Multi year satellite remote sensing of particulate matter air quality over Sydney, Australia

Abstract

Particulate matter (PM) air-quality information is usually derived from ground-based instruments. These measurements, while valuable, are not well suited to provide air-quality information over large spatial scales. In this study, using 4 years of satellite aerosol optical thickness (AOT) at 0.55 μm derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA's Terra and Aqua satellites, we present a multi-year air analysis of PM air quality over Sydney, Australia. We then compare the satellite data with PM2.5 mass concentration measurements from six ground-based stations in the area. Our results indicate significant diurnal variations and an overall increase in PM2.5 during Southern Hemisphere spring and summer seasons due to bush fires. The air quality in Sydney, Australia is good throughout the year except during major bushfires when PM2.5 mass loading can increase from normal (<20 μg m-3) to unhealthy conditions (>70 μg m-3). The satellite data also show corresponding AOT changes from less than 0.1 to greater than 1.0 during bushfire events. We conclude that satellite data are an excellent tool for studying PM air quality over large areas, especially when ground measurements are not available. While this is the first multi-year combined satellite and ground-based air quality analysis over Sydney, ancillary information from lidars, sun photometers, and size-resolved chemistry measurements will further enhance our capability to monitor and forecast air quality in and around Sydney.