Understanding high polluted events in a tropical megacity with air quality observations and ERA5-reanalysis data

Abstract

Already published studies found that 20% of the atmospheric pollution variations are linked to local meteorology. This relationship may be more important in places with dense populations such as Latin American cities since the topography and fast multiscale changes are part of the tropical climate. Even so, this possibility has not been addressed in previous studies. This research aims to characterize the relationship between tropical climate variables and PM2.5 levels during high pollution events. The relationship between wind field, Turbulent Kinetic Energy (TKE), radiation, temperature, relative humidity, boundary layer height, and atmospheric stability with PM2.5 concentration was investigated. Statistical correlations and the parcel method were used to analyze the relationship between vertical motions and PM2.5. Obtained results show that the stability, vertical velocity, and boundary layer height do not significantly affect pollution levels. We identified some signals that are strongly related to PM2.5 high concentrations: weaker than average horizontal wind speed and TKE throughout the day, easterly winds in the morning (associated with the transport of ashes from wildfires produced on the Eastern plains), combined with a higher than average radiation peak. These results lead to a better understanding of the PM2.5 variations, which can be applied for the improvement of air quality models and have the potential to be part of a novel policy to manage air quality risk.