Low-Cost Sensor and Imagers, Evaluation and Calibration, Data Fusion, and Applications

Poor air quality is the world’s single largest environmental health risk factor. Although air quality monitoring is crucial for developing informed air quality policies, efforts to monitor air pollution in different countries are uneven. In sub-Saharan Africa, for example, few cities operate air quality monitoring (AQM) systems. This is in large part due to the high capital and operating cost of reference air quality monitors, especially for airborne particulate matter. It is thus important to examine the potential of alternative monitoring approaches. We are exploring ways of combining low-cost air quality monitors, which can make detailed but generally not well-calibrated measurements, with satellite datasets offering stable, consistent snapshots over large areas that lack near-surface aerosol detail, but can be used to effectively calibrate the surface monitors and extrapolate the results.

This presentation develops a novel methodology to link the aerosol optical depth (AOD) derived from satellite data with ground-based particulate matter measurements from low-cost optical particle counters. It does this by fitting the size distribution of aerosols obtained from the ground-based monitors with particle size constraints derived from NASA’s space-based Multiangle Imaging Spectro-Radiometer (MISR) instrument. This linking works best when the mid-visible AOD is greater than a few tenths, and when the particles are concentrated near-surface, which is the case for most locally generated aerosols, as AOD is a columnar parameter, whereas air quality monitors measure surface PM. To account for aerosols aloft within the atmospheric column, we apply simulated aerosol vertical distributions from the GEOS-CHEM atmospheric transport model. To test our methodology we use MISR AOD coincident with data from five low-cost PM monitors deployed around the city of Nairobi, Kenya, from May 1 2016 to March 2 2017. This approach, combining data from low cost monitors with satellite observations, has the potential to greatly expand the range of cities that can afford to monitor long-term air quality trends and help inform public policy.