Recent progress in the use of satellite data for air quality forecasting and assessment

In the past 5 years, nadir-viewing satellites have provided an opportunity for evaluating the use of satellite observations with respect to atmospheric composition near the surface-- air quality. Historically, the only ongoing, systematic source of air quality data at national levels was provided from ambient air quality monitoring networks put in place by national environmental agencies. As part of NASA's Earth Science Applications program and in partnership with the US Environmental Protection Agency, our group has begun to evaluate satellite observations of ``criteria pollutants'': aerosol, ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, and formaldehyde, compared to surface observations. The application of satellite measurements adds a new dimension to emerging air quality forecast efforts by providing consistent observations of pollutants over large spatial domains. In retrospective studies, satellite data provide the temporal and spatial context for interpreting large-scale pollution outbreaks. In this paper, we summarize our initial comparisons of satellite and surface observations. We discuss one of our case studies of recent aerosol pollution outbreaks over North America using surface and satellite observations to demonstrate the new understanding that combining these data sets can achieve. We further touch upon the effects of satellite-derived boundary conditions for regional atmospheric chemistry models. Our early findings point to a need for satellite observation science teams to define and produce boundary layer estimates of constituent concentrations for air quality uses. We offer the surface observation networks as a largely untapped, rich source of validation data for such boundary layer estimates at locations where it is keenly important for observations and models to be correct.