LAUSR

To study the air quality in the Guadalajara Metropolitan Area (GMA), concentrations of suspended particles (PM10) and ozone (O3) reported by eight monitoring stations were analyzed. Also, six commonly found types of synoptic situations (TSS) during 1996–2016 were identified using an atmospheric pattern correlation method on the mean sea level pressure and geopotential heights (850 hPa, 500 hPa, and 200 hPa) of fields given by the North American Regional Reanalysis (NARR) database. Overall, 75% of the period of study was classified as one of the six TSS. Afterward, statistical significance tests (confidence level 95%) were applied to determine whether the TSS affected PM10 and O3 concentrations locally in the GMA. PM10 maximum hourly concentrations (~76.7 μg/m3) occurred around 8 am local time, while that of ozone (~0.054 ppm) occurred between 1–4 pm local time. Meanwhile, PM10 monthly levels were higher between December and May, and the highest O3 concentrations occurred between April and June. Average annual levels of PM10 have decreased through the years, while the annual trend of mean O3 concentrations seemed to respond to the 11-year solar cycle. It was also found that during “convective-allowing situations” (TSS VI) and “thermal low over California” (TSS I), PM10 concentrations remained low in the GMA, and O3 concentrations rose under the influence of a “low-pressure system over the United States (USA)” (TSS II). Further research is suggested to address the effect of the local circulation in the GMA linked to the TSS on O3 and PM10 concentrations.