Correlating particulate matter and planetary boundary layer dynamics in northwestern South America: A case study of Santiago de Cali

Abstract

The relationship between particulate matter (PM) levels and planetary boundary layer height (PBLH) is investigated in Santiago de Cali, a tropical city located above the equator in southwestern Colombia, in the northwestern region of South America. Correlations are studied during both the dry and wet seasons, at different locations of local air quality stations, and under different wind regimes. Hourly estimates of PBL height are derived from Lidar signals using the Extended Kalman Filter (EKF) method, while Bayesian linear regression is used to quantify the PM-PBLH correlation. The results indicate a negative correlation between PM and PBLH, observed during both dry and wet seasons. Furthermore, the location of the observation can influence the relationship between the variables. The correlation is negative for stations located near the western foothills, although the strength of this relationship is reduced at the easternmost air quality station, while a positive correlation was observed at the rural background station. We analyzed the air mass transport regimes for these stations using bivariate plots and cluster analysis, and were able to identify local and distant potential pollution sources that could explain the PM-PBLH correlation behavior. This study advances our understanding of PBL height, its temporal evolution, and its relationship with PM₁₀ and PM_2.5 in a Colombian tropical Andean city characterized by distinct dry and wet seasons and complex topography and wind patterns.