Dust pollution caused by an extreme Santa Ana wind event

In arid and semiarid regions from the southwestern USA and vast areas of northwestern Mexico, Santa Ana wind events modify the environment with high temperatures, very low humidity, and dust storms representing a recurrent phenomenon that triggers asthma and other respiratory diseases. While research has emphasized Santa Ana wind effects on the USA side, northwestern Mexico has been less investigated. Numerical modeling of a severe dust storm in November 2018, applying the Weather Research and Forecasting model coupled with a chemistry module (WRF-Chem), revealed that erosion, transport, and dust storms extend along the peninsula and the Gulf of California. Santa Ana winds eroded large areas, transported desert conditions to urban zones, causing high dust concentrations and reducing the relative humidity below 10%, deteriorating climatic conditions favorable to wellness. In Tijuana, Mexicali, Ensenada, San Diego, and Los Angeles, PM10 and PM2.5 concentrations (particle matter with diameter below 10 µm and 2.5 µm) reached values over 2000 µg/m3 for PM10, with daily mean concentrations well above national standards, leading to poor air quality and representing a health threat even in short-term exposure. This Santa Ana event transported dust particles several hundreds of kilometers over urban areas, the Gulf of California, and the Pacific Ocean. Severe soil deterioration was simulated within the study area, reaching dust emissions above 700,000 t, including croplands from the northern part of Baja California and Sonora's coastal area.