Santa Ana Winds of Southern California Impact PM 2.5 With and Without Smoke From Wildfires

• Published in: Geohealth 2020-01, Vol.4 (1), p.e2019GH000225
• Main Authors: Aguilera, Rosana, Gershunov, Alexander, Ilango, Sindana D, Guzman-Morales, Janin, Benmarhnia, Tarik
• Format: Article
• Language: English
• ISSN: 2471-1403; 2471-1403
• DOI: 10.1029/2019GH000225

Fine particulate matter (PM ) raises human health concerns since it can deeply penetrate the respiratory system and enter the bloodstream, thus potentially impacting vital organs. Strong winds transport and disperse PM , which can travel over long distances. Smoke from wildfires is a major episodic and seasonal hazard in Southern California (SoCal), where the onset of Santa Ana winds (SAWs) in early fall before the first rains of winter is associated with the region's most damaging wildfires. However, SAWs also tend to improve visibility as they sweep haze particles from highly polluted areas far out to sea. Previous studies characterizing PM in the region are limited in time span and spatial extent, and have either addressed only a single event in time or short time series at a limited set of sites. Here we study the space-time relationship between daily levels of PM in SoCal and SAWs spanning 1999-2012 and also further identify the impact of wildfire smoke on this relationship. We used a rolling correlation approach to characterize the spatial-temporal variability of daily SAW and PM . SAWs tend to lower PM levels, particularly along the coast and in urban areas, in the absence of wildfires upwind. On the other hand, SAWs markedly increase PM in zip codes downwind of wildfires. These empirical relationships can be used to identify windows of vulnerability for public health and orient preventive measures.