The impact of Los Angeles Basin pollution and stratospheric intrusions on the surrounding San Gabriel Mountains as seen by surface measurements, lidar, and numerical models

Abstract. In this work, the impact of Los Angeles Basin pollution transport and stratospheric intrusions on surface ozone levels observed in San Gabriel Mountains is investigated based a combination lidar measurements as well WRF-Chem (Weather Research Forecasting with Chemistry) WACCM (Whole Atmosphere Community Climate Model) runs. The number days exceeding National Ambient Air Quality Standards exhibit clear seasonal pattern, maximum during summer, when models suggest minimum influence largest from transport. Additionally, measured modeled PM10 were analyzed function season, time day, wind direction. Measurements are good qualitative agreement, for southwest west winds. For prevailing summer direction, slightly south corresponding to south-southwest winds, lower observed. Back trajectories that associated central Basin, where titration limits amount ozone. A quantitative comparison profiles revealed agreement near surface, showing an increasing positive bias altitude, reaching 75 % at 15 km above sea level. Finally, three selected case studies covering different mechanisms affecting near-surface concentration over Mountains, namely transport, measurements, co-located ceilometer models.