Sunday, 22 January 2012
Predicting Air Quality Through the Phasing of the Madden-Julian Oscillation in Santiago, Chile
Hall E (New Orleans Convention Center )
The Madden-Julian Oscillation (MJO) is the leading mode of intraseasonal variability in the tropics. This modulation is a slow moving eastward propagation that affects both precipitation and atmospheric circulation on a 30-60 day cycle. The MJO can be broken up into eight phases, and each phase is associated with unique precipitation and atmospheric circulation characteristics. Phases 8, 1 and 2 are associated with positive precipitation anomalies in central and south-central Chile (30–45°S), and negative precipitation anomalies are associated with Phases 3-7. These wet and dry phases modulate precipitation in central and south-central Chile primarily during Austral winter (May-August). Precipitation events have been found to clean the atmosphere of pollution particles such as PM10, thus contributing to improved air quality. In this study, hourly PM10 observations during winter months of 1987-2011 for stations in the Santiago, Chile metropolitan area were examined. These surface air quality data were supplemented by Aerosol Optical Depth (AOD) measurements from the NASA Aura satellite. AOD was used as a proxy for air quality and extended the PM10 data to a broader region of central Chile. The objective of this study was to test whether the MJO, which modulates winter seasonal precipitation events, would also modulate surface PM10 concentrations. The positive precipitation anomalies caused by wet (dry) MJO phases should cause lower (higher) concentrations of PM10 and lower (higher) AOD. The MJO can then be used to predict air quality in central Chile, and those predictions can then be used to reduce concentrations of PM10, which is critical for improving human respiratory health in the metropolitan area.