Nowcasting Applications of Geostationary Satellite Hourly Surface PM Data.

The mass concentration of fine particulate matter (PM; diameters less than 2.5 μm) estimated from geostationary satellite aerosol optical depth (AOD) data can supplement the network of ground monitors with high temporal (hourly) resolution. Estimates of PM over the United States (US) were derived from NOAA's operational geostationary satellites Advanced Baseline Imager (ABI) AOD data using a geographically weighted regression with hourly and daily temporal resolution. Validation versus ground observations shows a mean bias of -21.4% and -15.3% for hourly and daily PM estimates, respectively, for concentrations ranging from 0 to 1000 μg/m. Because satellites only observe AOD in the daytime, the relation between observed daytime PM and daily mean PM was evaluated using ground measurements; PM estimated from ABI AODs were also examined to study this relationship. The ground measurements show that daytime mean PM has good correlation (r > 0.8) with daily mean PM in most areas of the US, but with pronounced differences in the western US due to temporal variations caused by wildfire smoke; the relation between the daytime and daily PM estimated from the ABI AODs has a similar pattern. While daily or daytime estimated PM provides exposure information in the context of the PM standard (> 35 μg/m), the hourly estimates of PM used in Nowcasting show promise for alerts and warnings of harmful air quality. The geostationary satellite based PM estimates inform the public of harmful air quality ten times more than standard ground observations (1.8 vs. 0.17 million people per hour).