Strategies for Using Satellite Observations to Monitor PM_(2.5) in Low and Middle-Income Countries

摘要

Here we explore the opportunities and limitations of satellite-derived observations of surface-level PM2.5 for urban air quality monitoring in typical low to middle income countries (LMICs). We first review the approaches used (and their strengths and limitations) in each of the three key steps in combining satellite observations with ground level monitoring (GLM) measurements of PM2.5: the retrieval of aerosol optical depth (AOD) from satellite observations of reflected solar radiation; the translation of the vertically-integrated AOD observation into an estimate of the surface PM2.5 concentration; and simultaneously interpolating these satellite-derived PM2.5 estimates and the available GLM data. We examine various satellite datasets to identify which retrieval algorithm gives the most accurate and precise AOD retrieval under different conditions typical of LMICs (e.g., dusty regions, high altitude regions), with the goal of choosing the best AOD product for each city, rather than a single global product. We then use publicly available GLM data to identify promising new pathways for LMICs to use satellite observations in their air quality monitoring and forecasting. We compare statistical approaches with CTM-based approaches and discuss how to propagate the uncertainty in the retrieved AOD and the aerosol vertical profile through to the surface PM2.5 estimate. We then explore how additional measurement sites in a city within a LMIC could be placed to improve the information provided by a combined satellite and GLM approach, and make recommendations for further work that will facilitate the use of satellite observations in air quality modeling in LMICs.