Relationship Between Particulate Matter in the Central Chilean Valley and the Madden-Julian Oscillation

Global industrialization and urbanization over the past three decades, particularly in megacities in developing countries, has contributed to significant degradation in air quality. One of the most important and hazardous contributors to poor air quality is particulate matter (PM). Particulate matter is a complex mixture of fine (PM2.5) and large particles (PM10), where 2.5 and 10 define the aerodynamic diameters respectively. Both PM10 and PM2.5 have varying origins, physical and thermodynamic characteristics, and chemical compositions. Aerosols, smoke, soot, combustibles, sea salt, and trace toxic elements can be classifies as PM. The Chilean Health Ministry has set the daily maximum of PM10 to be 195 µg/m3N, any levels greater than that are hazardous to human health. There are a wide range of factors that influence particulate matter concentrations, including day of the week, time of day, altitude, wind conditions, precipitation and frontal passages. The topographical, economical and meteorological features of Santiago, Chile lead this metropolis to be plagued with dangerously high concentrations of PM during the autumn- winter months. The geographic location of the central valley and capital of Chile, Santiago combined with the fact that the valley is a closed basin and the region has suffered from poor air quality for several decades, makes it prime area to study the factors that impact PM concentrations. However, very few studies have focused on the variability of PM10 on the intraseasonal time scale, and that is the focus of this study. The objective of this study is to connect the phases of the Madden Julian Oscillation (MJO), as quantified by the commonly-used Wheeler and Hendon Real-time Multivariate MJO Index, with the levels of surface PM10 in the atmosphere in Chile's central valley during the winter months of March through August. The MJO is the leading intraseasonal oscillation that has been found to modulate precipitation and circulation on a regional and global scale, including in central Chile. By analyzing the meteorological conditions driven by the MJO, we can determine if there is a correlation to the high levels on particulate matter. Preliminary results from an analysis of nine observing stations in the Santiago metropolitan region, although with selected stations in the central valley, will be presented.