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Investigation of wintertime cold-air pools and aerosol layers in the Salt Lake Valley using a lidar ceilometer.

机译：使用激光雷达云高仪对盐湖谷冬季的冷气池和气溶胶层进行调查。

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摘要

This thesis investigates the utility of lidar ceilometers, a type of aerosol lidar, in improving the understanding of meteorology and air quality in persistent wintertime stable boundary layers, or cold-air pools, that form in urbanized valley and basin topography. This thesis reviews the scientific literature to survey the present knowledge of persistent cold-air pools, the operating principles of lidar ceilometers, and their demonstrated utility in meteorological investigations. Lidar ceilometer data from the Persistent Cold-Air Pool Study (PCAPS) are then used with meteorological and air quality data from other in situ and remote sensing equipment to investigate cold-air pools that formed in Utah's Salt Lake Valley during the winter of 2010-2011.;The lidar ceilometer is shown to accurately measure aerosol layer depth and aerosol loading, when compared to visual observations. A linear relationship is found between low-level lidar backscatter and surface particulate measurements. Convective boundary layer lidar analysis techniques applied to cold-air pool ceilometer profiles can detect useful layer characteristics. Fine-scale waves are observed and analyzed within the aerosol layer, with emphasis on Kelvin-Helmholz waves. Ceilometer aerosol backscatter profiles are analyzed to quantify and describe mixing processes in persistent cold-air pools. Overlays of other remote and in-situ observations are combined with ceilometer particle backscatter to describe specific events during PCAPS. This analysis describes the relationship between the aerosol layer and the valley inversion as well as interactions with large-scale meteorology.;The ceilometer observations of hydrometers are used to quantify cloudiness and precipitation during the project, observing that 50% of hours when a PCAP was present had clouds or precipitation below 5 km above ground level (AGL). Then, combining an objective technique for determining hourly aerosol layer depths and correcting this subjectively during periods with low clouds or precipitation, a time series of aerosol depths was obtained. The mean depth of the surface-based aerosol layer during PCAP events was 1861 m MSL with a standard deviation of 135 m. The aerosol layer depth, given the approximate 1300 m altitude of the valley floor, is thus about 550 m, about 46% of the basin depth. The aerosol layer is present during much of the winter and is removed only during strong or prolonged precipitation periods or when surface winds are strong. Nocturnal fogs that formed near the end of high-stability PCAP episodes had a limited effect on aerosol layer depth.;Aerosol layer depth was relatively invariant during the winter and during the persistent cold-air pools, while PM10 concentrations at the valley floor varied with bulk atmospheric stability associated primarily with passage of large-scale high- and low-pressure weather systems. PM10 concentrations also increased with cold-air pool duration. Mean aerosol loading in the surface-based aerosol layer, as determined from ceilometer backscatter coefficients, showed weaker variations than those of surface PM10 concentrations, suggesting that ineffective vertical mixing and aerosol layering are present in the cold-air pools. This is supported by higher time-resolution backscatter data, and it distinguishes the persistent cold-air pools from well-mixed convective boundary layers where ground-based air pollution concentrations are closely related to time-dependent convective boundary layer/aerosol depths.;These results are discussed along with recommendations for future explorations of the ceilometer and cold-air pool topics.
机译：本文研究了一种激光雷达云高仪（一种气溶胶激光雷达）在提高对城市化的山谷和盆地地形中形成的持续冬季稳定边界层或冷空气池的气象学和空气质量的了解的实用性。本文回顾了科学文献，以调查持久性冷空气池的当前知识，激光雷达云高仪的工作原理及其在气象调查中的实用性。然后，将来自持久性冷空气池研究（PCAPS）的激光雷达云高仪数据与其他原位和遥感设备的气象和空气质量数据一起用于调查2010年冬季在犹他州盐湖谷形成的冷空气池- 2011 .;与激光观测相比，激光雷达云高仪可以精确测量气溶胶层深度和气溶胶负载。在低层激光雷达后向散射和表面微粒测量之间发现线性关系。对流边界层激光雷达分析技术应用于冷空气池云高仪轮廓可以检测有用的层特征。在气溶胶层内观察并分析了细尺度的波浪，重点是开尔文-亥姆霍兹波。分析云高仪气溶胶的反向散射曲线，以量化和描述持续性冷空气池中的混合过程。其他远程和原位观测的叠加与云高仪粒子反向散射结合起来，描述了PCAPS期间的特定事件。该分析描述了气溶胶层与谷底反演之间的关系以及与大规模气象学的相互作用。;用液体比重计的云高仪观测来量化项目期间的浑浊和降水，观察到当PCAP达到50％时目前在高于地面（AGL）5公里以下有云层或降水。然后，结合确定小时气溶胶层深度的客观技术并在云量少或降水少的时期进行主观校正，获得了气溶胶深度的时间序列。 PCAP事件期间基于表面的气溶胶层的平均深度为1861 m MSL，标准差为135 m。因此，在谷底高度约为1300 m的情况下，气溶胶层的深度约为550 m，约为盆地深度的46％。气溶胶层存在于冬季的大部分时间，并且仅在强降雨或长时间降雨或地面风较强时才被去除。在高稳定性PCAP发作即将结束时形成的夜间雾对气溶胶层深度的影响有限;在冬季和持续的冷空气池中，气溶胶层深度相对不变，而谷底的PM10浓度则随总体大气稳定性主要与大型高压和低压天气系统的通过有关。 PM10浓度也随着冷空气池持续时间的增加而增加。由云高仪的反向散射系数确定，基于表面的气溶胶层中的平均气溶胶负荷显示出比表面PM10浓度弱的变化，这表明冷空气池中存在无效的垂直混合和气溶胶分层。这得到了更高时间分辨率的反向散射数据的支持，并且将持久性冷空气池与充分混合的对流边界层区分开来，在这些层中，地面空气污染浓度与时间相关的对流边界层/气溶胶深度密切相关。讨论了结果，并提出了对云高仪和冷空气池主题未来探索的建议。

著录项

  • 作者

    Young, Joseph Swyler.;

  • 作者单位

    The University of Utah.;

  • 授予单位 The University of Utah.;
  • 学科 Atmospheric Sciences.
  • 学位 M.S.
  • 年度 2013
  • 页码 120 p.
  • 总页数 120
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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