Air Quality

The atmospheric boundary layer plays a key role in air quality: wind transports pollutants from their various sources, turbulence mixes and dilutes pollution, boundary layer cumulus clouds vent pollution into the free troposphere, and temperature and humidity levels in the boundary layer affect chemical reactions and the rates at which many dangerous compounds are formed. Without accurate meteorological models, especially within the boundary layer, it would be impossible to forecast air quality reliably.

Methods

The Boundary Layer Team has been involved in numerous air quality field programs. Our role has been to deploy meteorological instruments, collect data, run meteorological models, and evaluate the models using the instruments we deploy. The most important instrumentation deployed for characterizing the boundary layer and its role on air quality are wind profiling radars, which identify transport directions and speeds and determine the depth of turbulent mixing in the convective boundary layer. Other instruments deployed include surface meteorological stations (temperature, humidity, wind speed and direction, pressure, solar radiation, and soil temperature and humidity); sodars; cloud radars; and turbulent heat and moisture flux systems.

Activities & Outcomes

Modeling-related research has focused on using high-resolution weather models. Science questions addressed are the ability of these models to accurately simulate flow in complex terrain; to correctly follow the growth of the convective boundary layer; and to assess the impact of observations from networks of boundary layer profilers on improving the analyzed wind fields. Meteorological simulations produced by the boundary layer team were used by the California Air Resources Board to develop their State Implementation Plan to meet EPA regulations on allowed ozone concentrations. We have worked on using Large Eddy Simulation (LES) models to address issues surrounding turbulent mixing within the boundary layer.

Evaluation of operational and research air quality models is another important area of research. In past field campaigns we have developed a real-time model evaluation web site, which incorporates meteorological observations, surface chemistry observations, and coupled (meteorology + chemistry) air quality forecast information. Analysis of these data sets has focused on the impact of meteorology on air quality, and especially on the impact of meteorological forecast errors on pollution concentration forecast errors.