Abstract. The NOAA Chemical Sciences Laboratory (CSL) conducted the Southwest Urban NO_x and VOCs Experiment (SUNVEx) to study emissions and the role of boundary layer (BL) dynamics and seabreeze (SB) transitions on the time evolution of coastal air quality. The study presented focuses utilizes remote sensing and in situ observations in Pasadena, California. Investigations of the synoptic conditions during days when O₃ was greater than 70 ppb led to the identification of high pressure conditions and an overall reduction in BL height throughout the day as being primary dynamical factors responsible for enhanced ozone. Enhanced trapping of pollutants at night resulted in reduced O₃ and increased NO_x (titration), while trapping during the day coincided with a simultaneous decrease in NO_x and increase in VOCs that promoted favorable O₃ conditions. To evaluate micrometeorological impacts, we selected a day when O₃ exceeded 70 ppb during a SB, used empirical mode decomposition to isolate higher frequency variations (micrometeorology), and developed a multivariate spectral coherence mapping (MSCM) technique using the Ricker wavelet to study the role of BL growth and SB transitions on the evolution of air quality measurements. The extraction of time-scales from chemistry and dynamics scaleograms led to a quantitative evaluation of dynamical contributions from BL growth and a SB transition. A statistical evaluation of chemistry data during August 2021 during BL growth supported findings from the case study, but with the caveat of SB interactions with land BL and complex chemical reactions contributing to the scatter distribution caused by day-to-day variation.

中文翻译：

---

西南城市氮氧化物和挥发性有机化合物实验 (SUNVEx) 期间洛杉矶盆地地区的空气质量和边界层动力学分析

摘要。 NOAA 化学科学实验室 (CSL) 进行了西南城市氮氧化物_和挥发性有机化合物实验 (SUNVEx)，以研究排放以及边界层 (BL) 动态和海风 (SB) 转变对沿海空气质量随时间演变的作用。该研究重点利用了加利福尼亚州帕萨迪纳市的遥感和现场观测。对 O ₃大于 70 ppb期间的天气条件进行的调查发现，高压条件和全天 BL 高度的整体降低是导致臭氧增加的主要动力因素。夜间加强污染物捕集导致 O ₃减少和 NO _x增加（滴定），而白天捕集则同时导致 NO _x减少和 VOC 增加，从而促进了有利的 O ₃条件。为了评估微气象影响，我们选择了 SB 期间 O ₃超过 70 ppb的一天，使用经验模态分解来隔离更高的频率变化（微气象），并开发了一种使用 Ricker 小波的多元谱相干映射 (MSCM) 技术来研究BL 增长和 SB 转变对空气质量测量演变的作用。从化学和动力学尺度图中提取时间尺度可以对 BL 生长和 SB 转变的动力学贡献进行定量评估。对 2021 年 8 月 BL 生长期间的化学数据进行的统计评估支持了案例研究的结果，但需要注意的是，SB 与陆地 BL 的相互作用以及复杂的化学反应导致了日常变化引起的分散分布。