Where are smog levels the highest?
Alpine’s smog levels in the west-facing lower mountain slopes are usually higher than the rest of the county because of how and where smog is created. Emissions from motor vehicles and industry are generated in the populated coastal plain and blown inland by the onshore breeze to the lower mountain slopes. These precursor emissions react in the area’s abundant sunshine to create ozone, commonly called smog. When a temperature inversion occurs, it traps the pollutants against the mountain slopes and prevents them from rising. An inversion is formed when warm, dry inland air overlies the cool, moist marine air. The inversion layer hovers around 2,000 feet. The monitoring station at Alpine is also located at about 2,000 feet. Measurements taken at Alpine reflect smog levels for all lower mountain slope areas of the county, from Palomar Mountain south to the Mexican border, at elevations between 1,500 to 3,000 feet.
