Collaborative Research: Topographic Influences on Extreme Warm-Season Precipitation

极端降雨影响着全球数百万人，但我们对这种高影响天气现象的理解和预测能力有限。太平洋极端降雨预测项目（precisip， 2020年5 - 8月）旨在提高对台湾和北太平洋西部富湿环境中极端降雨产生重要的多尺度过程的认识。总体的precp假设认为，极端降雨是由多尺度因素在富湿环境中的最佳组合造成的，但不同的关键因素和过程导致强垂直强迫和高降雨强度，强水平强迫和长持续时间，或强降水和持续降水的混合。智力优势：本项目聚焦于地形对极端降雨的影响，利用独特的雷达和无线电探空仪在台湾中央山脉（CMR）两侧的观测组合，通过热力学、动力学、运动学和微物理过程的组合，确定陡峭地形在增强降雨强度和持续时间方面的作用。总体假设是，地形通过增加产生强降雨所需成分的强度来增强极端降雨的强度和持续时间。除了促进抬升和集中水分外，地形还通过微物理过程的变化改变降雨强度和持续时间。在台湾的亚热带环境中，高效的暖雨过程可以产生高强度的对流降雨，而冰基过程在以层状降水为主的长时间事件中变得越来越重要。此外，TiMREX 2008的研究结果显示，沿台湾CMR相对较浅的对流向上倾斜可以促进降水大小的冰的生长。随后的冷池产生导致上游细胞的持续生长，并延长了CMR沿线降雨事件的持续时间。precp提供了进一步探索地形作用的机会，包括对微物理过程的影响，在各种事件中产生极端降雨，无论是在西部斜坡上还是沿着数据稀疏的台湾东海岸。为了验证上述假设，本研究将结合多频双偏振多普勒雷达（S-PolKa, sew -pol）、无线电探空仪和模式的PRECIP数据，探索地形对日强迫对流、梅雨锋内嵌入的中尺度对流系统和热带气旋的影响过程。更广泛的影响：本研究的一个重要的更广泛的目标是确定哪些台湾极端降雨事件的关键成分和过程也与其他环境或地点的地形降水有关。这个由三名早期职业女性科学家组成的团队带来了丰富的野外观测项目和地形影响降水研究方面的知识，涵盖了各种全球模式，包括西马德雷山脉、CMR、安第斯山脉、落基山脉和喜马拉雅山脉的暖季降雨，典型的信风流，经过多米尼加的热带气旋，以及奥运会上空的冷季降雨。precp将为研究山脉的迎风面和背风面各种降雨事件提供机会。该项目的研究结果将有可能通过在各种暴雨事件中收集的前所未有的数据，建立一个基于成分的框架，从而提供对全球极端降雨的最新了解。该项目由刺激竞争研究的既定计划（EPSCoR）和PREEVENTS，极端事件预测和恢复计划共同资助。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。

Extreme rainfall affects millions of people globally, yet our understanding and forecast skill of this high-impact weather phenomenon is limited. The Prediction of Rainfall Extremes Campaign in the Pacific (PRECIP, May-August 2020) field campaign aims to improve understanding of the multi-scale processes important for generating extreme rainfall in the moisture-rich environment of Taiwan and the western North Pacific. The overarching PRECIP hypothesis is that extreme rainfall results from an optimal combination of multi-scale ingredients in a moisture-rich environment, but different key ingredients and processes lead to strong vertical forcing and high rainfall intensity, strong horizontal forcing and long duration, or a mixture of both intense and sustained precipitation.Intellectual Merit:This project focuses on orographic influences on extreme rainfall, using a unique combination of radar and radiosonde observations on both sides of Taiwan's Central Mountain Range (CMR) to determine the role of steep terrain in enhancing both intensity and duration of rainfall through a combination of thermodynamic, dynamic, kinematic, and microphysical processes. The overall hypothesis is that terrain enhances both intensity and duration of extreme rainfall through increasing the magnitude of ingredients needed to produce heavy rainfall. In addition to promoting lifting and concentrating moisture, terrain modifies rainfall intensity and duration through changes in microphysical processes. In the subtropical environment of Taiwan, efficient warm-rain processes can produce high intensity convective rainfall, while ice-based processes become increasingly important for long-duration events dominated by stratiform precipitation. Additionally, results from TiMREX 2008 suggest that upslope tilting of relatively shallow convection along Taiwan's CMR can promote growth of precipitation-sized ice. Subsequent cold-pool generation leads to continuous growth of cells upstream and prolongs the duration of rainfall events along the CMR. PRECIP offers the opportunity to further explore the role of terrain, including the influence on microphysical processes, in producing extreme rainfall for a wide variety of events, both on the western slopes and along the data-sparse east coast of Taiwan. To test the above hypotheses, the study will use a combination of PRECIP data from multi-frequency dual-polarization Doppler radars (S-PolKa, SEA-POL), radiosondes, and models to explore terrain-influenced processes for diurnally-forced convection, mesoscale convective systems embedded within the Meiyu front, and tropical cyclones.Broader Impacts:An important broader goal of this investigation is to determine which of the key ingredients and processes identified for Taiwan extreme rainfall events are also relevant to orographic precipitation in other environments or locations. The team of three early-career female scientists brings a wealth of knowledge of observational field projects and terrain-influenced precipitation studies spanning a variety of global regimes, including warm-season rainfall in the Sierra Madre Occidentals, CMR, Andes, Rockies, and Himalayas, typical trade-wind flow, a tropical cyclone passing over Dominica, and cold-season rainfall over the Olympics. PRECIP will give an opportunity to investigate a wide variety of rain-producing events, both the windward and leeward sides of the mountain range. The findings from this project will have the potential to provide an updated understanding of extreme rainfall globally by building off an ingredients-based framework through unprecedented data collected in a wide variety of heavy rain events.This project is jointly funded by the Established Program to Stimulate Competitive Research (EPSCoR) and PREEVENTS, Prediction of and Resilience against Extreme Events program.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.