large-scale circulation. The work is conducted through both examination of observational data, including data from field campaigns, satellites, and reanalysis products, and the construction of simple models representing the hypothesized relationships.As noted above, processes leading to the development of convective precipitation in AEWs are of practical as well as scientific interest given that they can lead to landfalling Atlantic hurricanes. More specifically, the work focuses on the early stages of tropical storm genesis, which is among the most difficult challenges in tropical cyclone forecasting. The project also fosters international scientific collaboration, as it involves work with a collaborators in Chile and Croatia, and the work is performed at a Hispanic-serving institution. In addition, the project provides support and training for a graduate student and an undergraduate summer intern, thereby providing for the future workforce in this research area.