To assess values of air quality and visibility at risk from wildland fire in the United States, we generated a 40-year database that includes twice-daily values of wind speed and direction, mixing height, and a ventilation index that is the product of wind speed and mixing height. All values are generated at 2.5’ latitude/longitude (about 5km) spatial resolution. The database provides the first available, nationally consistent map of surface wind and ventilation index. In addition, it is the longest climate record of mixing height in the country. We built the database into an interactive Ventilation Climate Information System (VCIS) that allows users to assess risk based on frequency patterns of poor, marginal, fair, and good ventilation conditions.

Surface winds are generated with a one-level hydrostatic model that uses topography and upper-level data from NCEP Reanalysis as input. Mixing heights are determined from sounding observations using Holzworth’s parcel method and then spatially interpolated. Where they intersect terrain, a simple boundary-level approximation is imposed. Morning mixing heights are adjusted to account for local valley inversions when wind and cloud-cover observations indicate potential stagnation. The inversion location and depth is derived from terrain features using a unique GIS algorithm.

VCIS is being used by land managers to help plan for and mitigate the impacts of smoke from wildland biomass fires. Others use it to help determine impacts from a variety of pollution sources and to help identify cold pools of air that impact vegetation distribution. New efforts are underway to downscale the data, improve some of the approximated values, and make the raw data more readily available. We will describe some key features of the development and demonstrate the web-access tools.