Dry, Rapid Aerosol Downward Dispersion in Jet Streaks

The downward dispersion of particles from wildfires, volcanic eruptions, dust storms, and other aerosol sources, affects air quality hundreds of kilometers downwind from their sources. Using plume heights derived from the NASA Earth Observing System’s (EOS) MISR (Multiangle Imaging Spectro-Radiometer) space-based, multi-angle imaging, we examine case studies displaying the capture, transport, and dispersion of smoke particulates over continental distances from their sources, and in particular, the effect of jet streaks on particle deposition.

Traditionally, rapid aerosol deposition is associated with precipitation, whereas slow dispersion is connected to gravitational settling over large distances. However, our research group has observed a third phenomenon in the satellite data: rapid, downward aerosol dispersion. This occurrence is observed when smoke is ejected above the planetary boundary layer and subsequently encounters a jet streak, as indicated in the 250 mb wind vector diagram and in imagery from the NASA/EOS MODIS (Moderate Resolution Imaging Spectroradiometer) instrument. Surface air quality monitors show increased particulate matter concentrations below the jet streaks. We hypothesized that this dispersion process amounts to vertical advection by strong downdrafts in the exit regions of jet streaks. We are exploring the degree to which aerosol transport models, such as the NOAA Air Resources Laboratory's Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, account for this phenomenon. The multi-sensor, satellite-based observations from MODIS and MISR, as well as in-situ ground-based observations of air quality, all contribute to our investigation.This combination of data types provides the required accuracy, and high spatial and temporal coverage. It also offers the opportunity to explore how well the HYSPLIT aerosol transport model accounts for rapid, dry aerosol dispersion.