Improving correlations between MODIS aerosol optical thickness and ground-based PM2.5 observations through 3D spatial analyses

The Relation between Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Depth and PM2.5over the United States: A Geographical Comparison by U.S. Environmental Protection Agency Regions

“…It can be deduced that the screened AOD retrievals for v4.0.1 are located above the PBL or contaminated by cloud cover. A similar conclusion about the effect of cloud screening was recently published by Hutchison et al 18 Much smaller differences are observed in most regions between the whole set of v5.2.6 AOD retrievals and the corresponding subset because of the small differences in their numbers. One exception is region 2, where the averages of the two datasets appear to have a large difference.…”

“…It also has been noted in previous papers 6,17,18 that AOD in the west arises more from smoke events, which may be transported more aloft than the high-AOD pollution events in the east. High AOD-PM 2.5 correlations are usually found in areas with high variations of particulate matter.…”

“…Since launch, the aerosol products have experienced continuous updates from v3.0 to the most recent v5.2.6. 30, 31 Hutchison et al 18 showed that the correlation between MODIS AOD and PM 2.5 demonstrates an improvement with the newer version over Texas regions but with less data coverage. This influence over the United States will be discussed later in this paper.…”

“…For example, it was found that the correlation coefficient can range from 0.14 to 0.6 over 5 cities located at different parts of the Earth, 14 and that the correlation coefficient is small during the months from December to March and large during other months over the southeastern United States. 15 Efforts have been made to improve the correlation coefficients, including removal of the "hot spot" in AOD retrievals, 16 removal of pixels with high cloud fractions, 14 the use of Light Detection and Ranging (LIDAR) measurements to determine the vertical profile and remove AOD from aerosols aloft, 17,18 the use of multivariate regression regressions and neural network approaches to include meteorological parameters in the AOD-PM 2.5 relation model, 10,19 etc. The relation between AOD and PM 2.5 can be used for monitoring air quality, verifying the air quality model forecast, and data assimilation.…”

An Improved Method for Estimating Surface Fine Particle Concentrations Using Seasonally Adjusted Satellite Aerosol Optical Depth

“…28 Overall, there was increased variability in the MODIS relationship with hourly PM 2.5 data, likely because of temporary local spikes of particulate matter that were captured in the ground-based measurement but not in the corresponding, spatially averaged satellite measurement. These variations could arise because of sampling near a variable source or particles aloft that have had time to settle at the surface in the 24-hr concentrations but not at the time of the hourly surface observation.…”