Collaborative Research: Sundowner Winds EXperiment (SWEX) in Santa Barbara, California

野火是美国西部和世界其他地区最大的自然灾害之一。近年来在加利福尼亚州发生的许多悲惨事件暴露了人们对野火的巨大脆弱性，迫切需要增进对复杂地形中的风暴的了解和提高其可预测性。沿海的圣巴巴拉县(SB)人口超过13万，是南加州最容易受到野火危害的社区之一。圣伊内斯山脉突然从沿海地区拔地而起，南面是太平洋，北面是圣伊内斯山谷。下坡、干燥和阵风风暴经常出现在圣伊内斯山脉朝南的山坡上。这些风通常在日落前后和整个晚上增强，被称为“夕阳风”或“夕阳风”。它们被认为是沿海地区最重要的火灾天气机制，对航空构成危险条件。它们加剧了影响SB沿海人口的所有重大野火的严重性。因此，改进天气警告和预报提前时间，包括哪里的风将是最强的时空特性，对于提高对野火的复原力至关重要。日落现象表现出很大的时空变异性，并由独特的复杂机制驱动。夕阳风实验(SWEX)将研究夕阳风的这些独特方面，以促进对这些风的理解和预测，同时为在具有相似地理和气候特征的沿海环境中发展新的坡下风暴理论提供丰富的数据集。这将通过对大气过程的战略气象观测来实现，假定大气过程将调节夕阳风的强度和空间变异性。这些结果将大大有助于提高沿海环境复杂地形中风暴的可预测性，并对生活在火灾多发地区的大型社区产生重大影响。该项目将提供关键的宣传材料，分发给政府机构和媒体，并对公众进行有关火灾、天气和自然灾害的教育。此外，该项目将支持开发新的教育课程，并在美国六所大学培训本科生和研究生，包括少数民族。日落时的时空特征受发生在圣伊内斯山谷和圣拉斐尔山脉上游的大气过程之间复杂的相互作用控制，而下游由于凉爽和稳定的海洋边界层的影响而发生。SWEX活动旨在加强空间测量，以解决从边界层到对流层中层以及从SB海峡到Santa Ynez山谷的局部环流和垂直廓线。这些观测将被用来检验有关控制日落风的机制的假设，评估中尺度模拟，并改进日落风的提前期预报。更具体地说，多传感器平台和飞机将被用来调查海洋和大陆边界层的结构和动态如何影响日落和未受干扰期间的山流，包括下坡风、温度和湿度的强度、时间和地理特征。这些测量将能够检查与圣伊内斯山脉背风高幅度山波、临界层和地表风强有关的潜在机制。这些观测将被用来研究BL结构和对流层稳定性的变化如何控制山波流和背风坡急流，以及这些机制对日落风可预报性的重要性。SWEX带来了尖端科学、国家大气研究中心最先进的设施和多个仪器平台来解决这一重要问题。它将与该地区负责预测和火灾应对的人员建立联系，该地区代表着许多具有类似脆弱性的地区。SWEX将提高国家气象局预报洛杉矶地区，特别是沿海地区的天气灾害的能力。因此，该项目具有重大而广泛的影响。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Wildfires are among the greatest natural hazards in the Western U.S. and other parts of the world. The numerous tragic events in recent years in California have exposed the great vulnerability of the population to wildfires and the critical need to improve understanding and enhance predictability of windstorms in complex terrain. Coastal Santa Barbara County (SB), with a population exceeding 130,000 inhabitants, is among the most exposed communities to wildfire hazards in southern California. The Santa Ynez Mountains rise abruptly from coastal SB separating the Pacific Ocean on its south face from the Santa Ynez Valley on its north face. Downslope, dry and gusty windstorms are frequently observed on the southern-facing slopes of the Santa Ynez Mountains. These winds typically intensify around sunset and throughout the night, and are known as "Sundowner winds" or "Sundowners". They are considered the most significant fire-weather regime in coastal SB and pose hazardous conditions to aviation. They have enhanced the severity of all major wildfires affecting the SB coastal population. Therefore, improved weather warnings and forecast lead time, including spatiotemporal specificity of where winds will be strongest, are critical to increase resilience to wildfires. Sundowners exhibit large spatiotemporal variability and are driven by unique complex mechanisms. The Sundowner Winds Experiment (SWEX) will investigate these unique aspects of Sundowners to advance the understanding and predictability of these winds, while providing rich data sets for developing new theories of downslope windstorms in coastal environments with similar geographic and climatic characteristics. This will be accomplished with strategic meteorological observations of the atmospheric processes hypothesized to modulate Sundowner winds intensity and spatial variability. These results will significantly contribute to improve the predictability of windstorms in complex terrain in coastal environments, with significant impacts to large communities living in fire prone areas. The project will provide key outreach materials for dissemination to government agencies and the media and will educate the public about fire weather and natural disasters. Moreover, the project will support the development of new educational courses, and the training of undergraduate and graduate students, including minorities, in six universities in the U.S. Sundowners spatiotemporal characteristics are controlled by complex interactions between atmospheric processes occurring upstream, in the Santa Ynez Valley and San Rafael Mountains, and downstream due to the influence of a cool and stable marine boundary layer. The SWEX campaign is designed to enhance spatial measurements to resolve local circulations and vertical profiles from the boundary layer to the mid-troposphere, and from the SB channel to the Santa Ynez Valley. These observations will be used to test hypotheses concerning the mechanisms controlling Sundowner winds, evaluate mesoscale simulations and improve lead time forecasts of Sundowners. More specifically, the multi-sensor platforms and aircraft will be utilized to investigate how the structure and dynamics of the marine and continental Boundary Layers (BL) influence mountain flows during Sundowners and undisturbed periods, including intensity, timing and geographic characteristics of downslope winds, temperatures and humidity. These measurements will enable to examine underlying mechanisms relating high amplitude mountain waves, critical layers, and surface wind intensity leeward of the Santa Ynez Mountains. These observations will be utilized to investigate how variations in BL structure and tropospheric stability control mountain wave flows and the lee-slope jet, and the importance of these mechanisms for the predictability of Sundowner winds. SWEX brings cutting-edge science, the state-of-art facilities at National Center for Atmospheric Research and multiple instrumental platforms to bear on this important problem. It will build linkages with those responsible for predictions and fire response in a region that is representative of many areas with similar vulnerabilities. SWEX will improve the capability of the National Weather Service to forecast weather hazards in the Los Angeles area, specifically in coastal SB. Thus this project has substantial broader impacts.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.