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

山区稳定边界层(SBL)的中、微尺度气象是应用型和基础性地球科学中最具挑战性的课题之一。近年来，在对复杂地形上的大气边界层进行观测和模拟(直接数值模拟、大涡模拟、中尺度模拟)方面取得的快速进展导致了协同活动，这些活动有助于缩小气象学和地球物理学、基础研究和应用研究以及学术界和实务界之间的文化鸿沟。这个合作研究项目将是本着这种精神的另一项努力。与最近试图处理非常复杂地形的观测和模拟的其他SBL实地研究不同，首席调查员将强调了解SBL在理想的简单形状的小封闭盆地内、上方和附近的中、微尺度结构和演变。这项研究工作被称为陨石坑实验(METCRAX)，长达一个月的野外阶段的地点是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，如来自火山口外部的平流和坡度不对称，允许以受控的方式研究冷池结构和演变，这通常只在实验室环境中实现。现场观测的目的是捕捉(A)进出火山口的下坡和上坡气流的平均和湍流特征，(B)冷气池的积聚和破裂的日循环，(C)冷池中的海槽和其他波，以及(D)环境风的中尺度变异性，预计将在海盆引发海槽和海浪。观测将跨越从厘米到几十公里的长度尺度和从几十毫秒到几天的时间尺度。观测到的数据将得到最先进的DNS/LES和MM模拟的补充。这项研究将综合和推进各种学科的知识，包括边界层气象学、山地气象学、大气波和不稳定的物理、对流层低层的现场和遥感、DNS、LES和MM模拟，以及统计流体力学。四名首席调查员和他们的联合调查员代表了天文学家和理论家、仪器专家和模型师、应用和基础研究人员以及气象学家和地球物理学家的平衡组合。这项研究是第一次对冷空气池中的冷池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分解的理解，这将有助于解决广泛的应用和理论问题。在1990年至2000年的全国人口普查期间，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。该区域冷气池的社会经济影响继续增加，而且易受气候变化的影响。这项活动对整个社会的潜在好处包括更好地了解和预测冷池事件以及相关的危险天气条件和美国西部的空气污染问题。对这些SBL气象学的了解的提高可能会导致对冷气池开始和结束的预测的改进，这将具有重大的社会效益，并将提高对美国西部气候的了解。

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.