**3.4 Meteorological analysis**

To carry out the meteorological analysis at regional level, 24-h backward air-masses trajectories at 500, 1000, and 1500 m of altitude were obtained (a total of 85 trajectories) from HYSPLIT Model (National Oceanic and Atmospheric Administration), and choosing as representative site to CICEG-BOMBEROS, located at SE of the metropolitan area. In addition, meteorological surface data were obtained from SINAICA (National System of Air Quality Information) to estimate wind roses to identify the prevailing wind direction during the study period.

From surface analysis, it could be observed that wind direction showed a great variability between climatic seasons, for example, the prevailing wind direction during cold dry season was from SW (**Figure 11a**), during warm dry season was from NE (**Figure 11b**), and during rainy season was from E-NE (**Figure 11c**).
