Collaborative Research: Structure and Evolution of Diurnal Cold-Air Pools and Seiches in Small, Closed Basins

山地稳定边界层的中微尺度气象学是应用地球科学和基础地球科学中最具挑战性的课题之一。近年来，复杂地形下SBL观测和模拟（直接数值模拟，DNS；大涡模拟，LES；中尺度模拟，MM）的快速发展导致了协同活动，这有助于缩小气象与地球物理之间、基础研究与应用研究之间以及学术和业务社区之间的文化差距。这个合作研究项目将是本着这种精神的又一次努力。与最近其他试图处理非常复杂地形的观测和模拟的SBL实地研究相反，首席研究员将强调理解SBL的中观和微观尺度结构和演变，以及在一个理想的简单形状的、小的、封闭的盆地内、上面和附近被切割成一个几乎均匀的平面。这项研究工作被称为陨石坑实验（METCRAX），为期一个月的实地阶段是在亚利桑那州温斯洛附近的1.2公里宽，175米深的圆形对称陨石坑。简单的地形设置消除了复杂的因素，如陨石坑外部的平流和斜坡不对称，允许以受控的方式研究冷池结构和演变，通常只有在实验室环境中才能实现。野外观测的目的是捕获(a)进出火山口的下坡流和上坡流的平均和湍流特征，(b)冷空气池形成和破裂的日循环，(c)冷池中的积水和其他波，以及(d)预计会引发盆地积水和波的环境风的中尺度变率。观测的长度范围从厘米到几十公里，时间范围从几十毫秒到几天。观测数据将辅以最先进的DNS/LES和MM模拟。这项研究将综合和推进多个学科的知识，包括边界层气象学、山地气象学、大气波和不稳定性物理学、对流层低层的原位和遥感、DNS、LES和MM建模以及统计流体力学。四位首席研究人员和他们的合作研究人员代表了观测学家和理论家、仪器学家和建模师、应用和基础研究人员、气象学家和地球物理学家的平衡组合。本研究是首次对冷空气池中浮冰进行深入的观测和计算研究，预计将有助于加深对冷池形成和破裂的理解，这将有利于广泛的应用和理论问题。在1990年至2000年的全国人口普查中，人口增长最快的五个州是内华达州、亚利桑那州、科罗拉多州、犹他州和爱达荷州。该地区冷空气池的社会经济影响持续增加，对气候变率的脆弱性也在增加。这项活动对整个社会的潜在好处包括提高对冷池事件以及相关的危险天气条件和美国西部空气污染问题的理解和预测。对这些SBLs的气象学理解的改进可能会导致对冷空气池开始和停止的预测的改进，这将具有重大的社会效益，并将提高对美国西部气候的认识。

The meso- and micro-scale meteorology of the stable boundary layer (SBL) over mountainous terrain is one of the most challenging subjects in the applied and basic geosciences. The rapid progress in the observation and simulation (Direct Numerical Simulation, DNS; Large Eddy Simulation, LES; mesoscale modeling, MM) of the SBL in complex terrain during recent years has led to synergistic activities, which have helped close cultural gaps between meteorology and geophysics, between basic and applied research, and between the academic and operational communities. This collaborative research project will be another effort in this spirit. In contrast to other recent SBL field studies that have tried to deal with observations and simulations of very complex topography, the Principal Investigators will emphasize understanding the meso- and micro-scale structure and evolution of the SBL within, above, and in the vicinity of an ideal simple-shaped, small, closed basin cut into a nearly homogeneous plane. This research effort has been termed the Meteor Crater Experiment (METCRAX) and the site of the month-long field phase is the 1.2-km wide, 175-m deep, circularly symmetrical Meteor Crater near Winslow, Arizona. The simple terrain setting eliminates complicating factors such as advection from outside the crater and slope asymmetry, allowing the cold pool structure and evolution to be studied in a controlled manner that typically is only achieved in laboratory settings. The field observations are designed to capture (a) the mean and turbulence characteristics of the down-slope and up-slope flows into and out of the crater, (b) the diurnal cycle of buildup and breakup of the cold-air pool, (c) seiches and other waves in the cold pool, and (d) the mesoscale variability of the ambient wind, which is expected to trigger seiches and waves in the basin. The observations will span length scales from centimeters to tens of kilometers and time scales from tens of milliseconds to days. The observed data will be supplemented with state-of-the-art DNS/LES and MM simulations. This research will synthesize and advance knowledge in a variety of disciplines, including boundary-layer meteorology, mountain meteorology, the physics of atmospheric waves and instabilities, in situ and remote sensing of the lower troposphere, DNS, LES, and MM modeling, and statistical fluid mechanics. The four Principal Investigators and their co-investigators represent a well-balanced mix of observationalists and theoreticians, instrumentalists and modelers, applied and basic researchers, and meteorologists and geophysicists. This research is the first in-depth observational and computational study of seiches in a cold-air pool and is expected to lead to an enhanced understanding of the formation and breakup of cold pools that will be beneficial for a wide range of applied and theoretical problems. Between the 1990 and 2000 national censuses, the five fastest growing states were Nevada, Arizona, Colorado, Utah, and Idaho. Socioeconomic impacts of cold air pools in this region continue to grow, as well as vulnerability to climate variability. Potential benefits of this activity for society at large include improved understanding and prediction of cold pool events and the associated hazardous weather conditions and air pollution problems over the western United States. Improvements in understanding of the meteorology of these SBLs may lead to improvements in the forecasting of the onset and cessation of the cold-air pools that will have significant societal benefits and will improve the knowledge of western U.S. climate.